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DETERMINANTS ON THE USE OF ANGIOGRAPHY AND REVASCULARI'
ZATION PROCEDURES AFTER ACUTE MYOCARDIAL INFARCTION
(AMI) IN COMMUNITY HOSPITALS

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Qin Chen

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6/01 c:/CIRCJDateDue.p65-p. 15

DETERMINANTS ON THE USE OF ANGIOGRAPHY AND
REVASCULARIZATION PROCEDURES AFTER ACUTE
MYOCARDIAL INFARCTION (AMI)

IN COMMUNITY HOSPITALS
By

Qin CHEN

A THESIS
Submitted to
Michigan State University
In partial fulfillment of the requirements

For the degree of

MASTER OF SCIENCE
Department of Epidemiology
College of Human Medicine

2000

ABSTRACT

DETERMINANTS ON THE USE OF ANGIOGRAPHY AND
REVASCULARIZATION PROCEDURES AFTER ACUTE MYOCARDIAL
INFARCTION (AMI) IN COMMUNITY HOSPITALS
By

Qin CHEN

The rates of angiography and revascularization use have increased dramatically in the
US in patients with acute myocardial infarction (AMI) over recent years. Observational
studies have shown strong associations between demographic and some clinical
characteristics and the use of coronary procedure. MICH study was a hospital-based
study of the hospital care for AMI patients in five community hospitals in Michigan.
This study is to analysis the differences in demographic and clinical characteristics
among the 846 AMI patients. We found that increased age, female gender, no insurance
were associated with less use of angiography after adjusting for other factors. Except for
recurrent angina, patients developing complications of AMI such as cardiac arrest,
cardiogenic shock and patients with prior CV D-related history such as prior AMI, prior
CHF or prior cardiac arrest were less likely to have angiography. In contrast, we found
that once the angiography was done, the severity of coronary disease was the strongest
predictor of type of revascularization use. Patients with complications of AMI were
more likely to have CABG. However, blacks were less likely to have both PTCA and

CABG after adjusting for other factors.

ACKNOWLEDGEMENTS

This thesis, as well as a clear understanding of epidemiologic concepts, would not
have been accomplished without the time and effort put forth by Professor Mathew J.
Reeves. His insight and assistance have been invaluable throughout the process and I
thank him for his support and patience.

I also wish to greatly thank Dr. Daniel Murman, who have been invaluable in
giving generously of his time to read the whole manuscript even while he was very
busy running his clinics service. His encouragements and invaluable suggestions

helped me get the job done.

iii

TABLE OF CONTENTS

LIST OF TABLES ........................................................................................................ vi
LIST OF FIGURES ..................................................................................................... viii
LIST OF SYMBOLS OR ABBREVIATIONS ............................................................. ix
Chapter 1 ........................................................................................................................ 1
BACKGROUND ............................................................................................................ 1
1.1 Overall burden and costs of Coronary Heart Disease (CHD) .............................. 1
1.2 Mortality trends of CHD and relative contributions of prevention and treatment2
1.3 Standard therapeutic regimes for patients with AMI ........................................... 3
1.4 Utilization of coronary an gio graphy and revascularization ................................. 5
1.5 Variation in procedure use in patients with AMI and related outcomes .............. 6
Geographic variation of coronary procedure use in AMI patients ......................... 6
Gender variation of coronary procedure use in AMI patients ................................ 9
Race variation of procedure use in AMI patients ................................................... 9

1.6 Coronary procedures use and AMI outcome ...................................................... 11
Adjunctive angioplasty following thrombolysis .................................................. 12
Adjunctive angioplasty in specific subgroup AMI patients ................................. 14
Surgical reperfusion .............................................................................................. 18

1.7 Guidelines for coronary procedures use in AMI patients ................................... 18
1.8 Summary ............................................................................................................. 19
1.9 Thesis rationale ................................................................................................... 20
Thesis objectives .................................................................................................. 20
Specific questions ................................................................................................. 20
Chapter 2 ...................................................................................................................... 21
METHODS ................................................................................................................... 21
2.1 MICH Study ....................................................................................................... 21
Purpose ................................................................................................................. 21
Geographic setting ................................................................................................ 22
Methodology ......................................................................................................... 22

2.2 Thesis study ........................................................................................................ 25
Study population ................................................................................................... 25
Definition of variables .......................................................................................... 26

iv

Endpoints .............................................................................................................. 27

Statistical analysis ................................................................................................ 27
Chapter 3 ...................................................................................................................... 29
RESULTS ..................................................................................................................... 29

3.1 Demographics and clinical characteristics in total population ........................... 29
3.2 Clinical characteristics and complications of AMI ............................................ 30
3.3 Coronary procedures use during hospitalization ................................................ 30
3.4 Determinants of coronary angiography .............................................................. 31
3.5 Determinants of revascularization ...................................................................... 34

Univariate Analysis .............................................................................................. 34

Multiple polychotomous logistic analysis ............................................................ 36
Chapter 4 ...................................................................................................................... 38
DISCUSSION ............................................................................................................... 38

4.1 Angiography and revascularization rates in hospitalized AMI patients ............. 38
4.2 Demographics and an giography and revasularization procedures use ............... 39
Race, gender and cardiac procedure use ............................................................... 39

4.3 Clinical characteristics and cardiac procedure use ............................................. 42
Coronary angiography use .................................................................................... 42
Revascularization use ........................................................................................... 43

4.4 Study limitations ................................................................................................. 45
APPENDIX A .............................................................................................................. 47
APPENDIX B ............................................................................................................... 66
APPENDIX C ............................................................................................................... 75
APPENDIX D .............................................................................................................. 77

REFERENCES ............................................................................................................. 84

LIST OF TABLES

Table 1 Classification Recommended by ACC/AHA for Indications for a Diagnostic

Procedure, a Particular Therapy, or an Intervention in Patients with AMI ........... 48
Table 2 Baseline Characteristics and Prior CVD-Related Histories Among the Total

Population .............................................................................................................. 49
Table 3 Clinical Characteristics of AMI Among the Total Population ........................ 50

Table 4 Univariate Associations of Baseline Characteristic and the Likelihood of
Undergoing Coronary Angiography ...................................................................... 51

Table 5 Univariate Associations Between Prior CVD-Related Histories, Coronary
procedures and Cardiac Risk Factors and the Likelihood of Undergoing Coronary
Angiography .......................................................................................................... 52

Table 6 Univariate Associations Between Infarction Characteristics and the Likelihood
of Undergoing Coronary Angiography .................................................................. 53

Table 7 Model Selection for Coronary Angiography among 836 patients: Hierarchical
Backward Elimination Approach ........................................................................... 54

Table 8 Final Multiple Logistic Regression Model Relating Demographic and Clinical
Characteristics to the Likelihood of Receiving Coronary Angiography in 836*
Patients Hospitalized With AMI ............................................................................ 55

Table 9 Final Multiple Logistic Regression Model Relating Demographic and Clinical
Characteristics to the Likelihood of Receiving Coronary Angiography in 836 +
Patients Hospitalized With AMI (Cont’d) ............................................................. 56

Table 10 Univariate Polychotomous Logistic Model Estimating the Associations of
Demographic Characteristics and Initial Type of Cardiac Revasularization
Procedure Received During Hospitalization, Among 619 Patients with AMI Who
Received Coronary angiography ........................................................................... 57

Table 11 Univariate Polychotomous Logistic Models Estimating the Associations of
Prior Medical History and Initial Type of Cardiac Revascularization Procedure
Received During Hospitalization, Among 619 Patients with AMI Who Received
Coronary angiography ........................................................................................... 59

vi

Table 12 Univarite Polychotomous Logistic Models Estimating the Associations of
Infarction Characteristics and Initial Type of Cardiac Revascularization Procedure
Received During Hospitalization, Among 619 Patients with AMI Who Received
Coronary angiography ........................................................................................... 61

Table 13 Number of Diseased Coronary for Patients Who Underwent Angiography
(N=619) by Revascularization Procedures ............................................................ 63

Table 14 Multiple Polychotomous Logistic Regression Model Estimating the
Association between Predictors and Type of Cardiac Revasularization Procedure
Received During Hospitalization compared to Medical Therapy, Among 591+
AMI Patients Who Received Coronary Angiography ........................................... 64

vii

LIST OF FIGURES

Figure 1 Estimate Direct And Indirect Costs of Cardiovascular Diseases and Stroke,
United State 2000 ................................................................................................... 67

Figure 2 Age-Adjusted Death Rates for Disease of Heart by Race And Sex, 1960-9168

Figure 3 Flow of AMI Patients Undergoing Coronary Procedures .............................. 69
Figure 4 Diagnostic Coronary Angiography (CA) United States: 1979—97 ................ 70
Figure 5 Percutaneous Transluminal Coronary Angioplasty Procedures (PTCA)
United States: 1986—97 .......................................................................................... 71
Figure 6 Coronary Artery Bypass Graft Procedures and Patients United States: 1979—
97 ........................................................................................................................... 72
Figure 7 Outline of Study Samples Used for Each Analysis ........................................ 73

Figure 8 Coronary Anatomy Characteristics for Patients Who Underwent Coronary
Angiography (N=619)..... ........................................................................................ 74

viii

ACC/AHA
AMI
ARIC

CA

CABG
CHD

CHF

CVD

GUSTO

IAB
LAD
LCX
LVEF

PTCA

SAVE
SWIFT
TIIWI
TPA

TT

LIST OF SYMBOLS OR ABBREVIATIONS

American College Of Cardiology/American Heart Association
Acute Myocardial Infarction

Atherosclerosis Risk In Communities

Coronary Angiography

Coronary Artery Bypass Graft

Coronary Heart Disease

Congestive Heart Failure

Cardiovascular Disease

Global Utilization Of Streptokinase And Tissue Plasminogen Activator For
Occluded Coronary Arteries

Intraaortic Balloon Counterpulsation

Left Anterior Descending Coronary Artery

Left Circumflex Coronary Artery

Left Ventricular Ejection Fraction

Percutaneous Transluminal Coronary Angioplasty

Right Coronary Artery

The Survival And Ventricular Enlargement Study

Should We Intervene Following Thrombolysis Study

'1‘ hrombolysis In Myocardial Infarction Study

Recombinant Tissue-Type Plasminogen Activator

Thrombolysis Therapy

ix

Chapter 1

BACKGROUND

1.1 Overall burden and costs of Coronary Heart Disease (CHD)

Despite the decline of cardiovascular disease (CVD) mortality rate in the past 40
years, CVD remains the leading cause of death in the United States. Around 50% of
CVD deaths are due to coronary heart disease (CHD). According to 1997 estimates,
CHD claimed 466,101 deaths (50.9% were men). Age—adjusted CHD death rates (using

the year 2000 age standard) were 236.3 for white males and 223.9 for black males, and

139.7 for white females and 160.1 for black females per100,000 populationl. Among
American adults age 20 and older, the estimated age-adjusted (2000 standard)
prevalence of CHD was 6.9% for non-Hispanic white males and 5.4% for females;
whereas for non~HiSpanic black males it was 7.1% for males and 9.0% for females; and
for Mexican-American males and females, it was 7.2% and 6.8%, respectively. It is

estimated that 7.2 million Americans, aged 20 and older have a history of myocardial

infarction (MI) (61.1% of whom are men)1. Based on data collected, the incidence rate
of new and recurrent MI in non-black men aged 65-74 was 26.3 per 1,000 population,
39.7 for aged 75-84, and 53.6 for aged 85 and older per 1,000. For non-black women in
the same age groups, the rates were 7.8, 21.0 and 24.2, respectively. For black men, the

rates were 16.3, 54.9 and 40.8, and for black women, the rates were 13.3, 18.3 and 14.1,

respectively1 .

Because CHD may strike an individual during the most productive years, it can
have profound deleterious psychosocial and economic ramifications. Besides causing
death, CHD is the leading cause of premature, permanent disability in the US. labor

force, accounting for 19% of disability allowances by the social security

Administrationl. The estimated cost of CHD in the United States in 2000 was estimated
at $118.2 billion, while the cost of CVD was much higher -- $ 328.8 billion. This figure
includes health expenditures (direct costs, which include the cost of physicians and
other professionals, hospital and nursing home services, the cost of medications, home
health and other medical durable) and lost productivity resulting from morbidity and
mortality (indirect costs). It was said as much as half of this cost is related to acute

myocardial infarction (AMI) and its prevention and treatment (Figure 1).

