AgingNCT06842784
Impact of Extreme Heat on Myocardial Blood Flow and Flow Reserve in Young and Older Adults
An observational study of Aging and Heat Stress, run by University of Texas Southwestern Medical Center at 1 site in United States.
Trial 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. Read more about this study
- Who is it for?
- Ages 18 years and olderHealthy volunteers can take part
- Conditions the study is for
- Aging, Heat Stress, Hyperthermia
- What is being tested?
- Ambient heat stress
- How many people
- 24 participants
- Where
- 1 siteUnited States
- Study dates
- 3 Feb 2025to 1 Feb 2027
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Study population: The study population will be healthy younger and older individuals identified from the general population.
Who may be able to join
- Healthy male and female individuals
- 18-35 years or 65+ years of age
- Free of any underlying moderate to serious medical conditions
Who cannot join
- 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
Trial locations and contacts
1 site in 1 country.
United States1 site
Texas Health Presbyterian Hospital Dallas
Dallas, Texas, 75231
About this study
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.
- Conditions
- Aging, Heat Stress, Hyperthermia, Heat Strain
- Being tested
- Ambient heat stress
- Medical subject headings
- Heat Stress Disorders, Hyperthermia
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Ambient heat stressOther
3-hour ambient heating in 44°C and 20% relative humidity
| Study group | Role | What they receive |
|---|---|---|
| Young participants | Individuals aged 18-39 years Receives: Other: Ambient heat stress | |
| Older participants | Individuals aged 65 years or older Receives: Other: Ambient heat stress |
What is being measured
The primary outcome is the main question the study is designed to answer.
Myocardial flow reserve
Measured via myocardial contrast echocardiography.
Measured: The difference in the change from baseline to a vasodilator stress test and the change from baseline to after 3-hours of heat stress.
Myocardial blood flow
Measured via myocardial contrast echocardiography.
Measured: The change from baseline to after 3 hours of heat stress.
Secondary outcomes (4)
Core temperature
Measured via ingestible telemetric pill.
Measured: The change from baseline to after 3 hours of heat stress..
Indices of left and right ventricular function
Measured via echocardiography.
Measured: At baseline and after 3 hours of heat stress.
Heart rate
Measured via electrocardiogram.
Measured: At baseline, during exercise- after 20 minutes and 2 hours in the heat, and at rest after 3 hours of heat stress.
Blood pressure
Measured via automated auscultation of the brachial artery.
Measured: At baseline, during exercise- after 20 minutes and 2 hours in the heat, and at rest after 3 hours of heat stress.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted24 Feb 2025
- Study start3 Feb 2025
- Primary completion30 Apr 2026
- Study completion1 Feb 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for AgingStudies of the same condition, open and under way.
- More trials run by University of Texas Southwestern Medical CenterThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Cohort
- Time perspective
- Prospective
- Enrolment
- 24 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Texas Southwestern Medical Center
- Sponsor type
- University, hospital or other
- Collaborators
- National Institute on Aging (NIA), The Cleveland Clinic
- Responsible party
- Principal investigator, James MacNamara, University of Texas Southwestern Medical Center
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06842784
- Sponsor's protocol ID
- STU_2019_1759_MCE
- Other IDs
- 1R01AG069005
- Status last verified
- Aug 2025
- First submitted
- 18 Feb 2025
- Last updated
- 30 Jul 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 30 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Impact of Extreme Heat on Myocardial Blood Flow and Flow Reserve in Young and Older Adults
- ClinicalTrials.gov ID
- NCT06842784
- Acronym / sponsor ID
- STU_2019_1759_MCE
- Conditions
- Aging, Heat Stress, Hyperthermia, Heat Strain
- Study type
- Observational
- Recruitment status
- Active, not recruiting
- Enrolment
- 24 participants (estimated)
- Lead sponsor
- University of Texas Southwestern Medical CenterUniversity, hospital or other
- Collaborators
- National Institute on Aging (NIA), The Cleveland Clinic
- Study start
- 3 Feb 2025 (actual)
- Primary completion
- 30 Apr 2026 (actual)
- Study completion
- 1 Feb 2027 (estimated)
- First posted
- 24 Feb 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Observational model
- Cohort
- Time perspective
- Prospective
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Young participants | – | Other: Ambient heat stressIndividuals aged 18-39 years |
| Older participants | – | Other: Ambient heat stressIndividuals aged 65 years or older |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
- Study population
- The study population will be healthy younger and older individuals identified from the general population.
Key inclusion criteria (3 listed)
- Healthy male and female individuals
- 18-35 years or 65+ years of age
- Free of any underlying moderate to serious medical conditions
Key exclusion criteria (6 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Ambient heat stress3-hour ambient heating in 44°C and 20% relative humidity | Other | Older participants, Young participants |
Primary outcome
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.
Myocardial blood flow
Time frame: The change from baseline to after 3 hours of heat stress.
Measured via myocardial contrast echocardiography.
4 secondary outcomes
Core temperature
Time frame: The change from baseline to after 3 hours of heat stress..
Indices of left and right ventricular function
Time frame: At baseline and after 3 hours of heat stress.
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.
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.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 30 Jul 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Aging and Heat Stress, run by University of Texas Southwestern Medical Center at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 6 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 30 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
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.). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 30 Jul 2026.