Radiofrequency Catheter Ablation of Upper Septal Idiopathic Left Ventricular Tachycardia Exhibiting Left Bundle Branch Block Morphology

Abstract

Idiopathic left ventricular (LV) tachycardia usually exhibits right bundle branch block morphology. There are only a few sporadic cases that exhibit left bundle branch block (LBBB) morphology. We report a patient whose QRS complex during ventricular tachycardia (VT) was relatively narrow (100 msec) and exhibited LBBB (precordial R wave transition between V3 and V4) and a normal frontal plane axis. This VT was ablated successfully by radiofrequency current applied to the LV upper septum, where the earliest endocardial activation was recorded.

Upper septal transformation of verapamil-sensitive idiopathic left ventricular tachycardia during catheter ablation: Wolf in sheep׳s clothing?

“…In US ILVT, there is reversal of the reentrant arrhythmia circuit, with the “normal” Purkinje fibers in the region of the left posterior fascicle constituting the antegrade limb and the “abnormal” Purkinje fibers the retrograde limb of the arrhythmia circuit. In addition, the “upper turnaround point” is reversed in this case, and the convergence of the 2 limbs occurs at the anterior portion of the IVS in the vicinity of the left bundle, at a relatively more basal location than that of the LPF ILVT reentrant circuit5, 13 (Figures 2A and 2B). …”

Solving the puzzle of strong French coffee, palpitation and dizziness

“…Idiopathic fascicular VT can be classified into three subtypes,9 including (1) left posterior fascicular VT with left axis deviation and a right bundle branch block pattern; (2) left anterior fascicular VT with right-axis deviation and a right bundle branch block pattern and (3) upper septal fascicular VT with normal axis and right bundle branch block pattern. It should be noted however, that rare cases of normal axis and left bundle branch block (precordial R wave transition between V3 and V4) have been reported 10. Nevertheless, so far the most common form is that of the posterior fascicular type, which accounts for almost 90% of cases 11.…”

Catheter-based Ablation for Ventricular Arrhythmias

“…The majority of these VTs involve the posterior fascicle, and parts of the circuit can be identified along the inferoseptal aspect of the left ventricle. Two other forms of verapamil-sensitive VTs have been described; a left anterior fascicular VT with RBBB right axis deviation and an upper septal fascicular VT with a narrow QRS configuration and a normal or right axis deviation [33,34]. For the typical posterior fascicular VT, RF ablation is usually directed at the anterograde Purkinje potentials more apically rather than proximally to avoid injury to the left bundle.…”