29 - Ablation of Idiopathic Left and Right Ventricular and Fascicular Tachycardias

Abstract

Idiopathic ventricular tachycardias (VTs) usually occur in specific locations and have specific QRS morphologies. The most common idiopathic VT is VT from the outflow tract of the right ventricle (RV). Other idiopathic RV-VT is tricuspid annular VT. In idiopathic left VTs, there are left ventricular (LV) outflow tract VT, mitral annular VT, papillary muscle VT, crux VT, verapamil-sensitive left fascicular VT, and nonreentrant fascicular VT. The mechanism of mitral and tricuspid annular VTs is nonreentry. Radiofrequency catheter ablation (RFCA) of mitral annular VT is highly successful. RFCA eliminates approximately 90% of the free wall tricuspid annular VT, but only 57% of the septal tricuspid VT. RFCA of papillary muscle is challenging because catheter stability is very difficult because of papillary muscle contractions. Crux VT is rare and may arise from the epicardium. Ablation may be performed within the proximal coronary sinus or proximal middle cardiac vein, or by a pericardial approach. The mechanism of verapamil-sensitive idiopathic fascicular VT is reentry, and there are several subtypes. Ablation targets are the diastolic potential in the VT circuit, and the RFCA success rate is greater than 90% for the common type of fascicular VT. The mechanism of nonreentrant fascicular VT is abnormal automaticity from the distal Purkinje system. The recurrence rate after ablation for nonreentrant fascicular VT is much higher than that of reentrant fascicular VT.