86 Site of atrio-ventricular conduction block: insights from left bundle branch pacing (SAVE-LBBP)

IntroductionHis-Purkinje conduction system being a physiological pacing has evolved over the years and has overcome the complications associated with right ventricular pacing to a great extent due to normal ventricular activation [1]. Left bundle branch pacing (LBBP) outperforms his bundle pacing (HBP) with regards to fixation and sensing challenges [2]. LBBP provides synchronized activation of the left ventricle and can correct distal conduction system disease effectively at a lower pacing threshold. Although the advantages of physiological conducting system are well analyzed, limited data is available on assessing the level and site of conduction block in patients with both nodal and infranodal atrio-ventricular block.ObjectivesOur study was designed to assess the level of block in patients with symptomatic nodal and infranodal atrio-ventricular (AV) block and the feasibility of maximal correction by left bundle branch pacing. Clinical, electrocardiographic responses were also assessed during follow-up.MethodsIt is a prospective, single-center, single-operator, observational study. Consecutive patients with symptomatic AV block requiring permanent pacemaker implantation were included in the study after obtaining informed consent(n=89). Intracardiac electrograms and 12-lead electrocardiography were recorded continuously using electrophysiology system. LBB pacing was done using C315 sheath and 3830 select secure pacing lead. Mapping of the His-bundle region was done using 3830 pacing lead/quadripolar catheter to assess the level of block. Based on intracardiac electrograms four different sites of block were identified (a)Nodal – HB electrogram showing AH block and LB potential noted on pacing lead electrogram (b)Penetrating portion of HB(PHB) – HB electrogram showing split His signal (H and H’) and LB potential on pacing lead electrogram (c)Branching portion of HB(BHB) – HB electrogram showing HV block and LB potential on pacing lead electrogram (d) indeterminate with HB electrogram showing HV block without LB potential on pacing lead electrogram (Figure 1).ResultsLBBP could be successfully done in 87 out of 89 patients (97.7% acute success rate). Mean age 64±11years. Mean duration of follow up 12±7months (range 1-24). 17% had left ventricular systolic dysfunction (ejection fraction