Comparison of ventricular arrhythmic burden in patients with implantable cardiac devices undergoing cardiac resynchronisation therapy upgrade: biventricular pacing or left bundle branch area pacing?

Abstract Background Cardiac resynchronisation therapy (CRT) represents the standard treatment for heart failure with reduced ejection fraction. However, conventional biventricular pacing (BIVP) is associated with less physiological ventricular activation and potential pro-arrhythmic effects. Left bundle branch area pacing (LBBAP) is a novel technique that restores more physiological conduction by directly capturing the His-Purkinje conduction system. Limited data directly compare arrhythmic outcomes between LBBAP and BIVP in the specific context of implantable cardiac device upgrade; moreover, this represents a homogeneous population because the main reason for their upgrade is pacemaker-induced cardiomyopathy (PICM). Methods A retrospective analysis was conducted of 68 consecutive patients (45 BIVP, 23 LBBAP) undergoing CRT upgrade between January 2019 and September 2024 at two electrophysiology centres. The primary endpoint was composite arrhythmic burden at 12 months of follow-up, defined as the presence of premature ventricular complexes greater than the median burden of the study population (4 per hour), non-sustained ventricular tachycardia or delivery of antitachycardic therapy. Secondary endpoints included analysis of individual burden components. Multivariable logistic regression was used for adjustment of confounders. Results Composite arrhythmic burden was significantly lower in the LBBAP group (39.1% vs 68.9%, p=0.036; crude odds ratio 0.290, 95% confidence interval: 0.102–0.828), representing a 71% risk reduction. The protective effect was maintained after adjustment for age, sex, ischaemic cardiomyopathy and prevention type (adjusted odds ratio 0.328, 95% confidence interval: 0.104–0.989, p=0.048). All individual components demonstrated consistent favourable trends towards LBBAP without individually reaching statistical significance (premature ventricular complexes 4 per hour: 35.0% vs 52.5%, p=0.274; non-sustained ventricular tachycardia: 36.4% vs 48.9%, p=0.310; antitachycardic therapies: 0% vs 7.7%, p=0.557). Notably, no antitachycardic therapies were delivered in the LBBAP group compared with the BIVP group. Conclusions Left bundle branch area pacing significantly reduces composite arrhythmic burden compared with conventional biventricular pacing in the setting of device upgrade. These findings could lead to preferential adoption of LBBAP in patients with PICM undergoing CRT upgrade, when technically feasible.Composite Arrhythmic BurdenComponents of Arrhythmic Burden