Severity of Coronary Artery Disease Among Blacks with Acute Myocardial Infarction

Richard Cooper, MD, Angel Castanet-, MD, Adalberto Campo, MD, Najma Islam, and Brian Simmons, MD

A growing body of evidence suggests that survival after acute myocardial infarction (AMI) is consider- ably worse among blacks than whites. The severity of coronary artery disease (CAD), as measured by the number of diseased vessels and the degree of left ventricular dysfunction, is the major determi- nant of survival after AMI. To determine whether or not the severity of CAD could explain the poor prognosis in a cohort of blacks followed at this in- stitution, cardiac catheterization was performed in a consecutive series of 51 patients <70 years of age. All patients were studied within 2 weeks after AMI. The mean age of the patients was 56 f 8 (mean f standard deviation) and 71% were men. A SO narrowing in 0, 1,2 or 3 coronary arteries was noted in 5,24,40 and 31%, respectively. Left main stenosis was present in 3 patients (6%) and the mean left ventricular ejection fraction was 55%. In a subgroup of 20 patients echocardio- graphic estimates of left ventricular mass/height yielded a mean of 196 g/m, and left ventricular hy- pertrophy on echocardiogram was present in 74%. These data indicate that among blacks with AMI in this series CAD was only modestly more severe than expected and suggest that other factors most likely explain the high mortality in blacks after hos- pital discharge.

(Am J Cardiol 1989;63:788-791)

From the Division of Cardiology and Section of Clinical Epidemiology, Department of Medicine, Cook County Hospital, Chicago, Illinois. This study was supported by grant ROl HL36723 from the National Insti- tutes of Health, Bethesda, Maryland. Manuscript received October 7, 1988; revised manuscript received December 30, 1988, and accepted January 3, 1989.

Address for reprints: Richard Cooper, MD, Division of Adult Car- diology, Cook County Hospital, 1835 West Harrison Street, Chicago, Illinois 60612-9985.

A lthough it has been well recognized for several years that survival rates among blacks with chronic diseases, particularly cancer,’ are re-

duced, attention has only recently focused on racial dis- parities in survival with chronic cardiovascular disease. Controversy persists over incidence rates of coronary artery disease (CAD) among blacks,2-4 yet there is al- most universal agreement that blacks with symptomatic CAD have reduced long-term survival.5-g In addition to our own prospective reports on patients followed after acute myocardial infarction (AMI) and cardiac cathe- terization,6 data from 2 large clinical trials’,* and the Coronary Artery Surgery Study Registry9 indicate higher mortality in blacks compared to whites. Lower socioeconomic status, limited access to medical care and a higher prevalence of co-morbid conditions could all contribute to this increased mortality risk. Specific car- diovascular conditions that might be amenable to treat- ment should also be carefully considered. Blacks have been shown to delay in seeking care for CAD, and dem- onstrate less knowledge of coronary risklOJ1; these fac- tors could be associated with more severe disease when blacks present for treatment. At the same time, the catheterization studies published to date on black pa- tients with angina have reported significantly less CAD than among whites.12-l6 Is this also true when AM1 is the incident event?

METHOD5 Patient recruitment: In previous investigations a

high post-AM1 mortality was identified in the cohort of patients being followed in our registry.5 As already not- ed, previous research suggested the hypothesis that a greater prevalence of severe CAD might explain this observation. Therefore, we established a protocol to investigate this question prospectively. Between April 1986 and December 1987, 87 black patients under the age of 70 were admitted to our institution with a docu- mented AM1 and survived at least 7 days. Fifty-seven of these patients agreed to undergo catheterization (67%) and complete data were available on 51 (59%). AM1 was defined as the presence of 2 or more of the follow- ing: typical chest pain, 2 times the normal elevation of creatine kinase in association with an MB fraction of >5%, and serial electrocardiographic changes.lO During the study period a total of 163 patients were admitted with the confirmed diagnosis of AMI. Twenty-one died in hospital (13%). Of the remaining 142 patients, 30

788 THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 63

were over 70 years of age and another 33 were non- black.

