CATHETER ABLATION OF CONCEALED ACCESSORY PATHWAYS - SUDDEN OCCURRENCE OF VENTRICULAR PREEXCITATION

Catheter ablation using radiofrequency or direct current energy was performed in 19 consecutive patients with concealed accessory pathways. Four patients developed manifest preexcitation for the first time following ablation. The concealed accessory pathways of these four patients were localized at right lateral, left posteroseptal, left posterolateral, and left lateral sites, respectively. In two patients, manifest preexcitation developed immediately after attempted ablation. In the other two patients, preexcitation occurred after 4 and 14 days. Electrophysiologic testing revealed in all four patients that the origin of manifest preexcitation corresponded to the site of the concealed pathway. Successful catheter ablation using radiofrequency current was performed in three patients. One patient preferred surgical interruption of the accessory pathway. The reason for this sudden emergence of preexcitation in these patients with only retrograde conducting pathways remains to be investigated. The anterograde conduction capacity might have been modified by damaging the site of the accessory pathway insertion.