B-PO05-037 ELECTROCARDIOGRAPHIC CHARACTERISTICS WITH LEFT BUNDLE BRANCH AREA PACING: A SINGLE CENTER PROSPECTIVE STUDY

Abstract

Pure left bundle branch (LBB) capture should result in typical RBBB (rsR’) morphology. However, numerous paced QRS morphologies are observed during LBB area pacing (LBBAP). There are limited papers describing the various electrocardiographic (ECG) morphologies seen with LBBAP. To evaluate the various ECG characteristics encountered in LBBAP. Patients referred for pacemaker implantation between 02/2019-02/2021 were considered for LBBAP. LBBAP was performed by implantation of a Medtronic 3830 lead 2 cms distal to His and confirmed by previously published criteria. If unsuccessful, lead was repositioned distally and inferiorly on the septum to capture the left posterior fascicle (LPF). Paced QRS morphology and QRS axis was analyzed. Baseline, ECG, and implantation characteristics are summarized in table 1. Of 274 LBBAP ECGs, the most common morphology seen during unipolar tip pacing was an incomplete RBBB pattern (qR) in V1 in 131 (48%) patients. rSR’ pattern was seen in 38 (14%) and a narrow QS pattern in 34 (12.5%) patients. qR or rsR’ with left axis deviation, i.e., LPF capture was noted in 69 (25%) patients. One patient exhibited monophasic R in lead V1. Unipolar ring pacing resulted in wide QS in all patients due to RV septal capture only. Various ECG morphologies may be encountered during successful LBB area capture and are associated with similar QRSd, pacing characteristics and short-term lead performance. These morphologies are due to capture of various structures (RV or LV septum, capture of LBB, LPF +/- RBB) and are likely due to virtual-electrode effect.