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Heatwaves and Heart Health: Why Extreme Temperatures Can Be Dangerous for the Heart

Spokesperson : Dr. Pawan Poddar, Director of Cath Lab and Senior Consultant Interventional Cardiologist, Yashoda Hospitals, Hyderabad 

Heatwaves are no longer occasional seasonal events but a growing public health concern across many parts of the world. While most people associate extreme summer temperatures with dehydration, exhaustion, or heat stroke, excessive heat can also place tremendous stress on the cardiovascular system. For individuals living with heart disease, hypertension, diabetes, kidney disorders, obesity, or advanced age, prolonged exposure to high temperatures can significantly increase the risk of serious cardiac complications.

The human body naturally attempts to maintain a stable internal temperature. During hot weather, blood vessels widen in a process known as vasodilation, allowing more blood to flow closer to the skin surface so that heat can escape. At the same time, sweating helps cool the body through evaporation. However, these protective mechanisms force the heart to work much harder than usual. In extreme heat, the heart may need to pump two to four times more blood every minute compared to cooler conditions.

How Heatwaves Affect the Heart

Increased Heart Rate and Cardiac Stress

High temperatures increase the body’s demand for oxygen and circulation. To meet these demands, the heart beats faster and works harder. Even a slight rise in body temperature can significantly elevate heart rate, increasing the risk of palpitations, irregular heartbeat, chest discomfort, and cardiac strain, especially in people with existing heart conditions.

Fall in Blood Pressure

As blood vessels dilate to release heat, blood pressure may drop. This can lead to symptoms such as dizziness, weakness, fatigue, or fainting. Individuals taking antihypertensive medicines or diuretics are particularly vulnerable because these medications may further lower blood pressure or increase fluid loss.

Dehydration and Electrolyte Imbalance

Excessive sweating during heatwaves leads to significant fluid and electrolyte loss. Dehydration thickens the blood and can increase the likelihood of blood clot formation, heart attacks, and strokes. Loss of essential minerals such as sodium and potassium may also trigger dangerous heart rhythm disturbances.

Worsening of Existing Heart Disease

People living with heart failure, coronary artery disease, arrhythmias, or previous cardiac events often experience worsening symptoms during hot weather. Breathlessness, swelling of the legs, fatigue, and poor exercise tolerance may become more severe in high temperatures and humidity.

Higher Risk of Heat-Related Cardiac Emergencies

Prolonged heat exposure can precipitate acute coronary syndrome, severe dehydration, stroke, heat exhaustion, and heat stroke. Outdoor physical activity during peak afternoon hours without adequate hydration further increases the risk of medical emergencies.

Precautions to Protect Heart Health During Heatwaves

People with cardiovascular disease should minimize outdoor exposure during the hottest part of the day and stay in cool, well-ventilated, or air-conditioned environments whenever possible. Maintaining proper hydration is essential, although individuals with heart failure or kidney disease should follow fluid intake recommendations advised by their doctor.

Additional preventive measures include:

• Wearing loose, lightweight, and light-coloured clothing
• Avoiding strenuous outdoor exercise during peak heat
• Limiting alcohol, caffeine, and salty foods
• Monitoring blood pressure regularly
• Continuing prescribed cardiac medications without interruption
• Seeking immediate medical attention if symptoms such as chest pain, severe breathlessness, confusion, dizziness, fainting, or palpitations occur

Heatwaves should never be underestimated, particularly people with pre-existing cardiac conditions. Early precautions, proper hydration, medication monitoring, and avoiding prolonged heat exposure can play a crucial role in preventing serious cardiovascular complications during extreme summer weather.