Objective. The purpose of this study was to document the various causes of dilated cardiomyopathy in a large group of adult patients with congestive heart failure.

Background. Previous reports of the causes of dilated cardiomyopathy have usually been case reports of a single specific etiology or review articles. The frequency of any single specific heart muscle disease is largely unknown.

Methods. We evaluated 673 patients referred for congestive heart failure due to dilated cardiomyopathy. The evaluation included medical history, physical examination, routine blood chemistry and hematologic measurements, electrocardiography and echocardiography. Thyroid function tests, antinuclear antibody tests and urinary vanillylmandelic acid and metanephrine levels were also obtained. Endomyocardial biopsy with right heart catheterization was performed in every patient. Coronary arteriography was performed in patients who had at least two standard cardiovascular risk factors or a history suggestive of myocardlal ischemia. The cases were retrospectively reviewed, and a final cause for dilated cardiomyopathy was listed for each patient.

Results. The most common causes of dilated cardiomyopathy were idiopathic origin (47%), idiopathic myocarditis (12%) and coronary artery disease (11%). The other identifiable causes of dilated cardiomyopathy made up 31% of the total cases.

Conclusions. Idiopathic dilated cardiomyopathy is a common cause of congestive heart failure. Specific heart muscle diseases occur with much less frequency.