Bidirectional Ventricular Tachycardia After Radiofrequency Ablation of Idiopathic Left Ventricular Tachycardia

Abstract

A 32-year-old man was referred to this electrophysiological laboratory for evaluation and radiofrequency (RF) catheter ablation of a wide QRS complex tachycardia. He had a history of frequent episodes of paroxysmal palpitation for about 1 year. The electrocardiograph (ECG) in sinus rhythm showed a normal axis and QRS morphology ( Fig. 1A). During tachycardia, the ECG showed a sustained wide QRS complex tachycardia with a right bundle branch block morphology and inferior-axis deviation (Fig. 1B). Ventricular tachycardia (VT) was diagnosed by demonstrating fusion beats and atrioventricular dissociation (not shown). The first RF energy was delivered at the left side of the upper portion of interventricular septum after identifying a Purkinje potential of 23 ms preceding the onset of a surface QRS complex. A sustained bidirectional VT with a cycle length of 458 ms (Fig. 1C) appeared after this RF pulse. It was terminated within 5 seconds when RF energy was delivered at the region slightly higher than the first ablation site (Fig. 2), with a Purkinje potential of 33 ms preceding the onset of surface QRS. The ECG during sinus rhythm remained the same as baseline ECG, without right-or left-axis deviation. The tachycardia was no longer inducible after ablation. What is the mechanism of the bidirectional VT appearing after the first RF pulse? DiscussionBidirectional tachycardia was first described by Schwensen 1 in 1922 in the setting of digitalis toxicity. Rosenbaum and coworkers 2 proposed that bidirectional tachycardia originated in the atrioventricular junction with tachycardia dependent right bundle branch block and alternating conduction over the anterior and posterior fascicles of the left bundle. However, His bundle recordings in patients with digitalis induced bidirectional tachycardia demonstrated a ventricular origin of the tachycardia with two or more separate foci or a single focus with alternating aberrant conduction in the anterior and posterior fascicles of the left bundle branch due to enhanced phase 4 depolarization in the divisions of the left bundle branch. 3 This patient did not take digitalis and had no bidirectional tachycardia before RF ablation. Several mechanisms should be considered. First, it may be due to idiopathic left ventricular (LV) tachycardia using a figure eight circuit. Under this circumstance, the tachycardia should usually have two different cycle lengths and ventriculoatrial intervals. However, it was not seen in this case. Second, it may arise from a single circuit with double exit sites. One is at or close to the left anterior fascicle and the other at or near the left posterior fascicle, or the common division of left bundle branch. Third, it may arise from two very closely different circuits. Therefore, the tachycardia may have different frontal plane axis. Fourth, The tachycardia did not involve the normal left fascicular system but rather a mechanism (such as an alternate, abnormal fascicle, or false tendon) that was not part of the left fascicle but merely penetrated it seco...

Unusual Tachycardia After Cocaine Use

“…It is a rare arrhythmia that is mostly caused by digoxin toxicity. Other causes include aconitine poisoning, catecholaminergic polymorphic ventricular tachycardia, and familial hypokalemic periodic paralysis, as well as in rare cases myocarditis, Andersen Tawil syndrome, ventricular tumors, fatty replacement of the ventricle, exercise, after radiofrequency ablation of ventricular tachycardia, cardiac sarcoidosis, caffeine poisoning, and pulmonary embolus…”