SUCCESSFUL RADIOFREQUENCY ABLATION OF IDIOPATHIC LEFT-VENTRICULAR TACHYCARDIA AT A SITE AWAY FROM THE TACHYCARDIA EXIT

Objectives. This study sought to assess the possibility of ablating ve rapamil-responsive idiopathic left ventricular tachycardia at a site d istant from the tachycardia exit and thus to define the tachycardia ci rcuit. Background. The nature of the reentry circuit in idiopathic lef t ventricular tachycardia is unclear. If the circuit is of considerabl e size, then it should he possible to ablate the tachycardia at a site distant from the exit site. Methods. Electrophysiologic studies and r adiofrequency ablation were performed in 27 consecutive patients with verapamil responsive idiopathic left ventricular tachycardia. In all 2 7 patients, the tachycardia exit site was defined as the site where th e earliest Purkinje potential was recorded greater than or equal to 25 ms before the onset of the QRS complex during the tachycardia and whe re the pace map QRS complex resembled that during the tachycardia. A p otential ablation site other than the exit site was then sought around the midseptum, proximal to the exit site. At such sites the tachycard ia could be terminated transiently by pressure applied to the catheter tip, without induction of ventricular ectopic beats. Results. The pot ential ablation site, other than the tachycardia exit site, was identi fied in seven male patients (mean [+/- SD] age 31 +/- 12 years, range 13 to 52). Application of the radiofrequency current at this site resu lted in termination of the tachycardia within 1 to 5 s (mean 2.9 +/- 1 .6), and successful ablation of the tachycardia was achieved in all se ven patients (success rate 100%, 95% exact confidence interval 0.5898 to 1). The mean distance between the ablation site and the tachycardia exit site was 3.1 +/- 0.7 cm (range 2.0 to 4.0). A presystolic Purkin je 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 tachyca rdia in these seven patients. Conclusions. Successful ablation of idio pathic left ventricular tachycardia can be achieved at sites away from the tachycardia exit site in some patients. This finding suggests tha t the reentry circuit is likely to be of considerable size, encompassi ng the middle, inferior and lower aspects of the left interventricular septum. (C) 1997 by the American College of Cardiology.