v—y— -—-—_——

 

 

ElEBTIOHRBIBSHPfl STUDIES
II “RIM BM" BATTLE
TESTS FM THE DEEREE W I. 8.

NW STATE WEE

B. V. ALFREDBON
1940

31-15515

 

 

 

MMWARDIOGBAPH STUDIES m NORMAL DAIRY CATTLE

by

BERNARD VICTOR ALFREIBON

A 93313
Submitted to the Graduate School of Michigan
State College of Agriculture and Applied
Science in partial fulfilment of the
requirements for the degree of

MASTER 01' SC IENCE

Department of miry Husbandry

19ho

THESIS

ACKNWLENWTS

{The writer wishes to express his sincere appreciation to Dr.
F. N. lilson, Professor of Internal Medicine. University of Michigan,
Ann Arbor, for his guidance during the preliminary studies and. for his
advice and criticism in the preparation of this mnuscript, and to the
members of his staff for their assistance in solving many technical dif-
ficulties. Gratitude is also expressed to Dr. C. 1'. Huffman. Research
Professor in Dairy Husbandry, whose original suggestion and encourage‘
ment was the stimulus prompting this study, to Dr. W. D. Eaten. Associate
Professor of Mathematics, for his assistance in statistical treatment of
certain of the data, to Mr. Robert P. Iangham, Instructor and Research
Assistant in Animal Pathology, for aid in preparation of the photogra-
phic illustrations, and to Dr. J’. r. Sykes, Instructor and Research
Assistant in PhysiolOgy, for many valuable suggestions concerning the fin-

al arrangement of this manuscript.

his work was made possible through funds for the purchase of
apparatus and supplies furnished by the Physiology Agricultural Experi-
ment Station and the Department of Physiology and Pharmcoloy, and
through the cooperation of the Department of miry Husbandry which placed
at the disposal of the writer its entire dairy herd for experimental ob-

semt ions .

, i a»: ‘J
-30: l

FORE-Y 0RD

file results reported in this thesis are based upon data from bovine
electrocardiograms obtained on cattle in the dairy herd during the period

from January 1937 to June 1938.

Since an at tempt is being made to determine the normal bovine elec"
trocardiogram, the tabulation and discussion of the data is intentionally
detailed. All variations which could be construed to be even remotely
significant have been noted and an attempt has been nade to place upon

them a fair evaluation.

Since this study has been carried out on a relatively small group
of animls, it is possible that these data do not give a complete pic-
ture of the normal limits of the bovine electrocardiogram. However, the
animls used would seem to be representative of normal dairy cattle and
confirmation of these results must await further work using larger sam-

p198.

TABLE OF CONTEI‘T‘B

I INTRODUCTION AND REVIEW OF LITERATURE

II EXPERIMENTAL PROCEDURE
A. Selection of Subjects
Be TGChniqu.
1. Apparatus
2. Selection of Leads
3. Selection and Technique of Placement of
Electrodes
C. Tracing Analysis Methods
1. Record Treatment
2. Methods of Analysis
a. Nomenclature of Deflections
b. Determination of Heart mte
0. Measurement of Intervals
d. Determination of Systolic Index
e. Measurement of Potentials
f. Method of Determining the Cardiac
Electrical Axis

III m HEART RATE

IV INTERVALS OF THE BOVINE ELETROCARDIOGRAM
A. Esplanatory Remarks
B. The P-H Interval
C. be Duration 0 f Q33
D. lbs 9:! Interval
I. The Systolic Index

V BOVINE EKG MLETIONS '- lHEIR OCCURRENCE, POTENTIAL AND FORM
A. Explanatory Remarks
3. Occurrence of the Various Deflections
10 me P Wave
2. me QRS Group
3. file 1' Wave
0. Potentials of EEG Deflections
l. munatory Remarks
2. line Distribution of Potentials by Leads
a. The Potential of P
b. ‘Ihe Potential of Q
c. lhe Potential of R
d. (The Potential of S
e. 'me Potential of 3'
f. 1116 Potential of '1'
3. Occurrence, Distribution and Range of the
Highest Potential HG Deflections in Any
Lead of the First Monthly Tracings

(next:

19

2h
26
32

38

1414
In
51
52
33
5‘5
58

59

D. Form of QRS and Classification of the Bovine EKG
1. Variations in the Form of Q38 and Distri-

bution of the Various Types 63
2. Classification of the Bovine Electrocar-

diogram 71

VI THE ELECTRICAL ms or m 130va HEART 36
VII VARIATIONS IN THE BOVINE ELETROCARDIOGRAH

A. Monthly Changes 91

B. Changes Within Leads 9h

VIII SUMMARY lOl

~mmmcm 106

APPENDIX 109

IN'EROIIIC‘I'ION AND REVIEW OF LITERATURE

It has now been some three decades since Einthoven made electro-
cardiography experimentally and clinically feasible by adapting to
this use the string galvanometer. 'Ihis tremendous foreward stride
was the motivating stimulus to research of such intensity that the
science today occupies an important niche in the field of human
medicine. Unfortunately for those interested in animal investiga-
tion .of purely veterinary interest, much of our knowledge of electro-
cardiography is based on clinical work on the human subject. [The
bulk of the extant animal data are principally on such laboratory
species as the dOg and exist as the result of experimental pro-
cedures performed by workers seeking basic information primarily. of
interest to investigators in the human field. Since the larger
domestic animals are not employed for this purpose, there is little
that can be borrowed. It is interesting to note, however, that one
of the earlier reports comes from such a source. Waller, (l), in
1889 while employing the capillary electrometer in a study of vari-
ous lead comb inations on dogs and cats, mentions having used one
horse as a subject. ‘lhis same worker in a subsequent report, (2),
(1913) indicates that the species is of sufficient interest to

warrant study of a few more individuals.

A perusal of the available literature reveals that to date com-

paratively little has been done by way of a systematic attempt to

study the normal electrocardiogram of domesticated animals. Of the
several species included in this category, the horse has perhaps re-

ceived.more attention than any other. Ngrr, (3), in 1913 and.Kahn,
(It), later in the same year, employing a single lead from the xiphoid

cartilage of the sternum to the shoulder region, report their normal
findings on a few horses. More recently (1937) Yacoel and Spitz, (5),
studied 17 different combinations of experimental leads in this
species. In the case of cattle, the most comprehensive report is
that by Ngrr, (6), (1921) who studied the EKG of 11 animals employ-
ing, with but one exception, the single "regio apicis-regio praescap-
ularis" lead which is favored by continental workers. A rather ex-
tensive bibliography of the German reports concerning both normal and
abnormal electrocardiograms of domestic animals is cited by Neumann-
Kleinpaul and Steffan, (7). Barnes and associates, (8), (1938), while
studying the effect of cod liver oil in the diet of young calves on
EKG intervals, report normal intervals in four controls. A limited
amount of normal bovine EKG work is in progress in this country at

the present time, (9).

From the foregoing, it can be seen that this field of investiga-
tion as applied to the common domestic animals has scarcely been
touched. 'lhe paucity of work as evidenced by scarcity of reports
is the challenging stimulus prompting the present study. Since the
bovine species, especially the dairy breeds, figures so prominently
in animal research concerning nutrition, metabolism, and other prob-
lems of animal husbandry: and since the economics of milk production

requires more and more scientific knowledge to meet the needs for

3

increased efficiency, the value of the elec trocardiograph as an addi-
tional instrument to aid in certain phases of this work must be

de termine d.

Since progress cannot be made until the normal has been studied.
the present report will concern itself solely with this phase of

animal e1 ec trocardiOgraphy.

EXPERIMENTAL PROCEDURE

Selection g§_Sub1ects. Ninety-seven animals composing the major
portion of the institution‘s dairy herd, and representing the follow-
ing breed distribution, were selected for study:

Jersey - ‘ '-' - ----- 23
Guernsey ' - ' - r ' ' - - 22
Ayrshire - - - - ~ - - - - 13
Brown Swiss - - - - - - - -l9

Holstein --------- 20

It was felt that this group would be quite satisfactory for
several reasons. The subjects were, with but very few exceptions,
thoroughly accustomed to the presence of strangers and might be
expected to react least unfavorably when brought into the strange
surroundings of the EKG room. They were representative animals
kept under modern c onditions of herd management on a fairly high
plane of nutrition necessary for Optimum milk production. The age
distribution ranged from five months to 12 years inclusive. Varyr
ing stages of gestation and lactation were represented. Sick or
extremely nervous animals were not included. Males, being notori-
ouslyrpoor subjects in experimental work involving observations on
such physiological phenomena as heart rate, respiration, etc., were

excluded.

Apparatus. The apparatus employed was a Hindle #2 model of the

Einthoven electrocardiograph purthased from the Cambridge Instrument

5

Company. Current for the field coils of the galvanometer magnet was
supplied by three Edison storage batteries with a total maximum dis-
charge rate of six amperes. No tracings were taken when this rate
fell below three. Current for the projection lamp and camera motor
was supplied by an AC’ID motor generator unit placed in another room
at a distance of some fifteen feet from the galvanometer. All neces-

sary parts of the apparatus were carefully grounded.

me time-narker was the standard type controlled by a tuning
fork and arranged to form vertical time lines 0.01t seconds apart on

the record.

(the galvanometer string tension was unifomly adjusted so that
the introduction of a potential of one millivolt into the string
circuit would deflect the string shadow on the record one cm. Once
this was obtained for lead I. further readjustment was rarely required
for the other two leads. 'lhe apparatus was placed in a special room
in another building separated from the dairy barn by some 300 yards.
_It was thus necessary to lead the animals this distance prior to
taking the tracing. {they were then tied in an improvised stall and
sufficient time was allowed for the animal to return to as nearly a
norml state as was possible under the circumstances before a record

was attempted.

No effect of temperature variations or other environmental fac-
tors upon the efficiency of the apparatus could be discerned. These

were occasionally quite extreme. During the winter months the room was

often uncomfortably cold. At times the humidity was so high that
beads of moisture were discernable on the walls of the room and on
two or three occasions the lenses of the optical system of the
galvanometer had to be wiped frequently with lens paper to remove the
moisture which condensed so heavily as to almost completely obscure

the string shadow.

Selection o_f_ Leads. the three standard leads only were employed.
namely: lead I, right front leg to left front leg; lead II, right

front leg to left rear leg: lead III, left front leg to left rear leg.

Since there exists some difference of Opinion concerning the
choice of leads in electrocardiogram studies in the large domestic
animals, a brief review of the salient features involved may not be

amiss at this point.

Perusal of the available reports indicates that the various in-
vestigators are almost wholly unanimous in the Opinion that tracings
taken by the three standard Einthoven leads employed in the human
subject are entirely unsuitable for use in these animals. 'lhe princi-
pal reason given is the variations in the records obtained by this
method. 'ihese variations are attributed to the difference in ana-
tomical position of the heart in the horse and cow in relation to

the leads as compared to the human.

0f the three species, bovine, equine, and human. the former
possesses a heart whose long axis, through apex and middle of base,

is more nearly perpendicular to the ventral thoracic floor. In the

7
case of the equine heart it is known that, While it occupies a posi-

tion in the thorax roughly comparable to that of the bovine, its basal
attachment is such that the anatomical axis is more horizontal. To
elaborate further using the descriptive methods of Ngrr, (6), an
imaginary line drawn through the apex and middle of the base would
in the bovine pierce the skin anteriorly at about the level of the
cervical angle of the scapula, while a comparable point in the horse
would be at a more ventral level. Kahn. (14), indicates this point

to be at about the distal end of the middle third of the scapula.

It follows that the posterior emergence of this line would be slight-
ly more anterior in the ox than in the horse. 211113 is of little im-
portance. however. the apical region in each species being usually
selected by investigators for placement of one electrode in obtain-

ing tracings by this type of lead.

'Lhe long axis (base-'apex axis) of the human heart makes a
smaller angle with the frontal plane than the corresponding axis of

the bovine or equine heart.

Classifying these three species as to the relatively greater
proportion of the heart lying to the left of the median plane, the
human has 2/3 (11), the bovine 5/7 (6). and the horse 3/5 (12). of
its mass thus located. It can be seen that there is relatively little

dissimilarity.

From the foregoing discussion it is obvious that the standard

Einthoven leads applied to horses and cattle do not approach the

8
plane of the long axis Of the heart to the degree reached in humans.
11113 is the reasoning back of the decision by many workers (Ngrr -

3 - 6; Kuhn - Ll; Yacoel and Spitz - 5) to attempt other leads and
explains the usual dismissal of the matter with the remark that the
results with standard lead combinations are worthy of little more

than passing comment.

It is believed that, due to the relatively greater ease of elec-
trode application, and the more extensive information obtainable from
three derivations, as compared to the single lead of Kahn and others,
the possible significance Of results obtained by the three standard
Einthoven leads should be investigated first. 1316 necessity of
these data, if for no other purpose than as a basis for comparison
with results obtained from other lead combinations, can be readily

appreciated. ‘lhis is in general agreement with the Opinion of

Bikes (9).

Selection a__r_1§_ Technique o_i; Placement 91 ww. 'Ihe Cam-
bridge German silver plate electrodes similar to those employed in
human clinical work were used exclusively in this study. 'lhis deci-
sion resulted after a small amount of preliminary experimentation on

three cows using first warm saline pad electrodes", and comparing

these results with those obtained with German silver plate electrodes,

 

" 'lhis method consisted essentially of wrapping the l imbs with a soft
cloth soaked in very warm saturated saline solution around which
was wound five turns of #19 bars copper wire.

contacting the skin through the medium of a special saline paste*.

No appreciable differences were noted in the potentials recorded for
the same individual with the two types of electrode. It was further
observed that use of the former method was attended by greater uneasi-
mess on the part of the animal regardless of the temperature of the
saline solution employed. 'lhe latter method was therefore adepted,

the technique of which is discussed below.

me plate electrodes were applied to the front limbs on their
lateral surfaces immediately above the knee joint on a slightly con-
vex area formed by the distal portions of the ulnaris lateralis and
digital extensor groups of muscles. ‘me site of application of the
left rear limb electrode was on the anterO-lateral surface 2 to 3
inches above the humero-rsdial (hock) joint where the peroneus ter-
tins and digital extensor muscles form an exterior convexity most

nearly adapted to the slight concavity of the electrode plate.

In applying the electrodes the hair was first closely clipped
on the sites previously described over an area about two or three
times that required for its apposition. {the decision to merely close
clip the area of application resulted after tracings Obtained by this

method were compared with results obtained in the same individual

 

" Formula supplied through courtesy of Dr. F. N. Wilson, Dep't. of
Internal Medicine, University Hospital, Ann Arbor, Mich. 'Ihe paste
consists essentially of sodium chloride, potassium bitartrate,
glycerin, and pumice incorporated in a gum tragacanth gel with
phenol added as a preservative.

10
after the area was carefully shaved with no appreciable difference
in the recorded potentials. being noted, providing sufficient electrode
paste was used. the former method, because of greater convenience

and safety, was accordingly adopted.

'me skin was then vigorously rubbed with a liberal quantity of
electrode paste. 'ihe plates were immediately applied after first
covering their surfaces with the paste. A moderately firm pressure
accompanied by a very slight rotary motion was used to insure a good
contact before tightening the rubber straps binding the electrode
firmly but not too tightly to the limb. While a liberal quantity
of paste should be used, cars should be taken not to contaminate the
lead cable at the point of Juncture with the electrode since when

this happens polarization often occurs.

After the tracing was recorded, the paste was carefully removed
from the skin with a wet cloth. If this was not done, a peculiar

local vesicular type of dermatitis resulted in many cases.

‘l’ne patient leads approached the electrodes from above the sub-
ject to avoid lessening the contact surface by reason of separation
of the plate from the skin as the result of side pull from the weight
of the lead cable, which often happened when the approach was from.

below.

At no time during the recording of an electrocardiogram were the
subject's feet allowed to make a wet contact with the floor. In the

event that this happened, the wet area was liberally covered with

11

dry wood shavings before a record was attempted.

Record Treatment. 'mree serial electrocardiograms approximately
one month apart were recorded for each member of the entire series.
It was originally planned to allow an interval of four weeks between
tracings, but in practice this period was occasionally exceeded or
decreased by three to five days, and in a very few cases seven to ten

days. without exception, curves were obtained in the afternoon.

Bromide paper was the photOgraphic medium used. The exposed
strips were deveIOped, trimmed, and mounted one lead above the other
upon a special bristol board mounting card as shown in Fig. III. All
unused portions of records were carefully labelled and saved to be

used in making up composite groupings as exemplified by Fig. II, etc.

Methods QiAnalEis. In this study the nomenclature introduced
by Einthoven was employed, and the letters P, Q, R, S, and '1' were
assigned to the various electrocardiOgraphic deflections according to
the rules in common use in human electrocardiOgraphy. A second upright
QRS deflection encountered in certain cases was designated 3'. All
electrocardiograms used in this study were carefully analyzed accord.
ing to the sample analysis chart shown in Fig. X in the Appendix. 'Ihe

determinations made and methods employed will be considered in order.

'lhe heart rate was determined in each. lead by taking an average

of five or six R-R intervals.

'me intervals selected, namely P-R, QRS. and Q-“l‘ were measured

as carefully as possible by employing a reading glass and counting the

12
number of 0.024 second time spaces occupied by the interval. It is
probable that the accuracy of this method is somewhat less than
0.01 second for all intervals. Ellie grouping of values in Table XXIX
suggests, however, that “the measurements were often to an accuracy
of 0.02 seconds. Readable complexes were always selected for measure-
ment of intervals. Especial care was taken in choosing those display-
ing a level base line. In a few tracings, due to wandering of the
string, this was rather difficult. Contrary to the usual custom in
human investigations, the cardiac electrical axis range was too extreme
to permit arbitrary selection of any given lead for determination of

interval length.

The systolic index or systole: cycle ratio was calculated for
each electrocardiogram according to the formula devised by Bazett,

(13), which is stated as follows:

3,—9.1
43:5

in which Q“?! is the time interval from the beginning of QRS to the
end of 1' and R‘R is the interval from ops in one cardiac cycle to
Q38 in the next. Since K varies directly with duration of ventricu-
lar systole when calculated by the above formula, an increase in its
value represents an increase in the duration of q-T in preportion to
the length of the entire cycle (Ii-R). 'nie value K is commonly con-

sidered as being practically constant in normal human electrocardio-

grams. (2“)-

13

ills potential of the several waves, with the exception of P, was
measured according to the method. (1h), commonly employed in the
analysis of human electrocardiograms. Due largely to the tendency of
the galvanometer string to wander in many subjects, it was decided to
use the relatively'shorter’P-R,level as a base line in the measurement
of the potential of P as well as for QRS and R'. The Ti? segment
was employed as the base line in the measurement of T. Upward de‘
flections were measured from the tap of the string shadow to the
absolute upper limit of the wave while with downwardly directed.waves,
the procedure was reversed (i.e., from the bottom of the string sha-

dow at the proper segment to the bottom of the wave).

