Heart Beat: Heat and heart failure

Content provided by the Faculty of the Harvard Medical School

Heart Beat: Heat and heart failure

Heart Beat

Heat and heart failure

Deadly heat waves in the United States and Europe taught us that people with heart failure are especially vulnerable to high temperatures. Although their heart trouble is clearly one reason they have trouble with the heat, blood vessels supplying the skin may contribute to it.

One way we cope with excess heat is by rerouting blood flow. Responding to signals from deep in the brain, blood vessels that supply the internal organs narrow. This limits circulation to the stomach, intestines, liver, and kidneys. At the same time, tiny arteries (arterioles) near the skin relax and open. As extra hot blood flows just below the skin, some of its heat escapes into the air.

Two independent research teams, one at Presbyterian Hospital in Dallas and one at the University of Western Australia, looked at this response in people with heart failure. It turns out that arterioles under their skin don’t dilate with rising body temperature. This makes it difficult to radiate excess heat.

Rather than thinking of this as a faulty response, it may be one of the many ways the body adapts to heart failure. When blood floods toward the skin, the heart must beat harder and faster to keep blood pressure from plummeting. This isn’t an option for the failing heart.

In that case “the body has a choice to make — regulate body heat or preserve blood pressure,” says Craig Crandall, who led the Presbyterian Hospital team. “It looks like it is siding with maintaining blood pressure.” Beta blockers and other medications may also contribute to the imbalance.

If you have heart failure, keep this in mind as you plan summer days and cope with the heat. You may need air conditioning more than those around you. Drinking enough water — not sugary or caffeinated sodas, juices, or other beverages — is also important. Talk with your doctor about how best to make sure you get enough fluid without overdoing it.

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Last updated:	August 21, 2006

Medical content reviewed by the Faculty of the Harvard Medical School. Harvard Health Publications, Copyright © 2007 by President and Fellows of Harvard College. All rights reserved. Used with permission of StayWell.

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