BACKGROUND: Left bundle branch area pacing (LBBAP) may be associated with greater improvement in left ventricular ejection fraction and reduction in death or heart failure hospitalization compared with biventricular pacing (BVP) in patients requiring cardiac resynchronization therapy. We sought to compare the occurrence of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) and new-onset atrial fibrillation (AF) in patients undergoing BVP and LBBAP. METHODS: The I-CLAS study (International Collaborative LBBAP Study) included patients with left ventricular ejection fraction ≤35% who underwent BVP or LBBAP for cardiac resynchronization therapy between January 2018 and June 2022 at 15 centers. We performed propensity score–matched analysis of LBBAP and BVP in a 1:1 ratio. We assessed the incidence of VT/VF and new-onset AF among patients with no history of AF. Time to sustained VT/VF and time to new-onset AF was analyzed using the Cox proportional hazards survival model. RESULTS: Among 1778 patients undergoing cardiac resynchronization therapy (BVP, 981; LBBAP, 797), there were 1414 propensity score–matched patients (propensity score–matched BVP, 707; propensity score–matched LBBAP, 707). The occurrence of VT/VF was significantly lower with LBBAP compared with BVP (4.2% versus 9.3%; hazard ratio, 0.46 [95% CI, 0.29–0.74]; P 3 episodes in 24 hours) was also significantly lower with LBBAP compared with BVP (0.8% versus 2.5%; P =0.013). Among 299 patients with cardiac resynchronization therapy pacemakers (BVP, 111; LBBAP, 188), VT/VF occurred in 8 patients in the BVP group versus none in the LBBAP group (7.2% versus 0%; P 30 s was significantly lower with LBBAP than with BVP (2.8% versus 6.6%; hazard ratio, 0.34 [95% CI, 0.16–0.73]; P =0.008). The incidence of AF lasting >24 hours was also significantly lower with LBBAP than with BVP (0.7% versus 2.9%; P =0.015). CONCLUSIONS: LBBAP was associated with a lower incidence of sustained VT/VF and new-onset AF compared with BVP. This difference remained significant after adjustment for differences in baseline characteristics between patients with BVP and LBBAP. Physiological resynchronization by LBBAP may be associated with lower risk of arrhythmias compared with BVP.

Background: Conventional permanent His Bundle pacing (PHBP) can be challenging and associated with high fluoroscopy exposure. The aim of this study was to assess the feasibility and safety of performing low fluoroscopy PHBP using 3-dimensional electroanatomic mapping and comparing outcomes with conventional fluoroscopy guided PHBP implants. Methods: PHBP was performed at 2 centers using electroanatomic mapping-guided low fluoroscopy implantation in 10 patients using a novel protocol (group 1) and conventional fluoroscopy guided implantation in 20 patients (group 2). The primary end point was feasibility of achieving PHBP with low/zero fluoroscopy and safety end points included total radiation exposure (fluoroscopy time and dose area product), procedure-related complications associated with lead implantation or need for lead revisions. Results: PHBP was successful in 9 of 10 patients (90%) in group 1 and 100% successful in the group 2 patients. The mean His lead fluoroscopy time was significantly lower in group 1 (0.2±0.2 minutes) compared with 8±7 minutes in group 2 ( P =0.002) as was the total fluoroscopy time (0.8±0.3 versus 13±8 minutes, P =0.003) and the dose area product (96±83 versus 1531±923 microGy/m ² , P =0.003). The HB capture threshold was lower in group 1 (0.7±0.4 at 1 ms) compared with patients in group 2 (1.15±0.7 at 1 ms) P =0.04. There were no procedure-related complications or lead dislodgements in either group. There was an increase in HB capture threshold in 1 patient (5%) in group 2 at 1-month follow-up. Conclusions: Electroanatomic mapping-guided PHBP is feasible can be performed safely and results in a significant reduction in fluoroscopy duration and exposure.