The variations in the potential of the QRS deflections between.the
leads upon which is based the determination of the cardiac electrical
axis, is only superficially treated in the present study. Using a
series of triangular diagrams based upon the recommendations of Wilson,
(10), and representing axis gradations in steps of 30°, the approxi-
mate electrical axis of each electrocardiOgram in the series was deter-
mined. No attempt was made to accurately measure the potential in
the three leads at the same relative time instant using graphic methods
of the type employed. for example, by Fahr, (15). The only criterion
of evaluation of QRS was the approximate net area of its deflection,
as nearly as this could be estimated'by viewing the complex, (10).

No attempt was made to determine the manifest potential according to
the method of Einthoven, (16). Whether it is justifiable to apply the
principles of Einthoven's equilateral triangle to the analysis of the

bovine electrocardiogram is, of course, uncertain.

1h

THE HEART RATE

Since the heart rate has been shown to directly influence es-
pecially the Q'T and to a lesser extent the PE intervals in the
human subject, (1)4), it is necessary to include a discussion of this
factor as encountered in the present study and to compare these data

with the established normals for the various dairy breeds.

The subject has been reviewed by Fuller, (1?). It is noteworthy
that in the various per-minute frequencies given by the ten authori-
ties listed in this review there is considerable disagreement; the
variations being from 140-50, (18), to uo-so, (19). Fuller reports. in
the four major dairy breeds (Jersey, Guernsey, Ayrshire and Holstein)
embracing a total of 39 adult female animals, a range of from ‘46 to
96 per minute. 'lhe mean for the breeds ranged from 59.8 for Guernseys

to 69.6 for Ayrshires. me average for all breeds was 65.7 per minute.

The results in the present study obtained by the analysis of elec-
trocardiogrems show somewhat higher values. Examination of Table I
reveals that in the 97 animals composing the 5 breeds reported the
range is from a minimum of 1+8 to a maximum of 98 per minute with an
average per minute frequency for the entire series of 71.6. 'Ihe mean
for the breed groups ranged from 65.9 for the Jerseys to 76.6 for the
Ayrshires. The most striking difference between this and the data by
Mller is in the Guernsey group where the former exceeds the latter av-
erage by 13 beats per minute. Next in order is the Ayrshire group
where the rate exceeds Fuller's average by 7 beats. In the remaining

breeds compared, the difference is not great.

15

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table I. Summary of'Heart Bate Summary of Fuller's Data (17)
(Average of fires Leads and fibres (Placed Here for Comparison)
Monthly Tracings of.All Age Groups)
Heart Rate Heart Rate
a (Per Minute) a (Per Minute)
.4 r! a
a a a
Stand' *’
Breed “a g g Mean ard '8 '8 E E g Mean
. g Devia" . o 3 5 u
s s i non of s as :1 s
Means
Jersey 23 MS 83 65.91 1.7MMS 9 356’ 1&6 8h 62.7 I
Guernsey 22 kg 98 72.72 2.65M} 7 317 he 72 59.8
Ayrshire 13 61 96 76.38 3.uu17 8 332 52 90 69.6
'Friwn
Swiss 19 5o 90 7h.21 2.29M1 No Data
Holstein 2o 52 95 71.50 2.915u 15 687 51 96 68.6
m— :3: it
Total 97 M8 98 71.60 1.2226 39 1692 h6 96 65.7

 

 

 

 

 

 

 

 

 

 

 

 

 

fibers are several factors incident to the recording of electro-

cardiograms as performed in this study that could be responsible for

cardiac freQuencies even higher than those actually encountered. In

the first place it was necessary to lead each animal for a distance

of some 300 yards before tracings could be taken.

'fllis in itself

ordinarily would not be expected to cause a very marked increase, but

a few fractious individuals (especially Ayrshires and young animals of

other breeds) were led with considerable difficulty; invariably arriv-

ing at the ECG room showing a marked increase in both heart and re-

spiratory rate.

However, since it has been demonstrated by Lewis and

Cotton. (20). that the decrease in duration of the I"? interval coinci-

dent with the increase in cardiac frequency during exercise returns to

16
normal in three to five minutes in.human subjects, and, since it usually
requires about ten to fifteen minutes to prepare an animal for
the actual taking of tracings, it seems a reasonable assumption that

this should not be a factor of great importance.

The matter of nervousness, psychic, or emotional stimulation
(sympathetic effects generally always present in animals, to a greater
or lesser degree depending upon temperament, when transported to a
strange environment) cannot be thus casually dismissed. Rothberger
and.Winterberg, (21), have demonstrated that the increase in.heart
rate in dogs from sympathetic stimulation is accompanied by changes
in the electrocardiogram similar to those observed by Lewis and Cotton
during exercise. It is possible that emotional excitement whidh in-
creases the heart rate may also shorten the P-R interval of the bovine

electrocardiOgram.

Due to the troublesome nature of this factor further elaboration
seems necessary concerning environmental conditions responsible for
and.methods employed to minimize it as much as possible. The first
'precaution taken, as previously mentioned, was the selection of a herd
accustomed to the presence of strangers. Even some of these relative-
1y socialized animals in the presence of the electrocardiOgraph, the
buzzing of the tuning fork in the timer circuit, a semi-darkened room,

and a strange stall, showed evidence of excitement."I In nervous breeds

 

‘ It is interesting to note in passing that a marked increase in car-
diac frequency was observed during the act of urination. No tracing
was recorded in which this is shown.

17
such as the Ayrshire a few individuals maintained a relatively slow
cardiac frequency quite out of keeping with all the outward signs of
extreme uneasiness, while in a few individuals of other breeds (es-

pecially Holsteins) the reverse was occasionally observed.

The foregoing observations were obtained by watching the move-'-
ment of the galvanometer string shadow with everything in readiness
for the actual recording of an electrocardiogram. If any evidence of
excitement occurred prior to or during the taking of tracings result-
ing in an increased heart rate, Operations were halted until it was
evident solely in the opinion of the Operator, that the rate had.
returned to normal. In spite of this, however, a significant amount
of variation is seen between leads in a few tracings. Monthly varia-
tions in the same subject were very common."' These may have been in-
fluenced to a certain extent by any one or a combination of the follow-
ing factors: ingestion of food, period of the day, temperature, and
changes in status of pregnancy. As to the first two, since all records
were taken in the afternoon and since all the animals were on a fair-
ly strict feeding regimen which did not appreciably change througiout
the entire experiment, these may be considered to be of minor importance.
In the case of changes in environmental temperature it should be re-
marked that since this study extended over a period of eight months,

from October to the following June, this may have been a factor

 

"' For further information Table XXIX (Appendix), showing the rate
during each lead of the three monthly tracings for every individual,
may be consulted.

18
contributing to some of the monthly rate changes observed. The prin-
cipal change in the status of pregnancy would be the occurrence of
parturition between the recording of any of the three monthly tracings.
’mis occurred (exclusive of 2 abortions) in 9 individuals"I with results

too inconclusive to warrant the drawing of any conclusions.

Finally it must be pointed out that, While the majority of animals
investigated can be classified as adults, the inclusion of a few young
individuals" would naturally cause a wider standard deviation from the
mean than if the age group had been more restricted. Furthermore, the
majority of mature animals were on a relatively high level of milk
production, and the increase in heart rate coincident with the heightened
plane of nutrition necessary for maximum production has been thoroughly

established, (22; 17).

From the foregoing discussion it may be safely concluded that,
when all conditioning factors are considered, the heart rates found
in this series do not depart materially from the values found by

others and may be considered to be within normal limits for the bovine.

 

" Jersey Nos. 73, 79, 101, 100 and 63; Guernsey Nos. 7 and 1&7; and
Brown Swiss Nos. 239 and 300.

" Nineteen of the 97 animals were under 1 year of age.

19

INTERVAIS OF THE BOVIEIE ELECTROCARDIOGRAM

Ehe three intervals, P-R, Q38, and Q‘T, were measured.according
to the method described under procedure. These measurements in each
lead of the three monthly tracings as well as the computation of the
systolic index according to Bazett's formula are recorded in Table
XXIX (Appendix). The time values may all be read directly in decimal
fractions of seconds. It will be observed that the sign "NM" occurs
occasionally; indicating that the interval was not measurable. This
was usually due to the obscuring of at least one of the waves bounding
the interval by muscle tremor, interference by.L‘C induction, extreme-
ly low potential or, more rarely, complete absence of a wave. It is
thus apparent that an interval in a lead may be measurable one month

and not measurable the next.

Note that the data in this table are grouped according to breeds,
the individuals within sash group being arranged according to age,

beginning with the youngest and proceeding to the oldest member.

The distribution of the various intervals by breeds, arbitrarily
selected from the first monthly tracings, is shown in tabular fonn
integrated with the discussion of each. For the sake of uniformity
and since the longest interval in any lead of the first monthly elec“
trocardiogram was rarely exceeded in the two subsequent tracings, the
greatest interval in any lead of the former was arbitrarily selected
for these tables. In the case of the q-T interval a table is included
showing the average of three leads and three tracings making a total

of nine items.

A partial statistical summary of the minima, maxima, and mean
measurements for the three intervals as well as the value for K is
included in Table X. In connection with this table the standard

deviation of the means has been computed according to the formula:

SD a sum Of squares of items - (mean)2
no. of items

SD Mean an JA—

where
SD - Standard Deviation
H a. Number of items

I :- Items (intervals, etc.)

Due to the human tendency to read to the nearest 0.02 second in
the measurement of borderline intervals as discussed under procedure,
Table XI showing the distribution of all intervals in steps of this

value is included.

21

The P-P. Interval

Elbe duration of P-B as shown in Table I ranged from the minimum
of 0.1 to the maximum of 0.3 second with an average duration of 0.192
second. The S. D. Mean indicates very close grouping of the values
about the mean. his is borne out by Table II in which is set
forth the distribution of the longest P-B. interval in any lead of the
first monthly tracings. The grouping is even more apparent if the

values are distributed in steps of 0.02 second as is shown in Table XI.

Analysis of mble II reveals that 85 per cent of the 97 animals

are found in the range from 0.16 to 0.214» second inclusive.

Table II. Distribution of Values in 0.01 Second Found for the Longest
P‘R Interval in Any Lead of the First Monthly Tracings.

 

Inter-

vals
(0.01
sec.)» 10 11 12 13 1h 15 16 17 1s 19 20 21 22 23 2h 25 26 27 28 29 30

Totals

 

Jersey 1 1 33h h3h

 

Guern-
sey 1 21

 

4:4:
[-0
N
H

Ayr"
sh ire

 

Brown

2
2
Swiss 1‘

l 1

 

Hol-
stein

HHHN

3
u
h 1

2 3 1 1 1 5 1 1 1 1

 

 

TOTALS 1 1 3 3 10 8 1h 3 13 u 1n 3 9 2 1 1 1 1

 

 

 

 

22

Concerning variations in duration of P-R between the leads of
individual electrocardiOgrams, recourse must be had.to Table XXIX
in the appendix where all individual measurements are given. Here it
may be seen that agreement between the leads is very close. Taking
lead II as a standard for comparison, the values in leads I and III
are more often within 0.01 second of this measurement. Occasionally
the difference may be 0.02 second; only very rarely is this exceeded.
These variations agree rather closely with those found by Lewis and

Gilder, (23), in the human subject.

No particular lead seems more favorable for showing greater length
of P-R than any other. Study of Table XXIX.may create the impression
that lead I is slightly more favorable than leads II and III in spite
of the fact that this is most often the unfavorable lead.from the
standpoint of recorded.potential. It is a fair assumption that the
low potential Q35 in this lead.with perhaps absence of the initial
effects of P and QRS present in the favorable leads, are factors

contributing to errors in measurement.

Table x shows some slight differences between the breeds. Due to
the small size of each group the significance of these variations is
questionable. The mean diows some breed differences, ranging from
0.176 second for Jerseys to 0.217 for Holsteins. Data on a larger
number of animals are needed before conclusions can be drawn as to the

occurrence of significant differences between breeds in this respect.

23

Variations of'Pvfi between the three serial electrocardiograms of
each individual are relatively minor. .A monthly variation of 0.01
second occurs in one or more leads of every individual. This is
within the limit of human error in measurement previously mentioned.
Less frequently there is a variation of 0.02 to 0.03 second, and in a
very few cases (eight animals) 0.0H second, in one case 0.05 second,
and in two cases 0.06 second. The 0.0M second variation was usually
associated with a marked decrease in heart rate. However, a few of
these, as well as the more extreme variations, were due to monthly
variations in diphasic P waves. It is conceivable that should.the
initial phase be absent one month, the interval would be as much
shorter as the duration of the absent phase. This would also be true
if monthly inconstancy occurred in the initial effects of Q35 and may,
as previously mentioned, account for the longer P-R interval seen in
unfavorable low potential leads. This factor is only of interest when
leads are compared and.has no influence on tabulated data containing

only the longest interval in any lead.

Analysis of Table XXIX Shows little correlation of length of P-R
and heart rate between individuals. The lower values are more often
associated with the faster rate. Extreme changes of rate from month
to month in the same individual seem to affect the interval more mark.

edly than any other factor. Minor rate changes seldom exert any

influence.

214

Of the nine individuals freshening in the interim between the
recording of electrocardiOgrams, six showed no appreciable change in

P'R, while three exhibited a sligit increase (0.02 to 0.014 second).

'lhe Duration of QRS

The duration of QRS ranged from 0.06 to 0.12 second with an
average value of 0.0914 second. Table III below gives the distribu-
tion by breeds of the longest Q35 interval in any lead of the first

monthly trac ings .

Table III. Distribution of Values, in 0.01 Second Found for the
Longest Duration of QRS, in Any Lead of the First
Monthly Tracings.

 

 

 

 

 

 

 

 

(gfgirzzif) ~ 6 7 s 9 1o 11 12 Total
Jersey 3 7 10 l 2 23
Guernsey 3 7 7 5 22
Ayrshire 3 6 3 1 13
Br. Swiss 1 6 3 5 3 1 19
Holstein 2 l )4 5 2 5 l 20
TOTALS 2 2 19 28 27 10 9 97

 

 

 

 

25

Two subjects (both Holstein calves 9 and 5 months old.respective-
16) showed the minimum of 0.06 second, while the maximum of 0.12 second
was seen in nine individuals. There is considerable variability of
measurement between leads in any given electrocardiOgram. In general,

the Smallest value is seen in lead I and the greatest in lead III.

However, the difference between leads II and III rarely exceeds 0.01
second and quite often the measurements are equal. Very exceptionally
a variation of 0.02 second is observed. The only extremes noted were
the tracings of Brown Swiss No. 2ND where lead III exceeded II by about
0.0% second and.Jersey No. 63 where lead II exceeded III by 0.06
second. .As to lead I, the duration of QRS varied from equality to a
decrease of fifty percent below the value for lead II. If an average
were to be obtained for lead I of the entire series it would show a

definitely smaller interval than in the other two leads.

No apparent breed differences are observed in the statistical
sunuary in Table X. The average duration of QRS of 0.09M second
in the entire series compares very favorably with the mean for each

breed group.

Variations between serial electrocardiOgrams are relatively in-
frequent in leads II and III. When present they are usually within
the range of 0.01 second. The greatest variation is found in lead I
where differences of 0.02 to 0.03 second are occasionally seen. Since
this is usually the unfavorable lead in cattle, these results are not
surprising and are associated with monthly variations of the low po*

tential deflections.

26

Changes in heart rate or status of pregnancy were without influ-
ence on this interval in the entire series. The lower values (about
0.08 second or less) were most consistently present in animals below

two years of age.

The q-T Interval

The Q“! interval ranged from a minimum of 0.29 to a maximum of

0.147 second with an average duration of 0.389 second.

Table IV gives the distribution by breeds of the longest Q'T

interval in any lead of the first monthly tracing. However, due to

the inherent tendency of this measurement to vary inversely with the
heart rate and since the rate varies in many cases from lead to lead
within a given tracing as well as from month to month, it is believed
that an average of the longest QT interval in each lead of the three
monthly tracings for every individual would give a more uniform value
for this phase of the cardiac cycle. This distri‘mtion is incorporated
in Table V. is is to be expected, a more uniform distribution is ob-

tained with less scattering of the groupings under the various values.

In this table the minimum of 0.29 second was observed in two
cases. These were two calves five and nine months old respectively
showing a mean heart rate in the three monthly tracings of 95 per
minute in the former and 96 in the latter. The xraximum, 0.347 second,
was present also in two cases, a five year old Jersey with a mean
heart rate of 56 and an eleven year old Brown Swiss showing an average

rate of 149 per minute.

27

 

 

 

 

 

 

 

 

 

 

R H mNMHmm mum mHmmmm m HHH H 358
ON N H m m m 3 .H H 333cm
9 m w m s n m H m .35 an
m H H m m H . m H 2H€b2
mm m s H m m H H H H H H homage
mm H H m z m m m H m H . houses
mm. 3 m: 3 E a: m: is 9 ma 3 3 mm an R an R an R 3 Hm on a. a a mu .. cmflmwmw

 

.uwaHomua 35:0:
pang e5 5 JESS” and on» son coach onooom 8.0 3 Jonas» no 33.5.2qu .5 capes

 

28

Table V. Distribution of values, in 0.01 Second, Found for the Aver-
3g. q-T Time of Three Leads and Three Monthly Tracings.

 

 

 

 

 

 

 

Intervals ~ 29 3031 3233 3h35 3637 38 39 1+0 1+1 M2 1:31am,- h6 M7
(0.01 sec.)

