Fast pathway ablation for atrioventricular node reentrant tachycardia.

The pioneering surgical reports of Ross et al. (1) and Cox et al. (2) set the stage for catheter ablation of atrioventricular (AV) node reentrant tachycardia by demonstrating that this type of tachycardia could be cured without damage to the compact AV node or impairment of AV conduction. Several experimental and clinical studies (3-8) have indicated that the anterior and posterior inputs into the compact AV node are critical components of the AV node reentrant tachycardia reentry circuit, with the anterior AV node input serving as the "fast pathway" and the posterior AV node input as the "slow pathway". In the initial reports of catheter ablation for AV node reentrant tachycardia, direct current shocks or radiofrequency energy applications were delivered near the anterosuperior aspect of the tricuspid annulus, resulting in electrophysiologic effects consistent with fast pathway ablation. The success rates were 76% to 91%, but there was a 2% to 10% incidence of inadvertent high degree AV block (9-11). In subsequent reports, radiofrequency energy was delivered in the region of the posteroinferior aspect of the tricuspid annulus, near the ostium of the coronary sinus, resulting in electrophysiologic effects consistent with slow pathway ablation. With this technique, the success rate increased to 95% to 100%, with <2% incidence of inadvertent AV block (12-16). Although a randomized comparison of the anterior and posterior approaches to ablation of AV node reentrant tachycardia in 50 patients at one center demonstrated no significant differences in efficacy or complication rates between the two techniques (17), the pooled results of studies from several centers have indicated the superiority of the posterior approach, in which the slow pathway is targeted (12-16). Stepwise approach to fast pathway ablation. The study by Kottkamp et al. (18) in this issue of the Journal describes a stepwise approach to fast pathway ablation in which a radiofrequency energy application initially is delivered at a site that is posterior and superior to the site where the maximal His bundle depolarization is recorded. If necessary, subsequent