Non-invasive electrocardiographic imaging of His-bundle and peri-left bundle pacing in left bundle branch block

We reported a case of using non-invasive global epicardial electrogram electrocardiographic imaging (ECGi) mapping to demonstrate both His-bundle pacing (HBP) and peri-left bundle pacing (PLBP) were able to synchronize the electrical activation pattern of a lady with left bundle branch block (LBBB). Selective HBP (SHBP) with threshold of 1.8 V at 0.5 ms and sensing of 3.2 mV achieved correction of the LBBB and shortening of QRS width from baseline. Non-selective HBP (NSHBP) was observed at higher pacing output. Peri-left bundle pacing resulted in narrowing of QRS width and emergence of qR pattern in lead V1 indicating capturing of the left bundle. The pacing threshold was 0.8 mV at 1.0 ms and sensing was 4.5 mV. Electrocardiographic imaging recording of the intrinsic rhythm showed a line of conduction block in the left ventricle (LV) with the latest activation in posterolateral LV. In contrary, both SHBP and PLBP demonstrated synchronous activation of the LV. The LV total activation time for intrinsic rhythm, SHPB, and PLBP were 110 ms, 36 ms, and 42 ms, respectively. The total global activation time for intrinsic rhythm, SHPB, and PLBP were 117 ms, 38 ms, and 48 ms, respectively. In this case report the advantages of PLBP over SHBP, by pacing more distally and further away from the membranous septum, were lower pacing threshold and increased R-wave sensing. The full-length version of this report can be viewed at: https://www.escardio.org/Education/E-Learning/Clinical-cases/Electrophysiology.