Incidence of three presentations of acute myocarditis in young men in military service. A 20-year experience.

AIMS: The incidence of myocarditis is uncertain as diagnostic criteria have been vague. We evaluated the incidence of myocarditis presenting in three well defined forms (mimicking myocardial infarction, presenting as dilated cardiomyopathy, and as a cause of sudden death) in young men in military service over a 20-year period.

METHODS AND RESULTS: The study population consisted of 672 672 Finnish men at a mean age of 20 years conscripted from 1977-1996. All those suspected of having myocardial disease were studied prospectively in the same institution. A clinical diagnosis of myocarditis mimicking myocardial infarction required ECG signs (ST-segment elevation followed by T-wave inversion) and a simultaneous detection of serum markers of acute myocardial injury (CK-MB and/or troponin T) in an infectious patient with chest pain. This form of myocarditis was diagnosed in 98 men, the incidence being 0.17 (95% CI 0.14-0.21). 1000 man-years(-1). Causative microbes were those commonly infecting the conscripts, but Coxsackievirus aetiology could be confirmed in only 4% of the cases. Nine patients presented with dilated cardiomyopathy of recent origin (incidence 0.02. 1000 man-years(-1)). None had histopathological evidence of myocarditis. Myocarditis caused one of the 10 sudden unexpected deaths (incidence 0.002. 1000 man-years(-1)).

CONCLUSIONS: The usual presentation of acute myocarditis in young men mimicks alterations evoked by myocardial infarction but not those of dilated cardiomyopathy.