One Slow Pathway or Two?

Abstract

CaseA 56-year-old man with a history of palpitations and documented narrow complex tachycardia was referred to our center for assessment. There was no history of heart disease and left ventricular function was normal.Electrophysiology study and ablation were performed using standard methods with the patient in the postabsortive state and under conscious sedation. Catheters were positioned in the high right atrium, right ventricular apex, coronary sinus, and His position. Baseline intervals were AH 72 msec, This manuscript was processed by a guest editor. Figure 1. AV node reentrant tachycardia initiated by atrial extrastimulus testing at drive cycle length 400 msec and coupling interval 270 msec.HV 41 msec, and QRS duration 75 msec. Atrial extrastimulus testing demonstrated a rate-dependent increase in conduction time over the AV node without a discrete "jump" to a slow AV nodal pathway. Tachycardia was initiated at drive cycle length 400 msec and coupling interval 270 msec (Fig. 1). The rhythm was AV node reentrant tachycardia (AVNRT) as determined by diagnostic pacing maneuvers. Tachycardia was reliably induced at coupling intervals 240-270 msec, and single echoes were observed at coupling intervals less than 240 msec. Slow pathway ablation was performed and extrastimulus testing was repeated. Tachycardia was no longer inducible, but single AV nodal echoes were still observed at coupling intervals less than 270 msec. AV node conduction curves before and after ablation are demonstrated in Figure 2. What do these curves suggest regarding AV node conduction properties and the impact of ablation? DiscussionInitial atrial extrastimulus testing demonstrated that conduction over the slow AV nodal pathway resulted in typical

Changes in electrophysiologic properties of the conductive system of the heart in children with atrioventricular nodal reentrant tachycardia after 2–8 years following radiofrequency catheter ablation of the slow pathway

“…Although elimination of the SP conduction was the original paradigm for treatment of AVNRT by RF ablation, it has become clear that elimination of the SP conduction is not necessary for good outcome (11)(12)(13).…”