As temperatures soar during the summer, hospital admissions for cardiovascular conditions also increase, according to the Hellenic Society of Cardiology, which has issued new guidance warning heart patients about the dangers of extreme heat.
The medical association says the link between heatwaves and cardiovascular disease is well established, with scientific evidence showing that prolonged periods of high temperatures can significantly increase the risk of serious complications and death.
Heatwaves linked to higher cardiovascular deaths
According to the society, a meta-analysis of 54 epidemiological studies conducted across 20 countries and published in The Lancet Planetary Health found that heatwaves increase cardiovascular mortality by around 15% compared with periods of normal temperatures.
The risk rises as heatwaves become more prolonged. Research published in BMC Public Health found that when maximum temperatures exceed 35°C (95°F) for four consecutive days, cardiovascular mortality increases by 10%. From the fifth day onward, that increase can reach as much as 51%.
Older adults are particularly vulnerable. Among people aged over 65, mortality during heatwaves lasting five days or longer increases by 24%, compared with an 18% increase in the general population.
Air pollution adds to the danger
The Hellenic Society of Cardiology also highlighted air pollution as a major contributing factor during the summer months.
Higher temperatures promote the formation of ground-level ozone and increase concentrations of fine particulate matter (PM2.5). According to studies published in the Journal of the American College of Cardiology, exposure to these pollutants triggers inflammation of blood vessels, endothelial dysfunction and oxidative stress, all of which increase the risk of heart attacks, strokes and heart failure.
The society noted that urban areas frequently experience elevated pollution levels during heatwaves, particularly when combined with heavy traffic or wildfire smoke, further increasing the risk for people with cardiovascular disease.
Why extreme heat puts extra strain on the heart
When temperatures rise, the body redirects more blood to the skin to release heat. As a result, the heart must pump harder and faster while blood pressure drops. At the same time, sweating causes the loss of fluids and electrolytes, which can affect heart rhythm and alter the effectiveness of medications such as diuretics and antiarrhythmic drugs.
The association also warned that some commonly prescribed heart medications require careful medical supervision during periods of extreme heat. Beta blockers can limit the body’s ability to increase heart rate, diuretics may worsen dehydration, and blood pressure medications can increase the risk of dangerously low blood pressure.
People at highest risk include those with heart failure, a history of heart attack or stroke, cardiac arrhythmias such as atrial fibrillation, poorly controlled hypertension, adults over 65, and patients taking multiple medications.
Eight tips to stay safe during a heatwave
The Hellenic Society of Cardiology advises heart patients to:
- Drink water regularly, even if they do not feel thirsty, unless otherwise instructed by their doctor.
- Avoid outdoor activities during the hottest hours of the day, between noon and 5 p.m.
- Monitor air quality and stay indoors when pollution levels are high or wildfires affect the area.
- Wear lightweight, light-colored clothing and a hat to reduce heat exposure.
- Never change or stop prescribed medication without consulting a doctor.
- Check blood pressure more frequently during periods of extreme heat.
- Eat light meals and ensure adequate sleep to reduce cardiovascular strain.
- Seek immediate medical attention if symptoms such as chest pain, shortness of breath, dizziness, fainting, swelling in the legs or severe fatigue occur.
