Primary prevention of cardiovascular disease in high-risk patients: physiologic and demographic risk factor differences between african american and white american populations

Abstract

Ischemic heart disease is the leading cause of death in the United States among Americans of African as well as of European ancestry. African Americans have the highest overall coronary heart disease (CHD) mortality rate and the highest out-of-hospital coronary death rates of any ethnic group in the United States, particularly at younger ages. The reasons for this excess CHD mortality among African Americans have not been fully elucidated but may be attributed to a high prevalence of coronary risk factors, patient delays in seeking medical care, limited access to and utilization of cardiac services, and undertreatment of high-risk individuals. The high prevalence of modifiable risk factors in African Americans provides a major opportunity for CHD prevention and risk reduction in this high-risk population. Hypertension, left ventricular hypertrophy (LVH), diabetes mellitus, cigarette smoking, obesity, physical inactivity, and multiple CHD risk factors all occur more frequently in African Americans than in whites. –7 The predictive value of most conventional risk factors for CHD appears to be similar for African Americans and whites. However, the risk of death and other sequelae attributable to some risk factors, such as hypertension and diabetes, is disproportionately greater for African Americans, –11 and current risk assessment algorithms may not have the same predictive value in African Americans as in whites. Hypertension and LVH are more prevalent, develop at younger ages, and are associated with three to five times higher mortality rates in African Americans than in whites. Moreover, African Americans experience greater cardiovascular and renal damage at any level of hypertension than do whites. Elevations in both diastolic and systolic blood pressures increase cardiovascular risk. However, elevated systolic blood pressure is a more powerful predictor of CHD, heart failure, stroke, end-stage renal disease, and overall mortality than is elevated diastolic blood pressure. LVH, when present, is more predictive of CHD morbidity and mortality than is hypertension, cigarette smoking, or hypercholesterolemia. Hypertension and LVH increase the predisposition to arrhythmia and potentially lethal silent ischemic events. –10,12 Both hypertension and LVH impart a particular risk for a poor outcome in African Americans. In a study of African Americans with LVH and coronary disease, LVH accounted for 40% of the attributable risk of death. In the Meharry–Hopkins physician cohort study, hypertension was the best predictor of cardiac events in African American physicians, whereas smoking, cholesterol, and a family history of CHD were better predictors of cardiac events in white physicians. Thus, both hypertension and LVH are common and important risk factors for CHD events in African Americans. Risk prediction algorithms that do not include hypertension and LVH may have less predictive value in African Americans than in other populations. The prevalence of diabetes in African Americans has tripled during the past 30 years, is two to three times greater than in whites, and is associated with a greater burden of macrovascular and microvascular disease complications. Individuals with diabetes are two to three times more likely to experience a CHD event than are nondiabetics, with approximately 60% of deaths in diabetics due to CHD. It is not known why diabetes is substantially more prevalent in African Americans and other high-risk minorities than in whites or why the disease appears to run a more aggressive clinical course in these populations. The cornerstones of effective cardiovascular disease prevention and risk reduction in patients with diabetes are glycemic control, vigorous modification of other CHD risk factors, and ongoing patient monitoring to facilitate early disease detection and prompt intervention. Most population-based surveys indicate that African Americans have lower total serum cholesterol levels and a similar or lower prevalence of hypercholesterolemia compared with whites. – 6,18 The relation between total cholesterol levels and CHD mortality was the same among 23,490 black men screened for the Multiple Risk Factor Intervention Trial (MRFIT) as among 325,384 white men during an average follow-up period of approximately 12 years. However, the first National Health and Nutrition Examination Survey epidemiologic folFrom the Division of Cardiovascular Medicine, State University of New York Health Science Center at Brooklyn, Brooklyn, New York. Requests for reprints should be addressed to Luther T. Clark, MD, Division of Cardiovascular Medicine, State University of New York Health Science Center at Brooklyn, 450 Clarkson Avenue, Brooklyn, New York 11203.