Case report of hidden (yet visible) systolic fascicular potentials in a patient with left bundle branch block during conduction system pacing implantation.

Content Provider	Europe PMC
Author	Kaddour, Myriam Kozhuharov, Nikola Burri, Haran
Editor	Duncker, David Hillmann, Henrike Aenne Katrin Peverelli, Marta Jathanna, Nikesh
Copyright Year	2023
Abstract	BackgroundLeft bundle branch pacing (LBBP) is being increasingly adopted as a more physiological alternative to conventional pacing. At implantation, appropriate lead depth can be guided by monitoring a number of parameters, including the presence of a fascicular potential during conducted rhythm. However, in patients with left bundle branch block (LBBB), a presystolic fascicular potential is most often absent, due to upstream conduction block. We present for the first time a case where delayed fascicular potentials were visible within the ventricular electrogram (EGM) of the pacing lead.Case summaryAn 88-year-old patient with decompensated heart failure of ischaemic origin with a left ventricular ejection fraction of 0.30 and LBBB with a QRS of 180 ms was scheduled for LBBP pacemaker implantation. A pacing lead was screwed deep into the interventricular septum in the left bundle branch area. Upon close inspection, fascicular potentials within the ventricular EGM were visible during cycles with LBBB. A presystolic fascicular potential was visible during cycles with a narrow QRS following blocked atrial premature beats with a pause. Threshold testing revealed transition from non-selective to selective LBBP, confirming conduction system capture.DiscussionThe present case illustrates that fascicular potentials, which are most probably retrograde (or alternatively anterograde with very slow conduction), may be visualized within the ventricular EGM during LBBP implantation in patients with LBBB. Implanting physicians should scrutinize the EGM for these potentials, as they provide valuable information that adequate lead depth has been reached. The prevalence of these findings needs to be further evaluated.
Page Count	5
Journal	European Heart Journal: Case Reports
Volume Number	7
PubMed Central reference number	PMC9883728
Issue Number	1
PubMed reference number	36727139
e-ISSN	25142119
DOI	10.1093/ehjcr/ytad024
Language	English
Publisher	Oxford University Press
Publisher Date	2023-01-14
Publisher Place	US
Access Restriction	Open
Rights License	This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (https://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com © The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.
Subject Keyword	Left bundle branch pacing Conduction system pacing Fascicular potential Left bundle branch potential Left bundle branch block Case report
Content Type	Text
Resource Type	Article
Subject	Cardiology and Cardiovascular Medicine