Cardiac catheterization and other clinical data: Cardiac catheterization was performed within 2 weeks of the AMI. As described in detail elsewhere,6J2 both left- and right-sided heart studies were performed in all patients and coronary cineangiograms were obtained in multiple projections. t2 Left ventricular angiograms were obtained in the 30° right anterior oblique projection and the ejection fraction was calculated with the single plane method. CAD was defined as the presence of a diameter stenosis of 250% in any major coronary ves- sel; all other lesions were considered nonobstructive. Stenosis of the left main coronary artery was judged to be present if a 150% narrowing was observed as well.

Two-dimensional echocardiograms were performed in the 30° left lateral position and M-mode tracings were generated from the cursor-derived 2-dimensional images. Cardiac dimensions were estimated using stan- dards of the American Society of Echocardiography,17 and all estimates were made to the nearest 1 .O mm. Left ventricular mass was estimated from M-mode tracings, and indexed to height, as previously described.18

Measures of socioeconomic status: Socioeconomic status was estimated by matching home addresses to 1980 race-specific census tract data using procedures available from the Chicago Area Geographic Informa- tion Study, Department of Geography, University of Il- linois at Chicago.6 In this sample 84% of the patients could be matched to a census tract. (Nonmatches oc- curred primarily because of nonexistent addresses or less than 6 family units in the race-specific category in a tract and subsequent suppression of the data on the Census Bureau tapes.)

Statistical analysis: Data were analyzed with com- puter programs available on SPSS-PC+ (SPSS, Inc.). Descriptive data are presented as frequencies and means f 1 standard deviation.

RESULTS Descriptive characteristics of the study patients are

listed in Table I. There was a preponderance of men, and hypertension and diabetes mellitus were common. As noted previously,l” a very long delay occurred before patients sought medical care. Patients in this sample were uniformly poor or working class (Table II). Medi- an education level was just under that of high school completion and 84% of those employed held blue-collar jobs.

Angiographic studies demonstrated a 5% prevalence of normal coronaries, and left main stenosis was noted in 6% (Table III). Two- and 3-vessel CAD was com- mon; 71% of the patients were in this multivessel cate- gory. The mean ejection fraction was in the low normal range and 39% of patients had an ejection fraction <45%.

Echocardiograms performed in 20 patients demon- strated a high prevalence of left ventricular hypertrophy (Table IV). Seventy-four percent of patients were found

TABLE I Descriptive Characteristics of 51 Black Patients

Undergoing Angiography After Myocardial Infarction

Variable

nge brs) Men (%) Medical history

Prior MI (%) Stroke (%) Drabetes mellitus (%) Systemic hypertensron (%)

Cigarette smoking Never (%)

Current (%) Former (%)

Alcohol consumption Never (%) Current (%) Former (%)

Time before seekingmedrcal care (hrs) Peak creatine kinase (mg/dl)* Electrocardiogram

Q waves (%) Left ventricular hypettrophy (“IO)

*n=38 All f values are mean h standard dew&ion.

Response

56f8 71

31 6

39 81

24

56 16

51 18 29 17 f 25

558 f 331

29 29

TABLE II Socioeconomic Characteristics from Census

Tracts of Residence of 43 Black Patients with Acute

Myocardial Infarction

Variable Response I

TABLE Ill Angiographic Findings in 51 Black Patients with

Acute Myocardial Infarction

) Variable Response 1

No. of vessels with coronary stenosis 250% 0 (%) 1 (%) 2 (%) 3 (%) Left main (%)

Ejection fraction (%) Cardiac index (liters/mrn/m2) Left ventricular enddiastolic pressure (mm Hg) Pulmonary artery mean pressure (mm Hg)

All f values are mean f standard deviation.

5 24 40 31

6 55f16

2.57 f 0.53 13.7 f 6.7 18.1 f 6.0

to have left ventricular hypertrophy based on criteria from the Framingham Study,16 and septal thickening was particularly prominent.

