Identifying Strategies to Alleviate Cardiovascular Stress in Coronary Patients During Heatwaves

Study Overview
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Brief Summary
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The purpose of this study is to determine the optimal cooling strategies to alleviate cardiovascular strain of coronary artery disease individuals during a simulated North American and Australian heatwave.

Detailed Description
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Globally, heatwaves are occurring more frequently, are of greater intensity and longer in duration. The devastating health impacts of extreme heat are increasingly recognized, particularly in vulnerable populations, such as adults with coronary artery disease (CAD). While the most effective cooling strategy during a heatwave is the use of air conditioning (AC), economical concerns can limit AC use among vulnerable populations. In addition, widespread AC use places a significant burden on the electrical grid, causing brown-outs and black-outs during periods of extreme heat. Electric fans offer a cooling strategy with a 50-fold lower power requirement and cost compared to AC. However, the efficacy of fan use during heat waves remains contentious. The primary objective of this study is to identify the optimal cooling strategy to alleviate cardiovascular strain of CAD patients exposed to typical North American heatwave conditions (38°C with 60% relative humidity). The secondary objective is to identify the optimal cooling strategy to alleviate cardiovascular strain of CAD patients exposed to typical Australian heatwave conditions (46°C with 10% relative humidity).

Official Title
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Identifying Optimal Cooling Strategies for Coronary Artery Disease Patients During Heatwaves

Conditions
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Coronary Artery Disease

Intervention / Treatment
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* Other: No intervention
* Other: Fan
* Other: Skin Wetting
* Other: Fan + Skin wetting


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: History of angiographic coronary disease (≥70% arterial diameter narrowing of at least one major epicardial coronary artery) and/or prior coronary revascularization and/or documented prior acute coronary syndrome and/or stable angina and/or perfusion defect during exercise testing. No CAD-related hospitalisations or changes in cardiac medications or change in pattern of angina for at least 3 months prior to enrolment Exclusion Criteria: Body mass index ≥35 kg/m2. Currently undertaking estrogen therapy. Evidence of current fluid and electrolyte disorders, anemia, abnormal thyroid function, arrhythmias, diabetes, renal disease, liver disease, cerebrovascular disease, significant pulmonary disease, endocrine abnormalities, significant cognitive impairment, psychiatric disorder, substance abuse, degenerative neurological condition or any other medical condition deemed to pose risk during the proposed experiments. Uncontrolled hypertension (>180/110 mmHg). Recent (<3 months) coronary bypass surgery. Ejection fraction <40% and/or clinical evidence/history of heart failure. Significant valvular heart disease Resting ECG abnormalities interfering with observation of ST segment changes during testing.

Ages Eligible for Study
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Minimum Age: 50 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: 38°C and 60% RH + No intervention<br>The participant will enter an environmental chamber maintained at 38°C and 60% relative humidity. The participant will remain within the environmental chamber and will rest in a seated position for 3 hours. | Other: No intervention<br>* The participant will rest in a seated position.<br>|
| Experimental: 38°C and 60% RH + Fan<br>The participant will enter an environmental chamber maintained at 38°C and 60% relative humidity. The participant will remain within the environmental chamber and will rest in a seated position for 3 hours. | Other: Fan<br>* A fan placed in front of the participant will provide an airflow of 4 m/s throughout the exposure.<br>|
| Experimental: 38°C and 60% RH + Skin wetting<br>The participant will enter an environmental chamber maintained at 38°C and 60% relative humidity. The participant will remain within the environmental chamber and will rest in a seated position for 3 hours. | Other: Skin Wetting<br>* Tap water ( 18°C) will be applied every 5 minutes to the face, neck, upper and lower arms and upper and lower legs using a spray bottle.<br>|
| Experimental: 38°C and 60% RH + Fan + Skin wetting<br>Tthe participant will enter an environmental chamber maintained at 38°C and 60% relative humidity. The participant will remain within the environmental chamber and will rest in a seated position for 3 hours. | Other: Fan + Skin wetting<br>* A fan placed in front of the participant will provide an airflow of 4 m/s throughout the exposure. In addition, tap water ( 18°C) will be applied every 5 minutes to the face, neck, upper and lower arms and upper and lower legs using a spray bottle.<br>|
| Experimental: 46°C and 10% RH + No intervention<br>The participant will enter an environmental chamber maintained at 46°C and 10% relative humidity. | Other: No intervention<br>* The participant will rest in a seated position.<br>|
| Experimental: 46°C and 10% RH + Skin wetting<br>The participant will enter an environmental chamber maintained at 46°C and 10% relative humidity. The participant will remain within the environmental chamber and will rest in a seated position for 3 hours. | Other: Skin Wetting<br>* Tap water ( 18°C) will be applied every 5 minutes to the face, neck, upper and lower arms and upper and lower legs using a spray bottle.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Rate pressure product | Rate pressure product, in beats per minute per mmHg | Change from baseline to the end of the 3 hour exposure | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Body core temperature | In degrees Celcius | Change from baseline to the end of the 3 hour exposure |