Jersey 1 1 3 2 3 5 h 1 l l l
Guernsey 2 l l 2 l l 2 h l l l l h
Myrshire l 3 l l 1 3 1 2

Br. Swiss 1 2 2 3 1 1 l 3 2 2 l
Holstein 1 l 3 l 3 3 3 2 l 1 1
Totals 2 23214962911119111+7212

 

 

 

Examination of Table XXIX.prpendix) indicates that variability
between leads is more common with this interval than either P-R or
Q33. Equality is the exception.rather than the rule. Taking lead
II merely as a standard for comparison, a plus or minus difference
in leads I and III of 0.01 to 0.02 second is very common. A dif'
ference of 0.03 to 0.0M second between leads is present in a few
cases, with the maximum of 0.05 to 0.06 second of very infrequent
occurrence. 0n the whole there is a tendency for leads II and III
to be more nearly equal, with lead I Showing a slightly lesser value.
But considerable variation is seen and this statement should.be

accepted with some reservation.

The statistical summary of Q-T presented in Table X indicates no
significant breed differences as to minima and.maxima. With respect

to the mean values the table shows that the Guernsey, Brown Swiss,

 

29

and.Holstein groups show a close correlation with the average for the

entire series.

In the Jersey group the mean exceeds the total average by 0.018
second. This breed.also records the lowest average heart rate. The
average of Q-T in the.Ayrshires is 0.019 second less than the mean
for the entire series. The average heart rate in this group is two
beats less per minute than.the Brown Swiss. It is interesting to note
that the average duration of q-T in the latter breed exceeds that of
the former by 0.021 second. This difference in.Q-T between two breeds
showing approximately equal heart rates, while interesting, is perhaps

too minor to warrant the drawing of any conslusions.

Monthly variations are even more prominent than the differences
observed between the leads and are in general closely associated,with
variations in heart rate, there being an increase in the duration of
Q'T with a decrease inrheart rate and vice versa.‘ The range is too
inconsistent to be dealt with inta general discussion. For further

details reference can only be made to Table XXIX in.the appendix.

 

' Since monthly variations in diphasic T waves are common, it is
entirely possible that, should.the final phase be absent (isoelec-
tric) one month, the interval would.have a tendency to be as much
shorter as the duration of the absent phase. This would.also be
true of the monthly inconstancy seen in the initial effects of
QBS. Variations extreme enough to cause a marked difference in QrT
time are relatively infrequent providing the longest interval in
any 1ead.be chosen, and any influence this factor may have tends to
be lost in the variations due to rate. This phase of electrocardio-
graphy in the human subject is statistically treated by.Adams, (25).

30

To further clarify the relationship existing between duration of
Q‘T and heart rate in the various breed groups constituting this
series, Table VI, showing the duration of q-T at various levels of
cardiac frequency, was devised. In formulating this table the duration
of Q-T and the heart rate in each lead of the three monthly tracings
was used. Thus there are nine values for both the interval and rate
on each animal represented. It will be observed, however, that of the
total of 873 leads, only 839 appear in the table. The difference
represents unfavorable leads in which the interval or the rate (one

case) were not accurately measurable.

The results with this type of tabular treatment show a remark-
ably consistent decrease in duration of Q‘T with an increase in heart
rate. The mean values are especially uniform in this respect. Al'-
though the average bovine Q'T time is apparently somewhat longer at
comparable rate levels, the general trend in the table is similar to

the findings of Frideric is, (26), in the normal hunan subject.

Since considerable variation in heart rate is present in the
series, the facts elucidated in Table VI may largely explain the rela-

tively extreme variability of Q‘T previously discussed.

 

 

 

31

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table VI. 1116 mration of q-r at Various Levels of Cardiac Frequency.
9,-1- jin 0.01 sec.)
Bate Breed No. of Minimum Maximum Mean
Leads
.h . .1;
88:38.. 3 8.0: 8. 8.03
P43 to 50 Ayrshire 0
Br. Sides 5 0.1l6 0.30 0.1l82
Holstein 5 0,)+0 0. 6 0.1428
Total 22 0.140 0.50 0.1-+52
Jersey 1L0 0.38 0.30 0.1560
Guernsey 32 0.1l0 0. 8 0J4;
50 to 60 Ayrshire l3 0.1m 0.16 0.14
Br. Swiss 8 0.113 0.82 0.1450
Holstein 36 0.1m 0.fi8 0.145
Total 129 0.38 0.52 0. 32;
Jersey 7? 0.38 0.1-t8 0.1L11l
Guernsey )49 0.36 0.346 0.1410
60 to 70 Ayrshire ’41 0.32 0.141; 0.hoo
Bro S'i‘fl 514 0.36 Ooh? 00,420
Holstein “L 0.31% 0.1l-8 03401
" 'i'otel 263 0.32 0.!I8 0.1110-
Jersey 53 07311 dun 0.38?
Guernsey 59 0.33 0.1-lit 0.378
70 to 80 Ayrshire 17 0.32 0.1!»2 0.381
Br. Swiss 52 0.32 0.1m 0.387
Holstein 51 0.3M 0.10; 0.316
gotel 232 0.32 (IRE 0.382
Jersey 0.32 0,36 0.31%—
Guernsey 26 0 . 30 0. ml 0. 350
80 to 90 Ayrshire 17 0.30 0.10 0.323
Br. Swiss 23 0.30 0.1L0 0.3 9
Holstein 39; 0.3L 3A0 0.35”.
Total 101 0.30 0.1m 0.3L
Jersey 8 0.30 0.36 0.322
Guernsey 2’4 0.28 0.36 0.312
90 to 125* Ayrshire 2h 0.26 0.31: 0.302
Br. Swiss 21 0.28 0.38 0.328
Holstein 15 03.18 0.36 0.308
Total 3:2: 0.32:6 0.38 0.113_

 

 

 

"‘ Only 10 leads in this group showed a rate greater than 104 beats
per minute.

32
Tue Systolic Index
Due to the wide range of Q-T as the result of the variability in
heart rate in this study, it was thought highly desirable to apply
Bazett's formula, as discussed under procedure, to each of the three
electrocardiograms of every individual constituting the series. The
selection of a complex for this purpose was solely on the basis of
distinctness of the necessary waves. While not invariably used, lead
II was usually most favorable. 'Ihe constant in each monthly tracing
is included in Table XXIX to which previous reference has been made.

Monthly changes only will be considered directly from this table.

'Ihe value for K in this series, as shown in Table X, ranges from

0.314 to 0.1l8, with an average of 0.1!,18.

Table VI: below gives the breed distribution of the various values
for I! encountered in this study. To obtain more average figures, the
mean of the constant in the three monthly tracings of each individual was
taken and expressed to the nearest second place decimal fraction.

Table VII. Distribution of Value for K (Bazett's Formula) to the Nearest
Whole Decimal No. Average of the rlhree Monthly Tracings.

 

 

 

 

 

 

X" fixaflRgaggnggggfi? Totals
o'o'cho'o'cSo'do'o’cSo’do’

Jersey 3147111112 5'3
Guernsey 1111653 21 1 22
Ayrshire 1111 22M 1 13
Brown

Swiss 1112121631 19
FHolstein 1 11¢ M52111 20
TOTALS 11131466172111+87521 97

 

 

33

,In this table the lower values of 0.3M, 0.35, and 0.36 were seen
in.three young animals, 5, l3, and.8 months old respectively. The two
individuals showing the value of 0.“? were five and two years old.
The maximum of 0.h8 was observed.in only one case, an eight-year-old
Guernsey. The statistical summary of the value for K in.this series
presented in Table X.shows a range in the minimum values of from 0.3M
in.the Holstein to 0.h0 in the Jersey group with the maxima remaining
remarkably constant. It must be pointed oum that the Holstein group
contained the youngest member (5 months of age) of the entire series.
The average values for the several breeds is very close to the mean
for the entire group. Examination of Table XXIX shows considerable
minor variation from.m0nth to month with little correlation between
Changes in K and rate in.the same individual. Using the values in
the second monfihly tracing merely as a basis for comparison we find

the first and third.monthly values showing the following plus or minus

differences:

Table VIII. Distribution of.Agreement of value for K (Bazett's Formula)
in the Second.Month With the First and Third.Month1y
Records.

 

.Agreement 7 Range of plus or minus disagreement

 

In.a11 lst or 0.001 0.010 0.020 0.030 0.0M0 0.050 0.060
three 3rd month to to to to to to to

Hmnthly with 2nd 0.010 0.020 0.030 0.0u0 0.050 0.060 0.070
tracings‘ month

6“" 18 51 59 27 20 3 3 1

 

 

 

 

' This agreement is within 0.001.

314

This table shows that the value for K was identical in all three
serial tracings in only six of the ninety-seven animals constituting
this series. 0f the 182 possibilities in the remaining ninety-one
subjects, perfect agreement of the first or third month with the
second occurred eighteen times. Disagreement within the range 0.001
to 0.020 occurred almost two and oneihalf times more frequently than
the wider range of 0.020 to 0.0h0. In but seven instances was the
difference greater than 0.0h0 and only one of these whowed the widest
variation recorded in the series. This was in the range 0.060 to
0.070. While not indicated in Table VIII, there are many cases in
which the first and.third months are in closer agreement with each
other than with the value for K in the second monthly tracing. It
is believed that of the three possible combinations for comparison,
the one selected would serve the purpose here as adequately as either

of the other two.

In an effort to further explain the variation of K between in-
dividuals, the following table showing the relationship between age

and the systolic index is presented:

35

Table II. Minimum, Maximum, and Mean Values for K (Bazett) at
Various Age Levels.-

 

 

 

 

K zett's Formula "'
Age No. of
Groups Cases Minimum - Maxim Mean
5 to 8 m0. 3 0.3h 0-M0 0.377
8 to 10 mo. 6 0.36 0.111 0.390
10 mo. to 1 yr. 8 0.37 0.142 0. 98
1 to 1 1/2 yrs. 7 0.35 o.uu o. 8
1 1/2 to 2 yrs. 13 0.38 0.u7 0.u15
2 to yrs. 12 0.38 0.u6 0.u29
a to yrs. 17 0.39 0.16 0.h28
to 5 yrs. 10 0.39 0.h7 0.h26
5 to 6 yrs. 9 0.10 0.1-:3 0.1+3
6 to 8 yrs. 5 0.n1 0. 0.h
8 to 10 yrs. 3 0.113 0.118 0.150
10 to 12 yrs. 0.39 0A2 0.h10

 

 

The table shows a relatively uniform increase in the value for
K in the age groups from five months to about two years. It is
possible that this my be a failure on the part of Bazett's formula
to correct for rate in the higher frequencies obtaining in young

subjects.

 

" Average of the three monthly tracings on each individual.

 

36

 

 

 

 

 

 

 

 

 

 

 

Table x. Partial Statistical Summary of the Value for K and Duration
of Bovine EKG Intervals.
P-H (Sec.) qHs (Sec.)
St. Dev. St. DeV.
Breed Mini. Maxi. Mean of Mean Mini. Maxi. Mean of Mean
Jersey 0.10 0.22 0.176 0.0131 0.08 0.12 0.096 0.0128
Guernsey 0.1M 0.28 0.197 0.0073 0.08 0.12 0.098 0.0035
Ayrshire 0.17 0.2M 0.206 0.0005 0.08 0.11 0.091 0.002h
Br. Swiss 0.1“ 0.25 0.183 0.0067 0.07 0.12 0.093 0.0031
Holstein 0.12 0.30 0.217 0.0091 0.06 0.12 0.091 0.0037
. Total
All
Bgeeds 0.10 0.30 0.192 0.0002 0.06 0.12 0.09h 0.0018
Q-T‘ (Sec.) K (Bazett's B’ormula)""'I
Breed Mini. Maxi. Mean St. Dev. Mini. Maxi. Mean St. Dev.
of Mean of Mean
Jersey 0.35 0.h7 O.h07 0.0061 0.h0 0.h7 0.h25 0.00M3
Guernsey 0.31 o.uu 0.38M 0.0095 0.37 o.u8 0.h19 0.005u
Ayrshire 0.29 0.h2 0.370 0.0117 0.35 0.h6 0.h07 0.0097
Br. Swiss 0.33 0.h7 0.391 0.009h 0.37 0.h6 0.h2h 0.0059
Holstein 0.29 0.h5 0.38M 0.0077 0.3M o.h6 0.hll 0.0058
Total
All
Breeds 0.2g_ 0.u7 0.3893 0.0039 0.3M 0.h8 0.u18 0.0027

 

 

‘ The values used.here are averages of all three leads in three tracings.

" The figures for K are purely numerical.

 

37

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38
BOVINE EKG DEFLECTIONS ‘ THEIR OCCURRENCE, POTENTIAL AND FORM

While this phase of electrocardiography is usually more logically
considered before the intervals, it was decided to reverse the order
in this report. The principal reason for this decision lies in the
fact that here is encountered the greatest confusion and difficulty

of classification and discussion.

As previously mentioned, the nomenclature of the waves is the
same as that employed for electrocardiOgrams taken by the three standr
ard leads in the human subject. Due to the rather frequent occur-
rence of a second positive 038 deflection, it was necessary for pur-

poses of convenience to designate this as R'.

Deflections were considered to be present even when of so low a
potential as to be not accurately measurable. As will be noted, the
inconstancy of low potential waves unfortunately increases the occur-
rence of monthly variations in the summary tables. These variations
are probably due to a combination of several factors. It must be
borne in mind that the taking of electrocardiograms of animals While
in the standing position, with the possible exceptiontaf the horse*,
introduces the factor of potential from contraction of voluntary
muscle. This may be one or both of two forms. The most common is
a steady tremor from persistent muscular contraction (Fig. VII) inci-
dent to maintenance of a quiet standing position. Less frequently

there is a wandering of the string (Fig. VII, and lead III of Fig. IX)

 

* Due to the peculiar anatomy of this species relatively complete
muscular relaxation may be present while in the standing position.

39
in certain animals, possibly from normal body sway in maintaining

balance, but also associated with nervousness. this effect is some-
what similar to that seen in human subjects during emotional excite‘ _
ment. While marked changes in the bovine electrocardiogram from month
to month are most probably due to a shift in the axis of the rather
mobile heart, the interference due to muscular effects accounts for

the failure to rec0gnize nany low potential deflections (below 0.3 m v).
For this reason any changes between the three monthly tracings must

not be considered too seriously. The summarized occurrences should

rather be viewed as a total unit indicating a species tendency.

It must be emphasized that voluntary muscle effects with the ap-
paratus employed were seldom serious enough to obscure deflections of
definite measurable potential. This is contrary to the observations
of Ngrr, (6). Alternating current induction was a troublesome factor

in low potential waves in a very few cases.

140

Occurrence of the Various Deflections

The 2 Wave. 'lhe auricular deflection or P Wave, in common with

 

all the deflections composing a bovine cardiac cycle, shows character'-
istics differing materially from those encountered in human tracings.
mess differences are largely an increase in the incidence of diphasic

and extremely low potential or, more rarely, complete absence of waves.

Monophasic P occurred 23 times in lead I, 35 times in lead II, and

80 times in lead III. ‘lhe direction of this wave was almost without
exception upward. In two or three instances an unfavorable low po-
tential deflection showed a negative tendency (Table XXX). Diphasic
P occurred 61’: times in lead I, 62 times in lead II, and 8 times in
lead III. 'lhe two phases composing this type of wave were always of
either approximately equal potential or with positive (upward) summa-
tion, never of negative summation. In other words, there was never a
diphasic P the potential of whose positive phase was not equal to or
greater than its negative phase. 'Ihe sequence of events in all but
four individuals showing this form was an initial quick, downward de-
flection followed by a much slower upward phase. Regardless of how
inconsequential the character of the minor phase, a wave showing this
characteristic was always classified as diphasic. Approximately 80
per cent of the diphasic P waves in all leads of the first monthly
tracings in this series showed a positive phase of greater potential
than the negative phase. Four individuals displayed diphasic P with a
plus to minus sequence. [this always occurred in lead III and showed a

marked tendency to vary from month to month. The potential of the

141

two phases did not depart from the tendency displayed by the other

type of diphasic P discussed previously.

In a few cases P was totally absent or when present was of such
extremely low potential that its form could not be accurately deter-
mined. 'mis occurred 10 times in lead I and 9 times in lead III. 'Ihe

deflection was always present in lead II.

'Ihe general form of this wave presents no other outstanding
features worthy of critical discussion which may not be obtained by
careful examination of Figures II - A, B, C, D. and E. It may not be
amiss to note that true notching of P, such as was found by Hahn, (h),
in the horse and to a lesser extent by Ngrr, (6), in the bovine, when
employing the single regio-apicis: regio praescapularis lead, did not

occur in a single instance in this series.

In Table XII is summarized the occurrence of the various com-
binations of P wave types with respect to leads in the first monthly
tracings. Of the 6’4 possible combinations of positive and negative
monOphasic, diphasic, and non-determinable waves in the three leads
only 15 occurred. Of these the DD" combination occurred most fre-
quently (314 times). The sum of the instances in which DD+. DH'.

mm, and +++ occurred accounts for 68 per cent of the 97 animals consti-

tuting this series with the balance distributed as shown in the table.

 

" 'me symbols DDi- means that the deflection was diphasic in leads I
and II, and positive monophasic in lead III. Similarly, +++ indi-
cates a positive monophasic wave in leads I, II, and III, etc.

Me
When monophasic P occurs in only one lead of an electrocardio-
gram, it almost invariably appears in lead III. Its presence in any
other lead than III is always coincident with its appearance in more
than one of the leads. For example, monophasic P never occurs in lead
II without also being present in leads I and/or III. Diphasic P appear-
ed.with about equal frequency in the single leads I and II. Its most

frequent occurrence, however, was in the lead I and II combination.

 

1‘3

Table III. Summary of the Occurrence of Various Combinations of P
Waves With Respect to Leads in the First Monthly Tracings.

 

 

 

 

 

 

H >. o 3 a
H H o n «4 a
H H H h m Or! h 3 3
" '3 t? E E E "3 :3 s
3 s .9. .2 s 4 a s a
D D D - - 2 l 1L 7
D D + 8 10 3 5 3h
D + + 7 2 3 1 3 16
+ D D 1 - - - - l
+ D + 1 l l 2 - 5
- D + " - r - 2 2
+ + + 3 2 - 2 2 9
+ + - - - - 1 - 1
+ D NM - l - - - 1
NM + + 1 - - - - 1
NM D + 2 5 - r r 7
D D m - 1 2 3 - 6
NM + + - - l l l 3
+ + NM - - l 2 - 3
M + + - - - 1 - 1
Tom 23 22 13 19 20 97
Key: + 3 upward deflection
- a. downward deflection
D - diphasic wave
NM I.- absent, non-measurable, or non-determinable wave
31 c M shaped complex with positive summation

 

uh
SEE.QE§.§EEEE! Before considering the several deflections com-
posing the QRS group it might be well to again.emmhasize the fact
that waves were considered to be present even when of so small a por
tential as to constitute merely a trace (below 0.03 millivolt). It
should be borne in mind that the ease with which these may be obscured

by A‘C induction and muscle tremor doubtless gives rise to apparent

variations that do not exist.

