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

Recruiting

• Conditions: Aging; Heat Stress; Hyperthermia; Heat Strain

• Registration Number: NCT06842784
• Lead Sponsor: University of Texas Southwestern Medical Center

Brief Summary

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.

Detailed Description

Not available

Study Timeline

• Status Verified: 2025-02
• Study Start: 2025-02-03
• Study First Submitted: 2025-02-18
• Study First Submitted QC: 2025-02-18
• Last Update Submitted: 2025-02-18
• Study First Posted: 2025-02-24
• Last Update Posted: 2025-02-24
• Primary Completion: 2026-02-01
• Study Completion: 2027-02-01

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 24

Inclusion Criteria

• Healthy male and female individuals
• 18-35 years or 65+ years of age
• Free of any underlying moderate to serious medical conditions

Exclusion Criteria

• Known heart disease; other chronic medical conditions requiring regular medical therapy including cancer, diabetes, neurological diseases, uncontrolled hypertension, and uncontrolled hypercholesterolemia.
• Taking of any medications (such as beta blockers and non-dihydropyridine calcium channel blockers) that have known influences on either cardiac function or sweating responses.
• Abnormalities detected on routine screening.
• Current smokers, as well as individuals who regularly smoked within the past 3 years.
• Body mass index of greater than 30 kg/m^2
• Pregnant individuals

Study & Design

• Study Type: OBSERVATIONAL
• Study Design: Not specified

Primary Outcome Measures

Name	Time	Method
Myocardial flow reserve	The difference in the change from baseline to a vasodilator stress test and the change from baseline to after 3-hours of heat stress.	Measured via myocardial contrast echocardiography.
Myocardial blood flow	The change from baseline to after 3 hours of heat stress.	Measured via myocardial contrast echocardiography.

Secondary Outcome Measures

Name	Time	Method
Core temperature	The change from baseline to after 3 hours of heat stress..	Measured via ingestible telemetric pill.
Indices of left and right ventricular function	At baseline and after 3 hours of heat stress.	Measured via echocardiography.
Heart rate	At baseline, during exercise- after 20 minutes and 2 hours in the heat, and at rest after 3 hours of heat stress.	Measured via electrocardiogram.
Blood pressure	At baseline, during exercise- after 20 minutes and 2 hours in the heat, and at rest after 3 hours of heat stress.	Measured via automated auscultation of the brachial artery.

Trial Locations

Locations (1)

Texas Health Presbyterian Hospital Dallas; 🇺🇸 Dallas, Texas, United States