Why does exercise intolerance occur in heart failure?

Reported by Susan Aldridge, PhD, medical journalist

New study takes a fresh look at the exercise intolerance problem in heart failure.
People with heart failure generally have exercise intolerance, which means they have problems carrying out everyday activities. This is thought to be because the heart is not pumping enough oxygenated blood to the muscles. However, this cannot be the full story, because exercise intolerance tends to persist even with treatment that improves heart function.

It is known that blood flow to the legs is an important factor in exercise performance. So is it an issue in exercise intolerance? Researchers at Wake Forest University looked at blood flow to the legs in a group of 30 participants with heart failure. Blood flow to the legs was relatively normal among those with diastolic heart failure. It was, however, impaired among those with systolic heart failure. The distinction between the two different types of heart failure has only been made relatively recently. In diastolic heart failure, the heart muscle is stiff and does not take in enough blood. In systolic heart failure, the heart muscle is too weak to pump efficiently.

If blood flow to the legs is relatively normal in diastolic heart failure, then there must be some other reason for exercise intolerance. Trying to solve this problem is important as it may lead to new treatments that will enable this group of heart failure patients carry out daily activities better.

Source
American Journal of Physiology - Heart & Circulatory Physiology online

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