How Summer Heat Affects Your Heart

Have you ever noticed those signs near saunas and hot tubs, warning you to limit use or consult a doctor before entering?  Whether it comes from a spa or the summer sun outside, heat can put a significant strain on your body, especially if you have heart disease. As temperatures spike during the summer months, understanding the risks that come with high heat can help protect your health, according to cardiologist Minisha Kochar, MD. “If you're in an extremely hot situation, your body has to make adjustments, and these changes can put pressure on the heart,” said Dr. Kochar. “Knowing your limits and staying hydrated can make a big difference.”

Blood Clots and Dehydration

When temperatures are higher, your risk for blood clots increases. Blood clots are masses that form when blood cells stick together. Most of the time, blood clots are a welcome part of the body’s healing process, working to plug up injuries. However, when they form spontaneously in certain parts of the body, they can disrupt blood flow and lead to severe health events such as a pulmonary embolism or a heart attack.

Blood clots are more likely during high heat conditions because of dehydration. While releasing sweat to cool the body and regulate temperature, you’re also losing fluid that plays a vital role in circulation. “When you’re dehydrated, your blood volume decreases,” said Dr. Kochar. “Your blood gets thicker, and the risk of blood cells sticking together and forming clots increases.”

Dehydration also can deprive your kidneys of the fluid they need. Your kidneys help to manage fluid throughout the body, and when they’re not functioning well, it can create problems for your heart. “If the fluid level is down in the body, the heart has to pump harder and faster to try to compensate,” said Dr. Kochar. “That increases the stress on the heart.”

Dilation and Low Blood Pressure

Another way the body copes with high heat conditions is by dilating (widening) the blood vessels. This allows for more blood to travel to the skin, heating the surface. It may seem counterproductive to deal with high temperatures by heating the skin, but your body has an ingenious strategy. By heating the skin, you’re causing sweat to evaporate. The chemical process of evaporation requires energy, which is drawn from your skin, lowering the temperature.  

The problem is that this dilation also can cause your blood pressure to get too low. Suddenly, the body is struggling to supply important organs with blood, which is why extreme heat can make you dizzy. Your brain isn’t getting the blood it needs. “This is another thing that puts a strain on the heart,” said Dr. Kochar. “To compensate for the low blood pressure, your heart has to work harder to move blood around the body.”

Age and Risk

The risks caused by exposure to high temperatures depend on several factors. If you have heart disease, the increased strain caused by hotter conditions increases the risk of cardiac events. Age also plays a role, but not in the way you might expect. “The people at the highest risk of health problems from hot weather are actually the youngest people,” said Dr. Kochar. “Small children are still developing the ability to regulate temperature. They also don't have the same body surface area to get rid of the heat.” The risks from heat to the very young also extend to the very old, according to Dr. Kochar, as the mechanisms for regulating heat begin to decline as we age.   

Stay Cool and Hydrated

Staying cool isn’t just about comfort. It’s important for your health not to let the heat get to you during the summer season. Don’t stay out in the sun too long, especially if the temperature is approaching triple digits. And because hot weather can deplete you of fluids and put more of a strain on your heart, it’s crucial to stay hydrated. “You should always drink more water when it’s hot,” said Dr. Kochar. “Your body needs more hydration. It’s also a good idea to maintain your electrolytes,” said Dr. Kochar. “We lose electrolytes when we sweat, and they’re another factor in regulating your body temperature.”

So next time you’re heading outside to enjoy some summer fun in the sun, make sure you bring plenty of water (and perhaps a sports drink). Your heart will thank you for it.