Fatal myocarditis: morphologic and clinical features.

BACKGROUND: Autopsy studies report a frequency of myocarditis ranging from 0.11 to 5.5% in the general population, reaching almost 50% in selected groups. Myocarditis is often undiagnosed and the incidence of fatal course myocarditis has never been evaluated. The aim of our study was to assess the frequency of fatal course myocarditis in a consecutive series of autopsies and to describe the clinical, histological and morphologic features of the disease.
METHODS: From January 1, 1995 to January 31, 1996, 2560 autopsies were performed, and 143 cases of active myocarditis were diagnosed (5.6%).
RESULTS: In 39 cases (1.5%; 12 males; 4/39 aged < or = 35 years) active myocarditis was identified as the final cause of death. Only in 1 case was myocarditis suspected ante-mortem. The histological pattern was lymphocytic in 64% of cases. A mixed inflammatory infiltration was found in 33% and a granulomatous infiltration in 3%. In 49% of cases myocarditis was localized in both ventricles and the interventricular septum. The clinical presentation of myocarditis was heart failure in 18/39 patients (46%), cardiac arrest in 4/39 patients (10%) and syncope and chest pain in 1/39 patient (3%). The mean creatine phosphokinase levels were 890 +/- 2742 IU/I (assessed in 11/39 patients, 28%) but they were increased only in 7/39 (18%). ECG (performed in 29/39 patients, 74%) showed sinus rhythm in 16/39 patients (55%, > 100 b/min in 41%), atrioventricular or interventricular conduction defects in 10/39 patients (34%) and a pathological Q wave in 4/39 patients (14%). At echocardiography (performed in 7/39 patients, 18%), right and/or left ventricular dysfunction was found to be present in 5 cases (71%) and a pericardial effusion in 4 cases (57%).
CONCLUSIONS: Myocarditis is underdiagnosed ante-mortem. A high index of clinical suspicion is mandatory for prompt diagnosis and treatment of this fatal disease seen also in the young.