Systemic hypertension and the kidney in black patients

Renal outcomes in hypertensive Black patients at high cardiovascular risk

The ACCOMPLISH trial (Avoiding Cardiovascular events through Combination therapy in Patients Living with Systolic Hypertension) was a 3-year multicenter, event-driven trial involving patients with high cardiovascular risk who were randomized in a double-blinded manner to benazepril plus either hydrochlorothiazide or amlodipine and titrated in parallel to reach recommended blood pressure goals. Of the 8125 participants in the United States, 1414 were of self-described Black ethnicity. The composite kidney disease end point, defined as a doubling in serum creatinine, end-stage renal disease, or death was not different between Black and non-Black patients, although the Blacks were significantly more likely to develop a greater than 50% increase in serum creatinine to a level above 2.6 mg/dl. We found important early differences in the estimated glomerular filtration rate (eGFR) due to acute hemodynamic effects, indicating that benazepril plus amlodipine was more effective in stabilizing eGFR compared to benazepril plus hydrochlorothiazide in non-Blacks. There was no difference in the mean eGFR loss in Blacks between therapies. Thus, benazepril coupled to amlodipine was a more effective antihypertensive treatment than when coupled to hydrochlorothiazide in non-Black patients to reduced kidney disease progression. Blacks have a modestly higher increased risk for more advanced increases in serum creatinine than non-Blacks.

Subclinical atherosclerotic changes related to chronic kidney disease in asymptomatic black and white young adults: the Bogalusa heart study

PURPOSE

Chronic kidney disease (CKD) remains asymptomatic until its late stage, and also significantly increases the risk of cardiovascular (CV) disease morbidity and mortality. However, information in scant on the prevalence of CKD, and its association with subclinical atherosclerosis as depicted by carotid intima media thickness (IMT) in younger adults.

METHODS

This cross-sectional study included 1193 participants (43% males, 30% blacks) aged 23 to 43 years, residing in the semi-rural biracial (black-white) community of Bogalusa, Louisiana. The measured variables include estimated glomerular filtration rate (eGFR) to determine functional renal changes and urine album creatinine ratio to diagnose albuminuria, along with CV risk factor variables, and both segmental and composite carotid IMT.

RESULTS

Ninety-nine (8.5%) subjects had CKD, with blacks showing higher prevalence than whites (p = .01). Subjects with albuminuria had significantly greater internal carotid IMT (p = .03), common carotid IMT (p = .005), and composite carotid IMT (p = .04) than those without. In the multivariate logistic regression model, albuminuria was associated with black race (odds ratio [OR], 1.92; p = .005), female gender (OR, 2.24; p = .002), diabetes (OR, 6.26; p < .001), hypertension (OR, 2.36; p < .001), obesity (OR, 1.73; p = 0.02), and composite carotid IMT (OR, 1.83; p = .02), after adjusting for age. However, reduction in eGFR did not show significant independent association with carotid IMT.

CONCLUSION

Among asymptomatic young adults, subclinical atherosclerosis and structural renal damage depicted by albuminuria coexist, which has implications for early prevention and control.

The association of low birthweight and chronic renal failure among Medicaid young adults with diabetes and/or hypertension

OBJECTIVE

The purpose of this study was to assess the effect of low birthweight on chronic renal failure among young Medicaid patients with diabetes and/or hypertension.

METHODS

The study included Caucasian and African American young adults, aged 18-50, who enrolled in the Medicaid program from 1993 to 1996 in South Carolina and were diagnosed with diabetes and/or hypertension. The odds of chronic renal failure by low birthweight (< 2,500 grams) was estimated using logistic regression.

RESULTS

Of the 7,505 Medicaid patients with diabetes and/or hypertension, 179 (2.4%) were diagnosed with chronic renal failure. These patients were younger (mean age of 33.9 vs. 37.6, p = 0.0024) and had a higher proportion of low birthweight (15.1% vs. 11.4%, p = 0.07) compared with the 7,326 patients without renal failure. The odds ratio of chronic renal failure for low birthweight was significantly higher compared with normal birthweight (2,500-3,999 grams) (adjusted odds ratio [OR] 1.56, 95% confidence interval [95% CI] 1.0, 2.4). The association between low birthweight and chronic renal failure was stronger among the 888 patients with both diabetes and hypertension (OR 2.6, 95% Cl 1.3, 5.7) than the 1,812 diabetes or the 4,805 hypertension patients.

