Restrictive cardiomyopathy refers to a group of disorders in which the heart chambers are unable to properly fill with blood because of stiffness in the heart.

In restrictive cardiomyopathy, the heart is of normal size or only slightly enlarged. However, it cannot relax normally during the time between heartbeats when the blood returns from the body to the heart (diastole).

Later in the disease, the heart may not pump blood efficiently. The abnormal heart function can affect the lungs, liver, and other body systems. Restrictive cardiomyopathy may affect either or both ventricles. It may be associated with a disease of the heart muscle.

The most common causes of restrictive cardiomyopathy are amyloidosis and scarring of the heart from an unknown cause (idiopathic myocardial fibrosis). It frequently occurs after a heart transplant.

Other causes of restrictive cardiomyopathy include:

• Carcinoid heart disease
• Diseases of the heart lining (endocardium), such as endomyocardial fibrosis and Loeffler's syndrome (rare)
• Radiation fibrosis
• Sarcoidosis
• Scleroderma
• Tumors of the heart