ESSENTIAL HYPERTENSION IN BLACK AND WHITE SUBJECTS - HEMODYNAMIC-FINDINGS AND FLUID VOLUME STATE

Systemic hemodynamics (cardiac output, intra-arterial pressure, total peripheral resistance) and intravascular volume (plasma volume and red cell mass) were measured in a population of 126 black and white patients, 51 with borderline hypertension and 75 with established essential hypertension. The findings were compared with those in 29 age-matched normotensive control subjects of both races. The white patients with established hypertension showed a faster heart rate than the black patients (< 0.05); the difference was more pronounced during upright tilt (P < 0.02). No significant difference in cardiac index, total peripheral resistance, plasma volume or total blood volume was found between the 2 racial populations. Cardiac index correlated directly with plasma and total blood volume in black patients (r [correlation coefficient] = 0.32, P < 0.05), white patients (r = 0.35, P < 0.001) and in the whole study population (r = 0.36, P < 0.001). The regression lines were similar in the 2 races. A negative correlation was seen between the total peripheral resistance and plasma volume (r = -0.31, P < 0.001) or total blood volume (r = -0.34, P < 0.001) and it was similar in both races (black r = -0.48, P < 0.01; whites r = -0.25, P < 0.05). Age correlated significantly with total peripheral resistance in the white patients (r = 0.35, P < 0.001) and in the total study population (r = 0.28, P < 0.001). Apparently, for every given age or level of arterial pressure, systemic hemodynamics are similar for the black and white patients with essential hypertension. The data do not support the clinical impression that basic pathophysiology and hypertensive vascular disease are different in the black patient with essential hypertension.