CONCLUSIONS

The odds of chronic renal failure by low birthweight was highest in patients with both diabetes and hypertension, suggesting that the mechanism(s) involved in the disease progression to chronic renal failure may have a fetal early life origin.

Design and statistical aspects of the African American Study of Kidney Disease and Hypertension (AASK)

The African American Study of Kidney Disease and Hypertension (AASK) is a multicenter randomized clinical trial designed to test the effectiveness of three anti-hypertensive drug regimens and two levels of BP control on the progression of hypertensive kidney disease. Participants include African-American men and women aged 18 to 70 yr who have hypertensive kidney disease and GFR between 20 and 65 ml/min per 1.73 m(2). The three anti-hypertensive drug regimens include an angiotensin converting enzyme inhibitor (ramipril), a dihydropyridine calcium channel blocker (amlodipine) or a beta-blocker (metoprolol) as initial therapy. The BP control levels are a lower goal (mean arterial pressure, Collapse

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MESH Headings

• Adolescent
• Adrenergic beta-Antagonists/administration & dosage
• Adult
• Black or African American/statistics & numerical data
• Aged
• Angiotensin-Converting Enzyme Inhibitors/administration & dosage
• Antihypertensive Agents/administration & dosage
• Calcium Channel Blockers/administration & dosage
• Dose-Response Relationship, Drug
• Drug Administration Schedule
• Drug Therapy, Combination
• Female
• Follow-Up Studies
• Humans
• Hypertension/complications
• Hypertension/diagnosis
• Hypertension/drug therapy
• Kidney Failure, Chronic/complications
• Kidney Failure, Chronic/diagnosis
• Kidney Failure, Chronic/therapy
• Male
• Middle Aged
• Pilot Projects
• Risk Assessment
• Treatment Outcome
• United States

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Grants

• U01 DK048643 NIDDK NIH HHS
• RR11145 NCRR NIH HHS
• U01 DK048648 NIDDK NIH HHS
• RR-00080 NCRR NIH HHS
• M01 RR000071 NCRR NIH HHS
• DK 2818 NIDDK NIH HHS
• M01 RR000052 NCRR NIH HHS
• M01 RR000032 NCRR NIH HHS
• K24 DK002818 NIDDK NIH HHS
• RR11104 NCRR NIH HHS
• RR-00071 NCRR NIH HHS
• P20 RR011104 NCRR NIH HHS
• P20 RR011145 NCRR NIH HHS
• U01 DK045381 NIDDK NIH HHS
• RR00827 NCRR NIH HHS
• U01 DK045386 NIDDK NIH HHS
• RR00052 NCRR NIH HHS
• M01 RR000827 NCRR NIH HHS
• M01 RR000080 NCRR NIH HHS
• RR00032 NCRR NIH HHS

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Affiliation(s)

Jennifer J Gassman Cleveland Clinic Department of Biostatistics, Ohio, 44195, USA.
Tom Greene
Jackson T Wright
Lawrence Agodoa
George Bakris
Gerald J Beck
Janice Douglas
Ken Jamerson
Julia Lewis
Michael Kutner
Otelio S Randall
Shin-Ru Wang

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Microalbuminuria in essential hypertension: significance, pathophysiology, and therapeutic implications

Some patients with essential hypertension manifest greater than normal urinary albumin excretion (UAE). The significance of this association, which is the object of this review, is not well established. Hypertensive patients with microalbuminuria manifest greater levels of blood pressure, particularly at night, and higher serum levels of cholesterol, triglycerides, and uric acid than patients with normal UAE. Levels of high-density lipoprotein cholesterol, on the other hand, were lower in patients with microalbuminuria than in those with normal UAE. Patients with microalbuminuria manifested greater incidence of insulin resistance and thicker carotid arteries than patients with normal UAE. After a follow-up of 7 years, we observed that 12 cardiovascular events occurred among 54 (21.3%) patients with microalbuminuria and only two such events among 87 patients with normal UAE (P < 0.0002). Stepwise logistic regression analysis showed that UAE, cholesterol level, and diastolic blood pressure were independent predictors of the cardiovascular outcome. Rate of creatinine clearance from patients with microalbuminuria decreased more than that from those with normal UAE. In conclusion, these studies suggest that hypertensive individuals with microalbuminuria manifest a variety of biochemical and hormonal derangements with pathogenic potential, which results in hypertensive patients having a greater incidence of cardiovascular events and a greater decline in renal function than patients with normal UAE.

