As a result, the heart muscle's ability to pump blood is usually weakened.
Death rates are highest in older adults, men and blacks.
Eventually, the heart muscle enlarges from the additional work it must do in the absence of enough oxygen-rich blood, leading to ischemic cardiomyopathy. Nonischemic cardiomyopathies are less common, progressive diseases. Unlike ischemic cardiomyopathies, which tend to develop in older adults, nonischemic cardiomyopathies frequently occur in young people. According to the American Heart Association, dilated cardiomyopathy is the most common form, with 87 percent of all cardiomyopathy cases being dilated. The muscle damage that develops with all types of nonischemic cardiomyopathies can lead to congestive heart failure or irregular heartbeats known as arrhythmias.