Hot Weather and Heart Health: What to Know

When temperatures go up, your body works harder to cool down. The sweat glands activate and the blood vessels in the skin dilate, opening wider to allow more blood to flow to the skin’s surface and release heat from the body. 

High temperatures and high levels of humidity can trigger the cardiovascular system to work harder to pump more blood to reach the skin surface, which can increase heart rate and may affect blood pressure. The increased stress on the body can increase blood pressure.

Sweating, too, can affect the heart’s workload. When sweat evaporates, it pulls heat away from your skin. However, heavy sweating increases the risk of dehydration if water lost through sweat is not replaced. Dehydration reduces blood volume, which makes the heart work harder to get enough blood to the body. Heavy sweating that leads to dehydration can also impair the body’s ability to cool down.

Additionally, when you sweat, you lose essential electrolytes such as sodium and potassium that help keep the heart functioning normally. If electrolytes become unbalanced, the heart may beat irregularly, which is called arrhythmia.

“Any of these can put significant strain on the heart as it works harder to control your body temperature,” says David Cork, MD, a cardiologist at Scripps Clinic Torrey Pines.

“Many people are not aware how much stress their heart and cardiovascular system is under, but things can escalate pretty quickly if you don’t take action to mitigate the effects of the heat,” Dr. Cork says. “People with chronic conditions affecting the circulatory system, and those with underlying heart, kidney, or lung problems may be at the highest risk of heat-related injury.”

When hot weather hits, consider the following tips to help you and your heart handle the heat.

Try to schedule outdoor exercise or activities in the early morning or late evening, when temperatures are usually cooler. If this isn’t possible, do what you can to minimize time spent in the heat. Wear light-colored, loose clothing made of breathable fabrics or moisture-wicking materials that allow sweat to evaporate. Take frequent breaks indoors or in the shade. Most importantly, pay attention to how your body feels. 

“It’s a good idea to regularly check your blood pressure and heart rate, especially if you have pre-existing heart conditions,” says Dr. Cork. “If you experience symptoms such as dizziness, an irregular or fast heartbeat, or chest pain, stop what you’re doing, cool down, and hydrate. If symptoms persist, we generally recommend presenting to a local ER or urgent care.”

Drink plenty of water throughout the day, even if you don’t feel thirsty. Minimize alcoholic beverages, which can be dehydrating, and highly caffeinated “energy drinks” that increase your heart rate. Instead, look for beverages that contain electrolytes to help reduce lost sodium and potassium.

Snacking on juicy fruits can also help keep you hydrated; watermelon, for example, is 92% water and an excellent source of potassium and magnesium. Cucumber is another good option. One note if you have heart failure: Ask your doctor how much fluid you should drink daily, as excess fluids can cause swelling.

Fans, misters, cooling towels and cool showers can help bring your body temperature down. If it gets too hot in your house, seek out air-conditioned environments like grocery stores, libraries and movie theaters.

Certain medications can affect how your body handles heat and hydration. For example, beta blockers slow the heartbeat, which affects how quickly the heart can pump blood through the body to help release heat. Diuretics (water pills) raise the risk of dehydration. Talk to your doctor about any precautions you should take regarding your medications.

“Even with a heart condition, you can still enjoy summer if you do it wisely and take steps to protect yourself,” says Dr. Cork. “But if you feel any symptoms or just don’t feel right, immediately take action to cool down and seek medical care if necessary.”