Impact of Extreme Heat on Myocardial Blood Flow and Flow Reserve in Young and Older Adults

Extreme heat causes a disproportionate number of hospitalizations and deaths in older adults relative to any other age group. Importantly, many hospitalizations and deaths are primarily due to cardiovascular events such as myocardial infarction. Previous data indicate that older adults have attenuated skin blood flow and sweating responses when exposed to heat, resulting greater increase in core body temperature. Despite these observations, relatively little is known about the risk for myocardial ischemia potentially contributing to the aforementioned higher morbidity and mortality in older adults during heat waves. The broad objective of this work is to determine the impact of ambient heat exposure on myocardial blood flow and flow reserve in young and older adults. Aim 1 will test the hypothesis that older adults exhibit attenuated myocardial flow reserve compared to young adults during heat stress. Aim 2 will determine if the percent of maximal myocardial flow reserve (assess via vasodilator stress) during heat exposure is higher in older adults compared to young adults. The expected outcome from this body of work will improve our understanding of the consequences of aging on cardiovascular responses to ambient heat stress.

NCT Number	NCT06842784
Lead Sponsor	University of Texas Southwestern Medical Center Collaborators: National Institute on Aging (NIA), The Cleveland Clinic
Conditions	Aging, Heat Stress, Hyperthermia, Heat Strain
Enrollment	24 participants
Start Date	2025-02-03
Primary Completion	2026-04-30 (estimated)
Study Completion	2027-02-01 (estimated)
Updated on ClinicalTrials.gov	2026-07-30