Temperature-controlled radiofrequency catheter ablation with a 10-mm tip electrode creates larger lesions without charring in the porcine heart

Background: Radiofrequency catheter ablation of atrial flutter, atrial fibr illation or ventricular tachycardia may be favoured by large lesions. We co mpared lesions created in unipolar mode using 10-mm/8 F electrodes with tho se of 4-mm/7 F catheters. Methods: Ablations were first performed in porcine hearts in vitro (70 degr ees C, 60 s, tangential catheter tip-tissue orientation). Anaesthetized pig s were thereafter ablated with 10- or 4-mm catheters in the right atrial fr ee wall (RAFW), inferior vena cava-tricuspid valve (IVC-TV) isthmus and lef t ventricle (LV). Results: In vitro, lesion length doubled and lesion volume tripled using th e 10-mm catheter. Average power supply was 69 (SD12) (10-mm tip) versus 26 (SD7) W (4-mm tip). In vivo, lesion length increased by 50% and lesion volu me fivefold. Charring at the lesion surface or sudden impedance rises were not observed in vivo. Histologically, coagulation necrosis and minor haemor rhages were found. One RAFW lesion (10-mm) showed a dissection approaching the epicardium. Fibrinous platelet clots or overt thromboses covered the en docardial surface in half of all lesions. Three 10-mm electrode isthmus les ions extended to the right descending posterior artery and one LV lesion to the left anterior descending artery, but there was no damage to the arteri al walls. Following six ablations with the 10-mm electrode and two with the 4-mm tip, injury to the adjacent lung tissue of 0.5 to 6.0 mm depth was fo und (p = 0.22). Conclusion: RF ablation using 10-mm/8 F electrodes created significantly la rger lesions. 10-mm electrodes appeared safe in the porcine IVC-TV isthmus and LV, but not in the RAFW.