Cardiovascular response in black and white hypertensives.

Abstract

SUMMARY Sixteen untreated black patients with mild-to-moderate hypertension and no evidence of target organ damage were matched for age, sex, casual blood pressure (BP), and socioeconomic status with 16 white hypertensives. All patients were studied under standardized conditions in the hospital where they underwent continuous intraarterial ambulatory monitoring of BP and assessment of BP control mechanisms. BP characteristics over prolonged periods of recording were similar for both groups, as were sinoaortic baroreflex activity and pressor response to isometric and dynamic exercise and to cold. Fasting cholesterol and triglyceride levels in both groups were similar. Resting plasma renin activity (PRA) was significantly lower in blacks, but no difference was observed in resting plasma norepinephrine levels. Urinary excretion of Na + and K + was also similar in both groups. Thus, results showed that casual BPs matched for black and whites, and recorded over a prolonged period, were similar in pattern, variability, and response to pressor stimuli. It appears that, if BP contributes to the different patterns of morbidity in blacks and whites, it is more likely to be the actual level of BP rather than differences in BP characteristics. (Hypertension 4: 817-820, 1982) KEY WORDS • ambulatory blood pressure • reflex cardiac control * atheroma T HE observation that the black population in North America has a higher blood pressure (BP) than the white population 1 2 has excited much interest. Associated with the higher BP is an increased incidence of target organ damage in blacks manifested as left ventricular hypertrophy (LVH), 3 cerebrovascular accidents/ and changes in optic fundi. 5The pathophysiological basis for raised BP in blacks and whites may differ, and reduced levels of plasma renin activity (PRA), 6 resting heart rate (HR), 7 and dopamine beta-hydroxylase (DBH) 8 could reflect differences in activity of the central nervous system. In addition, pathological studies have shown a different distribution of atheroma in the arteries of blacks and whites, 9 ' l0 the former having an increased deposition in the cerebral arteries, but conversely the coronary arteries are relatively spared, and this might be related to different BP characteristics and control between the groups.The purpose of this report is to compare the responses of matched black and white hypertensive pa-

Resting and ambulatory blood pressure differences in Afro-Caribbeans and Europeans.

“…30 Interestingly, when recent (ie, less than a decade ago) migrants from West Africa to the United States were compared with native (18)(19)(20)(21)(22)(23)(24)(25)(26)(27) 17t (13)(14)(15)(16)(17)(18)(19)(20) 17t (14)(15)(16)(17)(18)(19)(20) African Americans and US whites, both US whites and the recent African migrants had a persistent nocturnal decline in systolic blood pressure, which was not seen in native African Americans. 31 Studies of Barbadian blacks have also shown that the usual decline in nocturnal blood pressure is preserved.…”

Why is plasma renin activity lower in populations of African origin?

“…However, several other studies of renal function and electrolytes excretion of freeliving black and white children revealed no differences between the blacks and whites in sodium excretion. 9,13,17,36 Similarly, lower PRA in blacks compared with whites has also been reported even when there were no significant differences in urinary sodium. Moreover, low PRA has also been found in blacks on diets where the intake of sodium has been carefully controlled and lower PRA has been found on both low and high sodium intakes.…”

“…12,28 Renin release and the sympathetic system Adrenergic receptors are found on JGA cells and there is considerable evidence demonstrating that even moderate increases in renal sympathetic activity leads to increases in renin release through ␤-adrenergic receptor stimulation; by contrast, there is still controversy on the role of ␣-adrenergic activation as both inhibition and activation of renin release have been reported. 26 No major and consistent differences in circulating catecholamines between blacks and whites under basal conditions have been reported, [35][36][37] though this does not exclude differences in sympathetic activity as plasma levels of catechoamines are not a good index of adrenergic activity. Reduced plasma levels of dopamine ␤-hydroxylase (DBH) have been described in both black adults and in children compared with whites.…”

Race and Diurnal Blood Pressure Patterns

“…Differences in results obtained using ABPM devices made by different manufacturers have been reported. 14 Two reports included here report data obtained through intraarterial monitoring during inpatient hospitalization, 22,31 which may result in fewer artifactually induced increases in nocturnal blood pressure due to cuff inflation.…”