Epicardial ventricular tachycardia (Epicardial VT)

Epicardial ventricular tachycardia (Epicardial VT)

Epicardial ventricular tachycardia: Most ventricular tachycardias (VT) can be approached for ablation endocardially.  But there are a few which needs an epicardial approach. VTs originating from the left ventricular outflow tract is likely to be epicardial and perivascular compared to the right ventricular outflow tract VTs. VTs in non ischemic dilated cardiomyopathy and those in Chagasic cardiomyopathy are likely to have epicardial origin. Among the ischemic VTs, those in the inferolateral region can have an epicardial origin. Sometimes VTs in arrhythmogenic right ventricular dysplasia can also be epicardial. When a previous attempt at endocardial ablation has failed, it is all the more reason to look for an epicardial focus. Difficulty with epicardial mapping and ablation is due to the higher learning curve and propensity for significant complications. Success rates for epicardial approach is around 85%. A previous failed endocardial ablation also makes it more likely that epicardial approach will be successful. Other reasons for trying an epicardial approach are difficulty in accessing the left ventricular cavity as in the presence of a thrombus or a prosthetic valve. But epicardial route will not be useful for VTs which involve the subendocardium and Purkinje system as in fascicular VT, bundle branch reentrant VT or VT originating from the papillary muscle.

An epicardial VT can be recognized by the slurred initial part of the QRS complex which resembles a delta wave. This occurs because of the slow transmural activation from the epicardial focus to the endocardial surface [1].

Reference

1. Antonio Berruezo. Arrhythmias: Complex ventricular arrhythmias: a therapeutic nightmare. Heart. 2010 May;96(9):723-8.