Effect of moderate exercise-induced heat stress on carotid wave intensity

Exercise disrupts the interaction between the left ventricle and the vasculature, as measured by wave intensity (WI) analysis. However, the effect of exercise-induced heat stress on WI amplitude is unknown. WI measures are calibrated using brachial or carotid artery blood pressure, but the influence of calibration method on WI outcomes is unknown.

(1) To compare WI analysis during low and moderate exercise-induced heat stress; (2) to examine differences in carotid WI analysis based on calibration method.

Eleven healthy, young men (22 ± 3 years) performed intermittent exercise in moderate- and low-heat stress conditions. WI was assessed pre- and post-exercise on the right carotid artery, and calibrated with brachial and carotid blood pressures.

A main effect of time was found for W1 when calibrated by brachial, but not carotid pressure. A time-by-condition interaction was observed for late systolic/early diastolic function (W2) in both brachial (p = 0.047) and carotid calibration methods (p = 0.042), where W2 increased following exercise-induced moderate-heat stress but decreased following low-heat stress. The elastic modulus exhibited a significant time-by-condition interaction (brachial p = 0.039; carotid p = 0.044), increasing following moderate-heat stress but decreasing following low-heat stress. Calibrations using carotid blood pressure significantly reduced WI amplitudes compared with brachial calibrations (p < 0.001).

Arterial-ventricular coupling is affected in different ways following moderate and low exercise-induced heat stress. Wave amplitudes were lower (~13 %) following carotid calibration compared with brachial.