Cardiomyopathy is a disease that affects the heart muscle. In restrictive cardiomyopathy (RCM) the heart muscle becomes rigid and unable to relax and fill with blood. The function or squeeze of the heart may be normal, but the relaxation is abnormal. When the lower left chamber of the heart, called the left ventricle, is unable to stretch and fill with blood, pressure builds up causing abnormal heart rhythms and symptoms of heart failure.

An illustration showing restrictive cardiomyopathy.