Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Cardiomyopathy refers to changes in the heart muscle. These changes prevent part or all of the heart from contracting normally.

There are three types of cardiomyopathy. The types are based on the physical changes that occur in the heart:

  • Dilated cardiomyopathy The damaged heart muscle stretches out of shape. The heart becomes enlarged. It loses its ability to pump blood effectively. This eventually leads to heart failure.

    Risk factors for dilated cardiomyopathy include:

    • Coronary artery disease

    • High blood pressure

    • Prolonged, excessive alcohol use

    • Myocarditis (heart muscle inflammation)

    • Untreated thyroid disorders

    • Inherited genetic diseases

    • Disorders in which the heart muscle is overloaded with iron or amyloid protein

    • Radiation and chemotherapy treatments

  • Hypertrophic cardiomyopathy The muscular heart wall thickens abnormally. As a result, the heart muscle cannot relax fully. As a result, the heart does not fill up with as much blood as in a healthy heart. So the heart has less blood to pump out to the body. There is another problem with hypertrophic cardiomyopathy, as well. The heart muscle wall can become so thickened that it blocks the flow of blood out of the heart. Both of these problems can lead to heart failure.

  • Restrictive cardiomyopathy Various diseases can cause substances to be deposited where they do not belong: in the heart muscle. This causes the heart's muscular walls to become so rigid that the heart cannot expand to fill up with all the blood that is returning from the body. The result is that the heart does not have as much blood to pump as the body needs.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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