Hypertension In Blacks Research Articles

Urinary levels of tissue kallikrein in the South African Black and Indian hypertensives.

It is accepted that Black subjects differ from White and Indian hypertensives in their response to hypotensive agents. Black hypertensives in the USA have a lower urinary tissue kallikrein (TK) excretion levels compared to White hypertensives. It has been suggested that Black patients respond better to thiazide diuretics compared to beta-blockers because thiazides increase whereas beta-blockers decrease tissue kallikrein excretion. This study compares the excretion of urinary TK in Black and Indian hypertensive and normotensive subjects. Urinary TK levels were measured with the selective, synthetic peptic substrate with the sequence of H-D-Val-Leu-Arg-pNA. Ten hypertensive patients on placebo therapy and 10 normotensive Black and Indian subjects provided three samples at weeks 0, 2 and 4 for the determination of urinary TK. The results were analysed using analysis of variance to compare the two racial groups. There were no significant differences in urinary TK values of the three bi-weekly individual samples. Urinary tissue kallikrein values (ng TK/microg protein) in Indian hypertensives were in general lower than Black hypertensives.

T594M mutation in the ENaC beta subunit and low-renin hypertension in blacks.

T594M mutation in the ENaC beta subunit and low-renin hypertension in blacks.

Abdominal adiposity in six populations of West African descent: prevalence and population attributable fraction of hypertension.

The objective of this investigation was to examine the prevalence of abdominal adiposity and its association with the prevalence of hypertension among African descent populations in Nigeria, Cameroon, Jamaica, St. Lucia, Barbados, and the United States (US). The data for this investigation were obtained from the International Collaborative Study on Hypertension in Blacks. Hypertension was defined as mean diastolic blood pressure > or =90 mmHg, systolic blood pressure > or = 140 mmHg or current treatment with prescribed anti-hypertension medication. Abdominal overweight was defined as waist circumference (WC) > or =94 and > or =80 cm for men and women, respectively. Abdominal obesity was defined as WC > or =102 and > or =88 cm for men and women, respectively. We estimated the site-specific prevalence of abdominal overweight and obesity across age and body mass index cut-points. We also calculated the population attributable fraction (AF) of hypertension due to abdominal adiposity. The prevalence of hypertension in these populations was tightly linked to abdominal adiposity. Increases in abdominal overweight accompanied an increasing degree of Westernization, rising from 6.4% and 26.3% in Nigeria, 16.5% and 62.8% in Cameroon, 15.8% and 58.6% in Jamaica, 14.3% and 62.1% in St. Lucia, 21.4% and 70.3% in Barbados to 38.9%, and 76.4% in the US for men and women, respectively. The corresponding values for abdominal obesity were 1.6% and 12.3% in Nigeria, 5.1% and 38.9% in Cameroon, 5.5% and 34.0% in Jamaica, 2.7% and 40.7% in St. Lucia, 7.8% and 44.7% in Barbados to 21.7% and 54.1% in the US for men and women, respectively. Body mass index-adjusted estimates of AF suggest that in most of these populations, especially in females, avoidance of abdominal overweight or obesity would help to curb the development of hypertension. An important public health challenge is to clarify how lifestyle factors influence risks of abdominal adiposity and ultimately the increased risk of cardiovascular diseases.

Sustained antihypertensive actions of a dual angiotensin-converting enzyme neutral endopeptidase inhibitor, sampatrilat, in black hypertensive subjects

Our objective was to evaluate the safety and antihypertensive efficacy of sampatrilat, a novel dual inhibitor of both angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP), in subjects poorly responsive to ACE inhibitor monotherapy. The ability of sampatrilat (50 to 100 mg daily) (n = 28) to lower blood pressure was compared with that of the ACE inhibitor lisinopril (10 to 20 mg daily) (n = 30) using a double-blind, randomized, parallel group study design over a 56-day treatment period in black hypertensives. Changes in systolic (SBP) and diastolic (DBP) blood pressure were determined using repeated ambulatory blood pressure (ABP) monitoring. Both sampatrilat and lisinopril decreased plasma ACE concentrations after 28 and 56 days. The decrease in plasma ACE concentrations (U/L) was greater after lisinopril ( −9.33 ± 0.52) as compared with sampatrilat ( −6.31 ± 0.70) ( P = .0001) therapy. Lisinopril, but not sampatrilat, increased plasma renin activity. Lisinopril produced a transient decrease in mean 24-h ABP (mm Hg) at 28 days (SBP = −9.0 ± 2.3, DBP = −5.7 ± 1.3; P < .01), which returned to pretreatment values by 56 days of therapy. Alternatively, sampatrilat produced a sustained decrease in mean ABP over the 56-day treatment period (day 28: SBP = −7.3 ± 1.8, DBP = −5.2 ± 1.2; P < .01: day 56: SBP = −7.8 ± 1.5; DBP = −5.2 ± 0.95; P < 0.01) with a greater treatment effect on DBP than that of lisinopril at day 56 ( P = .05). Treatment-emergent adverse events were noted to be similar between both treatment groups. We conclude that the antihypertensive actions of ACE/NEP inhibitor monotherapy in black subjects offers a novel therapeutic approach to patients otherwise resistant to the sustained antihypertensive actions of ACE inhibitor monotherapy.

