Restrictive cardiomyopathy is a condition in which the heart cannot fill properly, resulting in possibly severe malfunction and heart failure. Restrictive cardiomyopathy is distinguished from the more common dilated cardiomyopathy and hypertrophic cardiomyopathy because the heart ventricles stay a normal size and continues to function normally during the contraction phase. The problem arises, however, during the filling phase, or diastolic phase. In a heart afflicted with restrictive cardiomyopathy, the muscular walls of the heart are rigid and cannot expand when the heart should be filling with blood. As a result, blood pressure rises in the ventricles and the amount of blood pumped to the body is reduced. Also, the upper chambers of the heart, or atria, may expand.

This condition is relatively rare. It may be caused by certain other illnesses, infiltration of the heart by abnormal substance (e.g., amyloid, iron), exposure to radiation, or unknown factors. The disease is called restrictive cardiomyopathy for the following reasons:

The most common sign of restrictive cardiomyopathy is heart failure, which can cause shortness of breath, arrhythmias and general weakness. The symptoms often occur during physical activity when the body's demand for oxygen-rich blood rises. Various diagnostic tests can used to detect the presence of restrictive cardiomyopathy, including electrocardiogram, chest x-ray and echocardiogram. In some cases, a biopsy of the heart muscle may be conducted to rule out other cardiac conditions

Treatment for this condition is difficult. It generally involves taking medication and making healthy lifestyle changes to reduce the risk of heart failure. If abnormal heart rhythms (arrhythmias) are present and cannot be controlled by medication, the patient may benefit from the surgical insertion of a pacemaker or implantable cardioverter defibrillator. In very severe cases, heart transplantation may be recommended.