Giant cell myocarditis. Diagnosis and treatment.

Giant cell myocarditis (GCM) usually presents as acute dilated cardiomyopathy that does not improve with guideline-based treatments. Ventricular tachycardia and heart block occur in a substantial number of patients. Diagnosis by endomyocardial biopsy can allow for the addition of immunosuppressive therapy and timely use of mechanical circulatory support when indicated. Recent studies suggest that the ventricular arrhythmias in GCM may be mediated by a cytokine-induced change in desmosomal protein expression. Genomic and proteomic studies suggest that the regulation of inflammatory pathways differs in GCM from lymphocytic myocarditis. Transplantation remains an effective therapy despite a 20-25% risk of GCM recurrence in the allograft. Recurrence in the native heart occurs up to 8 years after initial diagnosis. The long-term management of GCM patients, who initially recover, is not known and highlights the need for continuing multicenter collaborative clinical investigations.