Epidemiologic and clinical comparison of renal artery stenosis in black patients and white patients

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1 ORIGINAL ARTICLES Epidemiologic and clinical comparison of renal artery stenosis in black patients and white patients Andrew C. Novick, MD, Safwat Zald, MD, David Goldfarb, MD, and Ernest E. Hodge, MD, Cleveland, Ohio Purpose: This study was undertaken to compare the epidemiologic and clinical features of renal artery stenosis (RAS) in black patients and white patients. Methods: Data on all patients identified with 50% or greater RAS from 1984 to 1990 were collected and analyzed. The study was conducted at the Cleveland Clinic Foundation, which is a referral center for patients with renal artery disease. Eight hundred nineteen patients with RAS were identified from an institutional registry that records information on patients with this disease. This group comprises 40 black patients (4.9%) and 779 white patients (95.1%). The presence of RAS was determined by abdominal aortography in all patients. Black patients and white patients with RAS were compared with respect to their age, sex, presence and severity of hypertension, renal function, type and extent of renal artery disease, extrarenal vascular disease, and risk factors such as history of smoking, diabetes, and hyperlipidemia. Results: The mean age of black patients and white patients was 62 years; however, a greater proportion of black patients were women (p = 0.01). RAS was due to atherosclerosis in 950/6 and 92% of blacks and whites, respectively. Although the extent and severity of RAS were equivalent in black patients and white patients, more blacks were diagnosed with severe (p = 0.01) or refractory (p = 0.05) hypertension. Extrarenal vascular disease was present in 95% and 70% of blacks and whites, respectively (p < 0.01). The incidence of coronary artery disease (p < 0.01), cerebrovascular disease (p < 0.01), and peripheral vascular disease (p < 0.01) was greater among black patients. A history of smoking was more common among black patients (p < 0.01). Serum total cholesterol and low-density lipoprotein cholesterol levels were equivalent among black patients and white patients; however, black patients had higher high-density lipoprotein cholesterol (p = 0.03) and lower triglyceride (p < 0.01) levels. Conclusions: There are significant differences between black patients and white patients with RAS. The basis for these findings and their relationship to the cause and true prevalence of RAS in blacks requires further study. (J VASe SURG 1994;20:1-5.) In the United States, hypertension among black patients represents an important clinical and public health issue. The prevalence of both chronic kidney failure and end stage renal disease is known to be From the Department of Urology, Cleveland Clinic Foundation, Cleveland. Reprint requests: Andrew C. Novick, MD, Department of Urology, Cleveland Clinic Foundation, 9500 Euclid Ave., Cleveland, OH Copyright 1994 by The Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter /94/$ /1/53330 significantly higher in the black population compared with the white population. This is primarily due to an increased incidence of kidney failure associated with hypertension among blacks. 1,2 Renal artery stenosis (RAS) comprises a potentially curable cause of hypertension and kidney failure in some patients. Although RAS is considered to be rare among blacks, there are scant published data on its occurrence in this population. This study was undertaken to characterize the distinguishing epidemiologic and clinical features of RAS in blacks by analysis of patient data at a referral center for this disease.

