A Study Of Clinical And Electrophysiological Characteristics Of Infrahisian Wenckebach

ABSTRACT

Background: Wenckebach periodicity has classically been considered an AV nodal phenomenon. Infra-Hisian Wenckebach (IHW) scarcely reported in the literature. The distinction, sometimes, becomes critical as IHW is a harbinger of complete AV block and demands permanent pacing contrary to AV nodal Wenckebach. We aimed too study clinico-electrophysiological profile of patients with Infrahisian Wenckebach (IHW) conduction. Method(s) Patients with a clinical diagnosis of atrioventricular (AV) block (excluding complete Heart Block) who underwent permanent pacemaker implantation(PPI) based on standard indications from July 2021-June 2022 at The Madras Medical Mission were prospectively subjected to pre- implant Electrophysiology study to document conduction pathology Results: A total of 94 patients underwent PPI for symptomatic AV block during the study period. EPS was performed in all but one patient (COVID pneumonia). Incidence of IHW was 9/93(9.6%) of patients with AV block. Suprahisian wneckebach was noted in 8/93 patients. There is no gender predisposition (M-4, F-5) and their mean age was 71.4+11.7 years. As many as half of the patients (5/9) had an underlying narrow QRS. The mean QRS duration was 130 + 19.3. Ischemic heart disease affected half of the patients and cardiomyopathy in 4/9 patients (mean EF 45.1+13.7%). Presentation was syncope in all and mean NYHA class was 2.1. Presentation ranged from isolated 1st degree AV block (1/9) to tri-fascicular block (3/9). At EP study, mean basal HV interval was 94.7+27.1ms. IHW was noted spontaneously in 4 patients and on atrial pacing in the remaining. Mean PR interval of the first beat of the Wenckebach cycle was 223 + 14.5 ms. Mean increment in PR interval from the first to the 2nd beat of the cycle was found to be minimal (14.1 + 6.7 ms) which was significantly less when compared to that in patients with suprahisian Wenckebach (44.1 + 10.8 ms), p=0.03). All patients received conduction system pacing implant. In the literature, a total of 11 documented cases have been reports (8 case reports). Ours is the largest case series and first to study the clinical profile of such patients. Conclusion(s) Wenckebach periodicity is classically considered an AV nodal phenomenon. IHW scarcely reported in literature. Distinction becomes critical as IHW is harbinger of complete AV block. However, the prevalence as reported in the current study may not be so less as previously reported, especially with the advent of conduction system pacing where EPS is routinely performed to localize the level of AV block. This is the largest series and first clinic-etiological profile of IHW patients published till date. [Formula presented] Copyright © 2022