Pathophysiology and treatment implications of hypertension in the African-American population

Regardless of the etiology, hypertension remains a major public health problem in African-Americans and is associated with significant morbidity and mortality. Additional data on the pathophysiology of this disease in this population are needed, as are data on the best therapies to decrease the high complication rate. Because many of the large studies on hypertension have included few African-Americans, recruitment of this ethnic group into clinical trials should be promoted. Further studies into the genetic factors in the pathophysiology of racial differences in hypertension may shed more light on this complex issue.

Accuracy of the diagnosis of hypertensive nephrosclerosis in African Americans: a report from the African American Study of Kidney Disease (AASK) Trial. AASK Pilot Study Investigators

African Americans have excess hypertension and end-stage renal disease presumed due to hypertension compared to Caucasians. The AASK was designed to examine the impact of antihypertensive therapies and two levels of blood pressure control on the rate of decline of GFR in African Americans with presumed hypertensive renal disease. During the pilot phase of the trial, eligible participants were requested to undergo renal biopsy to assess the underlying lesions in this population. Eighty-eight hypertensive (diastolic BP > 95 mm Hg) non-diabetic African American patients between the ages of 18 to 70 years, with GFR between 25 to 70 ml/min/1.73 m2 and without marked proteinuria were assessed for possible renal biopsy. Forty-three patients did not undergo renal biopsy due to refusal or contraindications. Adequate renal biopsies were obtained in 39 of the remaining 46 patients. Biopsy findings were analyzed and then compared to clinical parameters. The 39 patients studied, 29 men and 10 women, were on average 53.0 +/- 11.0 years old, and had a MAP of 109 +/- 15 mm Hg and GFR 51.7 +/- 13.6 ml/min/1.73 m2 (not significantly different from nonbiopsied patients). Thirty-eight of these 39 biopsies showed arteriosclerosis and/or arteriolosclerosis, severity on average 1.5 +/- 0.9 and 1.5 +/- 0.8, respectively on a 0 to 3+ scale. Interstitial fibrosis was moderate, 1.3 +/- 0.9 (0 to 3+ scale). Segmental glomerulosclerosis was present in five biopsies, and in one patient, biopsy and clinical findings were consistent with idiopathic focal segmental glomerulosclerosis. Additional lesions included mesangiopathic glomerulonephritis in one patient, basement membrane thickening suggestive of diabetic nephropathy in one, and cholesterol emboli in two cases. Arteriolar and arterial sclerosis were tightly linked, and correlated with interstitial fibrosis and the reciprocal of serum creatinine. Global glomerulosclerosis was extensive, involving on average 43 +/- 26% of glomeruli. The extent of this lesion did not correlate with degree of arteriolar or arterial thickening, but did correlate with systolic blood pressure (P = 0.0174), the reciprocal of serum creatinine (P = 0.0009), serum cholesterol (P = 0.0129) and interstitial fibrosis (P < 0.0001). These data underscore that renal biopsies in non-diabetic hypertensive African-Americans with mild to moderate renal insufficiency in the absence of marked proteinuria are overwhelmingly likely to show renal vascular lesions consistent with the clinical diagnosis of hypertensive nephrosclerosis.

Salt-sensitive hypertension: lessons from animal models

The underlying etiology of salt-sensitive hypertension has been elusive, in part because the term represents a syndrome rather than a specific disease entity and in part because of the difficulty in completely defining the characteristics of the syndrome. The introduction of inbred models of salt-sensitive hypertension has facilitated understanding blood pressure response to dietary salt. Careful examination of one of these models, the Dahl/Rapp rat, has shown that the L-arginine:nitric acid (NO) pathway is integrally involved in production of hypertension in response to an increase in dietary salt. This review provides an overview of NO, salt sensitivity, and the role of NO in the pathogenesis of salt-sensitive hypertension.

The kidney in the hypertensive black

Evidence suggests that the incidence of end-stage renal disease due to essential hypertension is five to six times more frequent in black than in white patients. The reason for this greater susceptibility is not clear. Several possibilities have been proposed, including socioeconomic factors, compliance with therapy, renal hemodynamic differences and anatomic differences. In this review, we propose that the greater propensity of black hypertensives to develop renal failure as a consequence of hypertension may be due to abnormal hemodynamic adaptation of the renal circulation to a rise in blood pressure caused by high dietary sodium intake. This would make the renal circulation of hypertensive blacks more susceptible to injury.

