AV block occurrence in normal AV conduction CRT fusion pacing: single center experience

Abstract Background Cardiac resynchronization therapy (CRT) in sinus rhythm (SR) currently involves mandatory biventricular pacing with often simultaneous ventricular pacing (interval VV=0). While LV-only CRT has shown comparable efficacy, debates regarding its use continue. Main criticism is AV block occurrence in order to benefit fusion CRT pacing. Despite proved benefits, data on the incidence of AV block in patients receiving LV-only CRT without RV lead remain limited. AV block occurrence in such population could compromise CRT and require device upgrades to a biventricular system to ensure hemodynamic stability. Objectives To assess the incidence of AV block over long-term follow-up and the need for true biventricular pacing in patients with preserved baseline AV conduction undergoing LV-only CRT without an RV lead. Methods A cohort of heart failure patients with preserved baseline AV conduction who met CRT-P indications received a dual-chamber DDD pacing system with leads in the right atrium (RA) and left ventricle (LV), omitting the RV lead. The primary endpoint was the incidence of AV block during long-term follow-up, evaluating the need for potential upgrades to a biventricular pacing system. Dosages of beta-blockers or ivabradine were optimized to stabilize the PR interval and promote fusion pacing. Results The study enrolled 135 participants with non-ischemic CRT fusion pacing and normal AV conduction, of which 87 CRT patients without RV lead were analyzed as final subgroup. Demographic data: 45 male, mean age 62 ± 11 years, with an average follow-up duration of 45 ± 19 months. During follow-up, two patients (2,3%) developed AV block requiring upgrades to biventricular pacing. The first patient, aged 60 years, developed AV block 27 months post-implant, while the second patient, aged 83 years, developed AV block at 107 months post-implant. No additional predictors of AV block were identified, and baseline characteristics were otherwise similar across patients. Of note, none of the other patients included in the study needed to pace RV for AV block which made the final incidence 1,5%. Long-term follow-up revealed a low incidence of heart failure progression-related mortality at 2.2%. Among the three patients who died, one developed severe aortic stenosis, while the other two died 9 and 7 years after CRT implantation, respectively. Conclusions In patients with preserved AV conduction undergoing LV-only CRT, the incidence of AV block necessitating device upgrade to biventricular pacing was low (1,5%) and does not influence the outcome. These findings suggest that LV-only CRT may be a option for nonischemic patients with preserved AV conduction.