Landiolol, an intravenous 1-selective blocker, is useful for dissociating a fusion of atrial activation via accessory pathway and atrioventricular node

IntroductionDuring ventricular pacing, a fusion of atrial activation may occur owing to the simultaneous retrograde conduction of the atrioventricular (AV) node and accessory pathway (AP), potentially leading to an inaccurate mapping of the atrial AP insertion site.ObjectiveWe tested the hypothesis that landiolol, an ultra-short-acting intravenous beta 1-blocker, could dissociate a fusion of atrial activation.MethodsWe conducted a prospective before-and-after study to investigate the effect of landiolol on retrograde conduction via the AV node and AP. We enrolled 21 consecutive patients with orthodromic AV reciprocating tachycardia who underwent electrophysiological studies at our hospital between January 1, 2018, and August 31, 2020.ResultsSix patients exhibited a fusion of atrial activation. After landiolol administration (10 mu g/kg/min), the effective refractory period was unchanged in AP (280 [240-290] ms vs. 280 [245-295] ms, p = .91), whereas that of the AV node was prolonged (275 [215-380] ms vs. 332 [278-445] ms, p = .03). The Wenckebach pacing rate via retrograde AV node decreased after landiolol administration (180 [140-200] beats per minute [bpm] vs. 140 [120-180] bpm, p = .02). Thus, landiolol decreased the minimum ventricular pacing rate required to dissociate a fusion of atrial activation (180 [160-200] bpm vs. 140 [128-155] bpm, p = .007). Radiofrequency catheter ablation under landiolol administration successfully eliminated AP in all patients during ventricular pacing without complications or recurrence.ConclusionLandiolol inhibited the AV node without affecting the AP and helped dissociate a fusion of atrial activation at a lower ventricular pacing rate. During ventricular pacing, a fusion of atrial activation may occur owing to the simultaneous retrograde conduction of the atrioventricular (AV) node and accessory pathway (AP), potentially leading to an inaccurate mapping of the atrial AP insertion site (A). Landiolol inhibited the AV node without affecting the AP and helped dissociate a fusion of atrial activation (B) at a lower ventricular pacing rate.image