Arrhythmias in Myocarditis

Myocarditis can be complicated by both atrial and ventricular arrhythmias. The arrhythmic burden and the underlying mechanisms vary between the acute and chronic setting, depending on the relative impact of acute inflammation versus post-inflammatory myocardial fibrosis. In the acute phase, ventricular arrhythmias vary from simple isolated ventricular ectopic beats to complex and life-threatening tachycardias that can lead to sudden death. Atrioventricular blocks are typical of specific forms of myocarditis, such as giant cell myocarditis, sarcoidosis, and bacterial myocarditis. Supraventricular arrhythmias such as atrial fibrillation can also be observed in case of atrial inflammation. In the chronic phase, mechanisms that may explain the occurrence of life-threatening arrhythmias include recurrent myocarditis or persistent myocardial inflammation, residual left ventricular dysfunction, and post-inflammatory myocardial scar.