CATHETER ABLATION OF VENTRICULAR-TACHYCARDIA WITH RADIOFREQUENCY CURRENTS, WITH SPECIAL REFERENCE TO THE TERMINATION AND MINOR MORPHOLOGIC CHANGE OF REINDUCED VENTRICULAR-TACHYCARDIA

During catheter ablation with radiofrequency (RF) currents, the incide nce of the termination of reentrant ventricular tachycardia (VT) durin g application of RF energy and the morphologic change of the reinduced VT were analyzed. Twenty-five patients (20 men and 5 women, aged 44 /- 17 years) were studied. After induction of monomorphic sustained VT , the ablation site was determined by endocardial activation mapping, identification of isolated mid-diastolic potential, and pacing during tachycardia. Thirty-six monomorphic VTs were induced in 25 patients an d terminated with programmed stimulation. The cycle length was 323 +/- 55 ms and all VTs were entrained with rapid ventricular pacing. The t arget site was the earliest site of activation of VT in 26 VTs in 16 p atients, and the area of slow conduction in 10 VTs in 9 patients. VT w as terminated soon after the application of RF currents in 33 VTs in 2 2 patients at 6.0 +/- 3.1 seconds, and VT was induced immediately afte r the cessation of RF currents in 11 patients. Of these, 4 patients wi th idiopathic left ventricular VT had an alternation in the QRS config uration before catheter ablation and required repeat ablation of the o ther VT morphology. In the other 7 patients, such morphology was not o bserved before ablation, but was observed in VT induced when the origi nal VT was terminated. Repeated attempts of catheter ablation 2 to 9 t imes at the remapped site was, however, successful in 7 of 8 VTs. In t he remaining 3 patients, ablation was attempted within the area of slo w conduction, but VT was not terminated during RF and only minor morph ologic change was observed in 1 patient. With the inclusion of these 3 patients, catheter ablation was unsuccessful only during 4 VTs in 4 p atients.