2 2 Novick et al. July 1994 Table I. Characteristics of black patients and white patients with RAS Blacks (n = 40) Whites (n = 779) p Value Mean age -+ SE (yrs.) N.S. Sex Male 14 (35%) 430 (55.1%) 0.01 Female 26 (65%) 349 (44.9%) Severe hypertension 15 (37.5%) 150 (19.3%) 0.01 Refractory hypertension 34 (85%) 529 (67.9%) 0.05 Coronary artery disease 29 (72.5%) 395 (50.7%) <0.01 Cerebrovascular disease 19 (47.5%) 168 (21.6%) < 0.01 Peripheral vascular disease 30 (75%) 344 (44.2%) < 0.01 History of smoking 32 (80%) 314 (40.3%) < 0.01 Diabetes 11 (27.5%) 139 (17.8%) N.S. Serum creatinine >2 mg/dl 10 (25%) 242 (31.1%) N.S. MATERIAL AND METHODS From January 1984 to December 1990, 819 patients with RAS were evaluated at the Cleveland Clinic Foundation. These patients were identified from an institutional renal vascular disease registry that records detailed information on patients with this disease. All patients had been studied with abdominal aortography and found to have 50% or greater narrowing of one or both renal arteries. Patients with less severe (<50%) RAS are not included in this report. The study group comprises 779 white patients (95.1%) and 40 black patients (4.9%). The epidemiologic and clinical characteristics of the black patients and white patients were analyzed and compared. Such characteristics included age, sex, presence and severity of hypertension, renal function, type and extent of renal artery disease, extrarenal vascular disease, and risk factors such as history of smoking, diabetes, and hyperlipidemia. Statistical analysis was performed with the chi-square test and Fisher's exact test for categorical variables, and Student's t test for continuous variables. A p value < 0.05 was considered statistically significant. The diagnosis of hypertension was established by recording untreated systolic blood pressure greater than 149 mm Hg or untreated diastolic blood pressure greater than 90 mm Hg on at least two separate occasions. Severe hypertension was defined as a history of systolic blood pressure greater than 200 mm Hg or diastolic blood pressure greater than 115 mm Hg at anytime. Refractory hypertension was defined as systolic blood pressure greater than 160 mm Hg or diastolic blood pressure greater than 95 mm Hg on maximum tolerated doses of three or more antihypertensive medications. Patients were categorized as to the presence and type of extrarenal vascular disease. Coronary artery disease was present in patients with angina pectoris, myocardial infarction, congestive heart failure, or an abnormal coronary angiography result. Cerebrovascular disease was present in patients with transient ischemic attacks, cerebrovascular accident or an abnormal carotid arteriography result. Peripheral vascular disease was present in patients with an aortic aneurysm, daudication, or angiographic evidence of occlusive disease involving the aorta or iliac or femoral arteries. RESULTS The clinical characteristics of black patients and white patients with RAS are compared in Table I. Hypertension was present in 38 of 40 black patients (95%) and 718 of 779 white patients (92.2%). There was no difference in the mean age of patients in these two groups ( vs 62 _+ 12 years). The proportion of patients aged less than 35 years, 35 to 55 years, 55 to 75 years and greater than 75 years was also equivalent among black patients and white patients. However, several other important differences were observed. A significantly greater proportion of black patients with RAS were women compared with white patients (65% vs 44.9%, p = 0.01). More black patients were admitted with a history of severe (37.5% vs 19.3%, p = 0.01) or refractory (85% vs 67.9%, p = 0.05) hypertension. Evidence of extrarenal vascular disease was present in 38 of 40 black patients (95%) compared with 546 of 779 white patients (70%) (p <0.01). The incidence of coronary artery disease (72.5% vs 50.7%, p <0.01), cerebrovascular disease (47.5% vs 21.6%,p < 0.01),