The deflection Q occurred 59 times in lead I, 78 times in lead II,
and 68 times in lead III. R was present 76 times in lead I, 96 times
in lead II, and 96 times in lead III. S was found 28 times in lead I,
8 times in lead II, and 20 times in lead III. The second.positive
OBS deflection (called R' in this study) occurred twice in lead I,

5 times in lead II, and 1h times in lead III. To gain a better con-
ceptiontaf the significance of these figures, Table XIII, showing the
approximate percentage incidence of occurrence of these deflections in
the various leads, is presented.

Table XIII. Percentage Occurrence of the Various Deflections Compos-
ing Q33 in the Three Leads.

 

 

 

" Per Cent
Lead Q R s R'
I . 60 . 78 23
II so 99 s h
III 70 99 20 1t

 

 

 

The above table indicates the almost invariable occurrence of
R in leads II and III, flhe great frequency of Q in all leads, and the

relative infrequency of S and R' waves.

1“5

Table XIV summarizes the occurrence of Q, R, S, and R' waves alone
and in combination in the various leads and lead combinations of the
first monthly tracings. QRS was represented by a single downwardly
directed (Q) wave in 20 instances and this only in lead I. QRS occurred
as a lone upward deflection (R wave) mainly in the single leads I and
III, and simultaneously in the two leads I and II, appearing ll, 10,
and 6 times in the order mentioned. Diphasicity of QRS (Q and R waves)
occurred most frequently simultaneously in leads II and III (36
times), and I, II, and III (22 times). Next in order comes the sin-
gle lead II which showed this combination in 11 instances. The
second.possible type of diphasicity (R and S waves) never occurred in
more than one lead of any electrocardiogram, being present 16 times
in lead I. once in lead II, and n times in lead III. The "typical"
complex composed of Q, R, and S waves occurred 10 times in lead I.

Its presence in any other lead or lead combination was relatively
negligible. As to QRS groups showing R' waves, little can be said

at this point beyond the fact that the RSR' sequence occurred.most fre-
quently, being present in the greatest number of instances in lead

III (9 times).

Concerning breed differences, conclusions based on such a small
number of animals as compose each group must be drawn with extreme
reserve. It is noteworthy that Q waves were most frequent in Jerseys
and least in.Holsteins, While this latter breed.showed.the greatest
incidence of R' waves. For the rest, the mean trend in the several

breeds presents no differences worthy of mention.

1L6

 

 

 

 

 

Hmmme mHOHszHmmmmHmmHHmmmongom 358
H e mH m o 00 H HH e m o «H o H o :H om 0 582.5
0 m o o o o o m o o H m m o m H e o H H s o H m 2:5
58.8

o m 0H 0 o om m cm m a H 00 m o o Hm MH 0 83S?
0 o co m H Hm 0 on m 20 co m o 0 0H cm : masses
0 H H o o H o o H o z m 0H 0 m H m H H o m o H 2 seats.
HHH HHH HHH HHH HHH HHH HHH HHH HHH HHH HHH HHH t :33
HH HH HH HH HH HH HH HH HH HH HH HH HH -uflpsoo
H H H H H H H .HL... H H 33

.m m use. use; sense 28 m m6 33H»

38 .u .m .. .m .d I -838

 

 

 

 

 

 

 

 

.umfloeaa haflnoz any; 05 no aaoaaapaoo
econ use meson 33.3» ofi 5 and no 23300.33 23 Mo 33530 on.» we assess.» .ER 038.

 

“7

Egg Wile; lThe final electrical effects of ventricular systole
evidenced in the electrocardiogram by the deflection T, like the P
wave presents characteristic peculiarities rarely encountered in
human tracings. Ifiphasicity is the outstanding feature of this wave.
It is not to be inferred that monOphasic deflections do not occur, but
tracings in which T was not diphasic in one, and.more frequently, two
leads are extremely rare. Monophasic waves resemble somewhat those
seen in the human subject except that the summit tends to be more
sharply defined and less rounded. One limb is often, but not always,
more quickly executed and therefore finer in outline than the other.
In this respect it is reminiscent of that portion of diphasic T where
the Change in direction of potential is recorded. Diphasic complexes
are largely characterized by relatively slow broad initial and.terminal
deflections, the movement of the string during change in direction of

potential being usually rather quickly executed. (See Figure II, etc.)

The sequence of events (as with the P wave) was, with but two
exceptions, an initial negative fbllowed by'a positive phase. In the
two individuals showing a positive to negative sequence, considerable

monthly variation occurred. (See Table XXX).

MonOphasic T occurred 79 times in lead I, 27 times in lead II,
and 29 times in lead III. Of these, 75 in lead I, 22 in lead II,
and M in lead III were negative. This indicates that, in.this series,
monophasic T1 and 2 were largely negative while T3 was mainly positive.
Diphasic T occurred 1M times in lead I. 70 times in lead.II, and 6N

times in lead III. The two phases composing this type of wave showed

148
negative sunmation in 107 instances, phases of equal potential in 25
instances, and.positive summation in In instances in the 1M6 leads in
which diphasic T occurred. From.this it can be seen.that diphasic

T is largely negative.

Triphasic T was seen only once’, and then only in the first month-
ly tracing. This wave varied from diphasic to positive monophasic in

the two succeeding monthly tracings.

Extremely low potential undeterminable T waves occurred four times
in lead I and four times in lead III. Unlike P, complete absence of

T was never encountered.

The occurrence of the various combinations of T waves with re-
spect to leads in the first monthly tracings is summarized in Table
XV. Of the 6% possible combinations of positive and negative mono-
phasic, diphasic, and nonrdeterminable waves in the three leads, only
19 occurred. The three most frequent combinations were the following:
-DD, 37 times; ‘*D, 1? times; 'D+, 13 times. The foregoing embraces
69 per cent of the 97 animals constituting this series. The remainder

are distributed as shown in the table.

The table further shows that When monOphasic T occurred in only
one lead of an electrocardiogram, it invariably presented itself in lead
I or III, never in lead II. Its occurrence in lead II was always coin-
cident with monophasic T1 and/or T3, the nest common combination being

leads I and II. Diphasic T occurred in all leads and lead combinations,

 

‘ Guernsey No. “6, see Table XXX.

“9
the most favorable single leads being II and III, and the most favor-
able leed combinations, lead II and III. Since the trend in all breeds
was roughly the same and since each group represented such a small num-

ber of individuals, no conclusions as to breed differences can be safe-

1y drawn.

 

50

Summary of the Occurrence of Various Combinations of T
Waves with Respect to Leeds in the First Monthly Tracings.

 

 

 

TableXV.
m
H homfi
HH 01-1-14

H HH main-030m
e as gfifimtg
G (U “5 h0g0?!
0 0 0 03 $400
.4 q .4 '1 «some
D D D 2111-5
D D + 1-2- 3
D D - 11- -2
n + + -3---3
+ D D 1----1
- D D 12 7 3 6 9 37
- v D 22-5817
+ D - l----1
- D +- - u M 3 2 13
- D - --1--1
+ - - -1---l
- + + l----1
- - + -l-2-3
+ DND 1----1
ND D D -1-113
ND D '- 1----1
D DND --1--1
- -ND ‘-11-'2
- D W" -l---l
Total 23 22 13 19 20 97

 

 

Key:

+ = upward deflection
‘ 3 downward deflection
D ' diphasic wave
ND " non-measurable or non-
determdnable wave
W = W shaped complex

" Triphasic wave with slightly positive sumation.

51
Potentials of EKG Deflections

In order to obtain a more accurate understanding of the signi-
ficance of the tabulated values to be presented in this section, a
brief explanatory discussion must be entered into at this point. The
prevalence of slight voluntary muscle tremor and, to a lesser extent
A‘C induction in certain tracings, precluded extreme accuracy in the
measurement of very low potential waves. Clearly recOgnized deflec'
tions of a potential of 0.03 millivolts or less were recorded.as having
this value. Deflections of such extremely low potential as to be
almost lost in a vibrating string shadow were recorded as non-determin-
able (N.D.). Totally absent waves were, of course, recorded.as such.
Where, as frequently occurred, slight variations were seen in.the po-
tential of a wave within a lead, the largest value was used. In the
case of diphasic waves, the potential of the largest phase was re-
corded; or, where the phases were of equal value, one phase was taken.
In so far as possible, measurements were made at points within.the
lead.where the string shadow was not wandering since it was observed
that this factor may produce apparent changes in potential leading to
considerable error. Since there is, with but few exceptions, rela-
tively little variation in size of potential from month to month, the
tabulated measurements in this section were arbitrarily taken from.the

first monthly tracings.

52
The Distribution of Potentials by Leads

_u'h__e_Pgtential 911:. With a wave of such absolute low potential,
breed differences, if any, are difficult to evaluate. For this reason
the series will be considered mainly as a group. Study of Table XVI
shows that the range for measurable waves is from the minimum of 0.03
millivolt in all three leads to the maximum of 0.12 in lead I, 0.18
in lead II, and 0.22 in lead III. It must be stated, however, that
non-determinable waves occurred in 28 instances in lead I and in l? in-
stances in lead III. Therefore, the absolute minimum is less in these
leads than is actually recorded in the table. It is interesting to
note that the Ayrshire breed displayed this type of wave in 6 out of
13 individuals composing this group. The remainder of the breed groups
exhibited non-determinable waves to a lesser and more uniform degree.
The mean values for the entire group was 0.06, 0.10, and 0.07 milli-
volt in leads I, II, and III respectively.

Table XVI. Minimum, Maximum, and Mean values for Potential of P in
the First Monthly Tracings.

 

Potent ial (Mill ivol ts )

 

 

 

 

 

 

 

D
Breed ‘3 g Occurrence

, ,P, Minimum Maxirmnn Mean
Lead-2 223 1* II In" I II III I II III I II III
Jersey 23 16 23 23 .03 .10 .011 .10 .15 .10 .06 .12 .08
Guernsey 22 1“ 22 2O .03 .03 .03 .12 .15 .22 .05 .ll .09
Ayrshire 13 7 13 7 .03 .03 .03 .08 .10 .08 .05 .08 .06
Brown
Swiss 19 15 19 12 .03 .03 .03 .10 .18 .12 .07 .10 .06
Holstein 20 17 20 18 .03 .03 .03 .10 .12 .10 .05 .09 .06
11
grease 37 69 97 80 .03 .03 .03 .12 .18 .22 .06 .10 .07

 

* ‘me discrepancy in numbers here is due to non-determinable waves.

 

 

53
The Potential g£_g, The occurrence of Q, alone and in combina-

tion with other waves, was more frequent in lead II, being present in

60, 80, and.70 per cent of leads I, II, and III respectively.

The range of potential for the group as set forth in Table XVII
is from the minimum of 0.03 millivolt in all three leads to the maxi-
mum of 0.60, 1.00, and 0.90 millivolt in leads I. II, and III respec"
tively. The mean for the group was 0.23 millivolt in lead I, 0.16

in lead II, and 0.11 in lead III.

Breed differences are not significant beyond the fact that of
the Hols teins in which Q occurred only two individuals displayed a
potential greater than 0.12 millivolt.

Table XVII. Minimum, Maximum, and Mean Values for Potential of Q in
the First Monthly Tracings.

 

 

 

 

 

 

m Potential (Millivolts)
Breed ‘3 H Occurrence

S Minimum Maximum Mean

0 0H

Lead -- 2 53 I II III I II III I II III I II III
Jersey 23 16 20 17 .08 .03 .03 .60 .60 .25 .26 .13 .07
Guernsey 22 15 22 2O .03 .03 .03 .60 1.00 .90 .26 .23 .17
Ayrshire 13 5 10 7 .10 .03 .03 .U0 .23 .30 .23 .09 .10
Brown
Swiss 19 16 17 12 .03 .03 .03 .50 .50 .MO .21 .19 .11
Holstein 20 6 11 12 .03 .03 .03 .ho .32 .30 .15 .08 .09
H1
Breeds 97 58 80 68 .03 003 .03 .60 1.00 090 023 .16 .11

 

 

 

 

 

5h

The Potential 21; ll. This wave was present in all cases in lead
III, in all but one case in lead II, and in 72 per cent of the indivi-

duals in lead I.

'Ihe potential ranged from the minimum of 0.03 millivolt in all
leads to the maximum of 0.70, 2.60, and 1.50 millivolt in leads I,
II, and III respectively. The average for the entire series was
0.16 millivolt in lead I, 0.37 millivolt in lead.II, and 0.35 millivolt

in lead III. liable XVIII displays the necessary tabulated data.

No marked discrepancies of average potentials between the five

breed groups are evident.

Table XVIII. Minimum, Maximum, and Mean Values for Potential of R in
the First Monthly Tracings.

 

 

 

 

 

 

«H a Potential (Millivolts)
Breed ° H Occurrence

6g Minimum Maximum Mean
Lead» 25}, I II III I II III I II III I II III
Jersey 23 11 23 23 .05 .10 .03 .70 2.60 1.50 .21 .5h .53
Guernsey 22 15 22 22 .03 .03 .05 .30 .60 .65 .12 .27 .29
Ayrshire 13 12 13 13 .05 .10 .10 .50 .801.00 .21 .33 .29
Brown
Swiss 19 13 19 19 .05 .OM .10 .30 .75 .95 .13 .30 .3
Holstein 20 19 19 20 .03 .13 .05 .h3 1.10 .93 .18 .MO .29
All
Breeds 97 70 96 97 .03 .03 .03 .70 2.601.50 .16 .37 .35

 

 

 

 

55

EgPotential Q}; §_. Next to R' this wave was of the least fre-
quent occurrence and showed the lowest potential of any deflection
composing the QRS group. It occurred 29 times in lead I, 6 times in
lead II, and 18 times in lead III. Table XIX indicates that, aside from
a tendency to occur most frequently in lead I of the Guernseys, no

outstanding breed differences are present.

Potentials were unifomly low and ranged from a minimum of 0.03
millivolt in all leads to a maximum of 0.20, 0.10, and 0.25 milli-
volt in leads I, II, and III respectively. Mean values were very low,
0.06 millivolt in lead I, 0.07 in lead II, and 0.12 in lead.III. The
lower potential specimens of this wave showed a marked tendency to
vary from month to month, often being present one month and complete-
ly absent the next or vice versa.

Table XIX. Minimum, Maximum, and Mean Values for Potential of S in the
First Monthly Tracings.

 

 

 

 

 

 

 

a Potential (Millivolts)

Breed 'H .4 Occurrence

OE Minimum Maximum Mean
Lead» £3 I II III I II III I II III I II III
Jersey 23 h 2 2 .03 .05 .05 .10 .10 .06 .07 .07 .05
Guernsey 22 10 2 3 .03 .10 .10 .20 .10 .20 .06 .10 .13
Ayrshire 13 s 0 u .03 - .06 .15 - .20 .06 - .12
Brown
Swiss l9 14 O l .03 - - .05 - - .03 - .lO
Holstein 20 3 2 s .03 .03 .03 .15 .05 .25 .07 .0h .13
All
Breeds 97 29 6 Is .03 .03 .03 .20 .10 .25 .06 .07 .12

 

 

 

 

56

The Potential 2£_EL, The significance of the second positive
QRS deflection is not clear. Since the R' wave seldom occurs, is con-
sistently associated.with bizarre, splintered R waves, displays consi-
derable monthly change, and is uniformly of such low potential as to
vary from zero to trace within a lead, the question arizes as to
whether or not it Should be considered as an actual deflection. Fur-
thermore, since its presence is apparently the result of an exaggerated
splintering or notching of R', perhaps it should.with more Justice be
accorded the scant notice usually evidenced when present in lead III
of human tracings, (27). Table XX shows that R' occurred 2 times in
lead I, 5 times in lead II, In times in lead III, and.was more preva-
lent in.Holsteins than in any of the other breeds. Due to the infre'
quency of its occurrence no definite conclusions can be drawn as to
the effect of breed or lead on differences in potential. Potentials
ranged from a minimum of 0.03 to a maximum of 0.20 millivolt, with a
mean of 0.15 millivolt in lead I, 0.11 in lead II, and 0.10 in lead

III.

 

* See discussion, page 65.

 

57

Table XX. Minimum, Maximum, and Mean Values for Potential of R' in
the First Monthly Trac ings.

 

 

 

 

 

 

 

s... ,3 Potential (Millivolts)

° 0 ur
Breed 6.§ cc rence Minimum Maximum Mean
Lead .. z 3 I II III I II III I II III I II III
Jersey 23 " 1 1 " " " " r r " .20 .10
Guernsey 22 - l 3 - - .03 - - .20 '- .15 .ll
Ayrshire l3 1 - 2 - - - " - '- .10 - .15
Brown
Swiss 19 - - 2 - - .06 - - .10 - - .08
Holstein 20 1 3 6 - .03 _.05 - .10 .15 .20 .07 .09
All
Breeds 97 2 5 In - .03 .03 - .10 .20 .15 .11 .10

 

 

 

The Potential 2: g; T was present in all individuals and in all
leads. The fact that potentials were not recorded for M cases in leads
I and III does not mean that this wave was absent in these instances.
The potential was merely so low as to fail to bring it under the 0.03
millivolt classification. Here, as with all the other deflections,

breed differences are not significant enough to merit consideration.

Table XXI shows the range of potential to be from a minimum of
0.03 millivolt in all three leads to a maximum of 0.60, 1.10, and
0.90 millivolt in leads I, II, and III respectively. The mean values
are 0.20 millivolt in lead I, 0.31 millivolt in lead II, and 0.18
millivolt in lead III.

