His Bundle Pacing Improves Left Ventricular Function in Patients with Bradyarrhythmia or Tachy-Brady Syndrome and Permanent Atrial Fibrillation: A Retrospective Analysis

<b>Background</b>: Permanent atrial fibrillation (AF) frequently coexists with heart failure (HF), leading to structural remodeling and progressive sinus node dysfunction. As the condition advances, bradyarrhythmia or tachy-brady syndrome may develop. Right ventricular pacing and cardiac resynchronization therapy may impair left ventricular function due to non-physiological ventricular activation. His bundle pacing (HBP) offers a more physiological alternative. This study evaluates HBP's impact on left ventricular function in patients with bradyarrhythmia or tachy-brady syndrome and permanent AF. <b>Methods</b>: A retrospective analysis included 41 patients with HF who underwent HBP implantation due to bradyarrhythmia or tachy-brady syndrome in permanent AF. LVEF, LVEDD, and MR were assessed before and after implantation, alongside the impact of comorbidities (e.g., ischemic heart disease and chronic kidney disease) and pharmacotherapy (digoxin, metoprolol, and mineralocorticoid receptor antagonists). Statistical analyses included the Wilcoxon test (LVEF and MR), paired Student's <i>t</i>-test (LVEDD), Spearman's correlation, and linear regression. Significance was set at <i>p</i> < 0.05. <b>Results</b>: HBP significantly improved LVEF (median increase: 14.58%; <i>p</i> < 0.001) and reduced LVEDD (mean reduction: 5.41 ± 1.30 mm; <i>p</i> < 0.001). MR severity also decreased (<i>p</i> < 0.001). Patients with lower baseline LVEF showed greater improvement in this parameter after HBP (ρ = -0.671, <i>p</i> < 0.001). Only chronic kidney disease was associated with a lower likelihood of MR improvement (<i>p</i> = 0.0486). <b>Conclusions</b>: HBP improves left ventricular function and reduces MR severity in patients with permanent AF and bradyarrhythmia or tachy-brady syndrome. A low baseline LVEF was the strongest predictor of subsequent improvement. Further studies are needed to confirm long-term benefits.