Idiopathic left ventricular tachycardia (ILVT), one of common idiopathic ventricular tachycardias which develop without structural abnormality of the heart. It has been reported that ILVT has a typical QRS morphology of right bundle branch block and left axis and unique clinical and electrophysiological characteristics. Intravenous verapamil is shown to be very effective in acute termination. However, radio-frequency catheter ablation is now recommended as the treatment of choice for long-term managemnt. This study was performed to determine the clinical and electrophysiological characteristics of ILVT and to evaluate the effects of radiofrequency catheter ablation (RFCA) of ILVT.

Seventeen patients (12 men, 5 women:mean age : 39±15 years) with ILVT were included in this study. ILVT was diagnosed based on the results of electrocardiogram, echocardiogram, cardiac catheterization, and electrophysiology study (EPS). EPS was performed with the standard technique in fasting state for more than 6 hours. In patients with their clinical VTs reproducibly induced during EPS, RFCA was attempted using endocardial activation mapping and pace-mapping. The mode of induction and termination, response to verapamil, and site of origin of the ILVT were evaluated. The local electrogram chacteristics at the sites of successful catheter ablation were also evaluated in patients undergoing RFCA.

All 17 patients presented with recurrent palpitation but none with syncope or sudden cardiac death. None had a significant heart disease. The spontaneous ventricular tachycardias were of right bundle branch block morphology with left superior axis in 11 cases, right inferior axis in 1, and northwest axis in 5. The VTs were terminated with intravenous verapamil in all of 14 patients receiving IV verapamil. VT of same morphology as the clinical VT was induced with programmed electrical stimulation in 13 cases (76.4%), of whom 2 cases required isoproterenol infusion. The most frequent mode of induction was single ventricular extrastimulation (7 cases). Mean cycle length of the induced VTs was 320±59 ms. RFCA was attempted in 11 cases and successful in 9 (82%). The successful ablation sites were and central mid septum (3 cases), posterior mid septum (3 cases), posterior apical septum (3 patients) of the left ventricle (3 patients). At the successful ablation sites, the local ventricular activation preceded the onset of QRS complex by 34±15 ms (range : 10-58) and the paced QRS complexes during pace-mapping were identical to those of the induced or spontaneous VTs in 11.7±0.4 leads (range : 11-12). However, Purkinje potential was recorded only in 2 cases. There were no complications associated with EPS and RFCA.

The present study suggests that ILVT is mild in symptoms, highly sensitive to verapamil, mostly caused by reentry, and can be cured by radiofrequency catheter ablation guided by pace-mapping and activation mapping.