1.2 Mortality trends of CHD and relative contributions of prevention and
treatment

A steady decline in the age-adjusted death rates from AMI and CHD have been

observed across several population groupsz'8 Since 19605. Figure 2 shows the decline
in mortality of heart disease in the US since the 1960. Reasons for the declines in CHD
may vary by period and across regions or socioeconomic groups. Prevention efforts and

improvement in early detection, treatment, and care have resulted in a number of
beneficial outcomes4.

Studies suggested that primary prevention accounted for a greater proportion of
the decline in CHD in the late 19605 and 197059. Goldman10 reviewed the literature

regarding the effect of various potential explanations for the reduction in coronary

mortality between 1968 and 1976. He found that 60% of the decline was related to

changes in lifestyle, specifically to reductions in serum cholesterol level and cigarette
smoking. In comparison, about 40% of the decline was directly attribution to specific
medical interventions, with Coronary Care Unit and the medical treatment of clinical
ischemic heart disease and hypertension. However, improvement in the treatment of
patients with CHD was thought to be the major factor in this decline in late 805.

According to a recent study looking at mortality data in the United States in the period

1980 to 1990, Hunink11 found that the actual coronary heart disease mortality in 1990
was 34% lower than would be predicted if risk factor levels, case—fatality rates, and
event rates in those with and without coronary disease remained the same as in 1980.
One quarter of the decline was explained by primary prevention, 29% was explained by
secondary prevention reduction in risk factors in patients with coronary disease, while
43% of the decline was explained by other improvements in treatment of patients with

CHD.

1.3 Standard therapeutic regimes for patients with AMI
The primary goal of therapy in AMI is rapid, complete, and sustained restoration

of infarction-artery blood flowlz. In the reperfusion era, a constellation of therapies for
the management of patients with AMI were introduced, including treatments with
thrombolytic agents such as streptokinase, tissue plasminogen activator (tPA) as well as
procedures such as percutaneous translurninal coronary angioplasty (PTCA), and
emergency coronary artery bypass graft (CABG) surgery in suitable patients. It also
included the extensive use of aspirin, beta blockers, vasodilation therapy, and the
common use of ACE inhibitors. In addition, this era has witnessed far more aggressive

techniques such as intraaortic balloon counterpulsation (IAB) in patients with clinical

markers of poor prognoses (e.g., hypotension, congestive heart failure, and continuing

ischemia). The combined use of all these therapies has resulted in an impressive

reduction in short-term and l-year mortality for patients with AM113'15.

Physician practices have changed dramatically as newer approaches to the care
of the AMI patient have become available. Invasive and/or noninvasive procedures such
as angiography, stress echocardiography and radionuclide imaging to evaluate
prognosis and the need for further therapy are now used in most post-MI patients,

whereas only a small percentage of patients had such procedures performed 25 years

agol6‘18. The National Registry of Myocardial Infarction, an Observational database19
of practice patterns reflecting treatment of 240,989 patients with AMI at 1073 hospitals »
between 1990 and 1993, reported the rates of invasive procedures in thrombolytic
recipients were 70.7% for coronary angiography, 30.3% for angioplasty, and 13.3% for

bypass surgery. Thrombolytic therapy and angioplasty are now the standard of care in

appropriately selected patients1 9'22.

Two goals for the clinical cardiologists are to reduce the mortality and morbidity
of AMI to their lowest possible rates and to do so in a cost-effective manner. Attaining
these goals requires the development of the most effective immediate treatments, the
most accurate risk stratification methods, and the selective use of revascularization
procedures in those patients most likely to benefit. However, the precise role of
diagnostic angiography and coronary angioplasty in reaching these goals is
controversia123. Specially, clinicians disagree on the appropriate use of diagnostic

angiography versus noninvasive methods of post-infarction risk stratification, as well as

the extent to which primary angioplasty should be emphasized over thrombolytic

therapy24'27. The controversies have far-reaching implicationszg.

1.4 Utilization of coronary angiography and revascularization

The growth of interventional cardiovascular procedures has been staggering
(Figure 4-6). In the United States, an estimated 1,194,000 inpatient CA procedures,

447,000 PTCA procedures and an estimated 607,000 CABG procedures were

performed on 366,000 patients in 19971. From 1979 to 1997, the number of CAS
performed in the US increased 3 folds; the number of PTCA increased 188% and the
number of patients treated increased by almost 2 folds. The average cost of PTCA in
1995 was $20,370. The number of CABG procedures increased 432%, and the number
of patients increased 227%. The average cost of CABG in 1995 was $44,820.

In the patients with AMI, the frequency of CA use has increased too. For

example, from 1987 to 1990, the proportion of Medicare patients with MI who had CA

increased from 24% to 33%18.

The growth in coronary procedures is also rapidly increasing worldwide too. For
example, in Germany, between 1984 and 1996, the number of CA rose 10 folds from
about 45,000 to more than 450,000, while the number of PTCA increased by a factor of
about 50 to 125,000 procedures in 199629. In the UK, the total number of coronary
procedures increased by 77% from 1 1,575 in 1992 to 20,511 in 19963. No other country
matched the procedure rate in the United States. For example, Germany, the country

that performs the most coronary procedures per capita in Europe, has a CA rate that is

only 75% as high as that in the U.S.3O. Great Britain performs only one-third as many

CA as the United States. Similarly, the rate of coronary revascularization is much lower

outside of the US.

1.5 Variation in procedure use in patients with AMI and related outcomes

Geographic variation of coronary procedure use in AMI patients

There is considerable geographic variation in the use of coronary angiography
and revascularization within the United States and internationally, both in general

population with chest pain or angina and among patients who had AMI. In the US,

there are substantial regional differences in the use of CA31’ 32. In the GUSTO-l

(Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded

Coronary Arteries) study of patients with AMI, Pilote32 compared the management of
AMI among census regions across the United State and found the proportion
undergoing CA varied substantially between the 7 regions evaluated. For example,
angiography use varied from 52 to 81%; angioplasty, 22 to 35%; and CABG, 9 to 17%.
The regional use of coronary procedures was closely related to their availability.
Despite these regional variations in utilization of angiography, there was no apparent
relationship between procedure rate and patient outcomes. For example, the incidence
of recurrent infarction or death at 30-day or one-year follow-up did not vary from

region to region.

In another study33 that evaluated Medicare patients with AMI, the proportion of
patients who received CA during their hospital stay or within 90 days of admission was
45% in patients in Texas but only 30% in patients in New York. Despite the increased

use of coronary angioplasty as well as CABG in Texas, the adjusted mortality after two—

year follow-up was significantly lower in New York and patients in New York had
fewer symptoms. Patients from Texas were more likely to report angina and more likely
to say they could not perform activities requiring energy expenditure of 5 or more
metabolic equivalents than patients from New York at the time of follow-up
assessment. So mortality rates and measures of health-related quality of life were no
better in Texas than in New York.

Selby found the percentage of patients who underwent angiography within three

months after infarction ranged from 30 to 77% at 16 Kaiser Permanente hospitals34.
The author then selected a cohort of 1,109 patients from three hospitals with higher
rates of angiography and four with lower rates to undergo a comprehensive record
review to determine the severity of infarction, the number of coexisting conditions,
treatments received, and the apprOpriateness and necessity of angiography, using
established criteria. The rates of angiography were inversely related to the risk of death
from heart disease (P= 0.03) and the risk of heart disease events (P<0.001) among the
16 hospitals, after adjustment for age, sex, race, coexisting conditions, and the location

of the infarction.

In addition to variation within the US, there are also international differences in
use of angiography in AMI35'37. Rouleau35 compared the treatment patterns for
patients with AMI in 19 Canadian and 93 US. hospitals participating in the Survival
and Ventricular Enlargement (SAVE) study, which tested the effectiveness of captopril
after a MI. Despite the similar clinical characteristics of the 1573 US. patients and 658
Canadian patients participating in the Randomized Control Clinical Trail, CA was more

commonly performed in the United States than in Canada (68% versus 35%, P < 0.001),

\J

as were revascularization procedures (31% versus 12%, P < 0.001). During an average
follow-up of 42 months, these coronary procedures were also performed more
commonly in the United States than in Canada. However, these differences were not
associated with any apparent difference in mortality (23% versus 22%) or rate of
reinfarction (13% versusl4%), although there was a higher incidence of activity-
lirniting angina in Canada than in the United States (33% versus 27%, P < 0.007).

Mark conrpared 2,600 US. and 400 Canadian patients from the GUSTO trial

with respect to their use of medical resources and their quality of life during the year

after AMI36. He found that the Canadian patients had a much lower rate of CA (25%
versus 72%, P < 0.001), PTCA (11% versus 29%, P < 0.001), and CABG (3% versus
14%, P < 0.001) during their hospitalization as well as at one-year. They also underwent
fewer invasive cardiac procedures and had fewer visits to specialist physicians. The
Canadian patients however had more cardiac symptoms and worse functional status one

year afier AMI than the US. patients.

Tu37 compared the use of coronary procedures and the mortality rates among
224,258 elderly Medicare beneficiaries in the United States and 9,444 elderly first MI
patients in Canada. The US. patients were significantly more likely than the Canadian
patients to undergo CA, PTCA and CABG during the first 30 days and 180 days of
follow-up after index infarction. The 30-day mortality rates were slightly but
significantly lower for the US (21.4% versus 22.3%, p < 0.03) patients than for the
Canada patients. However, the one- year mortality rates were virtually identical (33.4%

in American and 33.3% in Canada).

Gender variation of coronary procedure use in AMI patients

Variations in the use of procedures in AMI patients have also been observed

between men and women. A retrospective cohort study in community-based tertiary

teaching hospital conducted by Krumholz38, found women underwent angiography
during hospitalization for AMI much less frequently than men (OR 0.55, 95%Cl 0.46-
0.65), When adjustments were made for age, women had PTCA as often as men (OR
1.16, 95%Cl 0.83-1.62) but had CABG significantly less frequently (OR 0.58, 95%C1
0.37-0.91). When adjustments were made for age and the severity of coronary artery
disease, the difference in rates was large but of borderline significance (OR 0.65,
95%C10.41-1.01).

Myocardial Infarction Triage and Intervention Registry (MITIR) was a registry

database for hospitalized AMI in 19 hospitals in the Seattle metropolitan area. From that

database, Maynard39 found that women were older and more often had histories of
previous hypertension and congestive heart failure compared to men. Both CA and
PTCA were used less fiequently in women. For example, CA was performed in 40% of
women and 58% of men during hospitalization (P<0.001). However, of patients who
had CA, equal proportions of women and men received PTCA and/or CABG (p=0.25).
Race variation of procedure use in AMI patients

Giles used data from the National Hospital Discharge Survey to investigate race

and sex differences in rates of CA, PTCA and CABG among 10,348 patients

hospitalized for AMI4O. It was found that white men consistently had the highest
procedure rates, followed by white women, black men, and black women. After

matching for the hospital of admission and adjusting for age, in-hospital mortality,

health insurance, and hospital transfer rates, the odds ratio for CA were 0.67 (95% CI
0.51-0.87) for black men, 0.72 (95% CI 0.63-0.83) for white women, and 0.50 (95% CI
0.37-0.68) for black women, compared to white men. Similar race-sex differences were
noted for use ofPTCA and CABG.

Weitzman compared rates of cardiac procedure use in relation to gender, race,

and geographic location in patients’ hospitalization for AMI using data from the

Atherosclerosis Risk in Communities (ARIC) data“. This study provided population
data and standardized data collection methods, and found that women treated in these
hospitals were less likely than men to have CA and CABG (CA: OR 0.7, 95% CI 0.5-
1.0, CABG, OR 0.6 95% CI 0.4- 0.8), after controlling for age, race, severities of
myocardial infarction, co-morbidity, and geographic area. Blacks in the biracial
communities were significant less likely than whites to have CA, CABG and PTCA.

Maynard reported racial differences in the utilization of procedures in MITIR

study from 1988 to 199442. Similar proportions of black and white hospitalized AMI
patients underwent CA. However, only 18% of black patients underwent PTCA
compared with 26% of white patients (p=0.0004) and CABG was also used less
frequently in black patients compared to whites (7% versus 12%, p=0.002). Despite the
less intensive use of revascularization procedures in black patients, 2-year survival after
AMI was similar in both groups.

