Black Americans tend to die more often from and have more diseases associated with heart
disease than White Americans. The exact cause of this is unknown, but it is likely a
combination of genetics, behavior, risk factors, strategies for education and prevention,
and socioeconomic factors.
Recent studies have suggested that faster biological processes in blood vessels of Black
Americans may be the cause of increased amounts of heart disease. In addition, small blood
vessels in Black Americans seem to be less responsive to substances that relax blood
vessels, which may explain increased blood pressure levels.
In this study researchers plan to study artery relaxation (dilation) in response substances
affecting the cells lining blood vessels (endothelin). Researchers will compare the results
of this study in black and white people to find out whether racial differences may
contribute to increases in heart disease and heart related deaths in blacks.
Black Americans have a greater morbidity and mortality related to cardiovascular diseases
compared to whites. The cause for this phenomenon is probably multifactorial and includes
differences in pathogenesis, risk factor patterns, genetic background, behavioral variables,
strategies for education and prevention, and socioeconomic factors. Recent evidence
suggests that acceleration of some of the processes related to vascular biology may account
for the greater prevalence of cardiovascular disease in blacks. A diminished vasodilator
response of the microvasculature has been shown in African Americans and may therefore be
responsible for their increased prevalence of hypertension. Endothelial dysfunction is a
central mechanism in the development of atherosclerosis. It is therefore reasonable to
postulate that endothelial dysfunction of large conductance arteries may also contribute to
a greater susceptibility to atherosclerosis in blacks compared to whites, even in those
individuals without the known risk factors for coronary heart disease. In the present
study, we propose to investigate brachial artery dilation in response to
endothelium-dependent and -independent stimuli in black and white individuals to determine
whether racial differences in the vascular biology of large conductance vessels that might
contribute to the greater cardiovascular morbidity and mortality previously reported in
Black and white normal volunteers, approximately matched for age and sex, will be included
in the study.
All subjects must be capable of rendering informed consent for all procedures.
Volunteers with a history or evidence of present or past hypertension (BP greater than
140/90), diabetes mellitus, hypercholesterolemia (plasma cholesterol greater than 200
mg/dL), cardiac disease, peripheral vascular disease, coagulopathy, chronic smoking (2
pack-years or more), obesity (20% greater than ideal body weight), hyperhomocysteinemia
(plasma homocysteine greater than 17 umol/1) or any other disease predisposing them to
vasculitis will be excluded from the study.
No pregnant women.
Volunteers who are taking any medication will be excluded.