Table XXI. Minimum, Maximum, and Mean Values for Potential of T in
the First Monthly Tracings. -

 

 

 

 

 

 

a Potential (Millivolts)
O s .
Breed t3,§ ccuirence Minimum Maximum Mean
0 «4
Lead -* ,2 if; I II III I II III I II III I II III
Jersey 23 22 23 22 .03 .12 .06 .35 .70 .MO .17 .30 .18
Guernsey 22 21 22 22 .03 .10 .05 .33 1.10 .90 .1h .23 .17
Ayrshire l3 l3 13 ll .10 .03 .10 .MO .70 .32 .25 .30 .16
Brown .
Swiss 19 18 I9 18 .06 .06 .10 .60 .60 .ho .23 .31 .19
Holstein 20 19 20 20 .08 .10 .03 .H3 .70 .MO .2h .MI .21
All
Breeds 97 93 97 93 .03 .03 003 .60 1.10 .90 020 031 .18

 

 

 

 

Occurrence, Distribution, and.Range of the Highest Potential
EKG Deflections in Any Lead of the First Monthly Tracings‘

To gain a better conception of the distribution, size, and mean
values for the maximum potential waves of the bovine electrocardiogram.
this section has been included. The material presented will be limited
to a brief resume of the findings for each wave. For reasons mentioned
several times previously, conclusions concerning breed differences must
be accepted with reserve. Table XXII showing distribution and table
XXIII showing minima, maxima and mean values for the various breeds will

be found on pages 61 and 62.

222.2.EEX23 The maximum potential of the auricular deflection
ranged from 0.03 to 0.22 millivolt with a tendency toward.rather uni-
form distribution about the mean. Ten animals showed a potential of
0.08, 38 a potential of 0.10, and 19 a potential of 0.12 millivolt.
0f the remaining 30 animals, 15 were grouped in the range from 0.13
to 0.15 millivolt inclusive. The balance were distributed.above and
below these limits as shown in Table XXII. The mean potential in the
various breed groups ranged from 0.083 in the Ayrshires to 0.129 in

the Jerseys. The average for the entire series was 0.106 millivolt.

ghg_gfifiggg. Tables XXII and XXIII show extremely wide and uneven
scattering of the values about the mean. The absence of Q in all leads
of 10 individuals lowers the average potential in the latter table.
The range for actually occurring waves was from 0.03 millivolt in

eight cases to 1.00 millivolt in one individual. The mean in the various

 

* Due to the variabilitycif R', the maximum potential of this wave is
taken from any lead of the three monthly tracings.

6O
breed groups ranged from 0.093 millivolt in the Holsteins to 0.302
millivolt in the Guernseys; the average for the entire series (includ'
ing the ten zero, or absent cases) was 0.208 millivolt. The Holstein
group displayed rather definite characteristics deserving further men‘
tion. 0f the ten cases showing total absence of Q in all leads, seven
were in.this breed. Nine individuals displayed potentials of 0.12 milli-
volt or less, six of which were 0.05 millivolt or less. These latter
were usually associated with R wave preponderance and showed consider-
able tendency toward monthly variation from low potential to complete
absence and vice versa. This tendency, however, was seen in all breeds

showing not only low potential Q but also small 3' and S waves.

The §_Wave. The most consistently present deflectioncaf QRS. R

 

displayed even greater irregularity in distribution about the mean

than the previous wave. The range in maximum potential in any lead,was
from 0.10 millivolt in five instances to 2.60 millivolts in one in-
stance. It is interesting to note that the average in the various breed
groups ranged from the maximum of 0.618 millivolt in the Jerseys to

from 0.337 to 0.39M millivolt in the other breed groups. The mean for

the entire series was 0.h25 millivolt.

_T'l_i_§_ §_ and g; m. With such infrequently occurring irregular
waves as these, the statistical methods employed in this section may
not be applicable; and, since the treatment accorded these two deflec-
tions in the preceding section may be less apt to mislead, the picture

will not be further complicated by’a summary discussion of the data in

Tables XXII and XXIII.

Table XXII. Distribution of the Highest.Potential EKG-waves in Any Lead of the First Monthly Tracings*.

    

 

 

 

Potential
(Millivolts)

0.0
0.03.
0.05
-0.06
0.07
0.08
0.10
0.11

mrficszOF-bo
HHHHHH

I 00 o 0
000000

0.30
0.32
0-33
o Is

mom
kOh-Nbo

 

Jersey

Guernsey _
.Ayrshire ' 1
Brown Swiss
Holstein 1

P Wave

H
«IZ’I'UKNH
H

7 2 3 h
6.3 1 -

$7n3
H
H
1...:

 

Total

Jersey 2
Guernsey
Ayrshire 1
Brown Swiss
Holstein 7

M

Q wave

OQ\.QKOO\0QO\

H
O

\N

1 19 6’}

H
HI—‘HHI—IH
MHN

n)
is

turd
H

Hmcn

k‘h’

 

OQKNFONH

Total 10

N
LHnJ
N
H

1 2 3 1 1

KN
\N

 

Jersey
Guernsey
Ayrshire
Brown Swiss
Holstein

R Wave

NHNNNWON

HHKNt—lm

rdekflkfl
Hm
54 kaN
h‘PJKN
edea ruxu
sara
H-P‘

KN
H

 

Total

ONWH
H

\D HPJl-‘mKN-xlmk-‘Ir‘w
C3‘¢“¢JF‘P‘RJ‘4ldfuidtuld

N NNN

WW
H

 

Jersey 167 l
Guernsey 11 3
Ayrshire M 3
Brown Swiss 1h 3
3
3

5 wave

Holstein 9
Total 5M 1
Jersey 19
Guernsey 18 1
Ayrshire 7
Brown Swiss l6
Holstein 9 1

R! wave*

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41' NFONOQ

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Total 69 2

rdta
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Jersey
Guernsey
AyrShire
Brown Swiss
Holstein

T‘Wave

N

2 1

H
mmHmn—H-Im

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N.

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Total

The to the variability of R! the maximum potential of this wave is taken from.any lead of the three

monthly trac ings .

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63
variations in the Form of Q35 and Distribution of the Various Types

In figure I is presented.a complete general grouping of the vari-
ous representative types of QRS encountered in this study. 0n turning
to this figure, it will be apparent at a glance that for those familiar
with normal human electrocardiograms, considerable mental readjustment
may be necessary in order to eliminate the impression that one is deal-
ing with abnormal tracings. The arrangement is purely arbitrary. Be-
ginning with typical R wave predominance, the prOgression is through
varying types of multiphase complexes to negative (Q~wave) predominance
and finally representative unfavorable low potential QRS types. Be-
ginning with type 1, their form and occurrence will be considered in
order. The discussion will be based upon the figure referred to above,
and Tables XXIV and XXV showing various features concerning occurrence
of the several forms. Table XXIV indicates the per cent incidence of
occurrence in the entire series. Table XXV shows the actual number
of times each form was present in the three leads tabulated according
to breed groups. In compiling the data for this table, the sum of the
three leads in the three serial electrocardiograms for eadh of the 97
animals was used, making a total of 291 each of leads I, II, and III.
Due to the occurrence of monthly variations, it is believed that this
procedure will yield data upon which more accurate conclusions can be
based. For greater clarity of comparison, Table XXIV will be drawn
upon for occurrence of the QRS forms While Table XXV will be referred

to concerning possible breed differences.

6h
Under types 1 and 2 are grouped those complexes showing definite

R wave predominance varying from a quick fine up and downstroke to
more or less progressive degrees of coarsening of both limbs of this
deflection. Type 1, the only QRS most typical of normal human tracings,
occurred in but one individual and is reproduced in full in Figure III.
Type 2 appeared in 19 per cent of the instances in lead I, M per cent in
lead II, and 2 per cent in lead III. Table XXV indicates that this form
occurred about four times more frequently in lead I of the Holsteins

than in any other breed.

Types 3 and.u are characterized by a quicszi e upstroke of R
with slurring or coarsening of the descending limb which may be com-
plete (type 3) or merely confined to its terminal portion (type N).
Type 3 occurred in 2 per cent of the instances in lead I, 1C)per cent
in lead II, and h per cent in lead III. No significant breed differences
are shown in Table XXV. Type M was seen in lead I of only one indivi-
dual. However, it occurred in 36 per cent of the instances in lead II
and 26 per cent in lead III. There is an apparent tendency for the
occurrence of this type of QRS to be more frequent in the Jersey than
in any of the other breed groups. The two types together appeared in
about 2k per’cent of the 87} leads in the three serial electrocardio-

grams of the 97 animals constituting this series.

In type 5 is seen the beginning of the very troublesome and.change-
able group of vibratory complexes. Type 5a shows notching of the down-
stroke at the point where the terminal portion becomes coarsened. With
a lowering in potential of the initial spike, forked or somewhat M-shaped,

complexes such as 5b occur. Since these two closely related forms occurred

65
with about equal frequency, they will be considered tOgether. The two
types were totally absent in 1ead.I, present in,8 per cent of the instances

in lead II, and 17 per cent in lead III.

In type 6, the descending limb of the initial spike crosses the iso-
electric level giving rise (according to the accepted classification in
such cases) to a second.positive QRS deflection or R' wave of which the
coarsened terminal portion of R in type he seems to be the remote ana-
logue. This occurred in 7 per cent of the instances in lead III, and

was entirely absent in the other two leads.

From this point the forms pass through various stages of M-shaped
complexes in.Which the notching may (type 8) or may not (type 7) cross
the isoelectric level. Type 7 occurred in 1 per cent of the instances in
lead I, 3 per cent in lead II, and 7 per cent in lead III. Table XXV in-
dicates this form to be much more prevalent in the Brown Swiss and Holstein
groups. Type 8 was of negligible occurrence in'lead I, appeared in 2 per
cent of the instances in lead II, and 7 per cent in lead III. These two forms

complete the class showing initial upward (R.wave) deflections of QRS.

Types 9 to 12 inclusive, exhibit downwardly directed initial effects
of Q35. The complexes as a whole are W-shaped vibnatory (types 9 and
10b) or truly w-shaped (type 10a). In many of these the excursion of the
string shadow in executing the vibrations may be broad enough to cross
the base line at two points, giving rise again to a second.positive QRS
deflection or R! wave (type 10b and.possibly 9b). Due to their relative
similarity of form, types 9 and 10 are considered together. Comparative

occurrence in the three leads are not especially significant. The two

forms together were present in 8 per cent of all the leads.

__

66
Type 11 shows two typical variations of diphasic (QR) complexes
displaying opposite potential excursions which are broad.enough to
indicate considerable rotation of the electrical axis during systole.
Occurring with considerable uniformity in the several breed groups,
this form of QRS was present in 9 per cent of the instances in lead I,

22 per cent in lead II, and 8 per cent in lead III.

Type 12 is characterized by Q predominance reminiscent of human
electrocardiograms showing abnormal axis deviation. It is interesting
to note that the two limbs of Q in this class were prone to be less
broad or coarse than the Oppositely directed complex displayed in
type 2. The occurrence of this form was very largely in lead I, being
present in 22 per cent of the instances in this lead and only 7 and M
per cent in leads II and III respectively. Table XXV indicates this
type to be of most frequent occurrence in all three leads of the Guern-
sey group, while the Jerseys and Brown Swiss follow in order with occur-
rence principally in lead I. The appearance of this form in the two

remaining groups (Ayrshire and Holstein) is relatively infrequent.

Under type 13 of the figure is arbitrarily lumped all extremely
unfavorable low potential QRS. Examination of the four specimens will
reveal resemblances to previously classified complexes. Due to the
extremely low potential displayed by the members and_the difficulty
attending the accurate classification of many of these, a separate
group presented the only lOgical solution. Study of Table XXIV reveals
that unfavorable QRS is largely confined to lead I where it was present
in M0 per cent of the instances. The distribution was remarkably uni-

form in the five breed groups.

6?

Summa 1. To summarize the foregoing data more comprehensibly,

the resume below is presented.

In lead I, type 2 occurred in 19 per cent, type 12 in 22 per cent,
and type 13 in MO per cent of all individuals. Type 5, 6, and 8 were
totally absent, and the balance were thinly scattered among the remains

ing forms 0

In lead II the distribution is somewhat more uniform, the more
frequently occurring forms being types 3, h, and 11, which were present

in 10, 3b, and 22 per cent of the individuals respectively.

Lead III shows the most uniform distribution of all, with type h
occurring in 26 per cent of the individuals and the balance rather even-

ly distributed among the remaining types.

Type 1, being present in only one individual, was not considered

of sufficient importance to warrant mention in the foregoing summary.

Finally, attention must be directed to one constantly present
characteristic of Q35 in this series. Beginning with type 2 and end“
ing with type 11, the final effects are almost invariably broader and
slower than any other phase of the complex. A faint suggestion of this
is also definite enough in the remaining forms to warrant the conclusion
that this pheomenon is a characteristic feature of the bovine electro-

cardiOgram.

 

Table HIV.

Per Cent"I Incidence of Occurrence of the 13 QBS Types
Shown in Figure I.

 

 

 

QRS

Types ~ 1 2 3 1.1 a 5 9 IO 11 12 13
L I l 19 2 l O O )4 1 9 22 ’40
L II 1 h 10 36 5 3 5 2 22 7 u
L III 1 2 u 26 s 9 6 5 s u 7
All

Leads 1 s 5 19 5 h 5 3 13 11 17

 

"' To the nearest whole number.

 

 

69

Table XXV. Distribution of the QRS Types, Represented in Figure I, in
the Three Serial Electrocardiograms*.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Q33 5 Total
Type ~. 1 3, h a b 6 7 s 9 10 ll 12 13 Leads
L I 3 6 3 2 18 37 69
Jersey L II 3 2 3o 7 u 1 1 u 11 6 69
L III 3 1 5 31 8 6 .5 2:32 #3 3 69
Total 9 7 7 6h 15 10 5 1 23 6 16 an no 201_.
L I 11 3 5 2h 23 66
Guernsey L II 6 16 1 1 u 3 19 In 2 66
LIII 21156122186h10866
Total 13_ 7 31 6 2 2 3 l 15 9 28 us 33 198
L I 7 3 2 1 3 1 5 I“ 13 39
Ayrshire L II 6 10 5 7 8 3 39
L III 9 1 5 3 6 7 1 23 u 39
gptal g 9 19 6 5 5 7 17 2 16 n 20 117
L I 3 3 2 10 15 13 57
§;::: L 11 3 lo 11 1 3 3 3 19 1 3 57
L III 2 u 11 u 134g3749 3 u 1 35 57
Total 11 17 22 5 16 .3 12 3 s 33 17 an 171
L I 27 3 3 2 25 60
Holstein L II 8 6 22 3 2 3 5 s 3 6o
L_III 1 9 252 6 _5 25210 6 10 ,3 60
Total 35 7 31 3 s 5 s 15 3 6 21 2 31 180
11 L I 3 57 6 3 2 1 12 3 25 63 1163’291
A L 11 3 11 3o 89 16 10 s 6 15 6 65 21 11 291
Breeds p_III 232_5_11 75 23.26 20 19 19 17 16 2M 11 21 291
Total 9 73 M7 167 ho 36 20 29 26 nu 25 11h 95 IMS 873

 

 

* Since there are three serial electrocardiograms for each of the 97
animals represented, the data for this table is obtained from a total
of 291 records (873 leads). .Any discrepancies occurring are due to
monthly variations in form of QRS.

 

Figure I.

    

l3

   

7O

71

Classification of the Bovine ElectrocardiOgram

Since no two individuals in this series displayed identical elecr
trocardiograms, any method of classification will perforce not be en-
tirely satisfactory and above criticism. The form and character of
QRS based upon the type complexes exhibited in Figure I were arbi-
trarily taken as the basis for the arrangerent of major groups. The
occurrence of the several types in the different lead combinations and
the form of QRS in the aberrant lead were the criteria employed in the
arrangement of sub-groups. The final result of this arrangement is
the basis for the detailed outline on the following pages. The three
tracings from each individual were not separated. Where monthly
changes were extreme enough to permit placement of the individual in
more than one position, the predominant charaCteristics of the three
tracings were employed as the basis for final classification. Further-
more, it is conceivable that certain electrocardiograms may show un-
like QRS types in the different leads causing them to be unclassifiable.

These are grouped in a separate class.

Figure IIfA shows specimens of the various types encountered
and is so labeled as to be readily integrated with the outline pre-
sented on pages 72 to 78. Since the photographic reduction necessary
for inclusion of the entire figure within the dimensions of a page is
so great as to obscure the form.of the complexes, the components of the
figure have been broken up into smaller units and are reproduced as
figures II-B, II'C, II‘D, and II-E on pages 79 to 85. Figure III

on page 85 shows an unusual type of bovine electrocardiOgram.

72

Detailed Classification of Bovine ElectrocardiOgrams According
to Form of QRS
I. Tracings showing R wave predominance characterized by:
A. Coarsened ascending and descending limbs (Figure II‘l. 2,
and 3), entire (Figure II‘?). or terminal portion (Figure
11'”, 5, and 6) of descending limb of R wave.
1. In leads I and II -

a. Showing mainly low potential positive. coarse, and
somewhat vibratory type of QRS in lead.III:

Ayrshire #1M1 Figure II-l (EKG B312);

b. Showing split or M-shaped QRS in lead III:
Ayrshire #159 Figure II-2 (EKG 3336);

c. Showing diphasic (as) type of Q25 in lead III:
Holstein #186 Figure II-3 (EKG B568).

2. Coarsened terminal portion of downstroke of R in leads
II and III with a quick fine ascending limb -

a. Showing mainly positive Q35 in lead I:

Jersey #101 Figure II-u (EKG 3151):
Jersey #115:

Ayrshire #162;

Holsteins #252 and 25h;

b. Showing low potential mainly diphasic (QR) defleC'
tions in lead I:

Jersey #95 and 97;
Jersey #llh Figure II-5 (EKG 3267);
Guernsey #9;
Holstein #258 Figure II-6 (EKG-B650):
c. Showing mainly negative W'shaped QRS in lead I:

Guernsey #6 Figure II‘7 (EKG £338):

73
d. Showing mainly negative (Q) deflection in lead III:
Jerseyi#88;
Guernsey #1 Figure II-S (FKG 331.18);
Guernsey #30;
Ayrshire #1146 Figure II-9 (EKG 3130);
Brown SWiss #23h and 2u8.

B. Coarsened notched.terminal portion of descending limb of R
wave.

1. Notching of down-stroke in lead III with coarsened down-
stroke of R in lead II ‘

a. With mainly positive summation in lead I:
Jersey #80;
Guernsey #59 Figure II‘lO (EKG B325):
Holstein #269 Figure II-ll (EKG B3U5);
Holstein #275:
Holstein #282 Figure II-12 (EKG 3116);
Brown Swiss #301 and 307:

b. With mainly diphasic (QR) deflection in lead I:

Ayrshire #161;
Holstein #220 Figure II-13 (EKG shot).

