Background
Myocarditis, a disease of adult and pediatric patients, is an inflammatory disorder of the myocardium that is typically caused by a viral infection. Necrosis of the myocytes and associated inflammatory infiltrate are seen in this disorder. (See Etiology.)
myocarditis may be a manifestation of drug hypersensitivity or toxicity. (See Etiology.)
Although the use of myocardial biopsy is debated, suspected myocarditis can be classified into the following three types based on pathologic findings as defined in the Dallas Criteria (1987) (See Workup.)
:
Active myocarditis – Characterized by abundant inflammatory cells and myocardial necrosis
Borderline myocarditis – Characterized by an inflammatory response that is too sparse for this type to be labeled as active myocarditis; degeneration of myocytes not demonstrated with light microscopy
Nonmyocarditis
If an active or borderline inflammatory process is found, follow-up biopsy findings can be subclassified into ongoing, resolving, or resolved myocarditis. (See Workup and Treatment.)