Nonreentrant Supraventricular Tachycardia Due to Simultaneous Conduction Over Fast and Slow AV Node Pathways: Successful Treatment with Radiofrequency Ablation

Abstract

A 55-year-old woman with frequent problematic supraventricular tachycardia is presented. The tachycardia was irregular with predominantly normal QRS morphology and was refractory to multiple antiarrhythmic drugs. At electrophysiology study, the tachycardia was inducible with atrial or ventricular extrastimuli and dual pathways were observed. In contrast to the situation usually seen with dual atrioventricular node physiology, the slow pathway had a longer effective refractory period than the fast pathway and reentrant tachycardia was not induced. Simultaneous conduction over the fast and slow pathways during sinus rhythm was shown to be the mechanism for clinical tachycardia. The tachycardia was successfully treated using radiofrequency ablation of the slow pathway.

Incessant Non‐Reentrant Supraventricular Tachycardia Interrupted By Apparent Simultaneous Wenckebach Sequences along Both Nodal Pathways

“…First, the conduction time in each pathway should be long enough to exceed the refractory period of the lower common pathway and/or His bundle‐Purkinje tissue 1–4 . Second, retrograde conduction should be poor to absent in both the fast and slow pathways, 1–6 allowing successive uninterrupted anterograde conductions along both pathways and thus the perpetuation of the arrhythmia. If double responses can occasionally induce isolated slow‐fast nodal echoes 1 or AV node reentrant tachycardia, 7 non‐reentrant supraventricular tachycardia usually occur in an incessant fashion and are only exceptionally associated with reentrant tachycardia 2,3,6,8 because of the second mandatory condition.…”

“…The only exceptions have been linked to the existence of more than two pathways, 3 or to the fact that block of retrograde conduction was not fixed 2,3 or resolved under isoproterenol 6,8 . Non‐reentrant supraventricular tachycardia was first reported in 1979 by G. Csapo 9 and to the best of our knowledge, only 34—mostly isolated–cases have been published so far, 1–6,8 this entity being apparently rather exceptional, even if misdiagnosed cases are likely 4,6 . The elimination of conduction along the slow pathway by RF ablation led to the definitive cure of this unusual arrhythmia in all the reported cases.…”

Simultaneous Dual Fast and Slow Pathway Conduction upon Induction of Typical Atrioventricular Nodal Reentrant Tachycardia: Electrophysiologic Characteristics in a Series of Patients

“…Over the years, a few cases have been reported where simultaneous dual AV node conduction (SDNC) occurs at the induction of a typical atrioventricular nodal reentrant tachycardia (AVNRT), which has been amenable to a successful treatment by conventional slow pathway radiofrequency energy (RF) ablation 2–6 . Moreover, in some other rare cases, SDNC has been observed during normal sinus rhythm at a critical rate: if sustained, it causes a peculiar form of arrhythmia called non‐reentrant junctional tachycardia (NRJT) 7–19 …”

Nonreentrant Supraventricular Tachycardia Misdiagnosed as Inappropriate Sinus Tachycardia

“…Dual nodal responses have been misclassified as bigeminy 7 (supraventricular or ventricular) and as atrial fibrillation due to variable antegrade conduction down the fast and slow pathways in a case series of patients referred for pulmonary vein isolation 8 ; moreover, tachycardia‐mediated cardiomyopathy has been associated with nonreentrant SVT 9 . Fortunately, catheter ablation of the slow pathway is curative 10,11 …”