Cerebrovascular carbon dioxide reactivity and flow-mediated dilation in young healthy South Asian and Caucasian European men

摘要

South Asians living in the United Kingdom have a 1.5-fold greater risk of ischemic stroke than the general population. Impaired cerebrovascular carbon dioxide (CO_2) reactivity is an independent predictor of ischemic stroke and cardiovascular mortality. We sought to test the hypothesis that cerebrovascular CO_2 reactivity is reduced in South Asians. Middle cerebral artery blood velocity (MCA V_m) was measured at rest and during stepwise changes in end-tidal partial pressure of CO_2 (Pet_(co_2)) m South Asian (n = 16) and Caucasian European (n = 18) men who were young (～20 yr), healthy, and living in the United Kingdom. Incremental hypercapnia was delivered via the open-circuit steady-state method, with stages of 4 and 7% CO_2 (≈21% oxygen, nitrogen balanced). Cerebrovascular CO_2 reactivity was calculated as the change in MCA V_m relative to the change in Pet_(co_2) . MCA V_m was not different in South Asians [59 (9) cm/s, mean (standard deviation)] and Caucasian Europeans [61 (12) cm/s; P >0.05]. Similarly, cerebrovascular CO_2 reactivity was not different between the groups [South Asian 2.53 (0.76) vs. Caucasian European 2.61 (0.81) cm·s~(-1)·mmHg~(-1); P >0.05]. Brachial artery flow-mediated dilation was lower in South Asians [5.48 (2.94)%] compared with Caucasian Europeans [7.41 (2.28)%; P < 0.05]; however, when corrected for shear rate no between-group differences in flow-mediated dilation were observed (P >0.05). Flow-mediated dilation was not correlated with cerebrovascular CO_2 reactivity measures. In summary, cerebrovascular CO_2 reactivity and flow-mediated dilation corrected for shear rate are preserved in young healthy South Asian men living in the United Kingdom.