In the study of 1,165 AMI patients from January 1990 to December 1992 at
seven health maintenance organization hospitals43, CA was highly indicated in 854
(73.3%) patients using the American College of Cardiology/American Heart

Association (ACC/AHA) practice guidelines. Among these, women received

10

significantly fewer CA (hazard ratio (HR)=0.78) and revascularization (HR 0.62).
Crude CVD mortality for women was higher than for men (HR 1.7), but after
adjustment for age, Charlson Index, and congestive heart failure, the hazard ratio of

CVD mortality was not significantly difference than for men (HR 1.19)

These differences in rates of procedure use among the races and genders44 were
conceivably due to differences in confounders as well as selection criteria. More
complicated and detailed information was acquired by collecting data from individual
medical records rather than from computerized databases or from secondary analyses of
existing databases. Additionally, some studies reflected practice 10 to 25 years ago,
whereas now advances in practice had made angioplasty a common therapeutic option
for many patients with AMI.

Other studies have attempted to isolate additional factors that help to explain
variation Of procedure use. Infarction patients admitted to hospitals with angiography

laboratories are about 3 times more likely to undergo angiography than patients

admitted to hospitals without such facilities45a 46. Patients treated for AMI by invasive
cardiologists (defined as cardiologist who perform the procedures) have a similar
likelihood of undergoing CA as patients treated by noninvasive cardiologists, but the

likelihood of having PTCA or CABG is higher for patients treated by invasive

cardiologists47.

1.6 Coronary procedures use and AMI outcome

As discussed above, several studies have shown considerable variations in the
use Of CA after MI within regions of US, between the US. and Canada, between

health maintenance organizations and fee-for service hospitals, between primary care

11

physicians and cardiologists, and between invasive and noninvasive cardiologists.
These data do not Show a consistent relationship between the increased use of CA or
PTCA after MI and improved outcomes. Data on the impact of differences in cardiac
procedure rates in patients with AMI on subsequent quality of life are also conflicting.
The utilization of procedures has not been studied in typical, non-selected populations
of patients admitted to hospital with AMI. Most study population are fiom veterans, or
Medicare patients, or patients in Random Clinical Trial setting. In addition, the small

number of outcome studies published have produced opposing conclusions concerning

the impact of the high rates of these coronary procedures-34: 36, 37. These studies,
based largely on administrative data, attributed geographic variation in the use of
procedures to physician “practice style”.

Adjunctive angioplasty following thrombolysis

Several clinical scenarios have been described that represent different categories
of use of PTCA when it is not selected as the primary reperfusion strategy‘i8 (Figure 3).

The Thrombolysis in Myocardial Infarction (TIMI II-A) study49a 50addressed the use
of angiography after thrOmbolySis therapy (TT) in AMI patients. This study compared
three treatment strategies: immediate invasive, delayed invasive, and conservative. With
the immediate invasive strategy, angiography and angiOplasty (if indicated) were done
as early as possible after TT use, with the delayed invasive strategy, routine
angiography was done between 18 and 48 hours after thrombolytic therapy, and with
the conservative approach, angiography and angioplasty (if indicated) were done only if
the patient developed spontaneous or exercise-induced ischemia. The 24-hour

complication rate for patients who received the immediate invasive strategy was

Significantly higher (8.5%) than that for patients who received the delayed invasive
strategy (4.6%). No benefit for any of the major endpoints was shown. Patients who
received the conservative strategy had outcomes equal to those for patients who
received the delayed invasive strategy for major outcomes. For example, 6-week
survival (95.3% in the conservative group compared with 94.5% in the delayed invasive
group), absence of reinfarction (93.5% in the conservative groups compared with 93.1%
in the delayed invasive group), and ejection fraction (EF) at discharge (49.9% in the
conservative group compared with 50.5% in the delayed invasive group).

The SWIFT (Should We Intervene Following Thrombolysis) trial also compared

an invasive strategy with a conservative approach after thrombolytic therapy51. The
invasive strategy was early elective angioplasty (within 48 hours). AMI patients in the
conservative group had angiography only if they had recurrent ischemic symptoms or
positive results on exercise tests at 3 months. Mortality rates after 3 months were

similar between the conservative group (3.2%) and the invasive group (4.8%); ejection
fraction was also similar, thus confirmed those of the TIMI II-A study49a 50.

In the TIMI 11B trial52 patients who received tPA were randomized to receive
CA and PTCA within 18 to 48 hr of thrombolysis or conservative management. After
Six weeks, there was no difference in mortality, nonfatal recurrent M1, or left ventricular
ejection fraction (LVEF) between two groups. Follow-up reports from this study
showed no difference in survival, severity of angina or the frequency of bypass surgery
between the two groups after one and three years. Thus, there was no evidence to

support use of PTCA in patients without evidence of recurrent or provokable ischemia.

13

A summary of the design features and main findings of 16 randomized trials,
which assessed the effect of both primary and adjunct PTCA in AMI on mortality and

reinfarction rates, that collectively enrolled about 6200 patients had been published

along with meta-analysis of the mortality result853. Although none of the individual
comparisons of strategies achieved conventional statistical significance, a consistent

theme was observed--the routine empirical use of PTCA (either immediate or delayed)
following thrombolysis was associated with a trend toward increased mortality”, 53’

54. Conservative and invasive strategies did not differ in mortality rate or nonfatal
reinfarction or mortality rate at either 6 weeks or 1 year. Therefore, at least as seen in
these trials, the strategy of performing routing PTCA in a delayed fashion or immediate
fashion following thrombolysis did not improve the mortality rate or improve left
ventricular function.
Adjunctive angioplasty in specific subgroup AMI patients

While no benefit has been shown for immediate or routine PTCA in AMI
patients without complication, angiography and angioplasty may be useful in specific

subgroups that have such complications as angina and cardiogenic shock after MI.
Recurrent angina and persist chest pain
Patients who develop persistent chest pain after MI have a greater risk for

extension of the infarction and death55. The DANAMI (Danish Acute MI)

investigators56 reported that when patients with provokable ischemia after infarction
were randomized to angiography and revascularization versus conservative medical
therapy, they required less anti-angina medications, had less unstable angina, and

experienced fewer nonfatal infarctions. There were 1,008 patients with first AMI treated

14

with TT who had subsequent ischemia were randomized to coronary angiography and
revascularization versus medical management. In the invasive strategy, PTCA was
performed in 266 (52.9%) and CABG in 147 (29.2%) from 2 to 10 weeks after the
AMI. Of the 505 patients in the conservative treatment group, only 8 (1.6%) had been
revascularized 2 months after the AMI. At 2.4-year follow-up (median), mortality was
3.6% in the invasive treatment group and 4.4% in the conservative treatment group (not
Significant). However, invasive treatment was associated with a lower incidence of
recurrent AMI (5.6% versus 10.5%; P <.0038) and a lower incidence of admission for
unstable angina (17.9% versus 29.5%; P<.00001). The percentages of patients with a
primary endpoint were 15.4% and 29.5% at 1 year, 23.5% and 36.6% at 2 years, and
31.7% versus 44.0% at 4 years (P <.00001) in the invasive and conservative treatment
groups, respectively. At 12 months, stable angina pectoris was present in 21% of
patients in the invasive treatment group and 43% in the conservative treatment group.

In major randomized trials of thrombolysis therapy, patients with recurrent chest

pain usually have angiography. Although no data from randomized trials have proven
its efficacy, angiography is probably effective in this setting”.
CHF group

AMI patients who develop clinical congest heart failure (CHF) or who have
evidence of left ventricular dysfunction during the hospital management phase are
important subgroups. Numerous studies have demonstrated that prognosis afier AMI is

largely dependent on residual left ventricular function, as determined by global ejection

fraction589 59. Evidence from randomized trials comparing bypass surgery in patients

with medical therapy shows improved survival with surgery in patients with depressed

15

left ventricular function who have three-vessels disease or two-vessel disease with

involvement of the left anterior descending (LAD) coronary artery60‘62. Although
these studies were performed in patients with chronic stable angina, the results are

frequently extrapolated to patients with recent MI.

Cardiogenic shock
At the extreme of patients with left ventricular dysfunction are those who

develop cardiogenic Shock after MI. Data from the Worcester Heart Study63
accumulated over a l3-year period show that around 7.5% of patients with MI
developed cardiogenic shock after MI, and rates remained relatively constant from 1975
to 1988. Without any interventions, AMI patients with cardiogenic shock had a

mortality rate between 74% and 82% compared to patients without this complication
(13.5%). Because these patients often have poor outcomes49’ 50’ 64, they have been

excluded from many trials. A randomized study of PTCA versus medical therapy
(SHOCK trial) provided important, definitive data on the relative benefit of PTCA for
cardiogenic shock65. It showed that in-hospital mortality was lower in early
revascularization group (15% versus 67%, RR=0.74, 95% CI 0.54-1.02). After adjusting
for difference in age, the difference in mortality was still significant. This is the largest
multicenter prospective study of AMI patients diagnosed with cardiogenic shock.
Nonrandomized observational data from the GUSTO trial supported the use of PTCA
for management of Shock both in patients who arrive in shock and in those who develop
it during hospitalization too66. Mortality rate in 30-day was 33 to 40% in PTCA-treated

patients, compared with 75% in medically treated patients.

16

Prior MI

In TIMI-II, patients with a history of prior MI had a higher 42-day case-fatality
rate (8.8% versus 4.3%; p<0.001), a higher prevalence of multivessel coronary artery
disease (60% versus 28%; p< 0.001) and a lower LVEF (42% versus 48%; p<0.0001)
compared with patients presenting with a first MI. Among patients assigned to the
conservative treatment after TT, those with a prior MI had a significantly highly 42-day
mortality (11.5% versus 3.5%; p<0.0001), whereas with the invasive strategy, the
mortality outcome was essentially the same in the two groups. This mortality benefit
persisted up to 1 year67 (10.3% versus 17.0%, p=0.03). Based on these observations,
routine use of coronary angiography and coronary revascularization within 18 to 48
hours following intravenous thrombolytic therapy has been Suggested for patients who

have experienced a prior MI.

Diabetes

In TIMI-11B, patients with diabetes mellitus had significantly higher 6 week

(11.6% versus 4.7%), 1-year (18.0% versus 6.7%), and 3-year (21.6% versus 9.6%)

mortality rates compared with non diabetic patientség. In spite of these higher mortality
rates, diabetic patients with a first MI who were randomly assigned to the invasive post
thrombolytic strategy did worse than those managed conservatively in terms of 42-day
mortality, (14.8% versus 4.2%, p<0.001). Contrary to clinical intuition, the expected
benefits of an aggressive coronary angiography and coronary revascularization after

thrombolysis appear to be Offset in the presence of a first MI in diabetic patients.

17

Surgical reperfusion
About 10 to 20% of AMI patients are currently referred for CABG for one of the

following indications: persistent or recurrent chest pain despite thrombolysis or

PTCA69, high-risk coronary anatomy (e.g., left main stenosis) discovered at
angiography, or a complication of AMI such as ventricular septal rupture or severe
mitral regurgitation due to papillary muscle dysfunction. Patients with AMI with
continued severe ischemic and hemodynamic instability are likely to benefit fiom
enrergency revascularization. PTCA is the preferable technique when revascularization
is needed in the first 48 to 72 hours following AMI. Surgery Should be reserved for
those in whom PTCA has been unsuccessful or whose anatomy dictates the need for

coronary artery bypass grafting, such as patients with left main or extensive multivessel

coronary artery disease70.

1.7 Guidelines for coronary procedures use in AMI patients

Rigorous and expert analysis of the available data documenting relative benefit
and risks of procedures have been used to produce guidelines designed to improve the
effectiveness of care, optimize patients outcomes, and impact the overall cost of care
favorably by focusing resources on the most effective strategies. Panels have developed
criteria for the appropriateness and necessity of coronary angiography and
revascularization. The American. College of Cardiology (ACC) and American Heart

Association (AHA) have published guidelines for the care of patients with AMI and

guidelines for use of coronary procedureslza 71, 72. These guidelines categorize
indications for performing CA or revascularization as class I (usually indicated, always

acceptable), class Ha (controversial, but favored owing to the weight of evidence and/or

18

opinion), class Ilb (not well established by evidence, but probably not harmful) or class
[[1 (not indicated) (Table 1). The guidelines have been ,updated to include the most
significant advances that have occurred in the management of patients with AMI as well
as enable the medical profession play a significant role in critically evaluating the use of

diagnostic procedures and therapies in the management and prevention of disease states.

