Impact of catheter-tissue contact force on lesion size during right ventricular outflow tract ablation in a swine model

Background:The catheter-tissue contact force(CF)is one of the significant determinants of lesion size and thus has a considerable impact on the effectiveness of ablation procedures.This study aimed to evaluate the impact of CF on the lesion size during right ventricular outflow tract(RVOT)ablation in a swine model.Methods:Twelve Guangxi Bama miniature male pigs weighing 40 to 50 kg were studied.After general anesthesia,a ThermoCool SmartTouch contact-sensing ablation catheter was introduced to the RVOT via the femoral vein under the guidance of the CARTO 3 system.The local ventricular voltage amplitude and impedance were measured using different CF levels.We randomly divided the animals into the following four groups according to the different CF levels:group A(3–9 g);group B(10–19 g);group C(20–29 g);and group D(30–39 g).Radiofrequency ablations were performed at three points in the free wall and septum of the RVOT in power control mode at 30 W for 30 s while maintaining the saline irrigation rate at 17 mL/min.At the end of the procedures,the maximum depth,surface diameter,and lesion volume were measured and recorded.A linear regression analysis was performed to determine the relationship between continuous variables.Results:A total of 72 ablation lesions were created in the RVOT of the 12 Bama pigs.The maximum depth,surface diameter,and volume of the lesions measured were well correlated with the CF(free wall:b=0.105,b=0.162,b=3.355,respectively,P<0.001;septum:b=0.093,b=0.150,b=3.712,respectively,P<0.001).The regional ventricular bipolar voltage amplitude,unipolar voltage amplitude,and impedance were weakly positively associated with the CF(b=0.065,b=0.125,and b=1.054,respectively,P<0.001).There was a significant difference in the incidence of steam pops among groups A,B,C,and D(free wall:F=7.3,P=0.032;septum:F=10.5,P=0.009);and steam pops occurred only when the CF exceeded 20 g.Trans-mural lesions were observed when the CF exceeded 10 g in the free wall,while the lesions in the septum were non-trans-mural even though the CF reached 30 g.Conclusions:CF seems to be a leading predictive factor for the size of formed lesions in RVOT ablation.Maintaining the CF value between 3 and 10 g may be reasonable and effective for creating the necessary lesion size and reducing the risk of complications,such as steam pops and perforations.