Effect of beta-adrenergic stimulation on pulse wave velocity in black and white subjects

Background Reduced beta-adrenergic sensitivity has been reported in black subjects. We hypothesized that beta-adrenergic stimulation by isoproterenol would affect pulse wave velocity (PWV), a marker of arterial stiffness, differently in black and white subjects. Methods Healthy normotensive black subjects (n = 21) matched for age, gender, height and body mass index with healthy normotensive white subjects (n = 20), participated in a randomized, double-blind, placebo-controlled crossover study. The PWV was determined using an automated device at baseline and after 30 min of an equal volume infusion of isoproterenol (8 mug/kg per min) or placebo (dextrose 5%), separated by a washout period of 25 min. Results At baseline, heart rate (HR), systolic and diastolic blood pressure (SBP, DBP) and PWV were comparable in black and in white subjects. Placebo had no significant effect on haemodynamic variables. Isoproterenol increased HR, SBP and pulse pressure and decreased DBP with a comparable magnitude in both groups. Compared with placebo, isoproterenol decreased carotid-femoral PWV in white (from 5.9 +/- 1.2 to 5.7 +/- 1.1 m/s, means +/-SD, P = 0.05), but not in black subjects (from 6.2 +/- 1.3 to 6.6 +/- 1.7 m/s, P = 0.1). The difference in response between black and white subjects was significant (P = 0.04). Isoproterenol decreased carotid-radial PWV only significantly in white subjects. Conclusion These results are compatible with the hypothesis of an altered beta-adrenergic sensitivity, which is expressed by a blunted effect of isoproterenol on arterial stiffness in black subjects. (C) 2004 Lippincott Williams Wilkins.