The effect of passive heat stress on arterial wave reflection, pulse wave velocity, and cerebral blood flow

Ashton, Kimberly
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University of Delaware
It is well known that the prevalence of cardiovascular events is increased in extreme weather conditions. It has previously been shown that cerebral blood flow (CBF) decreases with heat stress, while the effect of heat stress on augmentation index and pulse wave velocity (PWV) has not been clearly investigated. The main purpose of this study was to determine the effects of passiveheat stress on CBF, PWV, and wave reflection. We measuredthe correlation between baseline measurements of Augmentation Index (AIx), PWV, wave reflection transit time (Tr) and changes in CBF. In addition, the correlation between changes in AIx, PWV, Tr and changes in CBF were also explored. We gathered data from sixteen apparently healthy young adults. Changes in variables from baseline to passive heat stress were evaluated with a paired t-test. While mean CBF did not significantly decline, it was found to trend downwards from baseline to passive heat stress (15 cm/s to 14.9 cm/s, p=0.06). AIx was found to significantly decrease from a baseline of -1% to -12% during passive heat stress (p<0.05). PWV and Tr did not significantly change from baseline. There were no significant correlations found between variables. The present study is the first to demonstrate a decrease in AIx during passive heat stress. In conclusion, these data suggest that while CBF and AIx both decline under passive heat stress, it is not likely that a correlation between CBF and AIx leads to cardiovascular events in the heat.