RACIAL-DIFFERENCES IN MYOCARDIAL-ISCHEMIA AND CORONARY FLOW RESERVE IN HYPERTENSION

Objectives Using invasive measurements of endothelium independent coro nary flow reserve and stress thallium testing with or without dipyrida mole, this study investigated racial differences in ischemia and coron ary reserve in hypertensive left ventricular hypertrophy. Background. African Americans compared with Caucasian Americans appear to have a h igher case fatality from coronary heart disease but lesser amounts of atherosclerotic coronary artery disease. This paradox may be explainab le by intrinsic or acquired racial differences in coronary arteriolar autoregulation acid vasoreactivity. Methods. The study enrolled 98 Afr ican and 81 Caucasian Americans referred for cardiac catheterization b ecause of suspected myocardial ischemia but found to have no significa nt coronary stenosis. Patients H ere stratified by degree of left vent ricular hypertrophy for comparison purposes after calculation of index ed left ventricular mass by means of echocardiographic M-mode measurem ents. Coronary how reserve measurements were made using the intracoron ary Doppler catheter and hyperemic doses of intravenous dipyridamole i n 100 patients and intracoronary papaverine and adenosine in 72 patien ts. Seventy-seven percent of patients underwent adequate stress thalli um testing with or without dipyridamole. Results. In African Americans , mean (+/-SD) coronary how reserve decreased from 4.4 +/- 2.3 for 38 without mass hypertrophy to 3.2 +/- 1.3 for 53 with hypertrophy (p = 0 .005) to 2.7 +/- 1.1 for 12 with severe hypertrophy (p = 0.02). Thalli um testing was abnormal in 31% of those without mass hypertrophy and 5 9% of those with hypertrophy. In Caucasian Americans, coronary how res erve decreased from 1.1 +/- 2 for 58 without hypertrophy to 3.6 +/- 1. 5 for 23 with hypertrophy (p = NS) to 3 +/- 1.5 for 6 with severe hype rtrophy (p = NS). Thallium testing was abnormal in 36% without mass hy pertrophy and in 39% with hypertrophy. Conclusions. This study establi shes that development of left ventricular hypertrophy in hypertension carries greater physiologic morbidity for African compared with Caucas ian Americans, typified by marked reduction in endothelium-independent coronary flow reserve and increased frequency of abnormal thallium te sts.