3 Volume 20, Number 1 Novick et al. 3 Table II. Type and extent of RAS in black patients and white patients Blacks Whites p Value Atherosclerosis 38 (95%) 717 (92%) N.S. Fibrous dysplasia 1 (2.5%) 50 (6.5%) Both 1 (2.5%) 12 (1.5%) Unilateral RAS 13 (32.5%) 368 (47.2%) 0.07 Bilateral RAS 27 (67.5%) 411 (52.8%) Severity of RAS ~ 50%-75% stenosis 30 (44.8%) 443 (37.2%) >75%-99% stenosis 26 (38.8%) 541 (45.4%) 100% occlusion 11 (16.4%) 206 (17.4%) NS *Includes all diseased renal arteries. and peripheral vascular disease (75% vs 44.2%, p <0.01) was also greater among black patients. The type and extent of RAS among black patients and white patients is detailed in Table II. RAS was due to atherosclerosis in 95% and 92% of blacks and whites, respectively. There were relatively more black patients with bilateral RAS (67.5% vs 52.8%), but the difference was not statistically significant (p = 0.07). When comparing all diseased renal arteries among black patients and white patients, there was no difference in the proportion with 50% to 75% stenosis (44.8% vs 37.2%), greater than 75% to 99% stenosis (38.8% vs 45.4%), or 100% occlusion (16.4% vs 17.4%). There was also no difference in the proportion of black patients and white patients presenting with a serum creafinine level greater than 2 mg/dl (25% vs 31.1%, Table I). Serum lipid values were available for some but not all patients in the study, and the available data for black patients and white patients were compared (Table III). There was no difference in the mean total cholesterol (231 vs 226 mg/dl) and low-density lipoprotein (LDL) cholesterol (144 vs 131 mg/dl) levels between these two groups. However, black patients had a significantly lower mean wiglyceride level (146 vs 197 mg/dl, p < 0.01) and a significantly higher mean high-density lipoprotein (HDL) cholesterol level (71 vs 37 mg/dl, p = 0.03). When considering only those patients on whom triglyceride and HDL cholesterol data were available, there was no significant difference between black patients and white patients with respect to the type, extent (tmilateral vs bilateral) or severity (degree ofstenosis) of renal artery disease; more black patients in this subgroup had extrarenal vascular disease (94.4% vs 77%), but the difference was not statistically significant (p = 0.14). With respect to other risk factors for vascular disease (Table I), there was no significant difference in the incidence of diabetes among black patients and white patients (27.5% vs 17.8%). However, a higher proportion of blacks had a history of smoking (80% vs 40.3%,p <0.01). Among smokers, there was no significant difference in the duration of smoking or the mean number of packs smoked per day between black patients and white patients. DISCUSSION Several previous studies have highlighted the rarity of RAS among black patientsy Simon reviewed data from the cooperative study of renal vascular hypertension and found that only 8% of patients with RAS were black, s Seedat and Reddy 6 recorded a single case of RAS among 500 black patients with hypertension at a South African Clinic. Keith reported RAS in only 0.65% of 7,200 black hypertensive adults from the University of Cincinnati. 7 Recently Svetlcy et al. 8 offered somewhat conflicting information by observing no significant difference in the prevalence of RAS among a clinically selected population of black patients and white patients; this population consisted exclusively of patients with one or more features indicative of renal vascular hypertension. In this study comprising patients at a referral center for renal vascular disease, only 40 of 819 patients with RAS (4.9%) were black. These data imply that RAS is either less common or less often detected among black patients. Our findings indicate that a greater proportion of black patients with RAS are women compared with white RAS patients (p = 0.01). Others have ob-

4 4 Novick et al. JOURNAL OF VASCULAR SURGERY July 1994 Table III. Serum lipid values in black patients and white patients with RAS Blacks Whites n Mean + S.E. n Mean + S.E. p Value Total cholesterol (nl = mg/dl) 30 Triglycerides (nl = mg/dl) 19 HDL Cholesterol (nl > 45 mg/dl) 19 LDL Cholesterol (nl = mg/dl) NS 146 _ _+ 123 < _ _ _ _+ 57 NS n, Number of patients in whom value obtained. served a predominance of women among black patients with RAS. In an earlier study, Foster et al.3 noted that RAS was present in five of 53 black women with hypertension but in none of 28 black men with hypertension. Thomas et al. 9 also noted that RAS was twice as common among female vs male black patients with hypertension. In this study, extrarenal atherosclerotic vascular disease was present in 95% of black patients with RAS compared with 70% of white patients with RAS (p < 0.01). Coronary artery disease, cerebrovascular disease, and peripheral vascular disease were all significantly more common among black patients (p < 0.01). Keith z reported extrarenal vascular disease in 26 of 32 (81%) black patients with atherosclerotic RAS. Ours is the first single-center study to offer a direct comparison of extrarenal vascular disease among black patients and white patients with