1.8 Summary

Though studies showed there are variations in the rates of procedure use in the
patients with AMI, it is less clear whether these variations result in important
differences in patients' outcomes. Most of ecological or observational studies have not
found significant differences in mortality between areas with high rates of use compared
to those with low rates of use. The variations in use of angiography and
revascularization and lack of clear benefit in general AMI patients have led many to
question the appropriateness of angiography or angioplasty for patients with M123, 36.
Because angiography and revascularization afier AMI are not risk-free procedures, and
the efficacy of routine CA and PTCA in improving prognosis has not yet been
determined in all MI patients. Given the potential benefits, risks, and costs of these
procedures, the marked variations in their utilization emphasize the difficulty in
choosing the appropriate degree of intervention in the absence of data on definite
outcomes, such as survival, recurrent cardiac events and quality of life.

The utilization Of coronary angiography and revascularization procedures has
important cost and resource implications in the provision of cardiologist services.
Establishment of the appropriate role of coronary procedures in patients with AMI

awaits demonstration of clear benefit, the definition of patients subsets most likely to

19

benefit, and better understanding of the cost effectiveness of such approaches.
Therefore rates of use, determinants of use and resultant patient outcome require further
study. However, it seems clear that coronary angiography and revascularization
procedures should be used selectively rather than routinely in the post-myocardial
infarction patient. Also the appropriate use of revascularization after AMI will be very
much dependent on national priorities in health expenditure. Also, it is important to
understand the sources of variation in procedure use from the standpoint of equity in the

delivery of health care services and their impact on mortality and morbidity.

1.9 Thesis rationale

Thesis objectives
The purpose of the study is to analyze the differences in demographic and
clinical characteristics among patients who receive invasive cardiac produces and those
who do not. The main outcomes of the study are the use of coronary angiography and
revascularization procedure in patients with AMI.
Specific questions
. Determine the rates of coronary angiography and revascularization (including
angioplasty and bypass surgery) in patients who were hospitalized with AMI.
. Identify demographic and clinical features that were associated with coronary

angiography and revascularization use

20

Chapter 2

METHODS

2.1 MICH Study

Purpose

The Michigan State University Inter-Institutional Collaborative Heart Study
(MICH) was a hospital-based collaborative study of the hospital care for AMI patients
in five community hospitals in Michigan. The area consisted of the counties of Genesee
and Saginaw in the east-central region of the lower peninsular of Michigan. The project
involved an organizing committee of the College of Human Medicine at three of MSU
campuses: East Lansing, Saginaw and Flint. The study investigated the health care
services in AMI and follow-up care in the first year following hospitalization. This
study also investigated variations in care and costs by ethnicity, social class, age,
gender, and payer type. In addition, the study examined how demographic
characteristics, comorbid conditions, severity of illness and treatment affect patients’
functional and mental States and impact upon family caregivers. The study included two
cohorts Of subjects. Phase I subjects were enrolled from January 1994 to April 1995.
Phase II subjects were from February to September 1997. Observations on both cohorts
continued for a minimum of one year after their hospitalization. This study is limited to
Phase I patients because the data collection and diagnosis criteria were different in two

phases.

21

Geographic setting

Saginaw County has a population of 212,295 in 1995. The largest city is the city
of Saginaw, which has a population of approximately 70,000. Genesee County has
436,381 residents in 1995, with its largest city of Flint having a population of 138,864.
In Genesee County, 51% of who were females and 18% were Afiican or other minority.
Five hospitals participated in the study. Those hospitals were Hurley Medical Center
and McLaren HOSpital located in Flint and Saginaw General, St. Mary’s and St. Luke’s
Hospitals located in Saginaw.

Methodology
Human Subjects and informed consent

The Institutional Review Boards of Michigan State University and of all five
participating hospitals approved this study. The consent form was approved by the
University Committee on Research in Human Subjects (UCRIHS) with IRB# 93-334
(see appendix C). At the time of the study, all five participating hospitals were certified
to offer coronary angiography (CA), percutaneous translUminal coronary angioplasty
(PTCA) and coronary artery bypass graft (CABG). None of the hospitals offered

primary angioplasty (direct angioplasty) as initial management of AIVII.
Case definition

MICH study is a hospital-based case series of AMI hospitalization patients

recruited form two counties of Genesee and Saginow.

Diagnosis criteria of AMI

The World Health Organization (WHO) criteria for the diagnosis of AMI were used

to identify all acute myocardial infarction cases. The criteria required at least two of the

following three elements be present.

1.

Symptoms - any of the following chest discomfort such as shortness of breath,
nausea, diaphoresis, dizziness, severe discomfort in the anterior chest, back,
epigastrium, jaw, neck, shoulders, elbow, forearm or wrist, arm.

Elevated creatirrine kinase (CK) and creatine kinase-MB (CK-MB) fraction >1.2
times upper limit of normal within 48 hours of onset of symptoms or acute
event, or elevation of aspartate amino-transferase (SGOT) or Lactate
dehyogenase (LDH) > 2 times the upper limit of normal within 72 hours of onset
of symptoms or event.

Evolutionary changes on serially obtained electrocardiographic (ECG) tracing:
Q waves ( 2 0.043) or OS finding ( 2 0.045) + 0.1mV ST segment elevation in

contiguous leads or 0.1mV ST segment depression or define T wave inversion.

Inclusion criteria

All patients from the five participant hospitals meeting the criteria of symptom of

chest pain, high enzymes, and/or positive EKG were eligible for the MICH study.

Exclusion criteria

1.

Those who were transferred from a non-MICH hospital. This is because the
information of presenting symptoms and treatment was not available in detail in

AMI patients transferred from a non-MICH hospital.

to
DJ

2. Those whose MI occurred as a complication of coronary angiography, coronary

angioplasty, coronary artery bypass graft surgery or any other surgical procedure

Recruitment

Recruitment occurred in two distinct phases. Phase 1 began January 1, 1994 and
recruited patients through April 30, 1995. Phase 2 began additional patient recruitment
on March 1, 1997 ending in September 30. 1997. Two trained nurses identified eligible
patients while they were hospitalized and approached them to obtain study consent. For
phase I ward logs and medical records in all units likely to manage AMI patients
(intensive care units, coronary care units, and surgical intensive care units) were
screened to identify potential eligible patients. In addition, each patient who was
admitted to a general medical ward with an admission diagnosis of chest pain, rule out
"AMI or congestive heart failure (CHF)" was screened for eligibility.

Each admission for AMI during the enrollment period was assigned a unique
study record number. Multiple hospitalizations occurred in the some individuals during
the study period. The first AMI that resulted in study enrollment (that is, occurred
during the enrollment period and that resulted in identification of the patient by the
research nurse) was designated the "index MI" and was used as the reference point for
follow-up. Patients were interviewed during hospitalization only once during a specified

enrollment period.

F ollow-up

Phase 1 patients who were interviewed during hospitalization were contacted by
mail at three, six, nine and twelve months after discharge and participated in a final

closing phone interview 12-36 months after their discharge. Data regarding function

24

status, stress score, quality of life, behavior changes and medication use were collected

during the follow-up.
Data collection from medical charts

Data regarding demographics, prior history related to cardiac disease, physical
findings, laboratory test, symptoms, complications, treatments (medical and surgical),
comorbidity, in-hospital mortality and morbidity, and discharge instructions were
abstracted from the medical charts. The data were recorded on a standard chart abstract
form developed for the study (See Appendix D). A manual describing coding rules for
each item on the chart abstract form was developed and used by all chart abstractors.

The data entry was performed by the study nurses at the time of the chart
review, with a laptop computer. Data were audited for accuracy by two cardiologists

who reviewed the medical records, ECGs and coronary angiogram when necessary.

Quality control of the data

For data abstracted from medical records, data quality control was maintained
by checking a random 5% sample of medical records to ensure >90% interrater
reliability. After data entry, similar random checks and range checks were performed to

ensure data accuracy.

2.2 Thesis study

Study population
From the MICH database, we included the patients only admitted directly to the
5 MICH study hospitals in Phase I. We did not included phase II patients because the

way the data colleted and diagnosis criteria for AMI were different in two phases.

25

Definition of variables

Demographic characteristics of study patients were grouped into categorical
variables. For example, age was classified as under 45, 45 through 54, 55 through 64,
65 through 74, and 75 year and older. Race was categorized into three groups: white,
black and other. There were four insurance types (commercial, Medicare, Medicaid,
self-insurance). Prior history of coronary artery disease, the development of AMI
complications, procedures and treatments received during hospitalization were
expressed as dichotomous variables (present or absent).

Complications of AMI during hospitalization were defined according to the
evidence in the hospital records of either cardiogenic shock, congestive heart failure, or
arrhythmia (VT/VF) having occurred during hospitalization. Prior medical history was
recorded based on the hospital discharge diagnosis (ICD-9 CM). Charts were also
reviewed to gather the information on prior medical history. For example, the diagnosis
of diabetes was also recorded if information on the patient requiring insulin, oral
hypoglycemic drugs, or dietary sugar restriction in the chart.

The diagnosis of new onset congestive heart failure (CHF) was defined from the
typed chest X-ray report on the chart which contained any or the following phrases:
congestive heart failure, pulmonary edema, pulmonary vascular congestion, puhnonary
venous cephalization, Kerly B lines.

Charlson comorbidity index was were computed for each patient according to

the weighted index of comorbidity at the time of enrollment into the study73.
The extent of coronary artery disease was summarized using a traditional

classification of one, two and three-vessel disease. In addition if left main disease was

26

presented it was noted”. Significant coronary artery disease was defined as 2 50%
occlusion of the lumen diameter of either the left anterior descending (LAD),
circumflex (LCX) or right coronary (RA) at diagnostic coronary angiography.
Significant left main disease was defined 2 40% of the lumen diameter of the left main
coronary artery. All coronary angiograms were read by one of two cardiologists.
Stenoses were measured by the use of hand-held calipers in multiple views and
quantified in comparison to the closest nonstenostic arterial segment.
Endpoints

The primary endpoints of this study were utilization of coronary angiography
(CA) and revascularization procedures. Coronary angiography was defined as
dichotomized variables, yes or no. Revasularization had three categories: medical
therapy, PTCA only and CABG only. We recoded 18 patients who underwent both
PTCA and CABG according to their first procedure.
Statistical analysis

In our primary analysis we examined the use of coronary angiography during
hospitalization after the index admission among each MI patient. We used logistic
regression analysis with specified predictors variables to predict whether the variables

were associated with CA use for the overall study sample. We calculated odds ratios

and 95 percent confidence intervals by exponent of the regression coefficient”: 76.

To investigate what factors in the use of coronary angiography, a multiple .
logistic regression analysis was performed. Race, gender, age, and insurance were set as
priority variables or prior confounders, which means that they stay in the model

regardless Of significance. Other potential independent variables in the full model were

selected on the basis of their univariate associations with a coronary angiography use.
Only the variables with significant level S 0.25 for univariate analysis were considered
as candidate variables. The following demographic and clinical predictors were tested in
the full model: demographic (age, race, gender, insurance), prior medical history and
procedure (MI, angina, CHF, previous PTCA, CABG), cardiac risk factors (diabetes,
hypertension, hypercholesterolemia), characteristics of AMI (chest pain at presentation,
infarction location), complication of AMI during hospitalization (recurrent angina,
cardiac shock, new onset of CHF) hospital and type of doctor involved. All the
variables were categorical variables. Non priority factors that were statistically
insignificant (i.e. P > 0.05) in the multivariable model were removed in a hierachical
backward elimination. The odds ratio of the remaining factors and the associated 95%
confidence intervals were reported to demonstrate the relative influence of each factor
on angiography utilization. We also evaluated the effect of adjusting for additional
comorbidity measures (Charlson Index) in the final model. All statistics analyses were
performed with SAS 8.0 statistical package programs. PROC LOGISTIC was used
(SAS Institute, Inc, Cary, N. C., USA).

