Thrombolytic therapy is the most common method used to restore blood flow after myocardial infarction, and primary angioplasty had been accepted as an alternative method of reperfusion. There is increasing evidence that reperfusion may be underused among blacks, women, and the elderly. The primary objective of this study was to examine the potential interaction of race and sex with respect to the rate of use of reperfusion therapy in a sample of patients of age 65 years or older.

The study was based on a random sample of the entire Medicare cohort with myocardial infarction during the period from February 1994 to July 1995. Black and white patients eligible for reperfusion therapy (patients presenting at the hospital after at least 30 minutes but less than 12 hours of chest pain and having ST-segment elevation of at least 1 mm on two contiguous leads on the initial electrocardiogram) were included. Patients were excluded if they were older than 80 years, if they were transferred from another hospital, if there was evidence that they refused thrombolysis, or if other contraindications to the administration of thrombolytic therapy were noted. A total of 26,575 patients met the criteria for the study.

On average, white women were older and black men were younger than the rest of the cohort. The prevalence of diabetes, hypertension, prior myocardial infarction, and prior renal failure was higher in blacks than whites (both genders). A history of percutaneous transluminal coronary angioplasty (PCTA) or coronary-artery bypass surgery (CABG) was more frequent among white men and least frequent among black women. At presentation, black women had the highest systolic blood pressure (SBP) and the highest heart rate. White men were more likely to present in Killip class I, and black women were the least likely to do so. Blacks were more likely than whites to present at urban hospitals, teaching hospitals, and hospitals with cardiac catheterization facilities.

Only 57% of patients eligible to receive reperfusion therapy received such therapy. White men were most likely (59%), followed by white women (56%), black men (50%), and black women (44%). In every group, the most frequently used method was thrombolytic therapy (ranging from 87.6% to 92.3% of those who received reperfusion therapy). This pattern persisted after adjusting for geographic region.

In a multivariate analysis that adjusted for age, medical history, clinical presentation, and hospital characteristics, the race and sex associations with receipt of reperfusion therapy were attenuated, but the race effect was still significant (OR for black men versus white men=0.86, 95% confidence interval=0.78 to 0.93, and OR for black women versus white men=0.90; 95% confidence interval 0.82 to 0.98). When the analysis was repeated with only the patients who presented within 6 hours after the onset of symptoms, the results were essentially the same. Finally, patients were stratified into four different groups: whites only, blacks only, men only, and women only. Evaluation of these groups confirmed that among Medicare beneficiaries with myocardial infarction who were eligible for reperfusion therapy, race, but not sex, was important in predicting receipt of this therapy.

The reason for the lower rate of reperfusion therapy in blacks is not readily apparent, but the authors note the following possibilities, which are commonly cited in this type of research: the preferences of the patient, the expertise and preferences of the physician, hospital-related factors, and residual racial differences in clinical presentation that were not captured in these data. They do not consider patient preference a likely explanation in these data since patients were excluded if there was sufficient documentation that they declined reperfusion therapy. Further, hospital-related factors were largely measured and controlled in this analysis, as were a range of clinical factors, making 'residual racial differences in clinical presentation' an unlikely explanation. The authors therefore argue that "the decisions of the physicians, as a result of clinical ambiguity, lack of adequate training, insufficient knowledge, or physicians' own preferences or biases, contributed to the racial differences observed in this study." The lack of difference by sex found in this study was inconsistent with previous studies. However, the authors state that it is unclear whether previously reported differences were due to confounding by other factors known to influence the rate of use of reperfusion therapy or were the result of true sex differences.

The authors conclude that these findings "emphasize the need to continue searching for explanations of racial differences in the risk factors for, incidence of, mortality associated with, and treatment of ischemic heart disease."