Active Myocarditis in the Spectrum of Acute Dilated Cardiomyopathies: Clinical Features, Histologic Correlates, and Clinical Outcome

We studied the clinical features and course (average follow-up time, 18 months) of 27 patients with acute dilated cardiomyopathy (symptoms for less than 6 months) who were referred for endomyocardial biopsy. Almost 40 per cent of the patients subsequently had a rise in left ventricular ejection fraction (on average, from 0.21 to 0.41) and substantial improvement in heart failure; the remainder died or had chronic dilated cardiomyopathy. Biopsy revealed myocarditis in 18 patients, and this finding was especially common (89 per cent) in patients who had been ill for less than four weeks. But the biopsy specimen was negative in four patients whose clinical features and later course were diagnostic of myocarditis. Nine patients received immunosuppressive drugs, and four improved—a rate that did not differ from the rate of spontaneous improvement. Neither the histologic features of the biopsy specimen nor the clinical features at presentation were clearly correlated with subsequent improvement, whether or not immunosuppressive drugs were given. We conclude that many cases of unexplained dilated cardiomyopathy result from myocarditis. Definitive histologic confirmation depends on the duration of illness. The efficacy of immunosuppressive treatment must still be established. (N Engl J Med 1985; 312:885–90.) The incidence and clinical course of active myocarditis are unknown. 1 Diagnosing myocarditis by clinical features is an exercise of uncertain validity. 2 Right ventricular endomyocardial biopsy can now be performed, so it is possible to obtain histologic evidence to support or refute the clinical diagnosis. Nonetheless, to our knowledge, no comparison has yet been made between clinically diagnosed and histologically verified myocarditis. Heart failure of recent onset owing to acute dilated cardiomyopathy represents one dramatic presentation of acute myocarditis. 2 3 4 We examined the relations among histologic and clinical features suggesting myocarditis, the type of treatment, and the clinical outcome in patients with . . .