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.