Radiofrequency catheter ablation of the left and right ventricles: anatomic and electrophysiologic observations

Certain untoward effects associated with the use of direct-current electrical catheter ablation of the ventricular endomyocardium have been noted. We assessed the efficacy and safety of closed-chest catheter ablation of the left and right ventricles using radiofrequency (RF) energy (750 kHz) in six dogs. Mean RF energies between 93 and 123 joules (J) were randomly delivered to three left ventricular (LV) sites via two distal adjacent electrodes (bipolar configuration) using 6-7F USCI tripolar or quadripolar catheters with an interelectrode distance of 5-10 mm. Another 90-143 J were given to two right ventricular (RV) sites in single or multiple divided applications between a distal electrode and an external patch electrode (unipolar configuration). Ventricular arrhythmias were not observed during application of RF energy. Programmed ventricular stimulation before and after the procedure did not induce ventricular tachycardia (VT) or fibrillation except in one dog who had inducible VT prior to ablation. There were no significant changes in LV and RV effective refractory periods after the procedures. Occasional premature ventricular beats and rare episodes of non-sustained VT (3-12 beats) were observed in ambulatory electrocardiographic recordings (13-24 hrs) done immediately after ablation. Dogs were sacrificed after 4-5 days. Pathology showed well-demarcated round or ovoid lesions of varying sizes. Mural thrombus was found in one dog. Microscopic findings consisted of circumscribed areas of coagulation necrosis with a peripheral zone of cellular infiltration. Transmural necrosis without perforation was occasionally seen in the thin RV wall when higher energies were delivered. In conclusion, discrete areas of desiccation injury in the ventricles can be achieved by transcatheter bipolar or unipolar ablation using RF energy. The complications associated with this method appear to be minimal. Further experiments are needed to evaluate its potential for catheter ablation of ventricular tachycardia.