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Harvard Medical School

Cardiomyopathy

What Is It?

Cardiomyopathy refers to changes in the heart muscle that prevent part or all of the heart from contracting normally. There are three types of cardiomyopathy, based on the physical changes that occur in the heart:

• Dilated cardiomyopathy — In this form of cardiomyopathy, the damaged heart muscle stretches out of shape. The heart becomes enlarged and loses its ability to pump blood effectively. This eventually leads to heart failure. The most common heart diseases that lead to a dilated cardiomyopathy are coronary artery disease, and prolonged untreated high blood pressure. Excessive alcohol use over a long time also can lead to dilated cardiomyopathy. Other diseases that can cause cardiomyopathy include myocarditis (heart muscle inflammation, often starting as a viral infection or after a women gives birth), untreated thyroid disorders, inherited genetic diseases, and disorders in which the heart muscle is overloaded with iron or a protein called amyloid. Radiation and chemotherapy treatments also can cause this condition.

• Hypertrophic cardiomyopathy — In this form of cardiomyopathy, the muscular heart wall thickens abnormally, and the heart muscle cannot relax normally during the filling phase. In certain types of hypertrophic cardiomyopathy, the muscle can become so thickened that it can block the flow of blood out of the heart.

• Restrictive cardiomyopathy — In this form of cardiomyopathy, the heart's muscular walls become so rigid that the heart cannot fill properly.