Maynard C, Fisher LD, Passamani ER.
Survival of black persons compared with white persons in the Coronary Artery Surgical Study (CASS).
Am J Cardiol 1987;60:513-8.

Utilizing data from the Coronary Artery Surgical Study (CASS), a longitudinal study of patients who underwent coronary angiography, the authors addressed three main questions. First, the survival rate has been reported for the entire patient group, but what is the survival rate for black patients and how does it compare with the survival rate for white patients? Second, it has been previously reported that black patients receive surgical treatment less frequently than white patients, but does treatment affect the long–term survival rate for black patients? Third, within treatment groups (surgical and medical), does race predict longer survival? Subjects were enrolled from July 1974 through May 1979 at 14 clinics in the United States and one clinic in Canada. It is noteworthy that eight of the fourteen clinics enrolled less than 20 black patients.

With regard to survival rates, the age-specific 5-year survival rate was significantly lower for black men than for white men in two age groups: the 40-44 year group and the 50-54 year group. There was also a statistical trend of lower survival for black men in the 55-59 year, 60-64 year, and 65-69 year age groups. For women, only whites in the 50-54 year age group had a survival advantage over blacks. The overall age- and sex-adjusted survival was significantly higher for whites than blacks (88% of whites survived 5 years compared with 82% of blacks, p<0.0001). When patients were stratified by occupational group (professional, clerical, laborer, homemaker, other), the 5-year survival was significantly different for blacks and whites only in the laborer category (87% of whites and 80% of blacks survived 5 years in this category, p=0.0002).

There was a trend for blacks to die of cardiac causes more frequently than whites (85% of blacks versus 80% of whites, p=0.12). Among those who died of non-cardiac deaths, blacks were slightly more likely to die of atherosclerotic causes (8% versus 4.3%), and whites were slightly more likely to die of non-atherosclerotic causes (14.6% versus 6.8%). There were no statistically significant differences in specific causes of death, but postoperative death within 30 days and cerebrovascular accidents were slightly more frequent in blacks.

With regard to treatment effects, the authors divided the study group into two categories, those who received surgical treatment (patients who had coronary artery bypass grafting within a specified time) and those who received medical treatment only (all others). After controlling for other clinical and demographic predictors of survival, among patients in the surgical group, the association between race and length of survival was non-significant (p=0.279). Among patients in the medical group, black patients had a higher mortality rate (p=0.0006).

In an assessment of black patients only, surgical treatment (versus medical treatment only) was a significant predictor of survival even after controlling for other known clinical and demographic predictors. Furthermore, only 30% of blacks who had severe disease (3-vessel or significant left main CAD or left ventricular dysfunction) underwent coronary artery bypass surgery. These data suggest that a group of black patients who were given medical treatment only might have benefited from surgical therapy. In the white group, the effect of surgical treatment on survival differed according to clinical subtypes and was not presented. However, for both black and white patients, other predictors included left ventricular wall motion score, congestive heart failure, number of diseased vessels (interacting with Canadian class for blacks), advanced age, cigarette smoking, and a history of hypertension. A stratified survival analysis was done for each of the most important predictors, and blacks had a lower survival in almost all strata. Only in the group without angina was the survival rate higher among blacks, but the difference was not statistically significant (92% of blacks versus 89% of whites survived 5 years, p=0.0004). There were no differences in survival for all categories of the congestive heart failure score, for hypertensives, or for those who were not current smokers.

The authors note that previous reports based on data from this study indicated that the blacks enrolled in CASS were characterized by high levels of risk factors and minimal coronary artery disease (CAD). This study showed that the black mortality rate in CASS was high when adjusted for extent of CAD, and it appeared to be higher for blacks than for whites. The under- utilization of surgical therapy for blacks might be a contributing factor. The authors attempt to explain the racial difference in survival, suggesting that “unmeasured factors may explain why black surgical patients had better survival than their medical counterparts” and listing such factors as “patient compliance, adequacy of medical management and socioeconomic status.”