DISCUSSION Our data suggest that in blacks AM1 occurs at the

same time interval in the course of the development of CAD as among other population groups.19-22 Multi- vessel CAD was more common among the patients re-

THE AMERICAN JOURNAL OF CARDIOLOGY APRIL 1, 1989 789

CAD WITH AMI AMONG BLACKS

TABLE IV Echocardiographic Findings in 20 Black Patients

with Acute Myocardial Infarction

Vanable

Diastolic internal diameter (cm) Systolic Internal diameter (cm) Septal thrckness (cm) Posterior wall thrckness (cm) Fracbonal shortening (%) LV mass-actual (g) LV mass/height (g/m) Prevalence of LV hypertrophy (%)

All f values are mean * standard deviation LV = left ventricular.

Response

5.4f 1.0 4.0 f 1.2

1.17f0.25 l.llf0.25

27f 10 322 f 134 125 f 82

75

ported here than in other published series, although our small sample size precludes firm conclusions about sig- nificant differences. In the National Hospital Discharge Survey,23 we previously reported that age-adjusted in- hospital fatality rates were the same among blacks and whites. This supports the contention that the underlying cardiac disease was of similar severity. Significantly more severe CAD is thus not likely to be the reason for the roughly 50% lower post-AM1 survival rate observed in this cohort5 The data in this study further suggest that the findings reported among blacks undergoing an- giography for chest pain12-16 are not representative of disease prevalence; the high rate of normal coronaries found in these studies probably reflects different refer- ral patterns and a higher prevalence of noncoronary chest pain syndromes among blacks.

The severity of CAD in the patients studied here is similar to that reported by Sanz et a1.20 In 259 consecu- tive men under 60 years of age the prevalence of l-, 2-, and 3-vessel CAD was 34, 33 and 26%, respectively; 7% of patients had nonobstructive lesions and left main ste- nosis was present in 1%.20 In a second report of a larger series from this group, 3-vessel CAD was noted in 24% of 462 consecutive patients.19 In a similar series of 229 patients under 60 years of age studied after AMI, 58% had l-vessel CAD, 26% had 2-vessel CAD and only 9% had 3-vessel CAD.21 Finally, De Feyter et a122 reported a 15% prevalence of 3-vessel disease in 222 patients catheterized after AMI. Coronary stenosis was de- fined as a 50% lesion by Sanz20 and DeFeyter22; in con- trast Roubin et a121 defined it as a 70% lesion. This might explain part of the discrepancy in their findings. From these angiographic studies it would appear that fewer than 25% of patients with AM1 have 3-vessel CAD, and not more than 60% have multivessel CAD. Combining patients with 2- and 3-vessel CAD in the present series yields a rate of 71%. After AM1 the ex- pected mean left ventricular ejection fraction would likewise be in the range of 45 to 55%.19 In our series it was at the upper end of this range. In contrast, there- fore, to extensive findings of a lower prevalence of CAD among blacks undergoing elective cardiac catheteriza- tion 12-16 in the present study of blacks after AM1 the pat;ern of CAD was at the upper range of severity de- scribed for other populations.

790 THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 63

The sample included in this study was of modest size, and it is possible that we were unable to detect important differences in the distribution of CAD. We also recognize that the recruitment procedures could have created a biased response. Patients dying early in the hospital course of AM1 will not be represented in studies based on nonemergent catheterization. At the same time the catheterization participation rate was less than two thirds, and it is possible that patients with a more benign course might have been less willing to un- dergo the elective procedure. Other studies have often excluded persons over 60, and CAD will be more severe on the average in the elderly. Studies restricted to pa- tients having their first AM1 will also report less severe disease.

Although data were available only in a subgroup, the prevalence of left ventricular hypertrophy was strik- ing. Previous evidence from our cohort strongly suggests that left ventricular hypertrophy on the echocardiogram is a powerful predictor of mortality.18 Left ventricu- lar hypertrophy is more common among blacks than whites24 and this is probably the most important biolog- ic factor accounting for the poor prognosis of blacks af- ter AMI. Additional prospective studies are needed to evaluate this hypothesis.

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