Cardiomyopathy is the measurable deterioration of the function of the myocardium (the heart muscle) for any reason, usually leading to heart failure; common symptoms are dyspnea (breathlessness) and peripheral edema (swelling of the legs). People with cardiomyopathy are often at risk of dangerous forms of irregular heart beat and sudden cardiac death [1]. The most common form of cardiomyopathy is dilated cardiomyopathy.

Although in theory the term “cardiomyopathy” could apply to almost any disease affecting the heart, in practice it is usually reserved for “severe myocardial disease leading to heart failure”. Cardiomyopathies can be categorized as extrinsic or intrinsic.

An extrinsic cardiomyopathy is a cardiomyopathy where the primary pathology is outside the myocardium itself. Most cardiomyopathies are extrinsic by far the most common cause of an extrinsic cardiomyopathy is ischemia. Ischemia can be understood as poor oxygen supply of the heart muscle (the demand for oxygen is higher than the current supply). The World Health Organization calls these specific cardiomyopathies:

An intrinsic cardiomyopathy is defined as weakness in the muscle of the heart not due to an identifiable external cause. This definition was used to categorize previously idiopathic cardiomyopathies although specific external causes have since been identified for many. For example, alcoholism has been identified as a cause for some forms of dilated cardiomyopathy. To make a diagnosis of an intrinsic cardiomyopathy, significant coronary artery disease should be ruled out first (amongst other causes).

The term intrinsic cardiomyopathy does not describe the specific etiology of weakened heart muscle. The intrinsic cardiomyopathies consist of a variety of disease states, each with their own causes. Many intrinsic cardiomyopathies now have identifiable external causes including drug and alcohol toxicity, certain infections (including Hepatitis C) and variousgenetic and idiopathic (i.e., unknown) causes.

It is also possible to classify cardiomyopathies functionally, as involving dilation, hypertrophy, or restriction.

Signs and symptoms
Symptoms and signs may mimic those of almost any form of heart disease. Chest pain is common. Mild myocarditis or cardiomyopathy is frequently asymptomatic; severe cases are associated with heart failure, arrhythmias, and systemic embolization. Manifestations of the underlying disease (e.g., Chagas’ disease) may be prominent. Most patients with biopsy-proven myocarditis report a recent viral prodrome preceding cardiovascular symptoms.

EKG abnormalities are often present, although the changes are frequently nonspecific. A pattern characteristic of left ventricular hypertrophy may be present. Flat or inverted T waves are most common, often with low-voltage QRS complexes. Intraventricular conduction defects and bundle branch block, especially left bundle branch block, are also common. An echocardiogram is useful to detect wall motion abnormalities or a pericardial effusion. Chest radiographs can be normal or can show evidence of congestive heart failure with pulmonary edema or cardiomegaly.

Treatment depends on the type of cardiomyopathy and condition of disease, but may include medication (conservative treatment) or iatrogenic/implanted pacemakers for slow heart rates, defibrillators for those prone to fatal heart rhythms, ventricular assist devices (LVADs) for severe heart failure, or ablation for recurring dysrhythmias that cannot be eliminated by medication or cardioversion.

The goal of treatment is often symptom relief, and some patients may eventually require a heart transplant. Treatment of cardiomyopathy (and other heart diseases) using alternative methods such as stem cell therapy is commercially available but is not supported by convincing evidence.