2. In leads I and II ‘
With vibratory B3:
Guernsey’#7 Figure II-lh (EKG B122).
3. In leads II and III ‘
a. With mainly'positive summation in lead I:

Jersey #62 Figure II-lS (EKG 3530):
Brown Swiss #300;

b. With mainly diphasic (QR) deflection in lead I:
Jersey #35 Figure 11-16 (FKG 3320);
Jersey #87 and 108;
Guernsey'fhs Figure 11.1? (EKG B89);

c. With very low potential Q35 in lead I:
Jersey #116 Figure II—ls (EKG 13328);

d. With mainly negative summation in lead.III:

Jersey #111;
Jersey #118 Figure II-19 (EKG 13639).

71;
II. Tracings showing vibratory type QRS Characterized by:
A. M type QHS with R wave predominance.
1. In leads II and III -
a. With mainly positive deflection in lead I:

Holstein #130 Figure II-20 (EKG-3570)?
Holstein #278:

b. With mainly diphasic (QR) deflection in lead I:
Brown Swiss #237 and 239*:

c. With mainly low potential negative deflection in
lead I:

Jersey #73 Figure II-21 (EKG B85).

2. In lead II only with negative (Q wave) QHS in lead I
and.upward deflection (R wave) with coarsened down-
stroke in lead III '

Brown Swiss #303.
B. W type wave showing split Q wave predominance.
1. In lead III with negative summation in leads I and II ‘
Guernsey #25 Figure II-22 (EEG B914).
2. In leads I and III with QR deflection in lead II '
Ayrshire #163 Figure II'23 (EKG-BUM2).
C. Splintered or split type QRS of sufficient breadth to often
cause the formation of a second positive QRS deflection
(R' wave) by reason of the passing of the downstroke of the
first spike of the complex below the isoelectric level.

1. Coarsened notched downstroke type in lead III (or exag‘
geration of the notching or splitting classified in part
13 of the outline) -

 

* Q38 in leads II and III were so nearly like that of Figure 11-21
that no specimen complexes were taken from this group.

75

a. Showing smallest R in lead.I with coarsened notched
or merely coarsened downstroke of R in lead II:

Ayrshire #152 FieUFe II-2h (EKG 3127);
Holstein #195. 226. and 286;
Brown Swiss #2MO;

b. Showing negative predominance in lead I with di-
phasic or vibratory QRS in lead III:

Jersey #86;
Ayrshire #160 Figure lI-25 (EKG H390).

2. M type or split complexes of sufficient breadth to pro-
duce generally distinct S waves -

a. In lead III with mainly positive deflections in
leads I and II:

Ayrshire #153;
Holstein #231 Figure II-26 (EKG B115);

b. In lead III with mainly negative lead I and slightly
negative or diphasic lead II:

Guernsey #3;
Ayrshire #156;
Holstein #260 Figure II-27 (EKG 3366);
c. In leads II and III:
(1) With positive deflection in lead I:
Holstein #280 Figure II-28 (EKG slit);
(2) With negative lead I:
Jersey'f90;
d. In leads I, II, and III:
Ayrshire #lhh Figure II—29 (EKG 330M).

3. Tracings showing varying degrees of W type split com-
plexes ‘

a. In leads I and II with very low potential diphasic
Q35 in lead.III:

Brown Swiss #ZHS;

76

b. In leads I and III with diphasic (QR) deflections
in lead II:

Guernsey fhl;
Brown Swiss #231 Figure 11-30 (EKG 3305);

c. In leads II and III:
(1) With R wave in lead I:

Guernsey fun Figure II-Bl (EKG 393);
Guernsey #57;

Holstein #253 Figure II‘32 (EKG B362);

(2) With extremely low potential of all waves in
lead I:

Guernsey'#50 Figure II~33 (EKG 392);
Ayrshire #151.

III. Tracings Whose QRS indicates rather extreme rotation of the elec-
trical axis during systole:

1. In lead II ‘

With mainly Sharp Q wave in lead I and coarsened
downstroke or splintered or notched summit of the
predominant Rwave in lead III:

Jersey #79 Figure II-su (EKG Bins);
Jersey #100 Figure 11-35 (EKG 397);
Jersey #317:

Guernsey flu;

Guernsey #28 Figure II-36 (EKG B96):
Guernsey #hé and 55:

Brown Swiss #230 and 305;

Brown Swiss #306 Figure II-37 (EKG BICO‘

,2/0

2. In leads I and II -
With vibratory R predominance in lead III:

Brown Swiss #232 Figure II-38 (EKG 3135);
Brown Swiss #302.

30 In lead III -

With mainly negative summation in lead II and low
potential slightly negative lead I:

Jersey #89 Figure II-39 (EKG 3319).

77
M. In leads II and III “
a. With small R wave in lead I:

Ayrshire #150;
Holstein #259 Figure II-ho (EKG 3552);

b. With very low non-determinable QRS in lead I:
Guernsey #37 Figure II-Ul (EKG Bluh):
c. With largely negative (Q wave) predominance in lead I:

Brown Swiss #233 Figure II-ME (EKG 3302);
Holstein #261 Figure II-M} (EKG B367).

IV. Tracings showing negative predominance of QBS characterized by:
a. Unfavorable negative or diphasic QRS in lead I:

Guernsey #3 Figure II~M5 (EKG Bah);
Guernsey #he;
Guernsey f“? Figure II-h6 (EKG B123);

b. Unfavorable diphasic Q33 in lead.III:
Jersey #63 Figure II-hu (EKG 3271).

V. Miscellaneous tracings presentingpeculiaritiegprecluding ra-
tional classification.*

a. Tracings showing low voltage Q38 in all three leads -
generally negative summation in lead I. diphasic
lead II, and positive lead III characterized by con-
siderable monthly change:

Guernsey #60 Figure II-u7 (EKG 3380):
Brown Swiss #238;

Brown Swiss #30h;

Holstein #256 Figure II-MS (EKG 3560);

b. Tracings Showing quick fine R.waves of extreme
amplitude in all three leads:

Jersey #Sh Figure III.

 

* While Justification could.perhaps be obtained for the disposition of
this group by placing them in the nearest correct position in the
preceeding outline, it was thought best to create for the time being
a separate class for these tracings.

 

78

Summary 22.392 Distribution gg_the Various Groups 12 the Classi-

fication.

The breed distribution of the various types through the

second subdivision in the outline is summarized in the table below.

ibis compilation shows that type I and II embraced 72 per cent of the

entire group of 97 animals, with type III next in order (18 per cent)

and type IV and V of relatively infrequent occurrence. The series is

too small to warrant conclusions as to breed differences if any. It

mey'be significant that of the 21 Jerseys I“ were in type I.

 

 

 

 

 

 

Table XXVI. Summary of the Distribution of EKG types according to
the Outline on pages 72 to 78 and.as illustrated in
FIgUJ'OIIo
Hoes-o I II III 1v
6: m N
Subgroups - A B .a __§ 3 C F. F,
3' 3 3
12123812121238.123115‘3
Jersey 6 l 7 1h 1 1 l 3 3 1 M 1
Guernsey 111117 1 1u6h 1‘53
Ayrshire 2 2 l 5 l 2 3 1 7 l 1
Brown
Swiss 2 2 1 5 2 1 1 2 6 3 2 1 6
Holstein 1314 s 2 3 3 1 9 2 2
All
Breeds 3 l7 9 l 9 39 5 1 1 l 7 8 8 31 10 2 1 5 18 M

 

 

 

 

 

 

 

 

 

 

 

 

 

79

F I G U R E S

The figures on the following pages are arranged to illustrate

the various types of bovine electrocardiograms encountered:

Figure II A shows various types of electrocardiograms arranged
according to the classification on pages 72 to 78. The Roman
numerals on the extreme right have reference to leads; the
Roman numerals to the left, as well as the capital letters,
have reference to the major subdivisions of the classification
referred to above, and.the Arabic numbers under each EKG

refer to individuals. The figure is reduced to about one-
fourth actual size of the original.

FiguraaII B, C, D, and E are the components of Figure II.A, as
indicated.by the number under each EKG, enlarged to the actual
size of the original records.

Figure III is an unusual type of bovine electrocardiogram,
about one‘half original size to show type of mounting card
employed. The arrangement of leads is I, II, and III in
descending order from top to bottom of the figure.

80

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86

NE MTRICAL AXIS OF THE BOVINE HEART

The approximate electrical axis of each electrocardiOgram in the
series was determined.by the method described‘under procedure. These
values are recorded.in Table XXX. Due to the superficial methods employed
and the general unfavorableness of many tracings, the data presented in
this section are only of the most general nature and do not warrant
definite conclusions. If the electrocardiograph should prove to be
of value in certain bovine experimental procedures, more detailed study

of the normal is essential.

Table XXVII shows the electrical axis distribution in the first
monthly tracings of the five breeds composing the present series. Study
of this table shows that practically 50 per cent of the animals are
in the axis range from +300 to +900 inclusive, and 65 per cent from
+300 to +1700. Only 17 per cent are grouned in the -30° to -160° range,

Table XXVII. Distribution of E1ectrical.Axes by Breeds in the First
Monthly Tracings.

 

 

 

+30° +91° ~3o° -910 Non-
Range«* to to to to 180° Determinable

+91° +17o° ~91° ~160° __
Jersey 13 5 O 3 2 O
Guernsey 7 5 N 3 2 1
Ayrshire’ 6 2 1 O l 3
Brown Swiss 8 5 O . 3 1 2
Holstein in o 2 1 o 3
TOTAL H8 17 7 10 6 9

 

 

87
with but 6 per cent showing the extreme deviation of 180°. It is inter-
esting but perhaps not significant to note that no individuals were
present in a radius of 30° on either side of zero. Considering the
relatively small size of the group and the methods employed in axis
determination, conclusions concerning breed differences should.perhaps

not be drawn.

Ten animals (about 10 per cent) displayed, in the course of the
three monthly tracings, electrocardiograms of a type precluding even
an approximate axis determination. This group is best described in
the following outline:

I. Electrocardiograms showing a non-determinable axis in all
three monthly tracings.

A. Due to marked rotation of the electrical axis during

systole‘:
1. Ayrshire #163 Fig. 111A 23;
2. Ayrshire #151;
3. Brown Swiss #302;
h. Holstein #280 Fig. VuJ:
5. Holstein #261 Fig. IIfiA H};

B. Due to unfavorable, low potential, and often vibratory
type of QRS in two or more leads:

1. Guernsey #57;
2. Brown Swiss #2h5;
3. Holstein #256 Fig. IIfA NS.
II. Electrocardiograms Showing a non'determinable electrical axis
in only one of the three monthly tracings.

A. Ayrshire #lhh (123 #B 131). This tracing (Fig. IV, page
90) is unique in that QRS in leads II and III are approxi-
mately mirror images of each other. This coupled with an
unfavorable vibratory type QRS in lead I renders axis de-
termination impossible. The succeeding two monthly records

 

o f
‘ Euscussed on page 60.

88

in this animal show a definite electrical axis of
approximately +90°.

B. Brown.SWiss #306. Since this individual is especially
prone to show changes* during the actual recording of
its EKG. Figure VIII (EKG #3316) is selected for dis-
cussion.here. Paying no attention to the last half
of lead III which will be taken Up later (page 97), it
can be seen that the low potential upward summation of
QRS in all three leads makes axis determination im-
possible.

To sum up the foregoing outline, it is apparent that records of
which the electrical axis is not determinable are largely confined to
those individuals whose QRS is either of two types:

(a) Tracings showing usually vibratory QRS of low potential;

(b) Tracings showing usually di- and sometimes triphasic QRS

the algebraic sum of Whose potential is very close to zero**.

In concluding this section the periodic variations in electrical
axis shown in Table XXX will be briefly considered. Taking the first
monthly record merely as a basis for comparison, the distribution of

the maximum deviation in either direction from thissatandard in the

two succeeding electrocardiograms is as follows:

 

’ This is evidenced by comparing the third monthly tracing in K of
Figure V with the figure referred to above. Both of these illus-
trations were obtained from the same recording.

‘* These are referred to in the discussion as showing considerable
rotation of the electrical axis during systole.

 

89

Table XXVIII. Distribution of the Maximum Monthly.Axis Variation
From Those Present in the Initial Tracings.

 

 

 

Degree of

Variation - 10° 20° 30° Moo 115° 60° soo Total
Jersey 0 O 2 1 O O O 3
Guernsey 3 1 3 O l O 1 9
Ayrshire‘ 2 O l O O 1 O M
Brown Swiss 3 2 2 O O O 0 7
Holstein O 1 2 0 O O O 3__
All Breeds s 14 10 1 1 1 1 26

 

 

From these figures it is evident that the most frequently occur-
ring deviation is in the 10 to 30 degree range, where we find grouped
22 of the 26 animals showing appreciable monthly variations. It must
be remarked further that many individuals displayed monthly axis changes
which were minor enough to be undetected because of the rough methods
employed. This warrants the Opinion that more accurate and pains-
taking analyses would bring to light a greater incidence of periodic
variation than that indicated in Table XXX. Finally, when one con-
siders the unfavorable plane from Which current is lead off by the
standard Einthoven leads in cattle and superimposes upon this the
relative mobility of the bovine heart, it is extremely doubtful that
axial changes in experimental procedures requiring repeated records can
ever be safely considered as significant in this species. That part
of this conclusion Which concerns cardiac mobility is in general agree-

ment with the findings of Katz, et al., in dOgs (28).

 

* These figures are exclusive of Ayrshire #lhh whose electrical axis
could not be determined in the first monthly tracing.

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VARIATIONS IN THE BOVIKE TLECTROCA3DIOGEAM

The three monthly tracings on each animal included in this series
affords a reasonable opportunity for studying any changes in the bovine
electrocardiogram occurring during these intervals. For convenience in
comparison Table XIX (appendix), showing the occurrence of all the waves
composing a complete cardiac cycle in each of the three monthly electro-
cardiograms arranged according to breeds, etc., was devised. In order
that the table embody as much information as possible, symbols indica-
ting the more general nature of the various deflections were necessary,
and detailed study cannot be made without strict reference to the appended
key. Since even the most minor changes were recorded, any attempt at
statistical treatment of this phase of the subject could only end in
confusion. Therefore, the discussion at this point will be of a far
more general nature than.has hitherto been employed. Concerning the
table, only a few more or less sweeping generalizations will be drawn.
Monthly'dhanges in the P and T deflections are largely but not always,
associated with the variable diphasicity so characteristic of these
waves in the bovine electrocardiOgram. The nature of this change is
discussed more completely on.pages 23 and 29. In the case of P, we have
superimposed‘upon this type of variability the inconstancy of low po-
tential waves in certain subjects. Variability in the occurrence of
deflections composing the Q33 groups is due in.many cases to incon-

stant low potential Q and S waves.

Since Table XXX fails to show certain significant changes in form

of the QRS group in serial electrocardiOgrams, further elaboration of

92

the general character of these variations is necessary. For this pur-
pose Figure V is presented. This illustration contains EKG complexes
from each lead of the three monthly tracings of the eleven animals
showing the nest outstanding periodic Variations. For purposes of
convenience only those subjects showing changes not only in QES but
also P and T waves were selected. It is not to be assumed_that these
represent an average cross section of the series. Many individuals
displayed varying degrees of change in P, QRS, or T alone. In many

cases these were quite minor. A few showed practically no monthly change.

To return to a discuss on of the figure, it will be seen that
subjects A, B, C, and D illustrate changes in R Wave types characterized
by varying degrees of coarsening with or without notching of the de-
scending linm. While the complexes of each individual in general tend
to resemble each other, the Changes show no definite trend, there being
no correlation between notching one month, and coarsening of the entire,
or the terminal portion of the downstroke in succeeding or preceeding
tracings. Subjects E, F, G, H, and I show, in addition to R and Q
wave types of QRS, mainly changes in the vibratory QRS complexes so
frequently encountered in this study. The change here is almost in-
variably an increase in excursion of the descending limb of the first
spike which is often great enough to cross the isoelectric level, or
vice versa in the case of QRS showing negative summation. Subject K

is representative of changes observed in unfavorable electrocardiOgrams.

Since monthly changes in potential of Q25 are in the main not

striking, it would seem difficult to reconcile these variations with

93
simple axial rotation of the bovine heart. Very little is known about
this subject. Prior to 1935, variations in serial electrocardiograms
of animals were given little thought. At about this time Katz, et al,
(28), working with serial electrocardiograms of dogs found significant
variations referable to changes in electrical axes due to the greater
mobility of the heart in the chest.of this species as compared to the

human subj ec t .

Konthly changes in P occur more frequently in the low potential
waves, (especially lead I and to a lesser extent lead III). The prin-
cipal variation is in potential, great enough to result in complete
absence in certain subjects (A, B, E, and I of the figure). This may
happen occasionally within a lead.(subject K. lead III of the first
monthly tracing). In one subject (C, lead I) there is direct reversal
of potential. The changes in diphasic P waves showing positive or nega-
tive summation one month to monophasic in the direction of their pre-
dominance in a subsequent or previous monthly tracing, so strikingly
illustrated in Table XXX, is unfortunately not well shown in the figure.
Lead II in subject C and G, and lead III in subject H illustrate this

somewhat.

Jonthly changes in T, unlike P, are not associated largely with
low potential. Here, as with the other deflections, no definite trend
is shown and classification is impossible. The principal variation
seen is diphasic to positive or negative monophasic, and this is not
always in the direction of predominance of the diphasic wave in a

previous or subsequent tracing. These changes occur quite regularly

9%
in the electrocardiograms shown in the figure and.appear in all leads.
More or less direct reversal is seen in leads I and III of subject A
and.K, and lead II of subjects E, H, and I. Subject A is interesting
in that complete reversal occurred the third month with diphasic waves

in the second monthly tracing.

Changes Within Leads. Reserved for final discussion in this
phase of the study are the changes occurring within a lead during the
actual recording of a bovine electrocardiogram. Since intra-lead
changes in QBS phasic with respiration is not infrequent in the
human subject (29), and has also been observed in cattle (6). it is
not inconceivable that this factor may be of importance here. This
was not carefully checked in the present study and must await further

investigation.

