When the Heat Is On: How Extreme Temperatures Affect Your Heart

Heat and Your Heart: What You Need to Know
As summers grow hotter and heat waves become more frequent, it is important to understand that extreme heat is not just uncomfortable - it can be dangerous for your heart. When the body is exposed to high temperatures, the cardiovascular system works overtime to cool you down. Blood vessels dilate, the heart beats faster, and the body loses fluid through sweating. This extra strain can lead to dehydration, thickened blood, increased inflammation, and a surge in stress hormones - all of which put added pressure on the heart and blood vessels.

Heat and Heart Attacks
One of the most serious risks of extreme heat is an increased chance of heart attack (myocardial infarction, or MI). Research shows that during heat waves, the risk of dying from a heart attack can increase by as much as 64%, and hospital admissions for MI rise by approximately 16% for every 1°C increase in temperature (Bell et all, N Engl J Med 2024;390:1793-1801). Heat causes the blood to become thicker and more prone to clotting, while also destabilizing fatty plaques in the arteries - the same plaques that rupture to cause a heart attack. These effects can happen quickly, often on the same day as the heat exposure, making it critical to take precautions as soon as temperatures climb.

Who Is Most at Risk?
Certain people are especially vulnerable during hot weather. Older adults, people with existing heart disease or diabetes, those taking medications such as diuretics (water pills) or beta-blockers, and individuals who work outdoors are at the highest risk. People living in urban areas may also face greater exposure due to the "heat island effect," where pavement and buildings trap and radiate heat. In Manitoba, where residents may be less acclimatized to prolonged heat, even moderate heat waves can pose a significant threat.

Protecting Yourself and Your Patients
Simple steps can make a real difference:

1.     Stay hydrated

2.     Avoid strenuous outdoor activity during peak heat hours

3.     Seek air-conditioned environments

4.     Check on your neighbours and family members, especially the elderly.

Healthcare providers should counsel patients with heart disease about the warning signs of heat-related illness. If you or someone you know experiences chest pain, shortness of breath, or unusual fatigue during a heat wave, seek medical attention immediately. Recognizing the signs of a heart attack and calling 911 promptly remains the most important step in saving a life.