In our second analysis we examined the use of revascularization procedures
(defined as medical therapy, PTCA only, or CABG only) during hospitalization for
these 619 patients who underwent angiography. Polychotomous logistic regression
analyses were performed to determine the associated ”with revascularization procedures
for the 619 patients who underwent coronary angiography. We also examined if the
information from the cardiac angiogram had an effect on the decision whether to

revascularization the patient and which procedure was used. Polychotomous logistic

28

analysis were performed with STATA 6.0 statistic package programs (STATA

Corporation, College Station, TX)

Chapter 3

RESULTS

In the period between January 1994 and April 1995, 849 hospitalized
myocardial infarctions were identified among the 5 MICH study hospitals. We obtained

medical records for 846 eligible patients (Figure 7)

3.1 Demographics and clinical characteristics in total population

Table 2 presents selected baseline characteristics and previous CVD-related
history of the 846 study patients. The mean age of the study population was 64.0 years
with standard deviation 13.7 (median age 65 years). Age was also categorized into five
groups, with 26.6% patients‘were 75 years older and more. Two-thirds of study
population was male (73.3%). The majority of the study population was white (83.6%)
with 15.2% black and 1.3% other race. Most of the patients had some type of health
insurance. This included 38.3% patients with commercial insurance, 54.4% with
Medicare, and 3.1% with Medicaid. Only 4.2% had no insurance. A majority of the
patients had a prior history of CVD-related disease or risk factor, including prior MI
(27.3%), prior angina (26.1%), hypertension (56.0%), and prior CHF (15.5%) (Table 2).
A substantial proportion of the study population had prior coronary procedures. For
example, 22.0% had prior coronary angiography, 10.3% had prior PTCA and 13.1%

had prior CABG.

3.2 Clinical characteristics and complications of AMI

Clinical characteristics on presentation of the AMI population are displayed in
Table 3. The majority of the 846 patients reported chest pain on presentation (74.5%).
Their median peak CK and CK-MB level was 760 and 72 IU/L, respectively. Almost
one-third of the patients had anterior infarction (30.1%), while other one-third (36.9%)
had inferior infarction. Complications after AMI were very common. For example, half
of the patients experienced recurrent angina pectoris (50.0%), and more than one-third
(31.6%) patients developed new onset congestive heart failure during hospitalization.
Nearly 7% patients had experienced ventricular tachycardia (2 3 consecutive ventricular

beats) at least once during hospitalization (Table 3).

3.3 Coronary procedures use during hospitalization

Seventy-three percent (619/846) of MI patients underwent angiography during
hospitalization in our study population. Among these 619 patients, approximately 30%
(168) of the patients underwent bypass surgery and 35.2% (218) underwent angioplasty.
However, a few patients (18 patients) were treated with both CABG and PTCA. We
recoded them into PTCA or CABG group according to their first procedure. Coronary
anatomy information was recorded for 600 patients (96.9%) who underwent CA.
Approximately 10% of patients had significant left main coronary artery disease; more
than one-third of the patients had significant one-vessel disease (31.5%); one-fourth of
the patients had significant two-vessel disease (27.1%), and one-fourth had significant
three-vessel disease (25.2%) (Figure 8). However, approximately 4.0% of the patients
had no significant coronary artery disease as determined by angiography. Overall,

approximately one-third of the patients had severe coronary disease as defined by either

31

2 50% stenose of the left main coronary artery or 2 40% stenose of the main other three
coronary vessels.

Among total patients, approximately 45% of patients were treated with TT
during hospitalization. This proportion was higher for the patients who underwent CA

than for those patients who did not receive CA (53.5% versus 24.7%).

3.4 Determinants of coronary angiography

We first examined the use of coronary angiography (CA) among patients
hospitalized for AMI, as coronary angiography is a necessary diagnostic prerequisite to
use of PTCA or CABG. The univariate analysis showed that women were significantly
less likely to receive CA compared to men during hospitalization (OR 0.61, 95% CI
0.45-0.94) and that increasing age was associated with decreased use of angiography.
When those less than age 45 years were compared to those 75 years old or more, the
percent of patients receiving CA decreased from 89.5% to 52.4% (OR 0.13, 95% CI
0.06-0.26). A higher prOportion of patients with commercial insurance received CA
than those with Medicare or Medicaid (Medicare 62.8%, Medicaid 68.2%, no insurance
71.4%, versus Commercial 89.7%, P < 0.0001). However, this findings was probably
confounded by age. Patients admitted to hospitals B, D, B were more likely to have their
angiography done during hospitalization compared to hospital A (Table 4).

In the univariate analysis, it was also found that most factors associated with a
worse prognosis or greater severity were associated with a lower likelihood of
undergoing CA (Table 5). For example, patients with prior AMI were significantly less
likely to undergo CA (OR 0.39, 95% CI 0.28-0.54) as were a patient with a history of

CHF (OR 0.22, 95% CI 0.15-0.32), a history of cardiac arrest (OR 0.13, 9 % CI 0.04-

U)
k)

0.38). Patients with complication of cardiogenic shock were less likely to undergo CA
(OR 0.36, 95% CI 0263-0498) (Table 5). Coronary angiography was used less
frequently in patients who developed new CHF during their hospitalization (OR 0.45,
95% CI 0.32-0.61, P < 0.0001). Coronary angiography was also performed less often in
the patients that developed VT/VF arrhythmia during hospitalization (OR 0.39, 95% CI
013-034) (Table 6). Patients who did not receive TT were less likely to receive CA
compared to patients who did receive TT (OR 0.29, 95% CI 0.20-0.40). The only
adverse prognostic factor associated with a greater use of CA was recurrent angina (OR
1.38, 95% CI 1.02-1.87).

Multiple logistic regression model was used to identify predictors of having
coronary angiography performed in AMI patients during hospitalization. All variables
with p value less than 0.25 in the univariate analysis were entered in a full model. Ten
patients whose race was categorized as other race were eliminated in the multiple
logistic analysis because of small number. Thus, a final sample size of 836 was used to
develop the multiple logistic regression model.

Age, gender, race, insurance status, prior cardiac history (AMI, CHF, cardiac
arrest) CVD-related risk factors (hypertension, hypercholesterolemia, diabetes), and
prior CABG, clinical characteristics (such as peak CKMB, peak CK, location of AMI),
complications of AMI (recurrent angina, cardiogenic shock, new CHF developed at
hospital, VT/V F arrhythmia, cardiac arrest), and thrombolysis therapy, hospital, type of
doctor involved, which were all significant in univariate analysis (P < 0.25). Four
variables were set as priority variables: age, gender, race and insurance status. We use

backwards elimination which sequentially deletes the non-significant variables to create

33

a final model. The stepwise model development is illustrated in Table 7. The final
model included age, race, gender, insurance type, prior AMI, prior CHF, prior cardiac
arrest, complications of AMI, (such as cardiac arrest, cardiogenic shock, recurrent
angina) and absence of TT use in the model. The final model included 827 observations .
due to missing values for the response or explanatory variables and was overall
statistical significant (p <0.0001). The deviance of the final model was 576.084 with 16
degree of freedom. The Hosmer and Lemeshow goodness-of —fit test statistic has a
value 0.7132 with 8 degree of freedom, overall, p value < 0.7132, so indicating a good
fit of the data.

The final model (Table 8) indicated that after adjusting for other factors, women
were as equally likely to have angiography as men (OR 0.98, 95% CI 0.63-1.54).
Blacks were equally likely to undergoing coronary angiography as whites (OR 0.84,
95% CI 0.46-1.56). However, insurance status had large effect on the receiving CA. For
example, patients with no insurance were significant less likely to have CA compared to
patients with commercial insurance (OR 0.19, 9 % CI 0.07-0.53). Patients 75 years old
or more were still significantly less likely to have coronary angiography performed
during their hospitalization compared to patients under 45 years of age (OR 0.19, 95%
CI 0.07-0.53).

The multiple logistic models confirmed that factors associated with worse
prognoses or greater se'verities were associated with a lower likelihood of undergoing
CA (Table 8). Coronary angiography was performed less frequently in the patients with
prior cardiac-related history. For example, patients with prior MI, or prior CHF, or prior

cardiac arrest were less likely to have CA done during hospitalization. Patients who

experienced severe complications of AMI during their hospitalization such as cardiac
arrest, cardiogenic shock were also significantly less likely to have CA. Patients who
did not receive TT use were almost half less likely to receive CA. The only factor that
was associated with high CA use was recurrent angina (OR 1.70, 95% CI 0.34-0.81)
(Table 8).

We also check the final model excluding the patients who had terminal disease,
such as patients with metastatic cancer, or patients with liver failure (15 patients were
excluded). We found that the ORs for each of predictors did not change.

We also evaluated the effect of adjusting for additional comorbidity measures
(Charlson Index) in the final model. With Charlson index in the model, which was
categorized into four groups (1, 2, 3, 4+), the overall model was significant with p

<0.0001. The ORs for each predictor variables did not change much (Table 9).

3.5 Determinants of revascularization

Polychotomous logistic regression model was used to estimate the odds of
having revascularization procedure (Medical therapy only, PTCA only, or CABG only)
performed in AMI patients who underwent CA during hospitalization. A total of 619
patients were in the univariate analysis. We recoded 18 patients who underwent both
PTCA and CABG according to their first procedure.

Univariate Analysis

Several factors were found related to the revascularization use in the univariate
analysis. Older patients were much more likely to have CABG over medical therapy
relative to patients under 45 years of age (OR 3.30, 95% CI 1.52-7.15 for age 65-74,

OR 3.18, 9 % CI 1.41-7.13 for age 75+), but they were equal likely to undergo PTCA

(OR 0.79 95% CI 0.42-1.50 for age 65-74, OR 1.07, 95% CI 0.56-2.06 for age 75+)
(Table 10). Men and women were equal in receiving PTCA or CABG as a treatment of
AMI compared to receive medical therapy (OR 1.01, 95% CI 0.69-1.48 for PTCA, OR
0.77, 95% CI 0.51-1.18 for CABG) (Table 10). However, blacks were less likely to
have their PTCA or CABG performed during hospitalization compared to whites (OR
0.51, 95% CI 0.30-0.87 for PTCA, OR 0.53, 95% CI 0.30-0.96). Medicaid patients and
no insurance patients were less likely to have CABG, however, here associations were
not statistically significant (Table 10). Compared to hospital A, patients admitted to
hospital B were more likely to have both PTCA and CABG procedure over medical
therapy. However, none of the other hospitals (C to E) showed statistically significant
difference.

The univariate analysis also found prior CHF had strong association with less
use ofboth PTCA and CABG (OR 0.46, 95% CI 0.24-0.88 for PTCA, OR 0.44, 95% CI
0. 21-0.90) compared to patients without history of CHF (Table 11). Patients who
developed complications during hospitalization were more likely to have
revascularization during hospitalization. For example, PTCA and CABG were used
more frequently in patients with recurrent angina and in patients with cardiogenic shock
complication (Table 12).

We found that once CA was done, the information on the number of diseased
vessels was the strongest predictor of the type of revascularization procedure. As
expected, among patients underwent PTCA procedures, 86.4% of those patients had
one- or two-vessel disease. Among patients underwent CABG, 71.6% of those patients

had high severity of coronary disease defined as three-vessel disease or left main

36

coronary disease (Table 13). Patients with left main coronary or three-vessel disease
were ahnost 6 times as likely to receive CABG over medical therapy relative to patients
with only one- or two-vessel disease (OR 5.82, 95% CI 3.73-9.08) in the univariate
polychotomous logistic analysis (Table 12). On the other hand, they were less likely to
received PTCA over medical therapy compared to patients who had only one- or two-
vessel disease (OR 0.36, 95% CI 0.22-0.59).
Multiple polychotomous logistic analysis

Multiple polychotomous logistic regression model was used to identify
predictors of having revascularization procedure performed in ANH patients who
underwent CA during hospitalization. All variables with p value less than 0.25 in the
univariate analysis were entered in a full model. Twenty-eight patients whose race was
categorized as other race or whose angiography data were missing were eliminated in
the multiple polychotomous logistic analysis. Thus, a final sample size of 591 was used
to develop the multiple polychotomous logistic regression model. '

Age, gender, race, insurance status, prior cardiac history (AMI, CHF, angina)
CVD-related risk factors (hypertension, hypercholesterolemia, diabetes), and prior
CABG, prior PTCA, clinical characteristics (such as peak CKMB, location of AMI),
complications of AMI (recurrent angina, cardiogenic shock, new CHF developed at
hospital, cardiac arrest), and thrombolysis therapy, hospital, type of doctor involved and
severity of coronary disease, which were all significant in univariate analysis (P < 0.25).
Four variables were set as priority variables: age, gender, race and insurance status. We
use backwards elimination which sequentially deletes non-significant variables to create

a fmal model. The final model included age, race, gender, insurance type, prior CHF,

prior CABG, hypercholesterolemia, complications of AMI, (such as onset of new heart
failure, cardiogenic shock, recurrent angina), type of doctor involved and severity of
coronary disease. The final model included 587 observations due to missing values for
the response or explanatory variables and was overall statistical significant (p <0.0000).