Very slight changes in potential of QRS (0.05 to 0.1 millivolt)
occurred in a great majority of the records. Potential changes slight-
ly greater than this, especially in.the type 5 and 7 complexes of Figure
I, results in.an apparent change in.the character of QRS. This is due
to the fact that the lowering of potential is preportionally greater
in the initial spike so that an R wave with a coarsened notched.down-
stroke, for example, or an M-shaped QRS with a higher usually fine
initial deflection during one cardiac cycle may in.a succeeding cycle
be more truly in.the shape of the letter M. Varying degrees of this

form of change are most outstandingly shown in the following subjects:

Brown Swiss #303 I. III of Fig. VI (EKG 31142)
Holstein #220 I III of Fig. II A-13 (EKG Enos)
Jersey #116 L II of Fig. II A-lS (me 3328)

Holstein.#180 L II of Fig. II.A-20 (EKG 3570)

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96
Sometimes the change is from R with a coarsened notched downstroke to
a coarsened blur suggestive of letter M as in Ayrshire #162 (L II of

Figure VII, EKG BHMO).

Marked changes were sometimes encountered after movement due to
restlessness or nervousness during the EKG recording. This is most
strikingly seen in lead III of Brown Swiss #306 (Figure VIII, EKG
B316). DUring the recording of the third lead in this tracing, suffi-
cient restlessness occurred to necessitate cessation of Operations for
a moment or two. When the record.was resumed it can be seen that grave
changes in the character of the entire complex had taken place. These
are mainly an increase in potential of all waves with direct reversal
of QRS. It must be further observed that the factor of heart rate is
probably of little significance here since sufficient time was allowed
for this to return to the normal which obtained in the first half of
the lead recording» .Another subject (Guernsey #1, Figure IX) during
the recording of lead I shows a change from mainly Q predominance with
only a faint suggestion of R to a definite QR type of complex after
restlessness so slisht as to be accompanied by muscular effects only
great enough to cause a shift of the string of approximately one cm.,

and no appreciable increase in heart rate.

97

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101

SWAARY

1. ‘Three serial electrocardIOgrams approximately one month apart
were taken on eadh of 97 normal cattle composing an entire dairy herd
and representing the Jersey, Guernsey, Ayrshire, Brown SWiss, and
Holstein breeds. The grOUp was kept under modern conditions of herd
management and maintained for Optimum milk production. All ages from
five months to twelve years were included. In this manner the effect
of variations in age, period of gestation and lactation, breed differ-
ences, and individual monthly variations on the electrocardiogram could

be studied.

2. The cardiac frequencies encountered ranged from a minimum of
MS to a maximum of 98 per minute, with a mean of 71.6 for the entire
group. These values very closely approximate the normals determined

by other investigators, when all conditioning factors are considered.

3. The deflection P was invariably present in lead II. In a
few cases it was totally absent in leads I and III or when present was
of such extremely low potential that its form could not be satisfactorily
determined. The potential of determinable waves ranged from below 0.03
millivolt in all three leads to the maximum of 0.12 in lead I, 0.18
in lead II, and 0.22 in lead III. The mean values for the entire group
were 0.06, 0.10, and 0.07 millivolt in leads I, II, and III respectively.
Broadly speaking the deflection was more prone to be diphasic in leads

I and II and monOphasic in lead III, although several combinations of

102
the two types in the three leads were present. In about 90 per cent
of the cases the net area of the deflection was positive. The bal‘
ance was composed of diphasic waves with opposite excursions of about
equal size. Negative P waves occurred in only two instances in lead I

and in a single instance in lead III.

M. The deflection Q was found to occur in 60 per cent of the
instances in lead I, 80 per cent in lead II, and 70 per cent in lead
III. Its potential ranged from below 0.03 millivolt in all three leads
to maxima of 0.60, 1.00, and 0.90 millivolt in leads I, II, and III
respectively. The means for the group were 0.23 millivolt in lead
I, 0.16 in lead II, and 0.11 in lead III. 0f the Holstein group
in which Q occurred, only two individuals displayed a potential greater

than 0.12 millivolt.

5. The deflection R occurred in 78 per cent of the instances in
lead I, and 99 per cent in leads II and III. Its potential ranged from
below 0.03 millivolt in all three leads to maxima of 0.70, 2.60, and
1.50 millivolts in leads I, II, and III respectively. The mean for
the entire series was found to be 0.16 millivolt in lead I, 0.37 in

lead II, and 0.35 in lead III.

6. The deflection S was present in 23 per cent of the cases in
lead I, only 8 per cent in lead II, and 20 per cent in lead III. Po-
tentials were uniformly low, never above 0 25 millivolt in any lead.
The mean for the series was 0.06 millivolt in lead I. 0.07 in lead II,

and 0.12 in lead III.

103
7. The second upright QnS deflection was of the least frequent
occurrence, being present in 2 per cent of the instances in lead I,
h per cent in lead II, and lb per cent in lead III. Potentials were
very low, ranging from the minimum of below 0.03 to the maximum of 0.20

millivolt.

8. The deflection T was present in all individuals and in all
leads. This wave was more frequently monophasic in lead.I and diphasic
in leads II and III. However, several combinations of the two types
in the three leads were present. MonOphasic waves were largely negative
in leads I and II, and positive in lead III. Diohasic waves showed
negative sunnation in most instances. Potentials were found to range
from a minimum of below 0.03 millivolt in all three leads to the maxima
of 0.60, 1.10, and 0.90 millivolts in leads I, II, and III respectively.
The mean values were 0.20 millivolt in lead I, 0.31 in lead II, and 0.18

in lead III.

9. The duration of the P'R interval ranged from a minimum of 0.1
to a maximum of 0.3 second, with an average duration of 0.19 second.
Some slight individual monthly variations as well as variations between

the breeds were found.

10. The duration.of QES ranged from 0.06 to 0.12 second with
an average value of 0.09M second. In general the lowest values were
more common in lead I and the highest in lead III. However, the differ-
ences between leads II and III were not very great. Monthly variations

were more common in lead I.

10M

11. The Q-T interval ranged from a minimum of 0.29 to a maximum
of 0.h7 second, with an average duration of 0.389 second. This inter-
val increases in duration with a decrease in heart rate and vice versa.

For this reason great variations occurred.

12. The systolic index as determined by Bazett's formula ranged
from 0.3M to 0.h8, with an average of O.h18. Individual monthly varia-

tions of from 0.031 to 0.030 were not uncommon.

13. The electrical axis of the bovine heart ranged in 65 per cent
of the individuals from +30 to +170 degrees. The balance were large-
1y grouped in the -30 to -160 degree range. Ten animals displayed, in
one or were of the three serial electrocardiograms, records of a type

precluding even an apnroximate axis determination.

In. An attempt was made to classify the bovine electrocardiOgram
according to the following general scheme:

Group I. Tracings in which R was the largest Q38 deflection
in at least two leads.

Group II. Tracings characterized mainly by extremely uneven rota-
tion of the electrical axis during the execution of
QES, thus giving rise to various tyces of bizarre
multiphase complexes.

Group III. Tracings showing mainly diphasic Q33 complexes of
rather extreme breadth.

Group IV. Tracings showing QRS complexes with a negative net
area in at least two leads.

Group V. Miscellaneous unfavorable, low potential, or otherwise
unclassifiable electrocardiograms.

105
The major groups were further subdivided upon the basis of QRS
type and its occurrence in the several lead combinations as well as the

form of Q33 in the indifferent lead.

15. Variations in serial electrocardiOgrams as well as variations
occurring during the recording of leads were studied. The former
occurred with great frequency, but were on the Whole relatively minor.
The various deflections usually retained a rather close-resemblance
to each other in the three serial tracings of most individuals. In
general, the auricular deflection was the most constant in form from
month to month.

Variations within a lead occurred infrequently and are discussed.

Breed differences were not sufficiently great to warrant the
drawing of conclusions in view of the relatively small number com-

posing each group.

16. No marked influence of stage of gestation upon the bovine
electrocardiogram could be discerned in this study. Whether some of
the variations observed were due to this factor could not be determined.

is above observations also hold true for any possible influence

of stage of lactation.

1.

-q

10.

11.

106

LIT EFJXTQTLF‘C IT; D

?:81] er, A. Do

1889.

On the Electromctive Cha ntes Conziected with the neat of

the Mammalian.Heart and of the Humen.Heart in.Particular.

Phil. Trans. Roy. Soc. 3180. Page 169

Vial» .,er A. Do

1913. “lectrocardicgrim of Horse.
J. Physiol. 47. Pages 32~3U.
,Tu
LOTT, J.
1913. Des Elektrofiardiogremm des T‘ferdes. Seine ai-nciie und
. o /"
Zeitschr. f. B101. Ed. 01. S. 197.
Hahn, .. H.

1913.

Des Pferde-EIG.

a ~ , 1. u
separcthodruck aus dem Arcniv fur die ges.
thsiologie. Bd. 15h

Yacgel, ;, and G. Spitz.

1937.

L'electrocardiogranhie et ses Applications Cliniqnes
iec. Med. Vet. ll}. 1. Pages lh-EE.

H
Norr, J.

1921.

Elektrokardiogramstudien am Rind.
Zeit. Biol. 7}. Pages lag-ho,

Neumann-Kleinpaul, K., and.H. Steffen.

1923.

Die Kombinierte Elektrokardiogramm.Hertztonpufnahme
bei Tier und “ ensch.

Form.

Archiv furl i'issenschaftliche und Prrktische Tierheilkunde.

66 Ed. Pages l-lU.

Barnes, L. L., G. K. Devi.s, and C. M. McCay.

193s.

Dukes

1939-

In Herv ls in the Electrocardiograms of Calves Fed Cod
T1 lVPl‘ Oil 0
Corn. Vet. XXVIII. 1. Pages 16-23.

H. H.

Personal Communication.

Wilson, r. N.

1933.

Recent Progress in ElectrocardiOgraphy and the Interpre‘
tation of Borderline Electrccardiograms.
The Association of Life Insurance Medical Directors of
America, New York. Pages SO‘Fl.

Henry.
Human.Anptomy

Lea and Febiger copyright, Philadelphia.

16.

170

19.

20.

92.

23.

an.

197

Sisson, S.
1921. The Anatomy of the Domestic Animals.
W. B. Saunders conyright, Fhiladelrhia.

Bazett, H. C.
1918*20. Heart. 7. Fares 353-370.

Parfiee. H. E. B.
1933. Clinical Aspects of the Electrocardi05r9m.
Paul B. Hoeber, Inc., cooyright, New York.

Fahr, G.
1912. Heart. Iv. Fig. 11. Faye 162.

Bill th OVGH ’ W o
Quoted,by-Pardee (1h). Pages 261‘69.

Fuller, J. M.

1923. Some Physical and.PhysiOIOEical Activities of Eairy
Cows.
N. H. Agr. Expt. Station. Tech. Bul. No. 35.

31 ases of Animals. 9th. Ed.
('1
“L

138
.noted by Fuller (17). Pages 111‘13.

Melkmus, Bernard.
192h. Clinical Diagnostics.
Alexander Ejer capyright, Chicago.

Lewis, Thomas and Thomas F. Cotton.
1913. Proc. Physiol. Soc. Pages lx-lxi.
J. Physiol. H6.

Rothberger and.Winterberg. -
1910. Pfluger's Archiv. XIXV. 506.
Quoted by Lewis and Cotton (20).

Benedict. F. Go. and. E. G. RitImano
1927. The metabolism of the Fasting Steer.
Carn. Inst. Wash. Pub. 377.

Lewis, T., and M. D. D. Gilder.

1912. The Human Electrocardiogram: a Preliminary Investigation
of Young Male Adults, to Form a Basis for Pathological
Study.

Phil. Trans. Roy. Soc. 202 B. Paee 367.

Cheer, S. N., and R. C. Li.

1930. Studies on the Electrical Systole ("Q‘T" Interval) of
the Heart.
Chinese J. Physiol. M. ages 191-213.

25.

27.

29.

103

Adams, W.

1936- The Norm-'41 fixation of the Electrocardiographic Ventricu-
lar Complex.
J. Clin. Invest. 15. Pages 3353);}.

Fridericia, L. S.

1920. Die Systolendauer im Elektrokardiogramm bei normalen
Kenschen und bei Herzkranken. I eni II.
Acta Med. Scand. 1iii. age h69 et. seq.

Ifatz, S. 1.5., and S. R. Slater.
1935. Tne Second Positive Wave of the QPS Complex.
Arch. Int. Med. 55. Page 98.

Katz, L. 11., S. Soslcin, and R. Frisch.

19311-35. Variations in Contour of the Records Found in Serial
Electrocarfiioegr'ms of the Dog.
Proc. Soc. E32913. Biol. and Med. 32. Pages 208‘9.

Einthoven, 17., G. Fahr, and A. De'Iiaart.
1913. Leber die Richtung und die Ix'anifeste Grosse der Potential-

sc‘manhmgen im Menschl ichen Herzen 11nd 11"ier den Einfluss
der Herzlage auf die Form des Elektroba rdiogram'ss.
Arch. 1‘. d. Ges. Physiol. cl. 275.

APPENDIX

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Table XXIX. EKG Intervals for All Lezj Cs in Each of the 1" rue XVII-31.111 Tr:..»;:~f.v; 9;, Inc‘vi ,i “Ba-«.zett' s Cong;- tent.
J E 9 s .E Y -1-.. ___......_..--. "—
Rate (Per Min) EKG Intervals (Sec.) K(Bazett)
..4 m
88 “39 e ..8 es ei PR 935 Q‘ 8 c: 8
«4:2 (181:2 8.93 Bug gig rig +75%. wig "dis; 4-) '5 vii} 'd'fi .3 '5' rd 5) 'd 5:3 7"" :1:
YrfigfthMO. F2! :1; :1 :1 2:8 (61:0: .5135; '2 .8 (5:1 :31 5:5 3 :6; : 78: PS: :31 E g a
I 91 100 59 0.19 0.16 0.16 0.09 0.09 0.09 0.32 0.32 0.90 79;; o
62 - 8 II 89 99 60 0.19 0.19 0.16 0.10 0.08 0.08 0.39 0.32 0.90 27:13.
III 89 99 65 0.19 0.19 0.16 0.08 0.08 0.08 0.32 0.32 0.90 O 0 $1....
I 65 103 72 0.16 NM 0.16 0.09 0.05 0.05 0.90 0.32 0.90 1;: 5}: 2.5
90 - 11 II 68 100 77 0.15 0.19 0.19 0.06 0.06 0.07 0.92 0.30 0.36 27.19.21.
III 72 100 99 0.19 0.13 0.12 0.08 0.07 0.07 0.90 0.32 0.36 0 0 0
I 75 58 63 0.16 NM 0.18 0.06 NM 0.07 0.37 NM - I \o o m
80 1 3 II 70 60 63 0.17 0.17 0.18 0.07 0.07 0.07 0.90 0.93 0.92 EDS-‘3‘
III 68 58 60 0.18 0.18 0.18 0.08 0.08 0.08 0.93 0.99 0.99 c; c‘. o'
I 72 63 65 0.18 NM 0.18 0.08 NM 0.06 0.36 0.38 0.38 {3; :3 g
89 1 9 II 72 63 63 0.17 0.18 0.17 0.08 0.08 0.08 0.38 0.90 0.90 .21-57...;
_ __ III 72 63 63 0.17 0.18 0.18 0.09 0.09 0.08 0.38 0.90 0.38 0 O 0
I 60 56 73 0.20 0.18 0.18 0.07 0.05 0.07 0.90 0.99 0.38 a 61%
88 1 6 II 65 59 68 0.18 0.18 0.18 0.08 0.08 0.09 0.90 0.99 0.90 3.7.2;
III 58 58 68 0.18 0.17 0.17 0.09 0.09 0.09 0.93 0.93 0.90 O O O
I 60 50 60 0.16 0.16 0.16 0.07 0.07 NM 0.90 0.99 0.90 8 8 g
85 1 7 II 57 98 58 0.15 0.16 0.16 0.10 0.09 0.08 0.38 0.99 0.90 2,2,9.
III 56 98 60 0.16 0.16 0.16 0.08 0.08 0.08 0.90 0.99 0.92 o o o
I 73 59 59 NM 0.18 0.19 0.07 0.06 0.06 0. 6 0.90 0.92 333
86 1 7 II 72 98 60 0.17 0.18 0.18 0.08 0.07 0.08 0. .0 0.99 0.99 .213,
III 72 50 58 0.16 0.17 0.17 0.08 0.08 0.08 0.90 0.99 0.99 o o o
I 75 68 79 0.16 NM 0.16 0.05 NM 0.06 0.90 NM 0.36 8:515}:
87 1 7 II 68 2. 9 0.16 0.16 0.15 0.08 0.08 0.08 0.38 0.90 0.39 3.272%
III 68 75 79 0.15 0.19 0.19 0.09 0.9 0.09 0.90 0.90 0.56 O O O
I 79 88 88 0.16 0.16 0.16 0.06 0.06 0.06 0.36 0.39 0.36 5mg}
73 1 9 II 79 9 89 0.17 0.16 0.16 0.09 0.09 0.09 0.37 0.36 0.36 :1,th
III 72 79 88 0.17 0.17 0.16 0.09 0.09 0.09 0.36 NM 0.36 o o o
I 75 65 65 0.10 0.10 0.10 0.08 0.08 0.10 NM NM 0.99 3; 15%.:
89 1 10 II 77 65 70 0.08 0.08 0.08 0.10 0.11 0.11 0.92 0.99 0.99 516121
111 77 65 75 0.08 0.08 0.08 0.10 0.10 0.10 0.90 0.90 0.92 0 0 O
I 63 75 68 NM NM 0.17 0.09 0.09 0.05 0.90 0.38 0.90 em m
79 2 1 II 63 75 68 0.18 0.17 0.18 0.10 0.10 0.10 0.95 0.92 0.99 :51:
III 63 15 68 0.16 0.16 0.16 0.10 0.10 0.10 0.99 0.92 0.90 o‘ c5 (3
I 59 79 72 0.18 0.18 0.18 0.06 NM NM 0.99 0.36 0.92 8 1.993
116 3 5 II 60 75 68 0.17 0.16 0.17 0.10 0.10 0.10 0.96 0.38 0.99 .::r..:r.:l
__I_II 63 75 67 0.17 0.16 0.17 0.10 0.10 0.10 0.99 NM 0.96 o o o
I 60 68 75 0.21 0.20 0.20 0.08 0.08 0.08 0.92 0.90 0.36 3:51:33.
117 3 6 II 58 72 72 0.20 0.18 0.18 0.09 0.08 0.08 0.91. 0.90 0.90 51:53:51.
III 58 68 79 0.20 0.18 0.17 0.09 0.09_ 0.09 0.90 0.38 0.36 O O O
I 96 98 98 0.22 0.21 0.22 0.06 0.06 0.06 NM NM 0.95 oxmo
119 3 7 II 97 51 0 0.22 0.20 0.20 0.10 0.10 0.10 0.99 0.96 0.96 mg:
III 97 50 8 0.20 0.20 0.20 0.10 0.10 0.09 0.95 0.98 0.98 o‘ o’ o’
I 59 72 68 0.22 0.20 0.22 0.06 0.07 0.07 0.93 0.38 0.90 8‘03
115 3 7 II 59 72 68 0.2 0.20 0.20 0.10 0.10 0.10 0.93 0.90 0.90 9333-1,
III 56 52 655 0.22 0.20 0.22 0.10 0.09 0.10 0.90 0.38 0.90 O o O
I 56 70 72 0.22 0.21 0.20 0.08 0.06 0.06 0.9 0.90 0.90 ““57 N
118 3 11 II 59 77 63 0.22 0.20 0.21 0.10 0.10 0.09 0. 0.90 0.92 ”.27.”.
III 52 77 65 0.22 0.20 0.20 0.10 0.10 0.10 0.99 0.90 0.90 0 O O
I 60 70 72 0.16 0.17 0.16 0.06 0.06 0.08 0.38 0.36 0.37 o m
111 9 1 II 60 68 68 0.17 0.17 0.17 0.11 0.10 0.10 0.90 0.38 0.38 2.9%:
III 60 68 72 0.17 0.18 0.17 0.10 0.10 0.09 0.90 0.90 0.38 o' c; o'
I 60 62 97 NM NM NM 0.08 0.08 0.08 0.99 0.98 0.99 w 39,
108 9 10 II 52 67 9 0.21 0.19 .21 0.08 0.08 0.09 0.97 0.98 0.50 «3.4:,
III 52 60 8 0.20 0.20 0.21 0.09 0.08 0.08___ 0.50 0.96 0550 O O O
I 56 58 55 0.22 0.22 NM 0.10 0.08 0.10 0.99 0.92 NM 10mm
101 5 7 II 59 56 56 0.22 0.21 0.22 0.08 0.08 0.08 0.99 0.99 0.98 273'};
III 50 57 59 0.22 0.20 0.20 0.09 0.09 0.99 0.99 0.99 0.98 2; c5 5
I 62 73 70 0.20 0.20 0.20 0.06 0.09 0.08 0.91 NM 0.90 M»...
100 5 8 II 63 72 70 0.20 0.18 0.20 0.08 0.09 0.09 0.99 0.90 0.90 § EFL—“P
III 63 73 72 0.19 0.16 0.20 0.10 0.10 0.10 0.91 0.38 0.90 0' o‘ o’
I 63 58 65 NM NM 0.20 0.08 0.08 0.08 0.90 0,173 0.38 g; g
95 5 10 II 62 58 69 0.20 0.21 0.20 0.09 0.10 0.09 0.90 0.90 0.90 '7. "’35":
III 62 60 61 0.19 0.20 0.20 0.09 0.09 0.08 0.90 0.92 0.90 O O O
I 63 61 60 NM NM 0.20 NM NM 0.08 NM NM 0.99 m um
97 8 9 II 63 59 63 0.20 0.20 0.20 0.10 0.10 0.10 0.92 0.99 0.92 .3993
III 60 63 61 0.17 0.17 0.17 0.12 0.10 0.10 0.99 MM 0.92 o’ c’ o’
I 72 65 68 0.21 0. -9 0.29 0.05 0.08 0.08 0.36 0.92 0.90 m w .2.
63 12 2 II 72 65 68 0.21 0.29 0.23 0.12 0.12 0.12 0.37 0.92 0.90 9351;.“
III 72 65m 68 0.20 0.25 0.23 0.06 0.06 0.06 NM 0.99 0.99 2.; 0' O-

