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CLINICAL STUDY: ENDOTHELIAL FUNCTION ASSESSMENT

Reduced endothelium-dependent and -independent dilation of conductance arteries in African Americans

Umberto Campia, MD^*, Wassim K. Choucair, MD^*, Melissa B. Bryant, RN^*, Myron A. Waclawiw, PhD, Carmine Cardillo, MD^*,1 and Julio A. Panza, MD, FACC^*,*

^* Cardiology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
Office of Biostatistics Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA

Manuscript received November 5, 2001; revised manuscript received April 25, 2002, accepted May 16, 2002.

^* Reprint requests and correspondence: Dr. Julio A. Panza, Washington Hospital Center, 110 Irving Street Northwest, Suite 2A74, Washington, DC 20010, USA.
Julio.A.Panza{at}medstar.net

OBJECTIVES: The goal of this study was to determine whether racial differences exist in the functional behavior of conduit vessels.

BACKGROUND: Compared with Caucasians, African Americans have a higher prevalence of cardiovascular disease and its complications, which may be related to reduced nitric oxide (NO)-dependent and -independent vasodilation of the microvasculature. However, whether a similar impairment is also present at the level of the conductance arteries is unknown.

METHODS: To this end, we studied endothelium-dependent (posthyperemia flow-mediated dilation) and -independent (nitroglycerin) vascular responses of the brachial artery by high-resolution ultrasound imaging. There were 46 black subjects (23 men and 23 women; age 37 ± 8 years and 38 ± 9 years, respectively) and 46 white subjects (23 men and 23 women; age 38 ± 11 years and 36 ± 9 years, respectively) in this study.

RESULTS: Baseline diameter was similar in blacks and in whites (4.4 ± 0.9 mm and 4.1 ± 0.7 mm, respectively). Mean reactive hyperemia after cuff deflation was similar in the two groups (793 ± 653% in black and 852 ± 734% in white subjects, respectively; p = 0.5). Flow-mediated dilation was significantly lower in black compared with white individuals (4.79 ± 3.5% vs. 8.87 ± 4.5%, respectively; p < 0.0001). Nitroglycerin-mediated dilation was also significantly lower in black individuals compared with white individuals (10.99 ± 4.6% vs. 14.98 ± 5.4%, respectively; p = 0.0002).

CONCLUSIONS: African Americans show reduced responsiveness of conductance vessels to both endogenous and exogenous NO compared with Caucasian Americans. These findings expand our understanding of racial differences in vascular function and suggest a mechanistic explanation for the increased incidence and severity of cardiovascular disease observed in African Americans.

Abbreviations and Acronyms   ANCOVA   analysis of covariance   BA   brachial artery   BMI   body mass index   cGMP   cyclic guanosine-monophosphate   FMD   flow-mediated dilation   NHBLI   National Heart, Lung, and Blood Institute   NMD   nitroglycerin-mediated dilation   NO   nitric oxide   NTG   nitroglycerin   SBP   systolic blood pressure   sGC   soluble guanylyl cyclase   VSMC   vascular smooth muscle cell

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