Racial differences in the significance of coronary calcium in asymptomaticblack and white subjects with coronary risk factors

OBJECTIVES To compare the significance of a specific feature of coronary at herosclerosis - coronary calcium-in asymptomatic black and white subjects w ith coronary risk factors. BACKGROUND The natural history and clinical evolution of coronary atheroscl erosis differs between blacks and whites. Differences in the underlying pat hobiology of atherosclerosis may be one determinant of the ethnic variabili ty in the clinical manifestation of coronary atherosclerosis. METHODS In 1,375 high-risk but asymptomatic subjects (93 blacks [6.8%] and 1,282 whites [93.2%]) with at least one risk factor but no prior evidence o f coronary disease, we assessed coronary risk factors, calculated Framingha m risk of a coronary event and evaluated coronary calcium with digital subt raction fluoroscopy. We then followed these subjects clinically for 70 +/- 13 months, noting the occurrence of the following coronary events: death du e to coronary heart disease (CHD); myocardial infarction (MI); angina pecto ris; and performance of coronary bypass or angioplasty. RESULTS Risk factor profiles were similar in black and white subjects (6-ye ar Framingham risk 15 +/- 7% in blacks, 14 +/- 8% in whites [NS]). Coronary calcium was present in 59.9% of white subjects but only 35.5% of black sub jects (p = 0.0001). Nevertheless, after 70 months of follow-up, more blacks than whites (22 blacks [23.7%] vs. 190 whites [14.8%]; p = 0.04) suffered one of the following end points: CHD death, MI, angina or revascularization The age, gender and coronary risk-adjusted odds ratio of black race for at least one event was 2.16 (95% CI 1.34 to 3.48). CONCLUSIONS Despite having a lowered prevalence of coronary calcium than hi gh risk whites, high risk blacks suffer more CHD events. Coronary calcium t herefore does not carry the same pathobiologic significance in blacks that it does in whites, consistent with the concept that there are specific raci al differences in the natural history of CHD and its evolution into clinica lly manifest events. (J Am Cell Cardiol 1999;34:787-94) (C) 1999 by the Ame rican College of Cardiology.