Acute viral myocarditis: current concepts in diagnosis and treatment

Acute myocarditis is one of the most challenging diseases to diagnose and treat in cardiology. The true incidence of the disease is unknown. Viral infection is the most common etiology. Modern techniques have improved the ability to diagnose specific viral pathogens in the myocardium. Currently, parvovirus B19 and adenoviruses are most frequently identified in endomyocardial biopsies. Most patients will recover without sequelae, but a subset of patients will progress to chronic inflammatory and dilated cardiomyopathy. The pathogenesis includes direct viral myocardial damage as well as autoimmune reaction against cardiac epitopes. The clinical manifestations of acute myocarditis vary widely--from asymptomatic changes on electrocardiogram to fulminant heart failure, arrhythmias and sudden cardiac death. Magnetic resonance imaging is emerging as an important tool for the diagnosis and follow-up of patients, and for guidance of endomyocardial biopsy. In the setting of acute myocarditis endomyocardial biopsy is required for the evaluation of patients with a clinical scenario suggestive of giant cell myocarditis and of those who deteriorate despite supportive treatment. Treatment of acute myocarditis is still mainly supportive, except for giant cell myocarditis where immunotherapy has been shown to improve survival. Immunotherapy and specific antiviral treatment have yet to demonstrate definitive clinical efficacy in ongoing clinical trials. This review will focus on the clinical manifestations, the diagnostic approach to the patient with clinically suspected acute myocarditis, and an evidence-based treatment strategy for the acute and chronic form of the disease.