Controversial issues and working practice in myocarditis: from scientific data to clinical grounds

Abstract

Although the cause of myocarditis often remains unknown, a large variety of infections, systemic diseases, drugs and toxins have been associated with this disease. In most cases, myocarditis is induced by cardiotropic viruses and often evolves silently without discernible prognostic impact. However, in some patients, the lack of complete viral clearance and/or the association of a heart-specific inflammation can cause persistent myocyte damage, ultimately leading to progressive myocardial dilation and dysfunction or life-threatening arrhythmias. Spontaneous improvement of left ventricular function is described for 40-50% of patients. The diagnostic work-up and prognostic assessment of myocarditis should be multiparametric and all available resources should be employed, i.e. biomarkers of myocardial damage and ventricular dysfunction (troponin I, brain natriuretic peptide), advanced echocardiography, cardiac magnetic resonance and, in selected cases, endomyocardial biopsy (with histopathologic, immunohistochemical and virological analyses). These are the necessary prerequisites for an evidence-based and personalized management of myocarditis, which may require in some cases specific immunoactive treatments. However, controversial issues regarding diagnosis (such as role and timing of cardiac magnetic resonance imaging, role of endomyocardial biopsy) and therapy of myocarditis still remain unsolved. The purpose of this review is to analyze these crucial features in order to provide useful instructions for clinical practice.