"Restrictive cardiomyopathy" referes to a group of disorders in which the heart chambers are unable to fill properly with blood because of stiffness of the heart. In restrictive cardiomyopathy, the heart is normal in size or only slightly enlarged, but it cannot relax normally during diastole (that is, the time between heartbeats in which the blood returns from the body to the heart).

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 and may or may not be associated with a disease of the heartmuscle.

The most common causes of restrictive cardiomyopathy are amyloidosis and idiopathic myocardial fibrosis (a scarring of the heart of unknown cause). Restrictive cardiomyopathy is frequently encountered after a heart transplantation. Other causes of restrictive cardiomyopathy include sarcoidosis, hemochromatosis, radiation fibrosis, and various tumor infiltrations of the heart. More rarely, restrictive cardiomyopathy is caused by diseases of the endocardium (the lining of the heart) such as endomyocardial fibrosis and Loeffler's syndrome.