Renal hemodynamics in essential hypertension. Racial differences in response to changes in dietary sodium

Previous studies have suggested striking racial differences in hypertension-related renal disease. To explore potential mechanisms responsible for these differences, we investigated changes in renal hemodynamics in white and black essential hypertensive patients in response to alterations in dietary sodium. Patients were untreated, age-matched, and blood pressure-matched white (n = 59) and black (n = 22) males with essential hypertension. Studies were conducted on an inpatient metabolic ward and included assessment of blood pressure, urinary sodium excretion, glomerular filtration rate, renal plasma flow, and renal blood flow after 5 days each of high and low salt diets. In response to high dietary salt intake, both white and black patients demonstrated significantly higher mean arterial pressure, renal plasma flow, and renal blood flow, and there were no racial differences in the changes in these parameters. However, whites and blacks differed significantly in glomerular filtration rate, with black hypertensive patients showing an increase in glomerular filtration rate (+17.3 +/- 5.3 mL/min per 1.73 m2, F = 7.586, P = .007) and white hypertensive patients showing no change (-0.2 +/- 3.3 mL/min per 1.73 m2) in response to high dietary sodium. These data demonstrate racial differences in the autoregulation of glomerular filtration rate in response to changes in dietary sodium. These differences suggest that glomerular hyperfiltration in response to a high salt diet may be a mechanism contributing to the racial disparity in hypertension-related renal disease.

Microalbuminuria in salt-sensitive patients. A marker for renal and cardiovascular risk factors

We previously showed that a high salt diet increases glomerular capillary pressure in salt-sensitive hypertensive patients and suggested that this may underlie the greater propensity of these patients to develop renal failure. Because microalbuminuria is considered an initial sign of renal damage, we have tested whether salt-sensitive patients display greater urinary albumin excretion than salt-resistant hypertensive patients. Twenty-two patients were placed on a low sodium intake (20 mEq/d) for 7 days followed by a high sodium diet (250 mEq/d) for 7 more days. Twelve patients were classified as salt sensitive and 10 as salt resistant. Urinary albumin excretion was greater in salt-sensitive than salt-resistant patients (54 +/- 11 versus 22 +/- 5 mg/24 h, P < .01). During the low sodium diet, glomerular filtration rate, renal plasma flow, and filtration fraction were similar between the two groups. During the high sodium intake, glomerular filtration, renal plasma flow, filtration fraction, and calculated intraglomerular pressure did not change in salt-resistant patients; in salt-sensitive patients, however, renal plasma flow decreased, and filtration fraction and intraglomerular pressure increased, whereas glomerular filtration rate did not change. Urinary albumin excretion was significantly correlated with glomerular capillary pressure. Salt-sensitive patients displayed higher serum levels of low-density lipoprotein cholesterol and lipoprotein(a) and lower levels of high-density lipoprotein cholesterol than salt-resistant patients. These studies have shown greater urinary albumin excretion and serum concentrations of atherogenic lipoproteins in salt-sensitive than in salt-resistant hypertensive patients, suggesting that salt sensitivity may be a marker for greater risk of renal and cardiovascular complications.

Regulation of aldosterone secretion in hypertensive blacks

Hypertension in blacks is common, often severe, and largely unexplained. Recent studies have suggested that aldosterone secretion in blacks may be reduced, whereas older data demonstrate no racial differences in aldosterone excretion. We performed this study to examine adrenal responsiveness in black hypertensive patients under controlled metabolic conditions. Thirty-one black hypertensive patients and 7 black normotensive subjects were studied on intakes of 10 mmol/d sodium and 100 mmol/d potassium, with the renin-angiotensin-aldosterone system further stimulated by upright posture or infusion of angiotensin II (Ang II). Forty-six hypertensive and 14 normotensive whites underwent the same protocol as a comparison group. Hypertensive blacks and whites had similar mean basal plasma aldosterone levels on a low salt diet, lower in both groups than in normotensive subjects. In the black patients, however, plasma aldosterone responses were significantly lower than responses in white hypertensive patients when further stimulated by either posture (1451 +/- 216 versus 2571 +/- 225 pmol/L [52.3 +/- 7.8 versus 92.7 +/- 8.1 ng/dL], P < .002) or Ang II infusion (843 +/- 122 versus 1617 +/- 189 pmol/L [30.4 +/- 4.4 versus 58.3 +/- 6.8 ng/dL], P < .001). Renin status did not account for the difference. Basal and stimulated plasma aldosterone concentrations, on the other hand, were similar in normotensive white and black subjects. Blunted adrenal responses to upright posture and Ang II infusion are common among black hypertensive patients. These abnormalities may be part of a larger constellation of abnormalities in blacks, reflecting perhaps a greater, more frequent underlying disturbance in salt handling than in whites.