RAS. Notwithstanding the infrequency of RAS among blacks, it appears to represent a manifestation of generalized atherosclerotic vascular disease in most affected patients. Atherosclerosis was the predominant cause of RAS among both black patients and white patients in this study. There was no significant difference in the extent or severity of RAS among black patients and white patients. Notwithstanding the latter, significantly more black patients were admitted with a history of severe (p = 0.01)or refractory (p = 0.05) hypertension. In comparing black patients and white patients with renovascular hypertension, and using the same definitions as in our study, Svetky et al. s also noted a higher incidence of severe (83% vs 71%) and refractory (33% vs 24%) hypertension among black patients. It may be that this presenting feature is even more suggestive of underlying RAS in black patients compared with white patients. An alternate possible explanation for this observation is that, perhaps, blacks are less apt to undergo evaluation for RAS until hypertension becomes more problematic. A novel aspect of our study was the direct comparison of risk factors for atherosclerotic vascular disease between black patients and white patients with RAS. An association between smoking and atherosclerotic RAS has previously been reported, 1 and, in our study, 80% of blacks had a history of smoking compared with only 40.3% of whites (p < 0.01); this finding may also account, in part, for the higher incidence of extrarenal vascular disease among black patients. Simon et al.5 previously observed that serum total cholesterol levels were significantly higher in patients with atherosclerotic renal vascular hypertension compared with those with essential hypertension. However, ours is the first study to compare lipid profile data in black patients and white patients with RAS. Our findings indicate no difference in serum total cholesterol or LDL cholesterol levels, but white patients had a higher risk profile with significantly lower HDL cholesterol levels (p = 0.03) and significantly higher triglyceride levels (p < 0.01). This may be analogous to atherosclerotic coronary artery disease data that indicate little difference in total cholesterol levels between black patients and white patients but higher HDL cholesterol levels among black patients. 1~'12 Further studies are needed to clarify the significance of this finding in patients with atherosclerotic renal artery disease. It is of interest that black patients with RAS had more extensive extrarenal vascular disease in spite of lower risk lipid profile data. In summary, this study indicates several significant differences between black patients and white patients with RAS. The basis for these findings and their relationship to the cause and true prevalence of RAS in blacks requires further study. REFERENCES 1. Gold CH, Isaacson C, Levin J. The pathological basis of end-stage renal disease in blacks. S Afr Med J 1982;61: Smith SR, Svetkey LP, Dennis VW. Racial differences in the incidence and progression of renal diseases. Kidney Int 1991;40: Foster JH, Oates JA, Rhamy RK, et al. Detection and treatment of patients with renovascular hypertension. Surgery 1966;60:

5 Volume 20, Number 1 Novick et al Morris GC, DeBakey ME, Cooley DA, Crawford ES. Experience with 200 renal artery reconstructive procedures for hypertension or renal failure. Circulation 1963;27: Simon N, Franklin SS, Bleifer KH, Maxwell MH. Clinical characteristics of renovascular hypertension. JAMA 1972; 220: Seedat YK, Reddy J. A study of 1000 South African non-white hypertensive patients. S Afr Med J 1974;48: Keith TA: Renovascular hypertension in black patients. Hypertension 1982;4: Svetkey LP, Kadir S, Dunnick NR, Smith SR, Dunham CB, Lambert M, Klotman PE. Similar prevalence of renovascular hypertension in selected blacks and whites. Hypertension 1991;17: Thomas J, Dale WA, Perry FA, Mitchell EA, Davachi AA, Weaver RA. The incidence of renovascular lesions in the hypertensive negro patient. J Nat Med Assoc 1965;57: Block HR, Cooper KA. Cigarette smoking and atherosclerotic renal artery stenosis, l Clin Hyper 1986;2: Morrison JA, Khoury P, Mellles M, Kelly K, Horvitz R, Glueck CJ. Lipid and lipoprotein distributions in black adults: the Cincinnati Lipid Research Clinic's Princeton School Study. JAMA 1981;245: Tyroler HA, Glueck CJ, Christensen B, Kwiterovich PO. Plasma high-density lipoprotein cholesterol comparisons in black and white populations. Circulation 1980;62(Suppl IV): Submitted July 28, 1993; Accepted Nov. 22, 1993.