Ethnic differences in the identification of left ventricular hypertrophy in the hypertensive patient

Left ventricular hypertrophy (LVH) is more prevalent in black than white hypertensives, but this difference is greater when identified by electrocardiography (ECG) than by echocardiography. We evaluated the proposal that current ECG criteria for LVH are less specific, and therefore, less useful, in blacks than whites. In a retrospective cross-sectional study, 408 subjects (271 white, 137 black) referred to a hypertension clinic for assessment of hypertension underwent measurement of blood pressure, ECG voltages (Sokolow-Lyon and Cornell sex-specific), and echocardiographic left ventricular mass index (LVMI). Black subjects had greater ECG voltages than whites, even when closely matched for LVMI. In black subjects, current ECG criteria were twice as sensitive as in whites (Sokolow-Lyon: 44.9% v 22.5%, P = .003. Cornell: 30.4% v 15.7%, P = .03). They were less specific in blacks using the Sokolow-Lyon criteria (73.5% v 86.8%, P = .02) but this failed to reach significance using the Cornell criteria (83.8% v 91.8%, P = .07). When voltage criteria were adjusted to give matched sensitivities and specificities, respectively, differences in specificity and sensitivity were no longer apparent. Receiver operating characteristic curve analyses confirmed no significant differences in overall performance of either ECG criteria between blacks and whites. In conclusion, ECG detection of LVH is insensitive in both ethnic groups. Sensitivity is higher in blacks due to higher LVMI in those with LVH. Apparent differences in specificity are due to ethnic differences in ECG voltages that are unrelated to differences in LVMI. When these differences are taken into account, there are no overall differences in test accuracy. However, given the prognostic importance of the detection of LVH, currently accepted ECG voltage criteria for the detection of LVH remain of equal or greater value in black hypertensives compared with whites.

Theme III: joint symposium of the American society of hypertension and the international society on hypertension in blacks : Up-date on control rates and the influence of the doctor-patient relationship

Theme III: joint symposium of the American society of hypertension and the international society on hypertension in blacks : Up-date on control rates and the influence of the doctor-patient relationship

The management of hypertensive disease in black patients.

The ethnic differences in the incidence, pathophysiology and management of hypertensive disease, are particularly pertinent to the Black or Afro-Caribbean populations, who have a high prevalence of hypertension and associated complications, such as strokes and renal impairment. Our understanding of the underlying pathophysiology of hypertensive disease and the optimal treatment of hypertension in Black patients continues to evolve, especially with the introduction of new drugs and the need for prognostic data in this ethnic population. We review the management of hypertensive disease in the black population, emphasizing race-related differences in the pathophysiology of hypertension and the importance of tailored management in this group of patients, including sensible application of non-pharmacological measures with effective antihypertensive agents. For example, diuretics and calcium antagonists are suitable first-line agents in black hypertensives, whilst beta-blockers and the ACE inhibitors tend to be less effective at lowering blood pressure, due to the low renin state in these patients.

Weight-height relationships among eight populations of West African origin: the case against constant BMI standards.

To ascertain whether constant body mass index (BMI) standards are appropriate in genetically similar populations. Data are taken from the International Collaborative Study of Hypertension in Blacks (ICSHIB), an observational study. Individuals of African descent who were included in ICSHIB. Subjects lived in eight different sites: Barbados; Cameroon (urban and rural); Jamaica; Manchester, UK; Maywood, IL; urban Nigeria; and St Lucia. Weight and height. Constant BMI standards effectively argue for the constancy of slope of the linear regression equations of In(weight) on In(height) across populations. Linear regression results indicate that the height/weight relationship implied by the use of constant BMI standards, is not found in these populations and that there is much variation across groups. The use of constant BMI standards in classifying individuals prognostically may be unwise, even in genetically similar populations.

