Clinical trial NCT06842784: Impact of Extreme Heat on Myocardial Blood Flow and Flow Reserve in Young and Older Adults
Official title: Impact of Extreme Heat on Myocardial Blood Flow and Flow Reserve in Young and Older Adults
Study type: OBSERVATIONAL
Overall status: RECRUITING
Conditions: Aging
Heat Stress
Hyperthermia
Heat Strain
Lead sponsor: University of Texas Southwestern Medical Center
Sponsor class: OTHER
Collaborators: name: National Institute on Aging (NIA)
name: The American Society of Echocardiography
First posted: 2025-02-24
Enrollment: 24
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: yes
Observational model: COHORT
Time perspective: PROSPECTIVE
Sampling method: NON_PROBABILITY_SAMPLE
Study population: The study population will be healthy younger and older individuals identified from the general population.

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.


Eligibility criteria: 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

Primary outcomes:
measure: Myocardial flow reserve
timeFrame: The difference in the change from baseline to a vasodilator stress test and the change from baseline to after 3-hours of heat stress.
measure: Myocardial blood flow
timeFrame: The change from baseline to after 3 hours of heat stress.
Secondary outcomes:
measure: Core temperature
timeFrame: The change from baseline to after 3 hours of heat stress..
measure: Indices of left and right ventricular function
timeFrame: At baseline and after 3 hours of heat stress.
measure: Heart rate
timeFrame: At baseline, during exercise- after 20 minutes and 2 hours in the heat, and at rest after 3 hours of heat stress.
measure: Blood pressure
timeFrame: At baseline, during exercise- after 20 minutes and 2 hours in the heat, and at rest after 3 hours of heat stress.
Other outcomes:
Locations:
city: Dallas
country: United States
facility: Texas Health Presbyterian Hospital Dallas
state: Texas
Study officials:
References: