Stepwise application of ECG and electrogram based criteria to ensure left bundle branch pacing

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: Public Institution(s). Main funding source(s): MPL received the Catalan Society of Cardiology Research Grant in 2019 and 2020 (Catalonia, Spain); the Josep Font Grant (2019-2022) from Hospital Clínic Barcelona (Catalonia, Spain). BACKGROUND: Left bundle branch pacing (LBBP) has emerged as an alternative to biventricular pacing. However, lack of a systematic stepwise application of the left bundle branch (LBB) capture criteria complicates implantation. OBJECTIVE: To define a stepwise application of LBBP capture criteria that will simplify implantation and ensure LBB capture. METHODS: A cohort of 24 patients from the LEVEL-AT trial who received LBBP and had electrocardiographic imaging (ECGI) at 45 days post-implant were included. The usefulness of ECG and electrogram based criteria to predict accurate LBB capture were analyzed. A two-step approach was developed to ensure LBB capture. The gold standard used to confirm LBB capture was the change in ventricular activation pattern and shortening in left ventricular activation time, assessed by ECGI. RESULTS: Twenty-two (91.6%) patients showed LBBP capture on ECGI. All patients fulfilled pre-screwing requisites: lead in septal position in left-oblique projection and W paced morphology in V1. In the first step, presence of either right bundle branch conduction delay pattern (qR or rSR in V1) or left bundle branch capture Plus (QRS ≤120ms) resulted in 95% sensitivity and 100% specificity to predict LBB capture, with an accuracy of 95.8%. In the second step, the presence of selective capture (100% specificity, only 41% sensitivity) or a spike-R<80ms (100% specificity, sensitivity 46%) ensured 100% accuracy to predict LBBP capture. CONCLUSIONS: Stepwise application of ECG and electrogram criteria ensured an accurate assessment of left conduction system capture. [Figure: see text] [Figure: see text]