Comparison of Ventricular Radiofrequency Lesions in Sheep Using Standard Irrigated Tip Catheter versus Catheter Ablation Enabling Direct Visualization

Abstract

In vivo assessment of RF ablation lesions is limited. Improved feedback could affect procedural outcome. A novel catheter, IRIS™ Cardiac Ablation Catheter (IRIS), enabling direct tissue visualization during ablation, was compared to a 3.5 mm open-irrigated tip ThermoCool™ Catheter (THERM) for endocardial ventricular RF ablation in sheep. Sixteen anesthetized sheep (6 ± 1 years old, 60 ± 10 kg) underwent ventricular RF applications with either the THERM (Biosense Webster) or IRIS (Voyage Medical) ablation catheter. In the THERM group, RF was delivered (30 W, 60 seconds) when electrode contact was achieved as assessed by recording high-amplitude electrogram, tactile feedback, and x-ray. In the IRIS group, direct visualization was used to confirm tissue contact and to guide energy delivery (10-25 W for 60 seconds) depending on visual feedback during lesion formation. A total of 160 RF applications were delivered (80 with THERM; 80 with IRIS). Average power delivery was significantly higher in the THERM group than in the IRIS group (30 ± 2 W [25-30 W] for 57 ± 14 seconds vs 21 ± 4 W [10-25 W] for 57 ± 27 seconds; P<0.001). At necropsy, 62/80 (78%) lesions created with THERM were identified versus 79/80 (99%) with IRIS (P<0.001). The lesion dimensions were not significantly different between THERM and IRIS. Despite best efforts using standard clinical assessments of catheter contact, 22% of RF applications in the ventricles using a standard open-irrigated catheter could not be identified on necropsy. In vivo assessment of catheter contact by direct visualization of the tissue undergoing RF ablation with the IRIS™ catheter was more reliable by allowing creation of 99% prescribed target lesions without significant complications.