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Harvard Commentaries
35320
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School


Healthy Heart Healthy Heart
 

When The Heart Can't Relax


August 29, 2012

By Thomas H. Lee M.D.

Harvard Medical School

Heart failure does not actually mean that the heart is on a downward spiral toward loss of all function. Heart failure means that the heart is not pumping as effectively and as efficiently as it normally should. In the past, heart failure used to be called congestive heart failure. The congestion has been dropped because today it is relevant to only half of those with heart failure, the ones with "systolic dysfunction." Systolic dysfunction indicates the heart muscles have weakened so that they cannot squeeze down and pump with full strength. The most common causes of systolic dysfunction are prior heart attacks due to coronary artery disease, toxins (like alcohol and drugs), and infections.

The Internet and your local library abound with excellent research studies about drugs and even new-fangled devices that can help heart-failure patients live longer and feel better. Unfortunately, most of this information is relevant to the one-half of heart-failure patients with systolic dysfunction.

What about the other 40 percent to 50 percent of patients with heart failure? They have a different problem with their heart-muscle cells. The main pumping chambers squeeze just fine. However, they still have a lot of the same symptoms and limitations of patients with systolic heart failure, including shortness of breath after light walking, swollen feet caused by pooling blood, and fluid-filled lungs that make breathing difficult, especially when lying down at night.

Why do these people have heart failure if their “pumps” are strong? Their hearts have trouble relaxing between beats. This condition is called heart failure with preserved systolic function, also know as diastolic dysfunction. Because the main chamber of the heart, the left ventricle, cannot fully relax, it cannot fill with blood as quickly between beats. As a result, the ventricle does not have much blood inside at the beginning of each heartbeat and therefore each heart contraction pumps less blood out of the ventricle. This inefficiency results in less forward blood flow to feed oxygen and nutrients to the body, and higher pressures behind the ventricle with more fluid backing up.

A simple test, called an echocardiogram (echo for short), uses sound waves to make the distinction between systolic dysfunction and diastolic dysfunction. The moving pictures of the beating heart provide doctors valuable information that helps to guide the correct diagnosis and appropriate treatments.

The new research on diastolic dysfunction explains why heart failure can occur in patients with big, thick hearts — very often older people who have had poorly controlled high blood pressure for many years. And it explains why these patients often get short of breath when their hearts speed up, despite normal systolic function. When the amount of time in between each heartbeat is shortened, there is even less time for the heart to relax and fill with blood, so that the amount of blood pumped out with each heartbeat decreases even more.

There are several “take-home messages” about heart failure that flow directly from this research:

  • Everyone with heart failure must get an echocardiogram to determine whether the problem is a heart muscle that is too weak or too strong.
  • If you have high blood pressure, be relentless about controlling it. Don’t wait until you have diastolic heart failure from a heart muscle that is too stiff to relax.
  • If you have diastolic heart failure, you may benefit from drugs that slow the heart down — giving your heart more time between beats to fill with blood. Such drugs include beta-blockers (like atenolol or metoprolol), verapamil and diltiazem.

We do not yet have drugs that can reliably relieve diastolic heart failure by making the heart relax more quickly. Such treatments may come with time. Until then, lowering blood pressure to normal levels and using medications to slow the heart rate can help many people with this common problem feel better.

Thomas H. Lee, M.D., is the chief executive officer for Partners Community HealthCare Inc. He is a professor of medicine at Harvard Medical School. He is an internist and cardiologist at Brigham and Women's Hospital. Dr. Lee is the chairman of the Cardiovascular Measurement Assessment Panel of the National Committee for Quality Assurance.

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