Clinical/Electrophysiological Characteristics of Infra-Nodal Wenckebach in Patients with Indication for Permanent Ventricular Pacing: A Prospective Study

Background Infra-nodal Wenckebach is rare and is not well characterized. Objectives We prospectively studied clinical and electrophysiological characteristics of patients with atrioventricular (AV) Wenckebach with an indication for permanent ventricular pacing. Methods Over a 2-year-period, all subjects with an indication for permanent ventricular pacing underwent targeted pre-implant electrophysiological study. Clinical/electrophysiologic characteristics at presentation and ventricular pacing percentage at 6-month follow-up were evaluated. Results A total of 163 patients [median age 68 (IQR 60-74) years, male 59%, median QRS duration 110 (90-130) ms, complete AV block in 123 (69.3%)] were included. AV Wenckebach was noted in 22 (13.4%) patients [median age 70 (63-76.5) years, male 54%, median QRS duration 120 (110-140) ms] and classified as infra-nodal (12/163 or 7.3%) vs. AV nodal (10/163 or 6.1%). Patients with infra-nodal Wenckebach (Infra-His in all), when compared to AV nodal Wenckebach, demonstrated higher frequency with LVEF <40% (41.7% vs. 0%, p=0.04), longer median HV interval (90 vs. 49 ms, p=0.005), lower frequency of isolated 1st degree AV block (8.3% vs. 60%, p=0.002), higher frequency of right bundle branch block with left-anterior fascicular block (75% vs. 10%, p=0.02), lesser PR increment at onset of AVW (20.5 vs. 80 ms, p=0.002), and onset of 2:1 AV block at longer cycle lengths (91.7% vs. 20%, p=0.002). Conclusions Among patients referred for pacemaker implantation, infra-nodal Wenckebach was present in 27.5% (11/40) of patients without complete AV block. It was as frequent as AV nodal Wenckebach and associated with characteristic electrophysiologic findings.