Acute effects of heat therapy on cardiovascular responses to exercise and walking endurance in patients with symptomatic peripheral arterial disease
Authors: Monroe Jacob C , Klein Janet S , Motaganahalli Raghu L , Roseguini Bruno T 
Published: June 2021

IntroductionPatients with symptomatic peripheral artery disease (PAD) suffer from severely impaired exercise tolerance and accelerated rates of functional decline, resulting, in part, from significant endothelial cell dysfunction and the consequent impairment in vasodilation of the vasculature supplying the leg muscles. Endothelial dysfunction stems, at least partially, from elevated circulating levels of endothelin‐1 (ET‐1), a potent endogenous vasoconstrictor secreted by endothelial cells. These patients exhibit an exaggerated pressor response to exercise coupled with increased release of ET‐1. We have previously shown that heating of the lower legs via water‐circulating trousers decreases blood pressure and circulating levels of ET‐1 in patients with symptomatic PAD. The purpose of the present study was to test the hypothesis that exposure to a session of leg heat therapy would attenuate the pressure response to exercise, reduce circulating levels of ET‐1 and improve calf oxygenation and walking endurance in patients with PAD.MethodsEleven patients with symptomatic PAD (65.1 ± 1.8 years) were assigned using a balanced, randomized crossover design to receive a single 90‐min session of heat therapy (HT) or a thermoneutral, control treatment. Immediately after the end of the interventions, patients were asked to complete a symptom‐limited exercise test on the treadmill. Blood pressure, heart rate, calf muscle oxygenation and pulmonary oxygen uptake were measured during exercise and recovery. Blood samples were taken prior to and after exposure to HT or the control intervention as well as 10 min after exercise for the quantification of plasma ET‐1 and tumor necrosis factor alpha (TNF‐alpha) levels.ResultsMean arterial pressure (MAP) was on average 4.077 ± .6234 mmHg lower during exposure to HT as compared to the control intervention. The area under the curve (AUC) for the change in MAP was significantly different between interventions (Control: −0.3643 ± 15.60, heat: −74.54 ± 30.58, p=0.044). Plasma ET‐1 levels were not significantly altered following exposure to HT or the control regimen, but tended to be reduced at the end of the exercise test following exposure to HT (n=6, Control: 0.3566 ± 0.2351 pg/mL, HT: −0.2493 ± 0.2541 pg/mL, p = 0.108). Pain‐free walking time and maximal walking time did not differ between trials. Likewise, calf muscle oxygenation, pulmonary oxygen uptake, and MAP during exercise as well as plasma levels of TNF‐alpha were similar after exposure to HT and the control treatment.ConclusionsA single session of HT lowers resting blood pressure and attenuates the exercise‐induced increase in circulating ET‐1 in patients with PAD. These findings suggest that HT may be a useful adjunctive therapy to reduce cardiovascular risk and possibly augment the adaptations to exercise training in these patients.Support or Funding InformationIndiana Clinical and Translational Science Institute Collaboration in Translational Research GrantThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.