New-Onset Left Ventricular Dysfunction After Left Bundle Branch Pacing

BACKGROUND Left bundle branch pacing (LBBP) provides stable pacing parameters and has been suggested as an alternative for right ventricular pacing and cardiac resynchronization therapy. OBJECTIVES The aim of the study was to assess the incidence and etiology of new-onset left ventricular dysfunction (NOLVD) following LBBP in patients with baseline normal left ventricular (LV) function and cardiomyopathy patients with normalized LV function. METHODS Patients undergoing successful LBBP for symptomatic bradyarrhythmia or as an alternative to cardiac resynchronization therapy were included. Normalization of LV function was defined as improvement in LV ejection fraction to >= 50%. Patients with baseline normal LV function and those with recovered LV function after LBBP constituted the study group. Loss of conduction system capture (LOCSC) was defined as complete or partial loss of right bundle branch delay pattern along with inability to demonstrate capture transition during threshold assessment. RESULTS A total of 426 patients were included; 59% (n = 250) had baseline normal LV function (group I) and 41% (n = 176) had recovered LV function after LBBP (group II). Mean follow-up duration of 28.3 f 16.7 months. NOLVD was noted in 3.75% (n = 16; group I, n = 5, and group II, n = 11) of patients. The etiologies for NOLVD were LOCSC in 62.5% (n = 10), suboptimal atrioventricular (AV) delay in 18.7% (n = 3), atrial fibrillation in 6.3% (n = 1), and idiopathic in 12.5% (n = 2). LOCSC occurred at a mean interval of 9.2 f 6.4 months after the initial implantation. Reinterventions (n = 6) including lead repositioning, AV delay optimization, and AV junction ablation resulted in renormalization of LV function in all 6 patients. CONCLUSIONS Periodic assessment in device clinic is required because NOLVD from reversible causes can occur during follow-up in patients after LBBP. (JACC Clin Electrophysiol. 2024;10:2494-2502) (c) 2024 by the American College of Cardiology Foundation.