Race, socioeconomic status, and the development of end-stage renal disease

The reasons for the increased annual incidence of end-stage renal disease (ESRD) in blacks compared with whites are unclear, but may include lack of access to treatment of the causative disease, which likely relates closely to socioeconomic status (SES). End-stage renal disease rates for diabetic glomerulosclerosis, hypertensive nephrosclerosis, and glomerulonephritis were determined in the 9,390 black and white New York State residents who began treatment within the Medicare program between 1982 and 1988. The relationship between the incidence of ESRD, age, and SES, as measured by the race-specific median family income in the patient's zip code, was estimated using a series of logistic-regression models for 12 populations: three causes of renal failure by two races by two sexes. For whites, incidence rates of diabetic glomerulosclerosis and hypertensive nephrosclerosis were significantly negatively associated with declining SES for the 45 to 65 year and 25 to 55 year age groups, respectively. In contrast, there was no relationship between the incidence of these diseases and SES in blacks. For glomerulonephritis, effects of SES were minor for both races. Better access to treatment of diabetes and hypertension might well decrease the annual incidence of ESRD due to diabetic glomerulosclerosis and hypertensive nephrosclerosis in whites. If the SES measures used for blacks are adequate, predisposition to progressive renal damage in response to renal injury or environmental factors other than SES are stronger risk factors for ESRD than SES.

Hemodynamic alterations and urinary albumin excretion in patients with essential hypertension

Salt-sensitive animals as well as patients with essential hypertension appear to have a greater propensity to develop renal disease as a consequence of hypertension. They also manifest an abnormal renal hemodynamic adaptation to changes in dietary sodium intake and blood pressure. This suggests that the two may be related. Some patients with essential hypertension manifest an increase in urinary albumin excretion (UAE). It is uncertain whether this is more common in salt-sensitive patients and whether it represents a marker for progressive renal disease. The effect of antihypertensive agents on UAE varies substantially depending on the agent used, and it is not necessarily related to the antihypertensive action. Whether antihypertensive agents that more effectively reduce UAE may also result in greater renal protective effects remains to be established.

Hemodialysis vascular access morbidity in the United States

Extensive morbidity related to hemodialysis vascular access exists among end-stage renal disease (ESRD) patients, but the risk factors for this morbidity have not been extensively studied. Medicare ESRD patient data were obtained from 1984, 1985, and 1986. Hospitalization for vascular access morbidity (ICD-996.1, 996.6, or 996.7) was analyzed among prevalent patients and, using survival analysis, among incident patients to assess sex, age, race, and underlying cause of renal failure as risk factors. We found that 15 to 16% of hospital stays among prevalent ESRD patients were associated with vascular access-related morbidity. Black race, older age, female sex, and diabetes mellitus as a cause of kidney failure were all independent risk factors for access-related morbidity. The rate ratio comparing Blacks to Whites was 1.12 (95% C.I., 1.09, 1.16); > 64 years to 20 to 44 years, 1.53 (1.46, 1.59); men to women, 0.81 (0.79, 0.84); and diabetes to glomerulonephritis, 1.29 (1.24, 1.35). We conclude that hemodialysis vascular access malfunction causes much hospitalization among ESRD patients. Women, Blacks, the elderly, and diabetics appear to be at particularly high risk, and additional studies are needed to understand these patterns.

Current issues in hypertension. Old questions with new answers and new questions

Hypertension is a systemic vascular disease that makes its mark upon the "target organs"--heart, brain, and kidneys--through the hemodynamic hallmark of the disease, a progressively increasing vascular resistance to the forward flow of blood. The effect of pressure overload upon the heart is one of concentric hypertrophy of the left ventricle that is, in turn, associated with an independent risk of morbidity and mortality. Reduction of arterial pressure reverses the risk associated with the elevated arterial pressure and also diminishes the risk from hemorrhagic and thrombotic strokes. Why the risk of the interaction of hypertensive and atherosclerotic diseases can be reduced on the brain but not as impressively on the heart remains to be learned, but certain recent lines of clinical and experimental evidence point to some answers. The issue as to why, in the face of increasing numbers of patients receiving the benefits of therapy, there is an alarming increase in patients with end-stage renal disease defies more imagination and study. Thus, many of the old questions seem to be achieving some meaningful answers; but associated with these new answers we are confronted with new questions.

Hypertensive nephropathy: is a more physiologic approach to blood pressure control an important concern for the preservation of renal function?