The multiple polychotomous logistic model found that severity of coronary
disease and complications of AMI were much more important determinants of
revascularization use, while the demographic characteristics and insurance status were
less important to determine the revascularization use. It consistently found that the
severity of the diseased coronary was the strongest predictor to receive the type of
revascularization (OR 6.68, 95% Cl 394-113 for CABG, OR 0.35, 95% CI 0.21-0.61
for PTCA) (Table 14). Presence of AMI complications, such as cardiogenic shock was
associated with greater likelihood of undergoing PTCA (OR 2.20, 95% CI 1.31-3.70)
and CABG (OR 2.30, 95% CI 1.30—4.07). The occurrence of recurrent angina was
associated with higher utilization rates of PTCA (OR 1.88, 95% CI 1.23-2.84) and
CABG (OR 1.51, 95% CI 0.91-2.49) too, However, the patients with prior CHF were
still less likely to receive CABG over medical therapy, patients with new onset CHF
during hospitalization although they were equally likely to have PTCA over medical
therapy.

In contrast to CA use in older age groups, patients 75 years and older were more
likely to undergo both PTCA and CABG compared to patients under 45 years of age.
However, the relationship between age and revascularization were not statistical
significant. There were no statistic significant relationships between gender, insurance

type, prior CVD-related history and PTCA use. However, many non-clinical factors

38

were associated with CABG use. Females were less likely to have CABG compared to
males. Patients who were cared by cardiologists were more likely to have CABG.
Interesting, race was the only demographic variables associated with less use of both
PTCA and CABG. After adjusted for other factors, blacks were significant less likely to
have PTCA compared to whites (OR 0.36, 95% CI 0.20-0.67). Blacks were also less
likely to have CABG either (OR 0.55, 95% Cl 032-096).

We also evaluated the effect of adjusting for additional comorbidity measures
(Charlson Index) in the use of revascularization for the patients who underwent
angiography. The ORs for each predictor variables did not change much with Charlson

Index in the model (Table not shown).

39

Chapter 4

DISCUSSION

4.1 Angiography and revascularization rates in hospitalized AMI patients

This study found that the majority of patients (two-thirds) with acute myocardial
infarction hospitalized in one of five community hospitals in mid-Michigan area
underwent coronary angiography during hospitalization. After angiography, 35.2%
patients received PTCA, 29.6% received CABG and 37.6%.received mediation therapy.
Our results are similar to the study of Pilote32 who evaluated the angiography and
revascularization use in the AMI patients according to region of the United States. He
found that there were region variations in coronary procedure use in AMI patients
among the US. The CA rate was 72% in the west-north central, and rate of PTCA and
CABG was 48% and 19% respectively. The rates of coronary procedures use were

lower in the study of 4823 AMI survivors in the Myocardial Infarction Triage and
Intervention Project 77. Only 47.2% underwent CA, 14.4% underwent PTCA and

10.4% underwent CABG. Other studies have shown that procedure use was much lower

in Medicare patients with AMI. Udvarhelyi16 found during the first 90 days after AMI,
that only 23% of all patients underwent angiography, 8% underwent CABG and 5%
underwent PTCA. High procedure rates in our study are probably due to the availability
of catheterization laboratory facilities in all five participating hospitals. Some studies

have shown that the patients admitted to hospitals with catheterization laboratory were

more likely to undergo coronary angiography or revascularization32’ 78.

40

4.2 Demographics and angiography and revasularization procedures use

Our study explored the relationship between demographic characteristics and the
use of angiography and revascularization procedures in patients with AMI. We found
that demographic factors (such as older age) were associated with a lower rate of
coronary angiography (CA) use. For example, although overall rate of CA use was two-
thirds in our study, patients 75 years and older were less likely to undergo CA,

compared to patients under 45 years of age after adjusting for other factors.

Krumholz79 also found that the percentage of patients who were referred for coronary
angiography decreased significantly with age, fi'om 60% among the patients younger
than 65 years, to 37% among the patients 65 to 79 years old, to 11% among the patients
80 years and older (p=0.0001). Our study indicated among the 591 patients who had
coronary angiography, no statistical significant relationship between age and the
likelihood of undergoing coronary revascularization (both PTCA and CABG) before
hospital discharge after adjusted for other factors, but several ‘large’ ORs indicated a
potentially strong age effect, but these had wide confidence intervals (Table 14).
Race, gender and cardiac procedure use

Numerous studies have reported racial differences in the use of angiography or
revascularization use in CHD patients as well as in AMI patients. Some of the studies

had consistently found that whites with CHD were more likely to undergo CA than
blacks or Hispanic 16, some studies of CA have found rates more than twice as high for

whites than blacks42, 80‘82, while others have found that the rates to be similar in

whites and blacks.

41

Several studies have found that men with CHD are more likely to undergo CA
than women after adjusting for other factors 43, 83, while other found there were no
difference in utilization of CA between men and women with CHD or AMI-7’8: 39, 84'

86 Many of these studies, however, have significant limitations. For example, these
studies often relied on medical-clairns data or administrative data, however, which do

not contain important clinical information needed to identify patients with CHD

accurately and to adjust for differences in the severity of disease or comorbidity87. For
instance, if blacks or women had less extensive coronary disease, fewer symptoms, or
fewer comorbidities, then low rates of coronary revascularization procedures would be
expected.

To overcome the limitations of those studies, we examined the use of CA and
revascularization among patients whose severity of coronary disease was
angiographically defined. We also adjusted our results to reflect baseline differences in
demographic variables, prior CVD history and risk factors, and CVD-related diseases.
Our study found that after adjusting for these confounders, whites and blacks were
equally likely to undergo CA. However, revascularization (both PTCA and CABG) was
performed less frequently in blacks than in whites, women were less likely to have
CABG over medical therapy compared to men. However, they were equally likely to

have PTCA as men (Table 14). Our study results were consistent with those of

Maynard42 who found among 4,891 AMI patients, similar proportions of black and
white patients received coronary angiography during hospitalization, while only 18% of

black patients underwent coronary angioplasty compared with 26% of white patients (p

42

= 0.0004); CABG was also used less frequently in black patients (7% vs 12%, p =
0.002).

Our data also showed on average, women with AMI were 7 years older than
men. Women had more comobidity, such as diabetes (39.2% vs 21.4%), hypertension
(64.3% versus 51.0%). Women also developed more complications of AMI, such as
congestive heart failure (36.7% vs 28.5%), cardiogenic shock (32.0% vs 29.0%)

recurrent angina (56.7% vs 45.7%) than men during hospitalization. Those findings are

consistent with other studies44> 88’ 89. Hendricks found women were on average 5
years older than men (p < .01). By univariate comparison, women were more likely to

have underlying hypertension (p < .01), diabetes mellitus (p < 0.05), and congestive

heart failure (CHF, p < .05) 88.

Explanations for these racial or gender differences in the use of
revascularization are few. It is possible that the patient's preferences for particular
cardiac revascularization may differ according to race or gender. The decision to
undergo coronary procedures is a complex one and can be influenced by the patient's
symptoms, the perceived risks and benefits of the procedures, and other factors, such as
one's trust in medical approaches involving advanced forms of technology. Because
these preferences can alter the final therapeutic decision in many instances, physician-

patient interactions become key to understanding practice patterns of revascularization
in races 90. In this regard, the Coronary Artery Surgery Study (CASS) found that blacks
were slightly more likely to decline CABG when their physicians reconnnend to it91,

92. Schecter and colleagues 93 found in a study of 272 patients that black patients were

more likely than whites to disagree with physicians’ recommendations that they

undergo coronary angiography. Unfortunately, no information has been available about
decision making by patients and physicians concerning coronary procedures in our
study.

Second, it remains possible that unmeasured differences in clinical factors
account forthe lower use of revascularization among blacks or women. Although we
did control for the extent of coronary disease, our measure of coronary disease severity
was relatively crude, we were unable to determine whether a given patient was
"angiographically" suitable for CABG or PTCA. Third, race or gender may be only a
surrogate marker for other socioeconomic factors (such as educational level,
employment status, and farme support structures) which were not available in our study
that may affect decisions about care to an equal or greater extent. Further investigations
must clearly be directed at determining how patients assess the risks and benefits of
coronary procedures and how their interactions with physician may affect that

assessment.

4.3 Clinical characteristics and cardiac procedure use
Coronary angiography use

Our study found that except for an association between recurrent angina and the
subsequent use of angiography, unfavorable prognostic factors such as prior AMI, prior
CHF, prior cardiac arrest, or developing AMI complications, were associated with a

lower and not a higher rate of CA. These findings are in contrast to the published

guidelines}; 71, 72 which stated that all of these factors as major indications for
angiography. While our data suggest that angiography is predominantly performed in

patients with the least potential to obtain a survival advantage from revascularization. It

44

appeared that patients at high risk, the group most likely to benefit from intervention,
had the least chance to undergo angiography and revascularization. The large proportion
of patients undergoing coronary procedures and the clinical variables that predicted the
use of CA in our study are not completely consistent with the criteria identified in
published guidelines and clinical trials. These sources suggest that uncomplicated
infarctions have an excellent prognosis regardless of whether efforts at revascularization

are made, whereas patients with complications have the most to gain from the

procedure353.

In our study, patients who had cardiogenic shock or congest heart failure that
developed during hospitalization as well as patients who had prior MI, CHF or cardiac
arrest were less likelihood to undergo CA than that of patients without these

complications or prior CVD-related history. Spertus and coworker came to a similar

conclusion in an analysis of 4823 MI survival patients77. In their study it was found
that except for recurrent angina, factors predicting higher mortality were associated with
a lower rather than a higher use of angiography, which suggests that many patients who
needed angiography did not receive it.
Revascularization use

In contrast to the angiography, we found that once the angiography was
performed, however, the coronary anatomy chiefly determined the use of
revascularization and the choice of the procedures. The choice of angioplasty as
compared with bypass surgery clearly followed the pattern of “angiography for one or

two-vessel disease” and “bypass surgery for three-vessels or lefi main disease”, as is

consistent with current guidelineslza 71: 72. In our study population, coronary disease

was less extensive in the PTCA group and more extensive in the CABG and medical
therapy groups. Majority of patients underwent PTCA are one or two-vessels disease
(86.4%), while majority of patients underwent CABG are left main disease or three
vessel disease (71.6%). All otherclinical or demographic factors were much less
important in determining PTCA use.

These findings point to a divergence between an ideal decision-making strategy
and the reality of clinical practice. First, clinicians appear to see younger age as a key
factor. Second, clinicians appear to be selecting the patients likely to have good
procedural outcomes rather than those who would derive the most benefit from a
procedure. Third, insurance type plays a role in the decision-making of angiography. In
an ideal world, clinicians would develop an overall estimate of the likely outcome given
one treatment as compared to another, and would preferentially allocate resources to
patients with more potential for benefit. If this had occurred in the cases we studied,
angiography would have been performed much more often in older patients, and the
majority of revascularization procedures would have been done in patients who develop
complications of AMI.

