Physiological responses of adults with coronary artery disease during extreme heat exposure

Introduction: Extreme heat is becoming more frequent due to climate change. Different regions experience different forms of heat, such humid or dry heat, a greater risk of morbidity and mortality becomes apparent with higher temperatures. Adults with heart disease are especially vulnerable to the health risks of extreme heat. One possible reason for this greater risk is that adults with heart disease might experience greater physiological heat strain during extreme heat exposure. The objective of this study was to determine if adults with coronary artery disease (CAD) experience greater physiological strain relative to adults without CAD during hot/humid and very hot/dry heat exposures.Methods: 28 adults with stable CAD (2 females/26 males, 66±7 y, 1.96±0.17 m 2 ) and 26 adults without CAD (non-CAD; 13 females/12 males, 69±4 y, 1.86±0.21 m 2 ) rested for 3 hours in hot/humid (HH; 38°C/60% relative humidity; n= 22 CAD and 26 non-CAD) and very hot/dry (VHD; 45°C/15% relative humidity; n=24 CAD and 13 non-CAD) environments on separate days. Participants consumed 3 mL/kg/h of water during each exposure. Core (rectal) and skin temperatures, heart rate, and whole-body sweat loss were measured. Results: During exposure to HH, adults with CAD experienced a greater increase in core (0.58±0.28°C vs. 0.37±0.23°C, p=0.009) and mean skin (5.08±1.11°C vs. 4.06±0.76°C, p=0.0005) temperatures and sweat more (832±252 g vs. 471±244 g, p<0.0001). The increase in heart rate (CAD: 9±7 bpm vs. non-CAD: 9±6 bpm, p=0.914) and percent change in body weight (CAD: +0.12±0.32% vs. non-CAD: +0.25±0.22%, p=0.106) did not differ between groups. During exposure to VHD, adults with CAD experienced a greater increase in mean skin temperature (5.79±1.06°C vs. 4.92±1.23°C, p=0.029), greater sweat loss (1239±171 g vs. 794±159 g, p<0.0001), and greater percent change in body weight (-0.41±0.29% vs. -0.11±0.16%, p=0.001). The change in core temperature (CAD: 0.62±0.37°C vs. healthy: 0.48±0.21°C, p=0.092) and heart rate (CAD: 9±7 bpm vs. healthy: 13±6 bpm, p=0.196) did not differ between groups. Conclusion: During hot/humid heat exposure, adults with CAD experience greater thermal strain and fluid loss, whereas they experience greater fluid loss and dehydration during a very hot/dry heat exposure. The greater physiological heat strain experienced by adults with CAD may reflect the impact of altered cardiovascular function and/or medications on internal distribution and ultimately contribute to a greater risk of heat-related mortality. National Health and Medical Research Council This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.