During the past 2 decades, there have been important reductions in stroke-related morbidity and mortality due to better control of hypertension. However, there has been a lesser effect on the reduction of coronary mortality and far less of an impact on all other forms of noncardiovascular disorders such as renal disease. This suggests that our ability to prevent hypertensive nephrosclerosis through traditional methods of lowering blood pressure may not be as effective as was once thought, particularly in high-risk patients such as blacks, diabetics, the elderly, and patients with preexisting renal disease. One reason that may partially explain the difficulty in protecting the renal circulation from hypertensive damage is the interaction between antihypertensive medications and the aged-related decline in renal perfusion. Depending on their mechanism of action, antihypertensive agents may impair renal blood flow (through plasma volume contraction or reduction) and further aggravate the age-related decline in renal perfusion. A worsening of renal perfusion may activate counterregulatory neurohormonal mechanisms, such as the renin-angiotensin-aldosterone system, which in turn may place the patient at increased risk for the development of glomerulosclerosis through promotion of vascular or mesangial hypertrophic changes or increased intraglomerular pressure, despite an associated reduction in systemic blood pressure. Since antihypertensive agents have such varied effects on systemic and renal hemodynamics, an understanding of the antihypertensive actions in a given patient may have significant influence on renal function. Thus, an improved understanding about the effects of aging and hypertension on the renal microcirculation will hopefully facilitate a more physiologically appropriate antihypertensive medication selection with the expectation that renal function will be benefitted over the long term.

End-stage renal disease in US minority groups

Medicare's End-Stage Renal Disease (ESRD) Program makes renal replacement services accessible for the majority of Americans with renal failure. National data from Medicare demonstrate complex and variable patterns of use of renal replacement services among US racial and ethnic groups. The black population has consistently suffered from a greater than 3.5-fold higher rate of treated ESRD than has the white population. The rates of hypertensive, diabetic, and glomerulopathic ESRD are all substantially greater in blacks than in whites, and hypertension has accounted for a far greater proportion of ESRD in blacks than any other diagnosis. There is a paucity of national data on the occurrence of ESRD in Hispanic Americans. However, data from Texas strongly suggest that the incidence rate of treated ESRD is much higher in Mexican Americans than in non-Hispanic whites. Higher rates are apparent for each of the three most important causes of ESRD: hypertension, diabetes, and glomerulonephritis. Native Americans experience ESRD at a rate intermediate between those of whites and blacks, but their rate of diabetic ESRD is higher than in either blacks or whites. However, considerable diversity exists among Native American tribal groups. Significant barriers to the acquisition of preventive care have been identified, especially for blacks. While these barriers to preventive care are accompanied by a significantly impaired health status of the black American population, a specific causal relationship between impaired access to care for blacks and their predisposition to ESRD has not been established.

Risk for renal injury in diabetic hypertensive patients. The physiologic basis for blood pressure control

In determining a therapeutic approach to coexistent adult-onset (type II) diabetes and hypertension in patients who are middle-aged, special attention must be given to the pathophysiology of the hypertensive disease and how it affects the kidneys. Diabetes and hypertension potentiate renal damage, which clearly leads to a reduced life span and increased morbidity. Nonpharmacologic measures (eg, exercise, weight control, glycemic control, protein-restricted diet) and pharmacologic approaches need to be combined so as to control systemic blood pressure yet maintain adequate renal perfusion. Clearly, preexisting accentuated vascular reactivity to vasoconstrictive growth factors in diabetic patients stimulates maladaptive compensatory responses in the kidney. This precipitates greater renal injury superimposed on the relative risk of the hypertension-diabetes combination itself.

Abnormal renal hemodynamics in black salt-sensitive patients with hypertension

African-Americans with essential hypertension are more prone to the development of renal failure and are frequently salt-sensitive as well. Because alterations of intrarenal hemodynamics are important in the progression of renal disease and because salt-sensitive animal models with hypertension manifest a greater propensity to develop glomerulosclerosis in association with a rise in glomerular capillary pressure, we tested whether the renal hemodynamic adaptation to high dietary Na+ intake differs in salt-sensitive and salt-resistant hypertensive patients. We studied 17 black and nine white patients with essential hypertension who were placed on a low Na+ diet (20 meq/day) for 9 days, followed by a high Na+ diet (200 meq/day) for 14 days. During the last 4 days of each diet regimen, they received 30 mg/day of slow-release nifedipine. Eleven blacks were salt-sensitive, and all whites were salt-resistant. During the low Na+ diet period, salt-sensitive and salt-resistant patients had similar mean arterial pressure, glomerular filtration rate, effective renal plasma flow, and filtration fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Racial differences in the incidence and progression of renal diseases

There is an excess incidence of ESRD treatment among non-White North Americans that is not completely explained by the racial prevalences of the underlying diseases, including hypertension, which can potentially cause renal disease. The racial difference is particularly striking for presumed nephrosclerosis from hypertension and for nephropathy from Type II diabetes, but is not yet substantiated for ESRD attributed to polycystic kidney disease or Type I diabetes. The existing data are insufficient to support the notion that poorer blood pressure control alone is responsible for the racial differences in incident ESRD. Black race (and possibly Mexican or Native American heritage) may be a specific risk factor for ESRD, independent of hypertension and its treatment.

