SEGMENT BY SEGMENT LINEAR ABLATION WITH AN ARTICULATED BILIMB CATHETER - INITIAL EXPERIMENTAL RESULTS

Transcatheter radiofrequency (RF) ablation of atrial fibrillation or f lutter requires the creation of linear lesions. However, conventional catheters are not predictably effective because of poor endocardial co ntact, and limited lesion size and penetration. The purpose of the stu dy was to assess, in the right atrium, the efficacy and safety of a ne w catheter designed to create long myocardial tissue lesions using RF energy. The main characteristics of this 8 Fr deflectable RF ablation catheter were: (1) a perpendicularly contacting articulated bilimb ele ctrodes ensuring stable and firm endocardial firm contact; and (2) an irrigated planar interface. Three different electrode prototypes were tested. Fourteen anesthetized sheep weighing 61 +/- 7 kg underwent RF ablation in the right atrium using three incremental power levels (25 to 45, 50, 55 to 75 W) with the aim of creating fully transmural (FT) lesions, defined as continuous and complete epicardial and endocardial lesion imprints. The animals were euthanized 2 hour later for macrosc opic and histologic examinations. Forty-three of the 80 right atrial l esions created, in smooth as well as in trabeculated areas, were FT. T he percentage of FT lesions increased with the applied power from 37% with 25-45 W, to 49% with 50 W, and up to 86% for 55-75 W. In all but two cases, histologic examination showed no discontinuity between FT l esions produced by both limbs resulting in 19 coalescent linear lesion s with an average size of 25 x 6 x 4 mm (length x width x depth). In s itu bipolar electrograms after ablation in the FT group showed split p otentials and/or a marked decrease in amplitude from 2.85 +/- 1.79 to 0.33 +/- 0.14 mV (P = 0.001) accompanied by-near complete disappearanc e of unipolar electrograms. There was no perforation due to RF ablatio n. In conclusion, continuous and FT lesions can be achieved in various areas of sheep atria, including the trabecular right atrium, with a p erpendicularly contacting bilimb electrode catheter. It represents a p romising tool for catheter ablation of atrial fibrillation and flutter .