Hypertensive mechanisms in the indigenous (black) population of South Africa

There are many published studies on hypertension in the black population from both South Africa and elsewhere on the continent. However, much information stems from studies on so-called ‘African-Americans’. While there may be some valid comparisons, it is important, both for genetic and environmental reasons, to he circumspect in the interpretation of studies of black hypertension performed in populations not resident in Africa. The purpose of this paper then is to briefly review some of the pathogenetic mechanisms and clinical effects of both benign and malignant hypertension with special reference to work done in our department. Some of the work is still ongoing, hut allows for reasonable postulates and from which stem logical avenues for future investigations. The Republic of South Africa is largely a temperate region with a population of about 40 million (75% blacks, 17% whites, 6% mixed race and 2% Asian). About 40% of the population are ‘semi-rural’ and the rest urban or peri-urban. Hypertension occurs in about 28% of the black population (HB) and about 18% in whites (HW).’-’ Because of Westernization of rural areas, the previously quoted prevalence of ‘rural’ hypertension of 10% is now fast approaching urban levels4 Hypertension is more severe in the black population, occurs at a younger age and more frequently causes end-organ fa i l~re .~ It is associated with a low renin status in over two-thirds of patients and the response to a pressure naturesis is subobtimal. As a group HB demonstrate the metabolic insulin resistance syndrome in which obesity, abnormal glucose tolerance and hypertension develops in the absence of overt dyslipidaemia. However, thiazide diuretics do produce dyslipidaemia but less so than in HW.6,7

The role of endothelin in heart failure and hypertension.

The endothelin family consists of three structurally similar isopeptides: ET-1, ET-2, and ET-3. The two receptor subtypes, ETA and ETB, have different receptor affinities for the isopeptides. Stimulation of ETA and ETB receptors results in vasoconstriction, and ETB stimulation also causes vasodilation. These receptors may have profound impact on the etiologies of various diseases, including heart failure and hypertension. Studies with endothelin-receptor antagonists in animals and humans with heart failure show promising short- and long-term results. The place of the agents in the treatment of essential hypertension remains controversial, but they may have a greater role in hypertensive blacks and transplant recipients.

Sodium-lithium countertransport activity in normotensive offspring of hypertensive black Africans.

To assess sodium-lithium countertransport (SLC) activity and erythrocyte sodium (ENa) levels in black (Nigerian) hypertensive (HT) patients, normotensive (NT) offspring of hypertensive parents and normotensive offspring of normotensive parents, and to determine if increased SLC activity is related to a familial predisposition to hypertension in black subjects as in Caucasians. The study was done using 60 Nigerian subjects of Edo ethnic origin in three groups of 20 each: (a) untreated new HT patients at the University Teaching Hospital, Benin City; (b) NT children of hypertensive parents (NTHT) traced home and matched for age, sex and body mass index (BMI) with (c) NT children of NT parents (NTNT). SLC activity was measured using a modified method of Canessa et al 1980 and ENa assessed by flame photometry. SLC was markedly higher in both HT patients and NTHT subjects than the NTNT subjects. The values were 0.351+/-0.011 vs 0.199+/-0.014 mmol Li/rbc (P < 0.0001) and 0.347+/-0.020 vs 0.199+/-0.014 mmol Li/rbc/hr (P < 0.0001), respectively. The values were not different between the HT and the NTHT group (P > 0.05). ENa was higher in the HT group than both NT groups which were similar. Values were 10.55+/-0.46 (HT) vs 7.78+/-0.62 (NTHT) (P < 0.0001) and 10.55+/-0.46 (HT) vs 8.62+/-0.47 mmol/L (P < 0.0001). There were no correlations between either SLC activity or ENa and any of the other measured variables such as age or BMT. SLC activity was elevated in normotensive children of hypertensive subjects to a similar degree as hypertensive patients and in a pattern reminiscent of that seen in Caucasians. SLC activity may thus be associated with a familial predisposition to hypertension in black subjects as in their Caucasian counterparts.

Ethnic differences in the hypertensive heart and 24-hour blood pressure profile.