Hypertension as a causative diagnosis of patients entering end-stage renal disease programs in the United States from 1980 to 1986

Treatment of hypertension has decreased the incidence of stroke and congestive heart failure consequential to hypertension. To determine whether the incidence of hypertension as a causative diagnosis of end-stage renal disease (ESRD) is also decreasing, we examined the records of the Health Care Financing Administration (HCFA) from 1980 to 1986 regarding the causative diagnoses of patients entering ESRD programs. We found that the incidence of patients entering ESRD programs increased during the study period. Hypertension as a causative diagnosis was a constant proportion of the increase. The greatest increase occurred in patients age 55 or more years. This was strikingly true of black patients. We conclude that there has not been a decrease in the incidence of hypertension as a causative diagnosis for patients entering ESRD programs and that this may be a reflection that treatment of hypertension does not prevent the development of ESRD in some patients. We propose that prospective studies be undertaken to determine whether this is the case.

IgA nephropathy in blacks: studies of IgA2 allotypes and clinical course

The prevalence of IgA nephropathy (IgAN) varies among racial groups, being most common among Caucasians and Orientals and rare in Blacks. Other investigators have hypothesized that the risk for IgAN may be influenced by the IgA2 allotype. It has been suggested that the rare Black patients with IgAN may be homozygous for the A2m(1) allele which predominates in Whites, but is less common in Blacks. In a multicenter study, 27 Black IgAN patients were enrolled to investigate this hypothesis and analyze the clinical course of disease in Blacks. The IgA2 allotypes of 18 Black patients and 14 controls were determined using restriction fragment length polymorphism analysis. Three patients were homozygous for the A2m(1) allele, four were homozygous for A2m(2) and 11 were heterozygous. The respective allelic frequencies of A2m(1) and A2m(2) were 0.47 and 0.53 and did not differ significantly from Black controls. Most clinical manifestations of disease did not significantly differ with respect to distribution of the two alleles, although the gender ratio differed between the homozygous A2m(1) and heterozygous patients. The presence of the A2m(1) allele did not increase the risk for IgAN, and the presence of the A2m(2) allele or homozygosity for this allele did not protect Blacks from the development of IgAN.

Hypertensive heart disease in African-Americans

Hypertensive heart disease is a frequent complication in hypertensive African-Americans because of inadequate high blood pressure control. Moreover, African-Americans may be predisposed to develop LVH earlier in life and more readily than Caucasians, and it may be more malignant. The appearance of both LVH and congestive heart failure are ominous developments in individual patients, and early detection of LVH is mandatory for adequate management and reversal of this complication, if possible. Additional research is needed, and new, sensitive tools for detecting LVH will accelerate such studies. Further investigations are also needed on the reversibility of LVH, preferred antihypertensive agents for accomplishing reversal, and whether expected benefits result.

Strokes in African-Americans

Hypertension is the most important risk factor for stroke, especially in African-Americans. Improved control of high blood pressure nationwide is a key factor in the recent dramatic decline in stroke frequency, most notably in African-American women. Hypertension control programs must be adequately funded and expanded. African-Americans have a disproportionately high incidence of risk factors for stroke, including hypertension. There is evidence that the cerebral vessels involved in ischemic stroke in African-Americans may differ from those of Caucasians. There is an urgent need for more research on stroke in general, risk factor relations in particular, and mechanisms in the pathogenesis of stroke in African-Americans.

