This study examined the characteristics of patients undergoing coronary arteriography; secular changes in the racial distribution of this population; patient selection for coronary artery bypass grafting (CABG); and possible explanations for the demonstrated fewer invasive diagnostic evaluations and less-frequent use of CABG among blacks compared with whites. Patients who underwent arteriography or CABG at a university medical center in Alabama during the period from 1970 to 1978 were eligible for the study. Prospective follow-ups were conducted annually through 1983 using a mail questionnaire and telephone interviews. (Follow-up rates were not reported.)

Of this population, 4.2% was black and 95.8% was white. In order to examine trends in patient registration, data were divided into two periods: 1970-1974, and 1975-1978. During the later period, 57.4% of black males, 80% of black females, 60.3% of white males and 62.9% of white females were evaluated. While there was an increase in the proportion of black females evaluated, there was no increase in the proportion of black males evaluated.

With regard to CABG, only 16.2% of blacks had CABG initially versus 42.5% of whites. The white population was older, had a higher prevalence of definite angina, and had more history of myocardial infarction (males only), but had fewer smokers, less hypertensives, lower average blood pressure, and fewer congestive heart failures. The percentage of individuals with multiple-vessel disease was highest in white males (74.8%) compared with black males (47.9%), white females (42.3%), and black females (36.0%). When severity of disease and age were taken into account, only the comparison between whites and blacks with two or three diseased vessels and over the age of 50 years reached statistical significance (p<0.001) for difference in the choice of initial therapy. Additionally, of the white males who were initially treated non-surgically, 31.8% were later treated surgically, while 15.5% of the black males, 17.4% of the white females, and 12.3% of the black females who were initially treated non-surgically were later treated surgically.

Using the Rose Questionnaire, whites who underwent catheterization were more likely than blacks to report definite angina (33.2% versus 23.8%). In order to determine if reporting definite angina helped to assign treatment, it was noted that in males and white females, patients treated surgically were more likely to report definite angina than patients treated medically. However, for black females, this measure did not differentiate treatment assignment as well (21.1% of those receiving non-surgical treatment and 20.0% of those receive surgical treatment reported definite angina).

Whites were more likely than blacks to be diagnosed with two or three vessel disease, even after controlling for hypertension, angina, coronary heart failure, myocardial infarction, age, smoking status, and blood pressure. Separate analysis for blacks and whites showed similar factors predicted a diagnosis of two or three vessel disease for both races. Whites were more likely to be treated initially surgically than blacks, even after controlling for the same variables listed above and having two or three vessel disease. Again, separate analysis for blacks and whites indicated that the same factors were of roughly equal importance in choosing initial surgical treatment. However, history of myocardial infarction and angina were only significant among whites (possibly due to the smaller sample size in blacks).

Finally, since the importance of initial allocation to treatment depends on whether the prognosis will be similar, an additional analysis of 5-year survival was conducted. Survival rates for blacks and whites were similar, except for older (>50 years) blacks who demonstrated a decreased survival rate relative to whites when managed surgically (65.7% blacks survived 5 years versus 87.3 % of whites).

The authors conclude that “both the selection process for diagnostic evaluations and the clinical decision for type of therapy appear to be discordant between black and white populations, even though the frequency of CHD in blacks approaches that of whites in this country (from other analyses)”. They discuss three main findings:

First, “a relatively lower percentage of black patients with manifestations of CHD are advised to have coronary angiography.” The authors note that the patient population referred to the study medical center comes primarily from the surrounding area and the state at large, which is approximately one-third non-white. This racial distribution differs greatly from the racial distribution of the study sample. Other possible explanations (other than not receiving appropriate advice to have coronary angiography) were not discussed.

Second, “the importance of clinical measures in determining the likelihood of coronary lesions differed little between blacks and whites. Nevertheless a white predisposition to multiple vessel disease emerged. Despite similarities between blacks and whites in risk factor associations for coronary artery lesions, they do not preclude the concept that black or white status, per se, may make a major independent contribution in explaining the extent of coronary artery disease.”
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Finally, “marked differences in therapeutic management occurred within clinically similar populations for blacks and whites. The preferential selection of whites for CABG even after adjustment for possible associated factors may be due to dissimilarities in education, income or occupation.” However, (SES) is not likely to be a major factor in this study since many patients were recruited from a VA hospital, where economic factors have little influence in treatment choice. “Both the current perception of the physician toward CHD in blacks and the acceptability of the procedure to the patient may provide other reasons for this racial difference in patient management.”