Cardiomyopathy, or disease of the heart muscle, is generally an acquired disease, although some level of genetic risk may be involved. Patients with myopathy typically retain normal cardiac anatomy, only the muscle function is abnormal. Myopathy often involves the left ventricle. The most dominant of the heart's four chambers, the left ventricle supports circulation to the entire body.

	Myocarditis as viewed on an MRA.

Cardiomyopathy most commonly stems from either coronary artery disease, hypertension, or a combination of those two diseases. Coronary artery disease can cause heart attacks that damage the heart muscle, while hypertension can lead to hypertrophy (thickening of the heart muscle) that ultimately creates muscular weakness. Less commonly, viral infections of the heart can inflame and destroy heart tissue. Fortunately, patients with viral myocarditis, another cause of cardiomyopathy, may ultimately recover function. However, such infections expose patients of any age to various degrees of heart muscle disease or heart failure. Patients whose hearts fail to respond to medical treatment may eventually require heart transplantations. Alcohol abuse has also caused myopathy, particularly when accompanied by a poor diet.