Successful Radiofrequency Ablation of Idiopathic Left Ventricular Tachycardi at Site Away From the Tachycardi Exit

Objectives. This study sought to assess the possibility of ablating verapamil-responsive idiopathic left ventricular tachycardi at site distant from the tachycardi exit and thus to define the tachycardi circuit. Background. The nature of the reentry circuit in idiopathic left ventricular tachycardi is unclear. If the circuit is of considerable size, then it should be possible to ablate the tachycardi at site distant from the exit site. Methods. Electrophysiologic studies and radiofrequency ablation were performed in 27 consecutive patients with verapamil-responsive idiopathic left ventricular tachycardia. In all 27 patients, the tachycardi exit site was defined as the site where the earliest Purkinje potential was recorded ≥25 ms before the onset of the QRS complex during the tachycardi and where the pace map QRS complex resembled that during the tachycardia. potential ablation site other than the exit site was then sought around the midseptum, proximal to the exit site. At such sites the tachycardi could be terminated transiently by pressure applied to the catheter tip, without induction of ventricular ectopic beats. Results. The potential ablation site, other than the tachycardi exit site, was identified in seven male patients (mean [± SD] age 31 ± 12 years, range 13 to 52). Application of the radiofrequency current at this site resulted in termination of the tachycardi within 1 to 5 s (mean 2.9 ± 1.6), and successful ablation of the tachycardi was achieved in all seven patients (success rate 100%, 95% exact confidence interval 0.5898 to 1). The mean distance between the ablation site and the tachycardi exit site was 3.1 ± 0.7 cm (range 2.0 to 4.0). presystolic Purkinje spike was recorded 14 ± 5 ms (range 8 to 20) before the onset of the QRS complex during the tachycardia. During the follow-up period of 24 ± 11 months (range 12 to 39), there was no recurrence of tachycardi in these seven patients. Conclusions. Successful ablation of idiopathic left ventricular tachycardi can be achieved at sites away from the tachycardi exit site in some patients. This finding suggests that the reentry circuit is likely to be of considerable size, encompassing the middle, inferior and lower aspects of the left interventricular septum.