Increased pulse pressure and carotid vascular resistance in normotensive black African subjects

To evaluate ethnic differences in cerebral circulation, an index of carotid vascular resistance (RI) was determined by continuous wave Doppler ultrasound. Validation of the index resulted from a significant correlation between RI and carotid vascular resistance obtained from direct measurement of blood pressure and carotid blood flow by means of range-gated pulsed Doppler (r = 0.64; P less than 0.01). We studied 37 normotensive men: 17 white and 20 black. The two populations were age, sex, body mass index and mean arterial pressure matched. In blacks, a significant higher RI was observed (74.10(-2) +/- 1.6.10(-2) versus 64.10(-2) +/- 1.9.10(-2); P less than 0.001) together with a significantly higher pulse pressure (51 +/- 3 mmHg versus 43 +/- 2 mmHg) in comparison with whites. Our findings suggest that the higher prevalence of stroke in blacks might be related to significant haemodynamic characteristics of the carotid-cerebral circulation involving cerebral vasoconstriction.