Black hypertensive persons have been observed to have a greater degree of left ventricular hypertrophy than white hypertensives. However, previous studies have matched groups for blood pressure (BP) measured in the clinic, and it has been demonstrated that black hypertensives have an attenuated nocturnal BP dip. Clinic BPs may thus underestimate mean 24-hour BP in this group. To investigate whether the differences in left ventricular hypertrophy can be accounted for by the greater mean 24-hour BP in black hypertensives, 92 previously untreated hypertensives were studied with 24-hour ambulatory BP monitoring and echocardiography. The 46 black hypertensives (24 men and 22 women) were matched with the 46 white hypertensives for age, gender, and mean 24-hour BP. Despite similar mean 24-hour BPs (blacks, 142/93 mm Hg; whites, 145/92 mm Hg; P=.53/.66), the black group had a smaller mean nocturnal dip than the white group (blacks, 8/8 mm Hg; whites, 16/13 mm Hg; P<.01). In addition, mean left ventricular mass index (LVMI) was greater (blacks, 130 g/m2; whites, 107 g/m2; P<.001). Mean 24-hour systolic BP was significantly related to LVMI in both groups (blacks, r=.45, P<.01; whites, r=.56, P<.01). However, systolic BP dip correlated inversely with LVMI only in the black group (blacks, r=-.30, P<.04; whites, r=.05, P=.76). In a multiple regression model, LVMI was independently related to both mean daytime BP and mean nocturnal BP dip in black subjects but only to mean daytime BP in white subjects. In conclusion, the increased left ventricular hypertrophy observed in black hypertensives compared with white hypertensives is not accounted for by differences in mean 24-hour BP. However, LVMI in black hypertensives appears to be more dependent on nocturnal BP than that in white hypertensives; this, coupled with the attenuated BP dip in black hypertensives, suggests that the BP profile rather than 24-hour BP may be important in determining the differences in left ventricular hypertrophy.

Renovascular Disease in Blacks: Prevalence and Result of Operative Management

ABSTRACT Hypertension in blacks differs in a quantitative sense from hypertension in whites; it occurs in blacks with greater frequency and severity and at a younger age when compared with whites. In addition, elevated blood pressure at any level is associated with increased cardiovascular morbidity and mortality in black patients. Several mechanisms have been suggested to account for this form of hypertension, implying that hypertension in black patients is intrinsically different from that in whites. Although these mechanisms remain unproven, it has generally been accepted that correctable renovascular disease and renovascular hypertension (RVH) occur infrequently in blacks; the authors, however, will review preliminary populationbased data which suggest that the presence of renal artery disease is not determined by raceor ethnicity. In addition, the prevalence of renovascular disease in a large group of consecutive hypertensive subjects will be presented.Finally, the blood pressure and renal function response after surgical renal artery repair in blacks will be compared with whites treated at the authors' institution. Taken collectively, these data and clinical experience support the search for and treatment of renal artery disease in properly selected hypertensive blacks. KEY INDEXING TERMS: Hypertension; Renovascular disease; Renovascular hypertension.[Am J Med Sci 1998;315(5):337-342.]

J016 Role of the renal dopaminergic system in the responses to sodium load in salt-sensitive and salt-resistant black normotensives and hypertensives

J016 Role of the renal dopaminergic system in the responses to sodium load in salt-sensitive and salt-resistant black normotensives and hypertensives

I020 Urinary levels of tissue kallikrein in black and Indian hypertensives and its implications to therapy

I020 Urinary levels of tissue kallikrein in black and Indian hypertensives and its implications to therapy

Racial Differences in Ambulatory Blood Pressure and Echocardiographic Left Ventricular Geometry

We examined the racial differences in left ventricular (LV) geometric pattern in relation to 24-hour ambulatory blood pressure (BP) monitoring and the presence or absence of a nocturnal BP dip. Our study confirms the blunting of nocturnal BP dip among black hypertensives. Body mass index, rather than race, was a major determinant of left ventricular hypertrophy. We did not observe a difference in prevalence of left ventricular hypertrophy by race. However, left ventricular adaptation to hypertension differed in hypertensive black and white individuals; whereas most ofthe white patients with Stage 1-2 hypertension had a normal ventricular pattern, LV concentric remodeling and concentric hypertrophy were the most common adaptive ventricular patterns in blacks with Stage 1-2 hypertension. A six-fold higher prevalence of concentric remodeling was observed in blacks as compared with whites. The impaired nocturnal BP dip in blacks may contribute to the different hemodynamic pattern. Determinants of myocardial oxygen consumption were significantly higher in black hypertensives.

