Abstract 16035: Cryoablation Achieves More Consistent Deeper Lesions With Improved Safety Compared to Radiofrequency Energy: An Experimental Model

Abstract

Introduction: Ablation strategies that require linear lesions often fail due to non-transmural tissue injury. In the current study we compared the efficacy and safety of cryoablation to radiofrequency ablation in an in-vivo canine model. Hypothesis: Cryoablation and radiofrequency ablation are equivalent in creating conduction block in ventricular tissue Methods: Anesthetized, ventilated canines (n=13) underwent thoracotomy. In in-situ RV outflow tract, blind alley (BA) that conducted to and from the RV only via an isthmus (IS) was created by cut and sew method by making a surgical incision. Cryoablation (7Fr, 8 mm tip FreezorMax3, Medtronic) or radiofrequency ablation (8Fr, 3.5 mm tip, saline irrigation 15-30cc/min Thermocool, Biosense Webster) was performed (4 -6 min and 2 min duration, respectively) from the endocardium at the IS. Epicardial temperature was monitored by a thermal camera (FLIR, Danderyd, Sweden). Entry and exit block was assessed by pacing and recording from inside the BA and from the LV. Acute and chronic block was defined as bidirectional block through the IS at 15 min and 90 min, respectively. Ablation was continued until acute block was achieved and observation continued for 90 min. Results: Data is summarized in the Table below. It was difficult to achieve transmural block using radiofrequency ablation unless high power settings (40-50W) and prolonged duration was used. These settings were associated with high incidence of steam pop and ventricular arrhythmias, yet chronic block was infrequently achieved. No complications were seen during cryoablation and conduction block was achieved at a higher rate. Development of chronic conduction block correlated with presence of transmural tissue injury. Conclusions: Cryoablation is safer and achieves deeper lesions and more persistent conduction block than RFA in this right ventricular experimental model.