Myocarditis

Abstract

Myocarditis is an underdiagnosed cause of acute heart failure, sudden death, and chronic dilated cardiomyopathy. In developed countries, viral infections commonly cause myocarditis; however, in the developing world, rheumatic carditis, Trypanosoma cruzi, and bacterial infections such as diphtheria still contribute to the global burden of the disease. The short-term prognosis of acute myocarditis is usually good, but varies widely by cause. Those patients who initially recover might develop recurrent dilated cardiomyopathy and heart failure, sometimes years later. Because myocarditis presents with non-specific symptoms including chest pain, dyspnoea, and palpitations, it often mimics more common disorders such as coronary artery disease. In some patients, cardiac MRI and endomyocardial biopsy can help identify myocarditis, predict risk of cardiovascular events, and guide treatment. Finding effective therapies has been challenging because the pathogenesis of chronic dilated cardiomyopathy after viral myocarditis is complex and determined by host and viral genetics as well as environmental factors. Findings from recent clinical trials suggest that some patients with chronic inflammatory cardiomyopathy have a progressive clinical course despite standard medical care and might improve with a short course of immunosuppression.

Figure 1. Histological samples from patients with myocarditis

(A) Endomyocardial biopsy showing an extensive interstitial lymphoplasmacytic infiltrate associated with myocardial necrosis in a patient with myocarditis. Presence of T lymphocytes (B) and macrophages (C) shown by antibody stains against CD3 and CD68. Image courtesy of Joesph J Maleszewski.

Figure 2. Lyme disease in a patient with myocarditis

(A) Erythema migrans (bull’s eye rash) in a patient with Lyme myocarditis. (B) Electrocardiogram from the patient revealed complete heart block.