Endocardial Versus Epicardial Ventricular Radiofrequency Ablation

Background— Contact force (CF) is an important determinant of lesion formation for atrial endocardial radiofrequency ablation. There are minimal published data on CF and ventricular lesion formation. We studied the impact of CF on lesion formation using an ovine model both endocardially and epicardially. Methods and Results— Twenty sheep received 160 epicardial and 160 endocardial ventricular radiofrequency applications using either a 3.5-mm irrigated-tip catheter (Thermocool, Biosense-Webster, n=160) or a 3.5 irrigated-tip catheter with CF assessment (Tacticath, Endosense, n=160), via percutaneous access. Power was delivered at 30 watts for 60 seconds, when either catheter/tissue contact was felt to be good or when CF>10 g with Tacticath. After completion of all lesions, acute dimensions were taken at pathology. Identifiable lesion formation from radiofrequency application was improved with the aid of CF information, from 78% to 98% on the endocardium ( P <0.001) and from 90% to 100% on the epicardium ( P =0.02). The mean total force was greater on the endocardium (39±18 g versus 21±14 g for the epicardium; P <0.001) mainly because of axial force. Despite the force–time integral being greater endocardially, epicardial lesions were larger (231±182 mm 3 versus 209±131 mm 3 ; P =0.02) probably because of the absence of the heat sink effect of the circulating blood and covered a greater area (41±27 mm 2 versus 29±17 mm 2 ; P =0.03) because of catheter orientation. Conclusions— In the absence of CF feedback, 22% of endocardial radiofrequency applications that are thought to have good contact did not result in lesion formation. Epicardial ablation is associated with larger lesions.