Idiopathic left ventricular tachycardia(ILVT) with no structural heart disease is not an uncommon disease and characterized by the ECG feature of right bundle branch block. This study was performed to evaluate the effectiveness of radiofrequency catheter ablation (RFCA) for the treatment of ILVT and the usefulness of Purkinje potential(P-potential) in determining the site of successful ablation and to compare the biophysical parameter according to the modes of energy application.

From January 1993 to July 1996, 18 patients with symptomatic ILVT underwent RFCA. The ablation site were guided by pace mapping, ventricular activation mapping or P-potential.

Of the 18 patients, there were 14 male and 4 female patients with a mean age of 34.1 years-old. RFCA eliminated VT successfully in 14 of total 18 patients(78%), 11 of 12 in leftaxis VT, 2 of 3 in right axis VT and 1 of 3 in northwest axis VT. Successful sites of wall in 3 patients with right axis deviation or northwest axis. Ablations in 5 of the 9 patients, guided by pace mapping or ventricular activation mapping, were successful and in 9 all patients, guided by P-potential, were successful. In 9 patients guided by the P-potential, the earliest P-potential appeared 22.7±7.7msec earlier than the QRS complex during sinus rhythm and 32.0±11.5msec earlier during VT. Pace mapping with similar QRS was not necessarily essential for a successful ablation. In comparing the biophysical parameters according to energy delivery modes, more energy was delivered safety during successful ablation in temperature mode(mean 1148.3J) than constant power mode(520.9J). No acute and late complication was developed during ablation and for a mean of 25 months follow-up. One case of VT with right axis deviation relapsed 2 months after successful ablation.

RFCA is useful for the effective and safe treatment of ILVT. The earliest P-potential might be a better guide than mapping or earliest ventriclar activation for the determination of ablation sites in ILVT with left axis deviation. More energy was delivered safety during successful ablation in temperature mode than constant power mode.