Ablation of Superior Slow Pathway in Atypical Fast-Slow Atrioventricular Nodal Reentrant Tachycardia

Abstract

The usual arrhythmogenic substrate of atrioventricular nodal reentrant tachycardia (AVNRT) is a slow pathway (SP) that can be ablated in the posterior or mid septum. We have proposed a rare, superior (sup-) type of fast-slow (F/S-) AVNRT incorporating a sup-SP located near the His bundle. Programmed ventricular stimulation induced retrograde conduction over the sup-SP with an earliest atrial activation near the His bundle. sup-F/S-AVNRT is characterized by a long-RP interval; a retrograde atrial activation sequence during tachycardia identical to that during retrograde conduction over a sup-SP during ventricular pacing; ventriculoatrial dissociation during ventricular overdrive pacing of the tachycardia or atrioventricular block occurring during tachycardia, excluding atrioventricular reentrant tachycardia; and a V-A-V activation sequence immediately after ventricular induction or entrainment of the tachycardia, including dual atrial responses. Elimination or modification of retrograde conduction over the sup-SP by ablation near the right perinodal region or from the noncoronary cusp of Valsalva eliminated and confirmed the diagnosis of AVNRT. sup-F/S-AVNRT is a distinct supraventricular tachycardia, incorporating an SP above Koch’s triangle as the retrograde limb, that can be eliminated by radiofrequency ablation. Its formal inclusion in the differential diagnosis of long RP tachycardia should be reflected in a corresponding adaptation of ablation therapy for refractory AVNRT.