Impact of whole-body passive heat stress and arterial shear rate modification on radial artery function in young men

Alali, Mohammad H, Vianna, Lauro C, Lucas, Rebekah AI, Junejo, Rehan T and Fisher, James P (2020) Impact of whole-body passive heat stress and arterial shear rate modification on radial artery function in young men. Journal of Applied Physiology, 129 (6). pp. 1373-1382. ISSN 8750-7587

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Abstract

We sought to determine how whole-body heating acutely influences radial artery function, characterized using flow mediated dilation (FMD) and low-flow mediated constriction (L-FMC), and the mechanistic role of shear rate modification on radial artery functional characteristics during heating. Eleven young healthy men underwent whole-body heating (water-perfused suit) sufficient to raise core temperature +1°C. Trials were repeated with (Heat+WC) and without (Heat) the application of a wrist cuff located distal to the radial artery examined, known to prevent increases in mean and anterograde shear rate but increase retrograde shear. Radial artery characteristics were assessed throughout each trial, with FMD and L-FMC assessed prior to and upon reaching the target core temperature. Heat markedly increased radial artery mean and anterograde shear rate, along with radial artery diameter and blood flow (P<0.05). Heat+WC abolished the heat-induced increase mean and anterograde shear rate (P>0.05), but markedly increased retrograde shear (P<0.05). Concomitantly, increases in radial artery diameter and blood flow were decreased (Heat+WC vs Heat,P<0.05). Heat attenuated FMD (8.6±1.2 vs. 2.2±1.4%, P<0.05), whereas no change in FMD was observed in Heat+WC (7.8±1.2 vs. 10.8±1.2%,P>0.05). In contrast, L-FMC was not different in either trial (P>0.05). In summary, acute whole-body heating markedly elevates radial artery shear rate, diameter and blood flow, and diminishes FMD. However, marked radial artery vasodilation and diminished FMD are absent when these shear rate changes are prevented. Shear rate modifications underpinthe radial artery response to acute whole-body heat-stress, but further endothelial-dependent vasodilation (FMD) is attenuated likely as the vasodilatory range limit is approached.