Autocapture algorithm behaviour in left bundle branch pacing

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. INTRODUCTION: Autocapture algorithms allow remote monitoring of patients, reducing the need for face-to-face hospital consultations and increasing patient safety. These algorithms are widely validated in patients with conventional pacing and are not recommended in His bundle pacing, but there is no information on its behaviour in left bundle branch pacing (LBBP). PURPOSE: The objective was to analyse the autocapture algorithm behaviour in LBBP and its differences with conventional pacing and manual thresholds during device first programming (acute phase), after 1-7 days (subacute phase) and 1-3 months later (chronic phase). METHODS: Prospective non-randomised single-centre comparative study. Consecutive patients with an indication for cardiac pacing were included. The implant was performed in the left bundle branch area or in the right ventricle endocardium (outflow tract or apex) at the discretion of the operator. LBBP was considered according to published criteria. Autocapture algorithm was activated in both groups whenever allowed by the device. The thresholds manual measurement was performed with the intracavitary electrogram and the surface electrocardiogram. RESULTS: Sixty patients were included, 40 with LBBP and 20 with conventional pacing. Baseline characteristics of patients are shown in Figure 1. The feasibility of the autocapture algorithm was more frequent in late phases, with a favourable trend toward bipolar pacing (Figure 2A). The failures in the activation of the algorithm were mainly due to the absence of adequate safety margins (90.9% in conventional pacing and 86.6% in LBBP), the rest were attributable to atrial tachyarrhythmias (9.1 and 6.7%, respectively) and electrical noise (remaining 6.7% in LBBP). In LBBP group, there were not statistically significant differences between manual and automatic thresholds except in subacute phase (unipolar) (Figure 2B), and both remained stable during follow-up (average increase of 0.46V). CONCLUSIONS: Autocapture algorithm is feasible in LBBP, with a favourable trend toward bipolar pacing. Automatic thresholds are similar to manual in patients with LBBP, and they remain stable during follow-up. [Figure: see text] [Figure: see text]