The term "cardiomyopathy" refers to "cardio" (heart), "myo" (muscle), "pathy" (disease of). The term is used somewhat loosely, which can create confusion.

In general, when someone refers to a cardiomyopathy they mean the three common types below. Some people will use cardiomyopathy in reference to an ischemic cardiomyopathy, which implies that atherosclerotic coronary disease has resulted in left ventricular systolic dysfunction. This is technically improper use of the term cardiomyopathy; however, it is much easier to say/write than "chronic systolic congestive heart failure from ischemic heart disease."  Likewise, the term "non-ischemic cardiomyopathy" is frequently used when the left ventricular systolic function is low from a non-ischemic cause (ie, dilated cardiomyopathy).

The three common cardiomyopathies are:

  1. Dilated cardiomyopathy: This results in left ventricular systolic dysfunction and clinical manifestations of congestive heart failure. Etiologies include viral, alcoholic, idiopathic, familial and other rare causes.
  2. Hypertrophic cardiomyopathy: Also known as hypertrophic obstructive cardiomyopathy (HOCM), this results in abnormal hypertrophic changes most commonly in the interventricular septum with pathologic "myocardial disarray." HOCM is familial in about 50% of cases and transmitted in an autosomal dominant fashion. HOCM can result in clinic heart failure, life-threatening arrhythmias, mitral regurgitation and sudden cardiac death. 
  3. Restrictive cardiomyopathy: This results in heart failure related to severe diastolic dysfunction. Causes include amyloid heart disease, infiltrative disorders and familial.

The two least common and least researched types of cardiomyopathy are:

  1. Left ventricular non-compaction: Also known as spongy myocardium or hypertrabeculation syndrome, left ventricular non-compaction is a pathologic cardiac condition in which the myocytes exhibit a "spongy" appearance. This is considered a genetic cardiomyopathy and is somewhat rare. The left ventricular myocardium exhibits pronounced trabeculae with intracavitary recesses, similar to diverticulum. This can lead to systolic dysfunction and arrhythmia.
  2. Arrhythmogenic right ventricular dysplasia (ARVD): This occurs when fatty tissue replaces that of the right ventricular myocardium and, as the name implies, frequently causes arrhythmia. Most commonly, ventricular tachycardia occurs. Sudden cardiac death is the main concern in ARVD. The classic ECG finding of Epsilon waves from early afterdepolarizations of the ventricles is actually rare.