Differential Responses of the Septal Ventricle and the Atrial Signals During Ongoing Entrainment

Abstract

S eptal accessory pathways (APs) and atypical atrioventricular nodal reentry (AVNRT) commonly mediate supraventricular tachycardia with concentric atrial activation and long ventriculoatrial (VA) intervals. Several diagnostic maneuvers can aid differential diagnosis, including a return cycle after continuous entrainment from the right ventricular apex (RVA), 1,2 tachycardia resetting with electrocardiographic fusion, 3,4 and even responses to single ventricular extrastimulus.5 However, it has been reported that ≤15% to 20% of the tachycardia mechanism could be interrupted by the entrainment maneuvers. 5 In these instances, the utility of RVA pacing during tachycardia at the beginning of the entrainment attempt has received less attention as a diagnostic technique. Recently, AlMahameed et al elegantly © 2015 American Heart Association, Inc. ). SVE advancement preceding atrial reset was observed in 98% of atrioventricular nodal reentries during 4±1.1 cycles; this phenomena was observed in 6 (8%) of the atrioventricular reentrant tachycardia mediated by septal AP (P<0.001; sensitivity 98%; specificity 93%; positive predictive value 90%; negative predictive value 99%) and lasted 1 single cycle (P<0.001). Right posteroseptal AP tachycardias were distinctly characterized by atrial reset preceding SVE advancement (with ventricular fusion; specificity 100%; positive predictive value 100%). In 11 cases, it was impossible to achieve sustain entrainment. In all of them, the differential responses at the entrainment attempt allowed for appropriate diagnosis. Conclusions-The differential response of the SVE and the atrial electrogram at the initiation of continuous right ventricular apical pacing during tachycardia effectively distinguishes between atypical atrioventricular nodal reentry and atrioventricular reentrant tachycardia mediated by septal APs. (Circ Arrhythm Electrophysiol. Circ Arrhythm Electrophysiol