 

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Table XXIX. Continued.
0 U 7873?; Y ' 77mm WW.- I ,-
Rate (Per Mi - .-
H 0 Age D7 EKG Intervaig £580 ) """‘""‘77'~7~~--«->——--- -7-
fig, ”St “dc; Mg «:55 9123‘ PR Q35 ' 212572226517“
a) $2: $3 ’
i H .95 7:0 “-3 fig 7.2% 8%: '69 +753 5.9 es «8 Q7332 £355
' 0’ Hg («fig .355 fig (64$: Lt: 12“; "9.4; «85‘. 2.23:7:
6 I 100 82 82 M7 7' 7“" =5" >3 "$9: '7' 9 N .5. 5: ‘5 7.2 '0 '8
- 10 I; 100 79 86 0114 0.16 MM 0.08 0.08 0 08 r " ' - ,5: .9. 85 m.
In 944 77 86 0' I 04.16 0.16 0.08 0.08 0'65 X'Eg 0'33 3'32 SEER
I 109 89 . '15 NM 071 6 0.09 0.09 0.00 5' 2: 9’3? 9' 32 "? "T "2“
g _ 10 n 104 82 400 0.16 0.16 NM 0.09 0- n; 57,} '7’ J 1.31 0.30 o o 0
II 0 0.19 0.15 0.19 r n ”"7 777“ 0°28 0-32 0.28 ,
I 100 79 9 0 1,4 J...8 0.08 0,713; r) «,1 27 mm M,
I 72 100 1 ' . 0’15 0'16 0.08 0.08 0.58 0.21 93; 1330 SE? 1:.
3 7' 11 II 70 86 23 0'15 0'1” M 0.10 0 08 0 08 A"? 0'1” 1'30 O O ‘5
III 72 89 89 8'12? 871: 31% 0.08 0:09 0.66 013% 21 0'3: $819765
I o ' 7 - , M 0.08 0.0 , " “'U’ 9'3 "377.5.
1 1 1 . II '87? 51: 91$ 0-15 0.16 0.19 0.06 O 0% 33% 9-3? 0.36 0.37 o o C)
III 89 100 7 0'15 9'16 0.19 0.08 0.08 p.61 0'34 0.311 W (3 o If
I 11'; 100 7E 0'15 0.16 0.19 o no (3.80 ”1.63 8-3“ 0.32 0.36 Sig) f“)
/ 0v 0~./ 0..) u. .1: . .3 . 7.,
III 125 88 88 0'1 ‘ 0‘15 ”'17 ’3-09 6.10 0.0Z "7'28 ""32 9'3” 19‘9“)
III 68 55 60 9.17 8-9: 2.16 3.08 0.08 0108 0'35 0}“ 2. W 93405 :9
60 I 88 79 75 0 18 ’ , #16 0.10 0.10 0.10 0,115 5‘55 {€738 :75; E9
1 5 H 100 70 TR . 0.16 0.20 0.06 0 55 0 0,, 7' '38 o o 0‘
III 91 79 73 8'12 0.16 0.20 0.08 0:08 0'6." 2'33 0'3” NM '66 8? 0“
I O7 75 88 .1 m 0‘20 0.08 0.00 008 0/6 0.31; 0.39 M MR
J a J .1; . 1.1. 9 o .
59 1 7 II 88 75 91 812 3'? 0’18 0'05 0.07 0.06 0 39 3'3 0'38 O O O ’
I” 33 75 91 0'17 0' 2 0‘16 0‘09 0-09 0.08 0.36 0'4‘ 0'32 73"“:
c: I 75 65 60 n. '1’ 1“" W38 0.08 0 08 0.737 0'4: 0'32 5;; 8"
- do __.- 'J .4) . .7, 9 I o
.5 1 11 III 68 72 58 0 42 011197 071116 0.06 0.06 0.06 0 36 0 32 2 J: O O 0
II . 1 . ' " J 0.08 O. r~ . ’7’ ’ " a
.72 58 0.17 0.16 0.20 0 05 n 06 1'95 0310 0.90 0.99 90 R61,
146 I 61 63 514 O 20 o v.08 J-OY C’.h—O 0.36 0 MO N.\,j;,:j;
2 8 Iii 21 63 63 0‘93 FM.) )NEA 0.09 0,10 (4‘).er 3 ‘71, A 11‘ P) 4 f O O O
"7 2...‘ . :- "fl I -. ,7. 271"“ '. " ' .41) 150 m
. , .21 4: 56: 5’: 0.18 0.18 0.19 0.10 0:} 3 .3 ,4‘ 73-27. :73?
f 0-.., \‘-"*f‘ A. .1 01:1 f“. "I": . .
5° 2 9 II .60 60 29 0'21 0'2" 0.29 0.08 5,58 0 0' , ‘ L '7“ 05331
III 50 5,, 55 gcie 0.21 0.23 0.09 0.00 0'52 37,42 @340 0.91 8 8 In
I 9 5 .-2 0°22 0'22 O~09 0.09 010 6'9; 0'92 0.99 '1 91';
v a. ' O o
1‘3 3 '7 II 3 53 23 8'3; NM 0.28 0.08 0.08 0 08 ,. , 0', 2 0.92 O O 0
III 113 .30 48 0'3: 0.28 0.2 0.10 0,10 0'10 34:? 0.99 0.92 m ... ...,
9 I 65 75 o 0..., 0'21; 0'2“ 0.10 0.10 0.11 0'99 0:: 0.99 R33
. J .9 o . . ' 4 . 4 \ 3 O o
7 3 1 II 55 75 75 0 ~2 0.21 NM 0.10 0,07 0 08 ’3 J 0.99 o o 0
III 58 75 75 0'50 0.21 0.20 0.09 0,58 0‘59 0'33 0.37 0.38 53::
99 I 75 79 72 0.1: W 0'20 0‘10" “-10 O'io 3'90 3%: 0'98 3,31%
3 10 II 75 ° 0-17 0 18 0 ' 7 - 0. 0 ~ - .
82 72 0. 7 ~08 0.08 0.02 O O 0
III 75 89 75 0.12 8.126 8.156 3'72 0.08 0.07 892 9'22; g'fig 5‘ “.372
I 68 68 68 ' o o 2 0.12 0.12 0,140 V.) . 4&2;
91 9 - II 68 68 79 0}ng 0.20 0.20 0.11 0.08 0 09 0 1, 0'38 0.90 O O O
In 65 68 72 0.90 0.19 0.18 0.10 0,09 0‘00 0'42 0.92 0.38 MN,
1,2 ,4 I 56 53 60 m; N“ 0.18 0.12 0.09 0210 01712, g’fifi 0.434 iii“?
I 5 72 52 0.16 W 0 18 0.10 gxlag 0.08 0.96 0 92 0 99 5972??
0 . . O. ' o . . .
37 9 7 II 3,? 28 52 0.22 0.22 0.22 0.08 0 08 10 0.96 0.92 0.99 o o o
I 79 65 75 O '4 NM NM 0.09 0.10 0.10 0:92 g'fifi 0.92 547.3,»?
30 5 11 II 79 63 70 O.-2 0.22 0.29 0.05 o 0,, 0 0 . 0.99 o o O
In 75 58 65 0.3; 3.52 0.29 0.12 0:10 0'1?) 3'3: ONE 0.37 6’ ”‘0
Ofi .,__ 0.22 O 1 9 o . 2 O 38 JMH
I 817 7 68 - 0 0.10 O 10 - gr: ,3-
23 6 10 0-20 NM ' 0'33 0.99 o 170 ° 0 ~
' II 7 8 0.20 0.06 0.0 ' O O O
In 735 75 g; 8.228 0.19 0.20 0.09 0,026, 8'83 0.36 0.90 0.99 33 8m
25 5 11 II 68 72 6151 0'23 0'2“ 0.29 0.10 0.06 0 09 w 0'36 0'10 O O C
III 72 72 63 0.23 0'22 0’22 0-10 0.12 0.08 0'98 0'38 O'L'O mm 00
4 I 79 79 66 . 0.22 0.20 0.12 0 12 0-12 8.93 0.940 0.92 5—7 1:99;
1 8 2 0.21 o 22 ' ° ' ' 0. O 0 9 7 V“
II ' 032 0.10 v 2 O O 0
III 7’: $1; 52 8.22 0.21 0.29 0.12 3:5 8%; 0.90 0.99 0.96 5;,
7 11 6 I 65 77 68 0.513 8.30 0.29 0'13 0.08 0.08 8.9121 8.191: OAS 3’6 (“1g
II 6 "’ 0 2 00211 0'08 0'08 ' I . 0.14.8 (50. o
In 7(5) 7]; 6‘: 0.22 0.22 0.29 0.10 0 10 0.08 0.37 0.36 0,38 5, 0
NM 0 20 o 9 ' 0'10 0.38 .0 r mB‘K'I
' 02 0.09 O 0Q .030 O'MO M
' , 0‘39 0.36 0 6 55:5
'3 0.)“) O O O

 

 

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Table XXIX. Continued.
A Y P. s H I 2 E

..ate (Per Min) MWEKGA fiferxrais (Sec.) 4:44.“:“4‘ K(%.zett)
H Age PR ‘2---...--.--........_-...- RI... -......... 7 0' .3
E6 (lst rd. .pfi .dfi <25 ,2; '2; Pg 4:: .2: .c: 4.: .5: .a 53:55

2 coo (as: :2 Ac: +942 76+: 87.7542 up 8:34.: 86+) +34: d-P 'U-P .

8 “—2.188“ 88 88 51882 :28 88 :28 .28 88 .88 .88 88 88 75.878
Yrs. Mo. ”:5“ :2- 2): :9 >1 17:28." "‘33. _ H M
I 97 72 89 0.18 0.16 0.17 0.08 0.08 0.08 0.29 0.32 0.32 5577358
163 - 8 II 99 68 97 0.16 0.16 0.16 0.07 0.07 0.06 0.32 0.32 0.32 my;
III 88 69 82 0.16 0.16 0.18 0.2.9 0.09 0.08 0.32 0.39 0.33 O O O
I 99 99 99 0. 20 NM NM 0.09 N _ NM 0. 29 :72. 0. 28 {3 3,83
162 - 9 II 107 99 97 0.18 1.: NM 0.06 0.06 0.06 0.32 0.28 0.28 8383 83
III 100 91 97 0.16 NM NM -_ 0.08 0.08 0.08 0.30 0.30 0.30 O o o
I 99 91 107 0.16 0.16 NM 0.06 0.06 0.06 0.39 0.32 0.32 mo».
161 1 1 II 89 99 107 0.17 NM NM 0.08 0.08 0.08 0.30 0.28 0.26 k951i.

III 89 91 107 NM 18 0.08 0.08 0'99; 0.35 0.540” 0.32 0’ 0‘5 _
I 89 63 89 . NM 0.20 0.19 0.09 0.08 0.09 0.39 0.36 NM N .9 ,_,
160 1 8 II 72 6 75 0.22 0.2 0.2 0.0 0.08 0.08 0.38 0.36 0.32 949qu
III 75 6 9 2 _ 0:19 0.20 0.147 0.10 0.08 0.08 0.38 0.90 0.28 O. 0' C;
Y .I 72 65 60 NM 0.20 1.7 0.07 0.08 0.06 0.90 0.38 0.90 BEER
159 1 8 II 52 65 ‘58 0.20 0.20 0.22 0.09 0.07 0.08 0.90 0.90 0.90 9727,9127,
III 60 58 58 0.20 NM 0.23 0.07 0.08 0.08 0.90 0.90 0.92 o o o
I 89 89 86 0.20 0.17 0.18 0.08 0.0 0.08 0.87 0.37 0.36 4.134qu
156 2 2 II 89 88 86 0.23 0.16 0.18 0.08 0.08 0.08 0.90 0.37 0.38 22,-8.9.
III 89 86 89 0.20 0.18 0.18 0.09 0.09 0.10 0.38 0.39 0.36 o o o
I 89 72 68 0.22 NM 0.29 0.06 0.09 0.09 0.36 0.90 0.38 .1833
153 2 5 II 79 68 68 0.22 0.22 0.22 0.08 0.08 0.08 0.38 0.90 0.90 22:21:.
III 75 65 68 NM 0.2 0.29 0.10 0.10 0.10 0.38 0.92 0.90 o o o
I 65 ' 58 65 0.22 NM 0.20 0.08 0.10 0.09 0.90 0.99 0.92 00 .90»
152 2 7 II 63 58 65 0.22 0.29 (7.20 0.08 0.08 0.08 0.90 0.‘ 2 0.90 35-33
III 65 58 63 0.29 0.20 0.20 0.09 0.10 0.10 0.99 0.99 0.99 6 o“ o'
I 68 69 68 0.22 0.22 0.22 0.07 0.07 0.08 0.38 0.90 0.90 mmxo
151 2 8 II 68 68 68 0.21 0.18 0.19 0.08 0.07 0.08 0.90 0.90 0.90 3’33“
III 68' 68 65 0.20 0.20 0.20 0.09 0.09 0.09 0.90 0.90 0.92 cto‘c‘;
I 91 72 58 0.18 NM 0.20 0.07 0.05 0.08 0.39 0.90 0.91 79,208?
150 2 11 II 75 68 58 0.16 0.20 0.18 0.10 0.10 0.10 0.38 0.90 0.99 "Tit”;
III 72 68 60 0.18 0.22 0.20 0.10 0.11 0.10 0.90 0.92 0.99 O O O
I 72 65 60 NM 0.29 0.29 0.07 0.05 0.05 0.92 0.92 0.92 :8 f): :3;
196 3 9 II 68 63 63 0.22 0.29 0.22 0.08 0.08 0.08 0.90 0.90 0.92 88:87.8.
III 68 68 58 0.29 0.20 0.22 0.08 0.08 0.08 0.90 0.90 0.91 0 O O
I 79 72 56 0.20 0.20 0.29 0.08 0.08 0.08 0.90 0.91 0.99 849425;;
199 3 6 II 79 65 58 0.20 0.21 0.23 0.11 0.12 0.11 0.38 0.90 0.99 8,-2.2;
III- 77 63 59 0.20 0.20 0.29 0.10 0.11 0.10 NM 0.92 0.96 o o o
I 115 90 814‘ 0'20 0.220 0020 0008 0.08 0.08 0028 0'32 0.36 I-T KO N\
191 9 9 II 125 90 79 0.18 0.17 0.20 0.08 0.09 0.08 0.28 0.33 0.36 235*
III 115 88 72 0.16 NM 0.20 0.09 MM 0.09 NM NM 0.38 c? o‘ o’

 

 

 

 

 

 

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