Clinical aspects of virus/immune myocarditis.

Although a cause-and-effect relationship between viral infection and myocarditis remains inferential, two distinct clinical syndromes can be identified. During the early viral phase, the cardiac manifestations emerge while the symptoms of active viral infection are also present. During the chronic phase, symptoms of the viral infection may be remote or nonexistent, and identification of active myocarditis is contingent upon an aggressive diagnostic approach with endomyocardial biopsy and gallium 67 imaging. The exact incidence of myocarditis in patients with heart failure of unknown cause is unclear due to lack of standardization of histologic parameters. There are no other clinical clues to the presence of myocarditis in those patients presenting with cardiomyopathy or ventricular arrhythmia. For further clarification of the incidence and various presentations of myocarditis a large multi-center trial is necessary.