Proarrhythmic effects of ventricular electrical catheter ablation in dogs.

Electrical catheter ablation of arrhythmogenic sites is a new therapy for ventricular tachycardia that is still being investigated. Recent studies have shown, however, that the procedure itself can provoke serious ventricular arrhythmias. The incidence, course and mechanism of these arrhythmias were studied in 10 beagles treated with a single R wave-synchronized cathodal shock delivered to the endocardial ventricular wall (5 dogs left ventricular, 5 dogs right ventricular). Shocks were delivered at 30 (four dogs), 80 (two dogs) or 250 J (four dogs). Each dog underwent programmed electrical stimulation at or near the ablation site before, within 1 hour after and 1 week after the shock. Holter electrocardiographic monitoring (24 hours) was performed during day 1 and 7 after the shock in all the dogs, and extended Holter monitoring was done during the first 5 days in four dogs. All dogs survived for 1 week. Within 10 minutes after the shock, a sustained ventricular tachycardia was recorded in nine dogs; deterioration into ventricular fibrillation occurred in two dogs. In nine dogs, 60 to 169 monomorphic ventricular tachycardia episodes (mean 101) occurred on day 1 and 0 to 11 (mean 3) occurred on day 7; Holter monitoring failed for technical reasons in one dog. Extended Holter monitoring showed a marked decline in the incidence of tachycardia during the first 3 days. Early activation during ventricular tachycardia was always derived at or near the ablation site, and the QRS configuration during pre- and postablation pacing at this site was identical to the tachycardia configuration. Ventricular tachycardia was never inducible with programmed stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)