The use of left bundle branch pacing as a bail-out in case of CRT pacing failure: a case series
Authors: Agelaki M , Christou A , Manolakou P , Fotos G , Serafeim G , Lampas E , Sidiropoulou E , Alexandris S , Boneti M , Mouratidou M , Chaldoupis A I , Theodosopoulou C , Teroli E , Progkaki Z , Flessa K 
Published: May 2024

Abstract

Introduction
LBBB pacing has emerged as a novel alternative to CS pacing for cardiac resynchronization therapy in patients with heart failure.

Purpose
We hereby present a series of four cases wherein the use of LBB pacing, although not initially planned as first choice, was able to overcome a variety of different limitations of traditional CRT pacing.

Presentation
Patient #1 was an 81-year old man with a history of ischemic HF and AF who was admitted with recurring episodes of sustained ventricular tachycardia (VT) below the detection zone of the CRT-D that had been implanted 11 years ago. Interrogation of the device revealed fracture in the RV lead, intact values of the RV defibrillation coil and inability to capture from an LV lead in an anterior vein. Following initial stabilization the patient underwent successful LBB lead implantation combined with a new RV pace-sense lead as backup due to acceptable but non-optimal LBB lead values attributed to ischemic septal scarring. We were able to retain the previous CRT-D device by relegating the LBB lead to the atrial port and with the use of DDDR programming with custom AV delay values in order to achieve LBB pacing with RV pacing as backup.
Patient #2 was a 51-year old man with a history of ischemic HF and permanent AF with a previously implanted CRT-D who was also admitted due to episodes of VT. Device interrogation revealed high threshold of an LV lead located in an anterior vein. The patient underwent supplementary LBB lead implantation which was then connected to the atrial port of the pre-existing CRT-D device, providing primarily LBB pacing with RV pacing backup through the use of custom DDDR programming same as in the previous case.
Patient #3 was a 71–year old man with newly-diagnosed ischemic cardiomyopathy and multiple episodes of hemodynamically unstable VT that persisted even after successful reperfusion, necessitating VT ablation. The patient had narrow QRS at baseline and was not eligible for CRT-D, however after medical therapy to suppress ventricular arrhythmias the patient seemed prone to developing LBBB-like QRS widening. The decision was made to proceed with standard ICD implantation and combine a standard defibrillation lead with an LBB lead through the use of a DF1 port, so as to be able to provide LBB pacing as needed in the future.
Patient #4 was a 62-year old man with a history of hypertrophic cardiomyopathy and HF with extensive apical scar scheduled for CRT-D implantation. CS venography during implantation revealed a single lateral vein draining the apical LV, lead was implanted but with no capture. An LBB pacing lead was successfully implanted and used instead of the LV lead in the conventional CRT-D set up.

Conclusion
In this case series we demonstrate that LBB pacing is a viable option as a bail-out in various cases of CRT pacing failure, including both septal scar and hypertrophy, as well as different anatomical substrates and CRT status.LBB pacing characteristics summary