Ablation of Antero-Septal and Intermediate Septal Accessory Pathways: How Safe Is It? How Can One Minimize the Risk of AV Block?

Abstract

The current goal of radiofrequency catheter ablation of supraventricular tachycardias is to cure a large cohort of patients with a primary success rate close to 100% and a complication and recurrence rate close to 0%. In this setting, the ablation of the atrioventricular (A-V) accessory pathway in the triangle of Koch may still represent a grey area, since the strict anatomical relationship between the bypass tract and the A-V node-His bundle may affect the feasibility and safety of the procedure. Consequently, the only rationale for successful ablation with no complication in this area relies on the assumption that the accessory pathway is more sensitive to radiofrequency energy delivery than the normal A-V conduction system [1]. The risk of damaging the normal A-V conduction pathway and of inducing a complete A-V block requiring a permanent pacemaker has been pointed out by both early [2, 3] and recent [4–6] reports, although successful and safe ablation has been described in limited series of cases [7, 8], even with “para-hissian” accessory pathways [1]. Moreover, in the risk/benefit ratio of ablation of by-pass tracts in the Koch’s triangle one must consider not only failure and the risk of permanent complete A-V block, but also the theoretical possibility of creating an incessant reentrant circuit by partially damaging both the accessory pathway and the A-V node conduction.