Given the observational nature of our study, our results are more likely to reflect
true practice patterns seen in communities. The ACC/AHA quality indicators are
practice guidelines based largely on evidence from randomized clinical trials and were
widely accepted even by the time this study was conducted. Why then does this gap

between the actual care provided and the guidelines exist? Physicians may be unaware
of the guidelines or disagree with their content, or they may be resistant to guidelines94a

95. Alternatively, changes in behavior lag behind knowledge.

46

Gaps between physician knowledge and practice have important consequences.
AMI is a common and Serious condition, and the evidence from clinical trials strongly
suggests that adherence to these established guidelines will result in better patient
outcomes. It is undoubtedly true that some AMI patients experience unnecessary
morbidity or mortality because they receive substandard medical care.

Although it may be possible to maintain or enhance the quality of care for
patients through lower rates of use of procedures, we need to suggest specific situations
in which clinicians should consider changes in current practice. To understand this
issue, we should focus on clinical strategies, studies of strategies that provided
information that can guide clinicians in making decisions and indicate opportunities for

improvement in the care of patients.

4.4 Study limitations

There are several limitations to this study that should be noted. First, the
analyses were restricted to the influence of a relative small number of clinical factors
and demographic factors. There was no method for evaluating the effects of other
factors that may influence the decision to undergo invasive patients management such
as fears of malpractice, types of patients employment, patient preferences, or physician
reimbursement. No information on physician and/or patient decision-making. Second,
we did not have the information on the time ordering of developing complications of
AMI and cardiac procedure use.

A third potential limitation of this study-is focus on procedures performed only

during the hospitalization and which is a relative short time frame. It is possible that the

47

use of an expanded time window to include post discharge procedure utilization may
have altered these findings.

The fourth potential limitation of this study is a single geographic location with
all five hospitals licensed to perform coronary procedures. Several studies have
demonstrated that the presence of an on-site coronary angiography laboratory at the
admitting hospital is an important predictor of subsequent angiography. The'presence of
an angiography laboratory appears to be a more important predictor than the clinical
characteristics of the patient, including whether he or she has postinfarction angina or
shock. Every and coworkers found that patients with AMI who were admitted to

hospitals with angiography facilities were about three times more likely to undergo

angiography than patients admitted to hospital without such facilities96.

In conclusion, the use of coronary procedures among patients with AMI is more
prevalent in our MICH population. Instead of the presence of high-risk clinical
characteristic, which is associated with a greater benefit from revascularization, younger
age appears to be the primary predictors of the use of coronary angiography. Aside from
age, the present of complications of AMI negative prognosis factors and no insurance
predominately determine the less likelihood of angiography use. However, once the
angiography is performed, the coronary anatomy largely determines the use of

revascularization and the choice of the procedure.

48

APPENDIX A

49

 

Table 1 Classification Recommended by ACC/AHA for Indications for 3
Diagnostic Procedure, a Particular Therapy, or an Intervention in

Patients with AMI

 

 

 

 

 

 

Class I Conditions for which there is evidence and/or general agreement that a
given procedure or treatment is beneficial, useful, and effective.

Class 11 Conditions for which there is conflicting evidence and/or a divergence
of opinion about the usefulness/efficiency of a procedure or treatment

Class H a Weight of evidence/opinion is in favor of usefulness/efficiency

, Class H b Usefulness/efficacy is less well established by evidence/opinion

Class III Conditions for which there is evidence and/or general agreement that a
procedure/treatment is not useful/effective and in some cases may be
harmful

 

 

50

Table 2 Baseline Characteristics and Prior CVD-Related Histories Among the

 

 

 

 

 

 

 

 

 

 

Total Population
Total (846)
N (%)
Age group, year
<45 86 (10.2)
45-54 142 (16.8)
55-64 188 (22.2)
65-74 205(24.3)
>75 225 (26.6)
Female Sex (% of patients) 319 (37.7)
Race
White 707(83.6)
Black 128 (15.1)
Other 11 (1.3)
Insurance
Commercial 321 (38.3)
Medicare 456 (54.4)
Medicaid 26 (3.1)
No-insurance 35 (4.2)
Hospital
A 168 (19.9)
B 344 (40.7)
C 71 (8.4)
I) 217 (25.7)
E 46 (5.4)
Cardiologist involved (yes) 774 (91.5)
CVD-related history (°/o of patients)
Myocardial infarction 231 (27.3)
Angina 221 (26.1)
CHF 131 (15.5)
Cardiac arrest 15 (1.8)
Risk factors (% of patients)
Hypertension 474 (56.0)
Diabetes 238 (28.1)
Hypercholesterolemia 186 (22.0)
Prior coronary procedures
Prior Angiography (CA) 186 (22.0)
Prior Angioplasty (PTCA) 87 (10.3)
Prior Bypass surgery (CABG) 111 (13.1)

 

CHF: congestive heart failure, CVD: cardiovascular disease

Table 3 Clinical Characteristics of AMI Among the Total Population

 

 

 

 

Total
(N= 846)

Median of peak cardiac enzyme (IU/liter)

CK 760

CKMB 72

LDH 293
Infarction location N (%)

Anterior 255 (30.1)

Inferior 312 (36.9)

Other 140 (16.6)

Missing 139 (16.4)
In-hospital Complication of AMI N (%)

Recurrent angina 422 (50.0)

Cardiogenic Shock 255 (30.1)

New onset CHF 267 (31.6)

VTNF arrhythmia 60 (7.1)

Asystole or AV block 81 (10.0)

 

CK: creatine kinase; CK-MB: creatine kinase MB, LDH: Lactate dehyogenase; SBP:
systolic blood pressure; DBP: diastolic blood pressure; HR: heart rate; VT/VF
arrhythmia: Ventricular tachycardia/ ventricular fibrillation arrhythmia

Table 4 Univariate Associations of Baseline Characteristic and the Likelihood of

Undergoing Coronary Angiography

 

 

 

 

 

 

 

Variables Total CA OR 95% CI P
N N (%)
Age group, year <0.0001
<45 86 77 (89.53) 1.00
45-54 142 121 (85.21) 0.65 028-151
55-64 188 155 (82.5) 0.55 0.24-1.16
65-74 205 148 (72.2) 0.30 0.13-0.62
>75 225 118 (52.4) 0.13 0.06-0.26
Gender <0.002
Male 527 405 (76.9) 1.00
Female 319 214 (67.1) 0.61 0.45-0.94
Race <0.2353
White 707 521 (73.7) 1.00
Black 128 88 (68.8) 0.79 0.53-1.19
Other 11 10 (90.9) 3.57 0.68-65.7
Insurance
Commercial 321 288 (89.7) 1.00 <0.0001
Medicare 456 284 (62.8) 0.19 0.17-0.28
Medicaid 26 18 (69.2) 0.26 0.10-0.64
No-insurance 35 25 (71.4) 0.29 0.13-0.65
Hospital 0.0127
A 168 106 (63.1) 1.00
B 344 257 (74.7) 1.73 1.16-2.57
C 71 50 (70.4) 1.40 077-257
D 217 170 (78.3) 2.11 1.35-3.30
E 46 36 (78.3) 2.11 1.01-4.75
Cardiologist involved <0.1 161
No 72 47 (65.3) 1.00 '
Yes 774 572 (73.9) 1.51 0.89-2.49

 

OR: Odds Ratio; CI: confidence interval; CA: coronary angiography

53

Table 5 Univariate Associations Between Prior CVD-Related Histories, Coronary
procedures and Cardiac Risk Factors and the Likelihood of Undergoing

 

 

 

 

 

 

 

 

 

 

 

Coronary Angiography
Variables Total CA OR 95% CI P
N N (%)
Prior CVD-related history
AMI <0.0001
Absent 615 483 (78.5) 1.00
Present 231 136 (58.9) 0.39 0.28-0.54
Angina <0.1249
Absent 625 466 (74.6) 1.00
Present 221 153 (69.2) 0.77 0.55-1.08
CHF . <0.0001
Absent 715 561 (78.5) 1.00
Present 131 58 (44.3) 0.22 0.15-0.32
Cardiac arrest <0.0005
Absent 835 4 (26.7) 1.00
Present 15 615 (74.0) 0.13 0.04-0.38
Risk factor
Hypertension <0.2221
Absent 372 280 (75.3) 1.00
Present 474 339 (71.5) 0.83 0.61-1.12
Diabetes <0.0366
Absent 608 457 (75.2) 1.00
Present 238 162 (68.1) 0.70 0.51-0.98
Hypercholesterolemia <0.0001
Absent 660 457 (69.2) 1.00
Present 186 162 (87.1) 3.00 1.93-4.85
Prior cardiac procedure
Prior Angiography <0.4435
No 660 487 (73.8) 1.00
Yes 186 132(710) 0.87 0.61-1.25
Prior Angioplasty <0.3938
No 759 552 (72.7) 1.00
Yes 87 67 (77.0) 1.26 0.76-2.17
Prior Bypass surgery <0.0001
No 735 555 (75.5) 1.00
Yes 111 64 (57.7) 0.44 0.29-0.67

 

OR: Odds Ratio; CI: confidence interval; CVD: cardiovascular disease; CA: coronary
angiography

Table 6 Univariate Associations Between Infarction Characteristics and the

Likelihood of Undergoing Coronary Angiography

 

Variables N CA OR 95% CI P
N (%)

Infarction Characteristics

Peak cardiac enzyme (IU/liter)

 

 

 

CK <0.0070
_<. 760 427 295 (69.1) 1.00
>760 419 324 (77.3) 1.53 1.12-2.08
CKMB <0.0090
S 72 444 308 (69.4) 1.00
>72 402 311 (77.4) 1.11 1.11-2.06
Infarction location <0.1637
Anterior 255 179 (70.2) 1.00
Inferior 312 241 (77.2) 1.44 0.99-2.10
Other _ 140 104 (74.3) 1.23 0.78-1.97
In-hospital Complications of AMI
Recurrent angina <0.0404
Absent 424 297 (70.1) 1.00
Present 422 322 (76.3) 1.38 1.02-1.87
Cardiogenic Shock <0.0001
Absent 591 470 (79.5) 1.00
Present ' 255 149 (58.4) 0.36 0.26-0.50
New onset CHF
Absent 579 454 (78.4) 1.00 <0.0001
Present 267 165 (61.8) 0.45 0.32-0.61
VT/V F arrhythmia <0.0005
Absent 786 589 (74.7) 1.00
Present 60 32 (53.3) 0.39 0.23-0.66
Cardiac arrest <0.0001
Absent 765 586 (76.6) 1.00
Present 81 33 (40.7) 0.21 0.13-0.34
TT use <0.0001
Yes 387 331 (85.5) 1.00
No 549 288 (62.8) 0.29 0.20-0.40

 

CK; creatine kinase; CK-MB; creatine kinase MB; LDH: Lactate dehyogenase; SBP:
systolic blood pressure; DBP: diastolic blood pressure; HR: heart rate; TT: thrombolysis
therapy; VT/VF arrhythmia: Ventricular tachcardiac/ ventricular fibrillation arrhythmia;
OR: Odds Ratio; CI: confidence interval; CA: coronary angiography

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Figure 4 Diagnostic Coronary Angiography (CA) United States: 1979—97

74

 

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Figure 5 Percutaneous Transluminal Coronary Angioplasty Procedures
(PTCA) United States: 1986—97

 

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Figure 6 Coronary Artery Bypass Graft Procedures and Patients United
States: 1979-97

76

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77

Missing None
Left main disease 3.1% 3.9%

9.2%

     

A I' , One-vessle
- 31.5%

Three—vessel ‘
25.2%

Two-vessel
27.1 %

Figure 8 Coronary Anatomy Characteristics for Patients Who Underwent
Coronary Angiography (N=619)

78

APPENDIX C

MICHIGAN STATE UNIVERSITY
INTER-INSTITUTIONAL COLLABORATIVE HEART STUDY (MICH Study)

Consent Form

1.

SUMMARY EXPLANATION OF THE STUDY: I am being asked to take
part in a research study sponsored by Michigan State University College
of Human Medicine. l have been diagnosed with a heart attack. This
study is being done in order to look at how heart attacks are being
treated in several hospitals in the State of Michigan. I will be interviewed
to determine my state of health at the time of my heart attack.
Information in my hospital chart will be studied to determine my medical
condition and the treatments that I received while I was In the hospital.
Also, I will be interviewed over the telephone at three, six, nine and
twelve months after I am discharged from the hospital to determine how I
am doing.