Strokes in Asians and Pacific-Islanders, Hispanics, and Native Americans

Stroke in Asian and Pacific-Islander populations remains the principal cause of death among adults, but its incidence in the United States approximates that of Caucasians. Although controversial, uncontrolled hypertension in certain population groups (e.g., northern Japanese) and high dietary saturated fat in others (e.g, Pacific-Islanders) are believed to be responsible for the high stroke incidence rates. The recent reduction in stroke frequency rates in these areas is thought to be the result of better hypertension control. In the Ni-Hon-San Study, the level of hypertension and its frequency were similar in Hawaii and Japan, but ischemic infarction and intracerebral hemorrhage were less frequent in Hawaii. Reduced meat and fat intake may contribute to small vessel disease in Japan. Stroke is the third major cause of death among Hispanic-Americans and Native Americans, yet there is a paucity of information, especially about stroke, in subgroups of these populations. There is also considerable ignorance and controversy about risk factors for stroke in these populations. The need for additional research is urgent.

Heart disease in Asians and Pacific-Islanders, Hispanics, and Native Americans

Heart disease is the leading cause of death for Asian-Americans and Pacific-Islanders, Hispanic-Americans, and Native Americans. Generally, heart disease death rates are lower in these population groups than in Caucasians, with the notable exception of Native Americans under the age of 35. Of particular interest are data for southwestern US Native Americans and Mexican-Americans, which indicate low CHD prevalence rates despite high rates of obesity, diabetes mellitus, increasing hypertension, and low socioeconomic status. Much more research is needed to explain these and other observations. Intervention in those risk factors already identified is necessary, particularly in prevention of obesity and diabetes.

Hypertension in Hispanics, Asians and Pacific-Islanders, and Native Americans

There is a paucity of information about hypertension and its risk factors, prevalence, morbidity, and mortality in many racial minorities in the United States. Most of the population groups discussed in this section are composed of several subgroups that differ culturally, socioeconomically, educationally, and ethnically. This fact, however, does not lessen the need for more information about the extent of hypertension and risk factors in these groups. Moreover, a bonus from expanded research in these areas will be new information useful to the general population.

Coronary artery disease in African-Americans

Contrary to opinions generally accepted in the past, CHD is very common in both African-American men and women, with incidence rates approaching those of US Caucasians. Higher prevalence of hypertension, diabetes, cigarette smoking, and obesity all contribute to the high level of CHD in African-Americans. Additional research is needed about the interrelations and management of various risk factors for CHD in African-Americans outside of the sudden death of African-Americans outside of the hospital is urgent, and special attention should be given to accessibility and use of health services by minority populations.

Renal vascular disease in African-Americans and other racial minorities

Hypertensive end-stage renal disease is about 10-fold more common nationwide in African-Americans than in Caucasians and 17-fold higher in some sections of the United States. These figures are alarming and require a much greater effort in understanding the causes of this disparity and improving blood pressure control in this population to prevent catastrophic renal damage. More information is also needed about the renovascular status of other minorities. Financial obstacles to antihypertensive care appear to be an important contributing factor to the disparities of end-stage renal disease in African-Americans and perhaps other minorities.

Renal and hemodynamic effects of intravenous fenoldopam versus nitroprusside in severe hypertension

The renal and hemodynamic effects of intravenously administered fenoldopam mesylate, a novel dopamine-1 receptor agonist, were compared with those of sodium nitroprusside in 28 patients (18 male; 26 black, two white; average age, 49 +/- 3 years) with an average blood pressure of 219/137 mm Hg, most of whom presented with acute target organ damage. Fenoldopam and nitroprusside lowered blood pressure safely to an average pressure of 176/105 mm Hg; highly significant dose-response relations were found for the 13 patients receiving fenoldopam and the 15 receiving nitroprusside. Volume and sodium, potassium, and creatinine concentrations were measured in freely voided urine specimens both before and during intravenous therapy. In the fenoldopam-treated patients, there were significant increases in urinary flow (92 +/- 21 to 168 +/- 37 ml/hr, p less than 0.003), sodium excretion (227 +/- 73 to 335 +/- 90 mu eq/min, p less than 0.001), and creatinine clearance (70 +/- 11 to 93 +/- 13 ml/hr, p less than 0.003). In the nitroprusside-treated group, however, all these parameters decreased, but not significantly. For direct comparison of the two agents, the increments in urinary flow rate (+76 +/- 20 vs. -16 +/- 15 ml/hr, fenoldopam vs. nitroprusside), sodium excretion (+109 +/- 28 vs. -39 +/- 28 mu eq/min), and creatinine clearance (+23 +/- 6 vs. -11 +/- 7 ml/min) were significantly greater (p less than 0.001 for each) in the fenoldopam-treated group. Significant differences were also obtained when these parameters were calculated as percentage increase over baseline. Fenoldopam and nitroprusside are effective therapies for severe, accelerated, or malignant hypertension, but fenoldopam had additional salutary renal effects in these patients.