RADIOFREQUENCY CATHETER ABLATION OF SEPTAL ACCESSORY PATHWAYS WITHIN THE TRIANGLE OF KOCH - IMPORTANCE OF ENERGY TITRATION TESTING OTHER THAN THE LOCAL ELECTROGRAM CHARACTERISTICS FOR IDENTIFYING THE SUCCESSFUL TARGET SITE

Radiofrequency (RF) catheter ablation of accessory atrioventricular (A V) connections in the proximity of His bundle or AV node is at high ri sk of developing complete heart block. A safe and effective protocol h as not been well established. Nineteen consecutive patients with 19 se ptal accessory pathways within the triangle of Koch underwent a protoc ol with power-titrated RF energy testing to identify the target site f or successful catheter ablation. At every potential target site presel ected by local electrogram characteristics, RF energy uas started at 5 W for 10 seconds, with an increment of 5 W (duration remained at 10 s ) until maximally 30 W or the observation of transient interruption of accessory pathway conduction. By this stepwise RF energy testing, we successfully localized and ablated 18 (94.7%) of the 19 septal accesso ry pathways, 10 close to His bundle (zone I) and 8 away from it (zone II). The test-effective RF power was 20 W or less in 9 of all 11 septa l accessory pathways in zone I, and 5 of the 8 in zone II (P = 0.68). Meanwhile, the final RF power for successful ablation was 30 W or less in 9 of the 10 zone I and 6 of the 8 zone II septal accessory pathway s (P = 0.83). One patient with an accessory pathway in zone I was comp licated with complete AV block after final ablation at 30 W. None of t he local electrogram characteristics except continuous electrical acti vity during retrograde mapping was helpful in the prediction of ablati on outcome. Careful RF energy titration testing could effectively help identify the target site for successful RF catheter ablation of septa l accessory pathways within the triangle of Koch. The dependence on lo cal electrogram manifestations could be frustrated by a low probabilit y of success.