ESTIMATE OF THE SUBJECT'S TIME: The interview in the hospital will
take about thirty minutes. The telephone interviews after I leave the
hospital will take ten to fifteen minutes. ~

VOLUNTARY PARTICIPATION l freely consent to participate in this
study. I may choose not to answer any of the questions during the
interview at any time. I understand that I may stop the interview at any
time if I choose to do so. I understand that I may also choose not to
answer any of the questions during the telephone interviews after my
discharge from the hospital. My participation in all aspects of this study
is voluntary. If I refuse to participate in this study, it will not make any
difference in the quality of any treatment that I may receive at this
hospital. If I agree to participate in this study, I may change my mind and
withdraw my participation at any time. If I later refuse to continue
participating, it will not make any difference in the quality of any
treatment I receive at this hospital.

CONFIDENTIALITY AND ANONYMITY: The investigators will keep all of
the information obtained in this study confidential. No information
obtained from this study that can be associated with me or my identity
will begiven to anyone without my permission within the limits of the law.
I understand that the information obtained in this study may be published
for scientific purposes provided that my identity is not revealed.

79

5. PAYMENT FOR BEING IN THE STUDY: I understand that I will not be
given any payment for participation in this study.

6. POTENTIAL RISK: The interviews should cause no significant risk to
me. I realize that I may refuse to answer any question that makes me
nervous or uncomfortable.

7. POTENTIAL BENEFITS: The benefits that I will receive personally from
participating in this study are minimal. If, during the interview, I think of
any questions that I want answered about my medical care during this
hospitalization, I will be encouraged to discuss this with my physician.
This could possibly improve communication between me and my
physician. Investigators hope that this study will be of very significant
benefit to society in general. It is hoped that this information will help
doctors better understand what tests and what treatments are most
effective for people who have heart attacks.

8. CONTACT PERSON: If I have any questions later, Dr. Susan Smith at
(313) 762-2063 or Dr. Ralph Watson at (517) 336-2404, will be happy to
answer them.

9. CONSENT: I have read, or had read to me, the above information
before signing this consent form. I have been given plenty of opportunity
to ask questions and have received answers that fully satisfy those
questions. If I do not participate, or if I discontinue my participation in
this study, it will not affect my treatment in this hospital and I will not give
up any of my legal rights. I volunteer to take part in this study.

I have received a signed, dated, and witnessed copy of this Informed Consent
Agreement.

 

 

 

 

 

 

Patient's Signature Date
Witness Date
Signature of Investigator Date

80

APPENDIX D

Study Record Number:

Hosp. of Initial Arrival .................................. __ _
Arrival date _ _ / __ _ _ _
mm dd yy
Transfer from Hospital ................................. _ _
Arrival date _ _ / __ _ _ __
mm dd yy
Transfer t_o Hospital (after identification) ............... __ _
Arrival Date _ _ / _ __ __ _
mm dd yy
Final Discharge Date ............. _ _ / _ _ _ _
mm dd yy
Primary Insurance NlC(99) .......................... __ _ _
Secondary Insurance NIC(99) ..................... _ __ _
Date ofBirth: __l__ __
mm dd yy
Sex: Male (1) /Fema/e (2) ........................................... _
Race (1)Aleut, Eskimo or American Indian/ ........................ __
(2)Asian/Pacific Islander, (3)Black, (4)White, (5)0ther, (9)NIC
Hispanic origin No(1)/Yes(5)/NIC(9) .......................... _
Marital status ..................................................... __
(1)/Married, (2)0ivorced, (3)Widowed, (4)8eparated, (5) Never married, (6)8ingle, (9)NIC
DateofMl ............................... __l__ __
mm dd yy
Did Ml occur in hospital? ................................. _
No ( 1) / Yes-ln-palient (5) / Yes Out-patient (8)
Onset of chest pain:
Date: .................................. _ _ / _ _ _ _
mm dd yy
Calculated( 1) or Explicit(2) ....................................... _
Time: ............................................. _ _'_ _
hh mm
Calculated( 1) or Explicit( 2) ....................................... _
Arrival of EMS:
Date: .................................. __ _ / _ _ _ _
mm dd yy
Time: ............................................. _ _'_ _
hh mm
Arrival in first ED:
Date: .................................. _ _ _ _ _ _
mm dd ' yy
Time: ............................................ _ _'_ _
hh mm
Cardiologist: ..................................................... __

Not involved{1)/ Admitting(5)/ Consulted(7)

81

 

 

 

 

 

 

 

Initial Peak Value Upper
ENZYMES Limit of
(NIC=9's) Normal
CK _ _ _ _ _ _ _ __ _ _ ...
CKMB (amt) ___-__ ____.__ _
CKMB (%) or Index __ _ ___ _. _.

 

 

Symptoms during present event:

Severe discomfort in the:
No( 1), Yes or non-specific(5), Right(2), Left(3), Both (4), NIC (9)
anterior chest .......................................

 

back ..................... _. ................................ _
epigastrium .......................................... _

jaw ....................................................... _

neck ...................................................... _
shoulders ............................................. _

elbow .................................................... _
forearm or wrist ................... l ................ _

arm ....................................................... __

No(1), Yesl5). MC (9)

Shortness of breath ........................................ __
Nausea ............................................................. __
Diaphoresis ..................................................... _
Dizziness ...... . ........... .. ...................................... _

Past Medical History
Smoke tobacco Never(1), quit(3), Current(5), NIC(9)

 

If quit, number of years since quit ............... _ _
Type of tobacco No(1l. Yes(5). MC (91
cigarettes ............................................... _
cigars ...................................................... _
pipe ........................... . ............................. _
other ....................................................... _

[Specify] ..

 

82

 

Years smoked ................................................

# cigarettes smoked per day ...................

(1 pack = 20 cigarettes)
. N(1)/Y(5)/NIC(92 Duration rs
History of DKA ......... . ................

Currently on diabetic diet ......... _

Hypertension .............................

High cholesterol Unknown(7) .........

Angina .......................................

Previous cardiac interventions
N(12/Y(52/NICL9) X261!
CABG ............................................

Angioplasty ..................................

Thrombolysis. ..............................

# of episodes ...................................

Type of most recent TT before this admission None(1)/tPA(2)/SK(3)/ UK(4)/APSAC(5)/ not
specified(6)/ NIC(9) ...................................... . ...............................

Catheterization .........................
Perm. Cardiac Pacemaker ...........
Prosthetic valve .................... , ......

Implantable Cardiac
Defibrillator ...................................

Cardiac arrest (suspected =7) .............

History of disease/Comorbidity at admission

Never ( 1) Notes
Suspected(3)
Cun'ent (5)
In past (7)
Both (8)
N349)

 

 

Myocardial infarct

 

Congestive heart failure

 

Peripheral vascular disease

 

Cerebrovascular disease

 

Dementia

 

Chronic pulmonary disease

 

 

 

 

83

 

 

Connective tissue disease

 

Ulcer disease

 

Diabetes

Evidence of end organ damage?

(I)N0/(5) Yes/ (9)NIC

(non-diabetic enter 9)

Duration of diabetes in
years:
(non-diabetic enter 0)
Treated by diet alone?
N(1)/Y(5)/NIC(9)

(non-diabetic enter 1)

 

 

Hemiplegia

 

Moderate or severe renal disease

 

Any tumor

 

Metastatic solid tumor

 

Leukemia

 

Lymphoma

 

Mild liver disease

 

Moderate or severe liver disease

 

AIDS

 

Other[specify in notes]

 

Other[specify in notes]

 

 

 

 

Hospital Course
Recurrence of angina or

ischemic symptoms ..........................................

Date:

Time:

Hypotension requiring Intervention .................

N/ll/WSZ/Nlegl

84

 

Diagnosed during hospital course
N(1 I/Y(52/NIC(92 confirmed

 

by X-ray
Pulmonary Vascular
Congestion .............................. _ _
Pulmonary Venous
Cephalization ........................... _ _

Pulmonary Edema
Kerley B-Lines .........................
Congestive Heart Failure ........ __

Arrhythmias N(1)/Y(5)/NIC(9) .................................
Date:

Time: '

Type .................................................... _ __

Type: (1)sinus tachycardia, (2)sinus bradycardia, (3)sinus dysrhythmia, (4)atn'al premature contractions/APC/PAC,
(5)3upraventn'culartachycardia/SVT, (6)atn'al flutter, (7)atn'al fibrillation, (8)Junctional escape mythmmodal),
(10)premature junctional contractions, (11)premature ventricular contractions/PVC, (12)ventricular tachycardia,
(13)torsades de pointes, (14)ventn'cu/ar fibrillation, (15)first degree AV heart block, (16)second degree AV heart
block/Mobitz type I/Wenckebach, (17)seconddegree AV heart bloc/Mobitz type II, (18)third degree AV block/complete,
(99)NIC

Tachycardia

Supraventricular tachycardia N(1)/Y(5)/NIC(9) .....
enter YES if either A. flutter or A. fib. present

Atrial flutter N(1)/Y(5)/NIC(9) ..................................
Atrial fibrillation N(1)/Y(5)/NIC(9) ...........................
Nonsustained ventricular tach. N(1)/Y(5)/NIC(9) ..
Sustained ventricular tach.(>3o sec) N(1)/Y(5)/NIC(9)__
Ventricular fibrillation N(1)/Y(5)/NIC(9) .................

AV block ..........................................................
1(1) ”(2) ”1(3) not specified(4) No(7) N!C(9)

Electrical defibrillation or cardioversion
None(1)/ During Transport(3)/ In Hosp. (5)/ Both(7)/ NlC(9) .......

 

Conggction _Defects ..................................... N(1l/Y(5l/NIC(92
Atrioventricular dissociation .......................... __
Asystole (sinus arrest) ........................................... __
Complete heart block ...................................... __

Pacemaker use None(1)/ Temporary(5)/ Permanent(8)

85

Complications durinLhospitalization
Date of procedure or NIC(9's)

Pleuritis (x-ray,ECHO) ................. _ _ / _ _ / _ _
Pleurocarditusrx-ray,ECH0) ....... __ _ / _ __ / _
Pleural effusion(x-ray, ECHO) ...__ _ / _ _ / _ _
Pericardial effusion

(x-ray or ECHO) __ _ __‘ __ _ _

Tamponaderrscrm) _ _ __ _ __ _
Cardiac arrest _ __ _ _ _ _
Ruptured Papillary muscle

or chordae tendinae ............. _ __ / _ _ / _ __
Ventricular septal rupture ..... _ / _ _ / _ _
Ventricular wall rupture ........ __ / _ _l _ _
Thrombus (ECHO) .................... _ _ / __ __ / __ _
Death ..................................... __/____/__

[complete mortality form]

 

 

Pneumonia N(1)/Y(5)/NIC(9) ................................... __
Sepsis N(1)/Y(5)/NIC(9) ........................................... _
Acute Renal Failure N(1)/Y(5)/NIC(9) ..................... __
Stroke N(1)/Y(5)/NIC(9) ........................................... __
Hemorrhage N(1)/Y(5)/NIC(9) ................................. _
Hematuria N(1)/Y(5)/NIC(9) ................................ _
Other N(1)/Y(5)/NIC(9) ............................................. _
[Specify]
Procedures l treaLments dam
Cardiac Catheterization #1 ............................. Egg
Cardiac Catheterization #2 ............................. _
Cardiac Surgery] CABG .................................. __
PTCA ............. . .................................................. _
Endotracheal Intubation ................................. _
Date .................................. _ _ / __ _ / __ _
lntra-Aortic Balloon Pump .............................. __
Date ...................... . ........... _ __ _ __ _ __
Echocardiogram ............................................ __

86

Radionuclide Ventriculogram (RVG)IMUGA.. _

 

 

 

 

 

Date .................................. _ _ / _ _ / _ _
LVEF % ................................................ _ _ _
RVEF % ................................................ _ _ _
Exercise tolerance test (577) (Rate Limited) ........... _
ETI' (Rate Limited) with radionuclide
SPECT scan .................................................... _
Dipyridamole or Adenosine SPECT scan ...... _
Stress Echo ............................ . ...................... _
Other procedure .............................................. _
Date .................................. __ __ / _ _ _ __
[Specify] .........
Abstractor’s Signature personnel code
Reviewer’s Signature personnel code

87

/ /

Date Completed

/

Date Passed

10.

11.

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