Restrictive cariomyopathy (RCM) is the least common cardiomyopathy. It is called this because it restricts the heart from stretching and filling with blood properly. Rhythmicity and contractility of the heart may be normal, but the stiff walls of the heart chambers (atria and ventricles) keep them from adequately filling. So blood flow is reduced, and blood that would normally enter the heart is backed up in the circulatory system. In time, restrictive cardiomyopathy patients develop diastolic dysfunction and eventually heart failure.