Landiolol, an intravenous β1-selective blocker, is useful for dissociating a fusion of atrial activation via accessory pathway and atrioventricular node.

Introduction: 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.
Objective: We tested the hypothesis that landiolol, an ultra-short-acting intravenous β1-blocker, could dissociate a fusion of atrial activation.
Methods: We 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.
Results: Six patients exhibited a fusion of atrial activation. After landiolol administration (10 μg/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.
Conclusion: Landiolol inhibited the AV node without affecting the AP and helped dissociate a fusion of atrial activation at a lower ventricular pacing rate.
Competing Interests: Dr. Masaomi Kimura is an associate professor, and Dr. Taihei Itoh is an associate professor/lecturer of the Department of Advanced Management of Cardiac Arrhythmias, which is an endowment department supported by Medtronic Japan Co., Ltd., Japan Lifeline Co., Ltd, and Fukuda Denshi Kita‐Tohoku Hanbai Co., Ltd. Dr. Yuji Ishida is an assistant professor of the Department of Cardiac Remote Management System, which is an endowment department supported by BIOTRONIK Japan Co., Ltd. Dr. Shingo Sasaki received research grant from Boston Scientific Japan Co., Ltd. and is a concurrent associate professor of the Department of Advanced Management of Cardiac Arrhythmias and the Department of Cardiac Remote Management System. Dr. Hirofumi Tomita is a concurrent professor of the Department of Advanced Management of Cardiac Arrhythmias, the Department of Cardiac Remote Management System, and the Department of the Advanced Therapeutics for Cardiovascular Diseases, which is an endowment department supported by Boston Scientific Japan Co., Ltd. Dr. Tomita also received research grant from Abbott Medical Japan LLC. Other authors have no relevant disclosures.
(© 2023 The Authors. Journal of Arrhythmia published by John Wiley & Sons Australia, Ltd on behalf of Japanese Heart Rhythm Society.)