Dilated cardiomyopathy or DCM, also known as congestive cardiomyopathy, is a condition in which the heart becomes weakened and enlarged, and cannot pump blood efficiently. The decreased heart function can affect the lungs, liver, and other body systems.

DCM is one of the cardiomyopathies, a group of diseases that primarily affect the myocardium (the muscle of the heart). Different cardiomyopathies have different causes, and affect the heart in different ways. In DCM a portion of the myocardium is dilated, often without any obvious cause. Left and/or right ventricular systolic pump function of the heart is impaired, leading to progressive cardiac enlargement and hypertrophy, a process called remodeling.

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. About one in three cases of congestive heart failure (CHF) is due to dilated cardiomyopathy. Dilated cardiomyopathy also occurs in children.

Causes

Although no cause (etiology) is apparent in many cases, dilated cardiomyopathy is probably the end result of damage to the myocardium produced by a variety of toxic, metabolic, or infectious agents. It may be due to fibrous change of the myometrium from a previous myocardial infarction. Or, it may be the late sequel of acute viral myocarditis, possibly mediated through an immunologic mechanism. Autoimmune mechanisms are also suggested as a cause for dilated cardiomyopathy. A reversible form of dilated cardiomyopathy may be found with alcohol abuse, pregnancy (peripartum cardiomyopathy), thyroid disease, stimulant use, and chronic uncontrolled tachycardia. Many cases of dilated cardiomyopathy are described as idiopathic - meaning that the cause is unknown.

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. The disease is genetically heterogeneous, but the most common form of its transmission is an autosomal dominant pattern. Autosomal recessive, as found, for example, in Alström syndrome, X-linked, and mitochondrial inheritance of the disease is also found. Relatives of dilated cardiomyopathy patients have been found to show preclinical, asymptomatic heart-muscle changes.

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

Associated symptoms

For many affected individuals, dilated cardiomyopathy is a condition which will not limit the quality or duration of life. A minority, however, experience significant symptoms and there is sometimes a risk of sudden death. Evaluation by a cardiologist is recommended to confirm the diagnosis and to assess the outlook and particularly the risk of complications. In some patients symptoms of left- and right-sided congestive heart failure develop gradually. Left ventricular dilatation may be present for months or even years before the patient becomes symptomatic.