Racial Differences in Outcome of Pregnancies Complicated by Hypertension

Racial differences in the outcome of pregnancies complicated by hypertension (HTN) were examined using data obtained from a large perinatal data base with 109,428 consecutive deliveries from 1982 to 1987. Black women had a higher prevalence of hypertension than white women (prevalence ratio 2.3, 95% CI 2.2, 2.5). However, when compared to normotensive women of similar race, white hypertensive women showed a higher risk for adverse pregnancy outcome than black hypertensives as indicated by the higher odds ratio for prematurity (OR: 1.7 for white [W], 1.2 for black [B]), low birth weight (OR: 2.4 W; 1.5 B), intrauterine growth retardation (OR: 4.4 W; 1.6 B) and perinatal death (OR 2.3 W; 1.2 B). Hypertension was associated with a 156 g reduction in birthweight of newborns in whites as compared to a 63 g reduction in blacks. Further studies are needed to understand the racial differences in the impact of HTN on pregnancy outcome.

Helping Poor Mothers and Children

This issue of JAMA contains 2 reports of randomized clinical trials showing that a nurse home-visit program has bettered the situations of disadvantaged mothers and their children. The trials are remarkable for demonstrating that the program improved not just poor mothers' infant care, but an array of health and social outcomes, as long as 15 years following childbirth. Olds et al 1 report that their program in Elmira, NY, reduced poor white women's subsequent pregnancies, child abuse and neglect, use of welfare, substance abuse problems, and crime and increased their labor force participation. Kitzman et al 2 report that the Elmira experiment, replicated in Memphis, Tenn, reduced poor black women's hypertension and subsequent pregnancies, improved home rearing environments for their children, and reduced the children's injuries. Such impressive findings from rigorous experiments suggest that a nationwide policy favoring nurse home visits based on models that have been tested and found

Hypertension in blacks.

The excess of hypertension among blacks has been recognized since early in this century and explains a substantial portion of the black health disadvantage. In a cohort study begun in the 1970s, hypertension accounted for 20% of all-cause mortality among blacks, compared to 10% among whites. National data on trends in hypertension (140/90 mm Hg or treatment) prevalence from 1960 to 1990 suggest a decline from 44% to 32%, although differences in survey technique likely account for this pattern. During this period the prevalence ratio of black:white remained constant at 1.5, suggesting that secular trends in causal factors, if any, effected both groups equally. Recent data demonstrate a gradient in risk across the African diaspora, with standardized prevalences of 14% in West Africa and 26% in the Caribbean, compared to 33% in the US. This pattern parallels the gradient in known risk factors, with obesity alone accounting for a third of the excess in the US compared to Africa. Why the black excess of hypertension in the US? Despite widespread speculation, unique characteristics of hypertension among blacks have yet to be established. Consistent evidence demonstrates a similar impact of the known risk factors in all population groups. Epidemiologic evidence likewise suggests that a similar risk of complications exists with blood pressure elevation among blacks and whites, level for level. Although the genetic epidemiology of hypertension is still in its infancy, no clear cross-population differences are yet apparent. Pathophysiologic traits that are known to be part of the causal etiologic pathway have not been shown to vary across groups. Unique features of this condition among blacks are likely to be restricted to the different mixes and intensities of risk factors. In the absence of evidence to support the hypothesis, it is perhaps surprising that credence continues to be given to the notion of black exceptionalism. Am J

Reduced dietary potassium reversibly enhances vasopressor response to stress in African Americans.

Acute vasopressor responses to stress are adrenergically mediated and hence potentially subject to differential modulation by dietary potassium and sodium. The greater vasopressor responsiveness in blacks compared with whites might then be consequent not only to a high dietary salt intake but also to a marginally reduced dietary potassium intake. Under controlled metabolic conditions, we compared acute vasopressor responses to cold and mental stress in black and white normotensive men during three successive dietary periods: (1) while dietary potassium was reduced (30 mmol K+/70 kg per day) and salt was restricted (10 to 14 days); (2) while salt was loaded (15 to 250 mmol Na+/70 kg per day) (7 days); and (3) while salt loading was continued and potassium was either supplemented (70 mmol K+/70 kg per day) (7 to 21 days) in 9 blacks and 6 whites or continued reduced (30 mmol K+/70 kg per day) (28 days) in 4 blacks (time controls). At the lower potassium intake, cold-induced increase in forearm vascular resistance in blacks was twice that in whites during both salt restriction and salt loading. Normalization of dietary potassium attenuated cold-induced increases in both forearm vascular resistance and systolic and diastolic blood pressures in blacks but only in systolic pressure in whites. In blacks but not in whites, normalization of dietary potassium attenuated mental stress-induced increases in systolic and diastolic pressures. In normotensive blacks but not whites, a marginally reduced dietary intake of potassium reversibly enhances adrenergically mediated vasopressor responsiveness to stress. That responsiveness so enhanced over time might contribute to the pathogenesis of hypertension in blacks.