Catheter ablation of the ventricular septum with radiofrequency energy

The safety and feasibility of performing catheter ablation of the ventricular septum with radiofrequency energy was assessed in a closed-chest canine model. Radiofrequency energy (750 kHz) was delivered in a bipolar manner via the distal electrodes of two quadripolar catheters positioned across the ventricular septum in 10 dogs at two sites. Each site received from 159 to 823 joules of delivered energy over one to three applications. Four additional dogs underwent unipolar radiofrequency ablation with 331 to 767 joules of delivered energy to each septal site. No significant acute or latent arrhythmias were noted. Dogs were killed at 1 day, and at 1, 2, and 4 weeks after the procedure. Out of a possible 40 potential ablation sites on each side of the septum after bipolar ablation, 21 (53%) discrete endocardial lesions were identified, ranging in size from 4 x 3 x 1.5 to 10 x 8 x 4 mm. When 352 joules or more delivered energy was applied per site, lesions were located at 18 of 28 (64%) possible sites. After unipolar radiofrequency ablation, similarly sized lesions were identified at 15 of 16 (94%) ablation sites. Histologic examination demonstrated well-delineated round or ovoid-shaped lesions with microscopic thrombi overlying two lesions. In conclusion, catheter ablation of the ventricular septum with radiofrequency energy appears capable of safely producing discrete areas of necrosis and may provide an alternative to direct current (DC) energy for catheter ablation of ventricular tachycardia originating from the septum.