Combination of current and new electrocardiographic-based criteria: a novel score for the discrimination of left bundle branch capture

AIMS: Most of the criteria used to diagnose direct capture of the left bundle branch (LBB) have never been validated in an external sample. We hypothesized that lead aVL might add relevant information, and the combination of several electrocardiograph (ECG)-based criteria might discriminate better LBB capture from left ventricular septal (LVS) capture, than each criterion separately. METHODS AND RESULTS: Single-centre study involving all consecutive patients who received LBB area pacing. LBB capture was defined according to QRS morphology transition criteria during decremental pacing. Multivariate logistic regression analysis was performed to develop a predictive score for LBB capture. A total of 71 patients with confirmed LBB capture were analysed. The optimal cut-off values of R wave peak time (RWPT) in lead V6 (V6-RWPT) and V6-V1 interpeak interval for the discrimination of LBB capture were <83 ms and ≥33 ms, respectively. The RWPT in lead aVL (aVL-RWPT) showed a good discrimination power for the differential diagnosis of LBB capture and LVS capture. The optimal value for aVL-RWPT was 79 ms [sensitivity (SN) and specificity (SP) of 71.2% and 88.4%, respectively]. A new score, with a good diagnostic performance (area under the curve of 0.976), was constructed gathering the information from V6-RWPT, aVL-RWPT, and V6-V1 interpeak interval. The optimal score of 3 points showed a SN and SP of 89.2% and 100%, respectively for the differentiation of LBB capture. CONCLUSIONS: ECG-based criteria are useful to confirm the capture of the LBB. The combination of V6-RWPT, aVL-RWPT, and V6-V1 interpeak interval values demonstrated better diagnostic performance than isolated measurements.