The Heat is On: Protect Your Heart this Summer

When George Gershwin wrote, “Summertime and the livin’ is easy . . .” he wasn’t considering how hot, humid summers affect a person’s heart health. That topic is top of mind for cardiologist Maria Carolina Delgado-Lelievre, M.D. 

“Temperatures above 90°F (32°C), combined with high humidity, significantly strain the cardiovascular system. Research has shown elevated risks of cardiovascular mortality and morbidity during heatwaves, especially among older populations,” says the director of the Comprehensive Hypertension Center at the University of Miami Health System. 

How does heat affect your heart?

Most people – even children – feel exhausted after a day in the summer sun, but why is heat especially hard on the heart? When the air temperature is nearly equal to or greater than your body temperature, your heart has to beat faster and pump harder to keep you cool. On a sweltering day, your heart might circulate two to four times as much blood per minute compared with a cool day. If your cardiovascular health is already compromised, you have a greater risk of dehydration, electrolyte imbalances, changes in heart rhythm or blood pressure, and blood clots. 

Heart medications can increase your risk even more. 

“It’s important to recognize the mechanisms linking extreme hot temperatures to various cardiovascular diseases,” says Dr. Delgado-Lelievre. “Dehydration, hemoconcentration, hypercoagulability, sympathetic activation, and inflammatory mediators are involved. Blood flow to the skin increases during extreme heat to facilitate sweating and evaporation, potentially leading to dehydration, electrolyte imbalances, and hypercoagulable states.”

She identifies the impact of hot weather on five of the most common cardiovascular conditions and steps you can take to prevent these impacts:

High blood pressure (hypertension)

Hot weather can exaggerate the effects of vasodilation (widening of the blood vessels). This can cause sudden changes in blood pressure when you stand up after sitting or lying down. Known as orthostatic hypotension (OHT), this situation is more common if you take high blood pressure medication. OHT can cause dizziness, fainting, heart palpitations, sweating, and nausea. To avoid OHT, stay out of the heat, “Monitor your blood pressure regularly, limit salt intake, and adhere to your prescribed medications,” Dr. Delgado-Lelievre says.

Low blood pressure (hypotension)

Similarly, low blood pressure can drop even more when heat causes the blood vessels to widen too fast. To prevent fainting or dizziness, “Avoid sudden changes in posture, stay hydrated, and keep your electrolytes in balance,” says Dr. Delgado-Lelievre. In addition to water, consider adding electrolyte-infused beverages to your daily fluids. 

Arrhythmia and pacemaker implants

Dehydration and excessive heat can trigger irregular heart rhythms. Getting overheated may also affect pacemaker function. Stay cool and drink plenty of non-caffeinated fluids to prevent these reactions. 

Congestive heart failure (CHF)

People with CHF must practice extra caution, especially if they take diuretic or vasodilator medication.

“Prolonged exposure to heat can exacerbate symptoms and strain the heart. The extra work for the heart, compounded by the loss of sodium and potassium and the internal flood of stress hormones, can push some people into trouble. The increased blood flow to the skin, combined with dehydration, may drop your blood pressure enough to cause dizziness or falls. People with CHF must also adhere strictly to fluid intake restrictions to prevent fluid overload,” Dr. Delgado-Lelievre says. 

Coronary heart disease (CHD)

Exercise is essential to managing chronic heart disease, but Dr. Delgado-Lelievre cautions against “excessive exertion in hot weather” to prevent insufficient blood flow to the heart (myocardial ischemia). During our sweltering summers, adjust your workout routine. 

How do medications affect heat tolerance?

While medications help the heart function better, extreme heat can amplify their effectiveness. “Beta-blockers and vasodilators can impair the body’s ability to regulate temperature and increase the risk of heat-related complications. Beta-blockers also reduce the heart rate and impede the body’s ability to dissipate heat. Diuretics increase urine production, leading to fluid and electrolyte imbalances, exacerbating dehydration in hot weather,” says Dr. Delgado-Lelievre. 

Despite these potential complications, don’t stop taking your medication. Instead, stay out of the heat and periodically discuss your medications and dosages with your doctor. Over time, adjustments may be needed. 

How to beat the heat.

The obvious first step is limiting your outdoor activities, especially when it is humid and above 90°F or 32°C. Pay attention to weather conditions and the heat index or “feels like” temperature. Move your midday walk to early morning or evening, walk around a climate-controlled shopping mall, or hit the treadmill at home or the gym. 

Be hyper-aware of hydration. 

“Consume 1.5 to 2 liters of fluid per day, including beverages and foods. However, during hot weather, additional fluids may be necessary to compensate for increased sweating and fluid loss through evaporation. Drink enough fluids to maintain proper hydration; pay attention to thirst cues and urine output. Managing fluid intake is even more critical for patients taking diuretics; these medications increase urine production, leading to fluid and electrolyte imbalances. It’s essential to balance fluid intake to prevent dehydration while avoiding fluid overload,” Dr. Delgado-Lelievre says.

Drink water throughout the day, even if you don’t feel thirsty. 

Caffeinated and alcoholic beverages don’t count; in fact, they dehydrate you further and can interact with certain heart medicines. Dr. Delgado-Lelievre advises monitoring your weight daily and reporting sudden increases to your doctor. “This allows for timely adjustments in your fluid intake and medication dosages.” 

She also recommends wearing “appropriate clothing”: light colored, loose-fitting, breathable fabrics, and a wide brim hat. 

Keep your indoor air temperature at a comfortable level. Concerned about utility bills? Use ceiling fans and electric fans to help cool the air and close curtains or blinds during the hottest part of the day. Learn the signs of heat-related illnesses and stay in touch with your healthcare providers throughout the summer to see if your medications or fluid intake need adjusting. 

“Research shows elevated risks of cardiovascular mortality and morbidity during heatwaves, especially among older populations. As climate change worsens, adaptation is crucial to mitigate the anticipated risk in heat-related health risks,” Dr. Delgado-Lelievre says.

Even if you can’t control the weather, you can control the habits that protect your heart. 

Nancy Moreland is a regular contributor to the UHealth Collective. She has written for several major health care systems and the CDC. Her writing also appears in the Chicago Tribune and U.S. News & World Report.

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Tags: cardiology care in Miami, Dr. Maria Carolina Delgado-Lelievre, heart arrhythmias, heat wave