Irrigated Versus Dry Radiofrequency Epicardial Ablations in the Treatment of Atrial Fibrillation

Background: Dry radiofrequency (RF) ablation is an established form of surgical treatment of atrial fibrillation and many groups have reported good clinical results . One limiting factor of this type of ablation is that transmural lesions are not consistently obtained . Several reports on percutaneous ablation have shown that catheter irrigation leads to larger volume lesions than nonirrigated catheters . When the catheter is irrigated with cold saline the temperature at the electrode/myocardium interface is artificially lowered and the generator keeps applying power to the tissue (up to 150W) in an attempt to bring the surface temperature up to the target value set by the user. By irrigating the catheter one is actually bypassing a very important safety mechanism of the generator, the temperature control, and one can expect lot more power to be delivered to the tissue during irrigated ablations than during dry ones. It is therefore important to determine the power that can be applied in order to ensure that tissue integrity is not compromised. There are several in-vitro and in-vivo studies of the impact of irrigation on RF percutaneous ablation using animal models (10-15) and computation models simulating irrigated epicardial ablations . However, there are to our knowledge no experimental studies of the effect of catheter irrigation on the lesion created by epicardial ablation on human tissues. We studied in-vitro and in-vivo the effects of external irrigation of the catheter on the sub-endocardial (Tsend) and subepicardial (Tsepi) temperatures during epicardial ablation under power control. We assessed lesion depth and compared the results with dry RF epicardial ablation under temperature control.