1. Introduction
Left bundle branch (LBB) area pacing (LBBAP) has been recently
introduced as an attractive alternative to His Bundle Pacing (HBP) to
deliver physiological pacing.[1–6] Compared to HBP, LBBAP benefits
of lower pacing thresholds, higher R wave amplitude, less atrial
far-field oversensing and more stable lead position. To engage the left
septal conduction system and obtain physiologic depolarization of the
left ventricle (LV), deep implantation of the LBBAP lead in the
interventricular septum is essential. As a result, the implant procedure
is associated with a significant risk of perforation into the LV cavity
around 3%.[3,4] To prevent perforation, recent published LBBAP
experience suggests controlling the penetration depth of the lead
repeatedly (using sheath angiography), and to monitor the unipolar
pacing impedance, the paced QRS morphology and unipolar EGMs (for LBB
potential). However, this requires repetitive interruption of the
implantation, to connect the programmer to the connector pin (CP) of the
lead. As initial transseptal deployment of the lead is based on the
assumption of the septal wall thickness, first evaluation rarely
confirms optimal lead positioning. Consequently, if no LV perforation
has occurred, careful further advancement of the lead is needed until
criteria of LBB capture are obtained. Recently, LBBAP using
stylet-driven (SD) leads has demonstrated similar high implant success
rate when compared to the mostly used lumen-less Medtronic Select Secure
lead.[7] Interestingly, the use of SD leads offers the unique
opportunity to perform unipolar pacing on the inserted lead stylet (LS)
instead of the CP, with the advantage that continuous unipolar pacing is
possible during lead rotations for implantation.
In the present study, we aimed first to validate that unipolar pacing
from LS and CP results in similar pacing characteristics. Secondly, we
aimed to demonstrate that uninterrupted lead implantation guided by
continuous unipolar pacing and monitoring of the impedance, QRS
morphology, and peak left ventricular activation time (pLVAT) is a safe
and efficient technique to obtain LBBAP.