Catheter tip orientation affects radiofrequency ablation lesion size in the canine left ventricle

While some factors influencing size of RF lesions in ventricular tissue hav e been characterized, the effects of catheter electrode-endocardial surface orientation on lesion generation have not been investigated. Therefore, th e effects of parallel versus perpendicular catheter electrode-endocardial s urface orientation on dimensions of RF lesion produced with 4-, 6-, 8-, 10- , and 12-mm distal electrode lengths were studied in 20 closed-chested dogs . Orientation was established by biplane fluoroscopy and confirmed by intra cardiac echocardiography for the majority of energy deliveries (71%). RF; V oltage was titrated to maintain constant catheter electrode temperature of 75 degrees C for 60 seconds. In the perpendicular orientation, lesion size did not change significantly with increasing electrode lengths. There was a statistically significant interaction between electrode orientation and ma ximum lesion length (analysis of variance [ANOVA] P = 0.04), lesion width ( ANOVA P = 0.01), lesion area (ANOVA P = 0.02), and estimated lesion volume (ANOVA P < 0.005) over all electrode lengths. With parallel tip-tissue orie ntation, lesion size wets a function of increasing electrode length. For 4- , 6-, 8-, 10-, and 12-mm electrodes, maximum lesion surface areas were 95 /- 38, 97 +/- 38, 119 +/- 29, 147 +/- 52, and 147 +/- 67 mm(2), respectivel y. For electrode lengths 8, 10, and 12 mm, estimated lesion volumes were si gnificantly greater with parallel orientation IP ( 0.05 for all). Thus, ven tricular lesion size is dependent on catheter electrode length, but only wh en the catheter is oriented parallel to the endocardial surface. This infor mation may De helpful in increasing lesion dimensions for RF ablation of ve ntricular tachycardias.