Ventricular arrhythmias in nonischemic cardiomyopathy: Overview

“Nonischemic cardiomyopathy (NICM)” is a myocardial disease which is characterized by ventricular dysfunction without significant coronary artery disease, including coronary spasms. Ventricular tachyarrhythmias are often observed in NICM, which lead to sudden cardiac death. Therefore, it is important to understand the anatomical and/or electrophysiological substrates in the different types of NICM. Because several new diagnostic approaches of cardiac MRI and/or genetic testing, and the specific management of antiarrhythmic drugs, catheter ablation, and defibrillators, have been available for some time, the risk stratification and specific management would change. In this special issue, we will summarize and overview the current understanding of each type of NICM, especially focusing on the risk stratification and specific management in the different types of NICM. In this first report, we selected arrhythmogenic right ventricular cardiomyopathy (ARVC), cardiac tumors, arrhythmia-induced cardiomyopathy (AIC), and Takotsubo syndrome (TTS). We also gave an overview of the recent progress in the diagnosis/management of NICM, including advanced catheter ablation. Arrhythmogenic right ventricular cardiomyopathy is a progressive cardiomyopathy characterized by myocardial cell death and subsequent fibrofatty infiltration of the myocardium and leads to sudden death due to serious ventricular arrhythmias. Some ARVC exhibits biventricular dilated cardiomyopathy, and genetic tests may help to identify asymptomatic carriers, but the risk stratification is still limited. Cardiac MRI would be useful for making a differential diagnosis of ARVC. In high-risk patients, internal cardioverter-defibrillators (ICDs) are important, but the prophylactic use of ICDs for primary prevention is still in debate. Cardiac tumors are a rare cause of arrhythmias, and the clinical manifestation varies with the patient's age and tumor types. Cardiac MRI would be a good tool for a noninvasive diagnosis, but the prognosis of a secondary cardiac tumor is poor. Arrhythmia-induced cardiomyopathy is characterized by tachyarrhythmias or ectopy-induced cardiomyopathy. It is sometimes called tachycardia-induced cardiomyopathy (TIC). There are two types of AIC, one is an arrhythmia-induced AIC and the other is an arrhythmia-mediated AIC. The related arrhythmias that have been reported are focal atrial tachycardia, atrial fibrillation, and premature ventricular contractions (PVCs). Recently cardiac MRI may provide additional information for AIC, but the precise mechanism is still unclear. Takotsubo syndrome is characterized by transient left ventricular dysfunction triggered by physical or emotional stress. Sympathetic overdrive is one of the crucial causes of this disease, but the precise mechanism is still unknown. It is thought that the prognosis is relatively benign, but recent data has shown that the prognosis of TTS is much worse than expected due to ventricular arrhythmias including polymorphic VT. The predominant mechanisms of the VT are reentry, triggered activity, and abnormal automaticity. Considerable TTS patients have QT prolongation, which is related to an acquired form of long-QT syndrome.

Abstract licence: CC BY-NC

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