Radiofrequency catheter ablation using long coiled electrodes: Impact of irrigation on lesion dimensions and incidence of coagulum formation

Ablation catheters with multiple long coiled electrodes have been recently developed to induce continuous linear lesions for the treatment of atrial f ibrillation. The efficacy and safety of ablation catheters with multiple lo ng coiled electrodes has not been evaluated. The aim of the present in vivo study was to investigate the influence of saline irrigation on lesion dime nsions and coagulum formation during RF current ablation using those ablati on catheters. In 14 anesthetized sheep, the thigh muscle was prepared as a cradle and filled with heparinized blood (37 degreesC). The quadripolar coi led ablation catheter (electrode length 7 mm, electrode distance 2 mm) was placed parallel to the muscle with standardized 10-g contact pressure. RF c urrent energy was delivered sequentially temperature- (70 degreesC) or powe r-controlled (10, 20, 30, or 40 W) with additional irrigation of the electr ode (20 mL/min normal saline) for 90 seconds. Forty-two of 129 RF current l esions were induced by temperature-controlled and 87 by irrigated ablation. Except for three lesions following low energy irrigated application (10 W) , all lesions were continuous. Significantly larger lesions following irrig ated RF current applications were produced with a power output of 30 Mi (de pth 0.74 +/- 0.13 cm, width 0.78 +/- 0.13 cml and 40 W (depth 0.75 +/- 0.16 cm, width 0.92 +/- 0.28 cm) as compared to 20 Mi (depth 0.47 +/- 0.13 cm, width 0.82 +/- 0.22 cm). Coagulum formation adherent to the electrode was e xclusively observed following 18 of 42 nonirrigated RF current ablations. I n conclusion, irrigated coiled ablation electrodes induce continuous linear lesions with a power output of 20-40 W. The risk of coagulum formation at the coiled electrode can be avoided by irrigation.