Dilated cardiomyopathy

Dilated cardiomyopathy or DCM (also known as congestive cardiomyopathy), is a disease of the myocardium (the muscle of the heart) in which a portion of the myocardium is dilated, often without any obvious cause. About one in three cases of congestive heart failure (CHF) is due to dilated cardiomyopathy.¹ more...

A cardiomyopathy is any disease that primarily affects the muscle of the heart. In DCM, left and/or right ventricular systolic pump function of the heart is impaired, leading to progressive cardiac enlargement and hypertrophy, a process called remodeling.¹

Dilated cardiomyopathy is the most common form of cardiomyopathy. It occurs more frequently in men than in women, and is most common between the ages of 20 and 60 years.²

Etiology

Although no cause is apparent in many cases, dilated cardiomyopathy is probably the end result of myocardial damage produced by a variety of toxic, metabolic, or infectious agents. It may be the late sequel of acute viral myocarditis, possibly mediated through an immunologic mechanism. Alcohol abuse is also strongly associted with the development of dilated cardiomyopthy in some cases. Autoimmune mechanisms are also suggested as a cause for dilated cardiomyopathy.³

A reversible form of dilated cardiomyopahty may be found with alcohol abuse, pregnancy, thyroid disease, cocaine use, and chronic uncontrolled tachycardia.

Genetics

About 20-40% of patients have familial forms of the disease, with mutations of genes encoding cytoskeletal, contractile, or other proteins present in myocardial cells.⁴ The disease is genetically heterogenous, but the most common form of its transmission is an autosomal dominant pattern. Autosomal recessive, X-linked, and mitochondrial inheritance of the disease is also found.⁵

Althought the disease is more common in African-Americans than in whites, it may occur in any patient population.

Associated symptoms

Symptoms of left- and right-sided congestive heart failure develop gradually in most patients. Left ventricualr dilatation may be present for months or even years before the patient becomes symptomatic.

Vague chest pain may be present, but typical angina pectoris is unusual and suggests the presence of concomitant ischemic heart disease. Syncope due to arrhythmias, and systemic embolism may occur.

Physical examination

The patients may present variable degrees of cardiac enlargement, and findings of congestive heart failure. In advance stages of the disease, the pulse pressure is narrowed and the jugular venous pressure is elevated. Third and fourth heart sounds are common. Mitral or tricuspid regurgitation may occur, presented by systolic murmurs upon auscultation (see mitral regurgitation and tricuspid insufficiency for more details about the findings).

Laboratory examinations

Generalized enlargement of the heart is seen upon normal chest X-ray. Pleural effusion may also be noticed, which is due to pulmonary venous hypertension.

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