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Active, Not Recruiting

NCT Number: NCT06842784

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.

Active, Not Recruiting

This study is active but is not currently recruiting participants.

Key information

Conditions

Aging Body Temperature Changes Heat Strain Heat Stress Heat Stress Disorders Hyperthermia Pathological Conditions, Signs and Symptoms Signs and Symptoms Wounds and Injuries

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

Texas Health Presbyterian Hospital Dallas

Dallas, Texas, 75231, United States

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Ambient heat stress

Other

3-hour ambient heating in 44°C and 20% relative humidity

Primary outcomes

  1. Myocardial flow reserve

    Time frame: 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.

  2. Myocardial blood flow

    Time frame: The change from baseline to after 3 hours of heat stress.

    Measured via myocardial contrast echocardiography.

Secondary outcomes

  1. Core temperature

    Time frame: The change from baseline to after 3 hours of heat stress..

    Measured via ingestible telemetric pill.

  2. Indices of left and right ventricular function

    Time frame: At baseline and after 3 hours of heat stress.

    Measured via echocardiography.

  3. Heart rate

    Time frame: 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.

  4. Blood pressure

    Time frame: 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.

Sponsors and collaborators

Lead sponsor

University of Texas Southwestern Medical Center

Other

Collaborators

  • National Institute on Aging (NIA)
  • The Cleveland Clinic

Registry information

Important dates

Study start
2025
Primary completion
2026
Study completion
2027
First posted
Feb 24, 2025
Registry last updated
Jul 30, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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