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 w ell defined forms (mimicking myocardial infarction, presenting as dilated c ardiomyopathy, and as a cause of sudden death) in young men in military ser vice over a 20-year period. Methods and Results The study population consisted of 672 672 Finnish men a t a mean age of 20 years conscripted from 1977-1996. All those suspected of having myocardial disease were studied prospectively in the same instituti on. A clinical diagnosis of myocarditis mimicking myocardial infarction req uired ECG signs (ST-segment elevation followed by T-wave inversion) and a s imultaneous detection of serum markers of acute myocardial injury (CK-MB an d/or troponin T) in an infectious patient with chest pain. This form of myo carditis was diagnosed in 98 men, the incidence being 0.17 (95% CI 0.14-0.2 1). 1000 man-years(-1). Causative microbes were those commonly infecting th e conscripts, but Coxsackievirus aetiology could be confirmed in only 4% of the cases. Nine patients presented with dilated cardiomyopathy of recent o rigin (incidence 0.02.1000 man-years(-1)). None had histopathological evide nce of myocarditis. Myocarditis caused one of the 10 sudden unexpected deat hs (incidence 0.002.1000 man-years(-1)). Conclusions The usual presentation of acute myocarditis in young men mimick s alterations evoked by myocardial infarction but not those of dilated card iomyopathy.