The Specific Value of Upgrading to Left Bundle Branch Pacing in Patients with Pacing-Induced Cardiomyopathy or Non-Pacing-Induced Cardiomyopathy: A Retrospective Study

Abstract

Aims: Left bundle branch pacing (LBBP) upgrade can improve cardiac function and clinical outcomes in patients with pacing-induced cardiomyopathy (PICM), but the specific value especially compared with the level before right ventricular pacing (RVP) in patients with PICM and non-pacing-induced cardiomyopathy (Non-PICM) is still unknown. Methods: This study retrospectively enrolled 108 patients with LBBP upgrade (38 patients with PICM and 70 patients with Non-PICM). PICM patients were defined as patients who had a normal left ventricular function and a > 10% decrease in LVEF after RVP, among patients experiencing > 40% RVP, when other organic heart diseases were excluded. Non-PICM patients were defined as patients requiring pacemaker upgrades with non-decreased cardiac function reasons, such as battery exhaustion, pacing system infection, and right ventricular lead failure. All upgrade patients experienced three stages: before RVP (Pre-RVP), before LBBP upgrade (Pre-LBBP), and after LBBP upgrade (Post-LBBP). QRS duration (QRSd) , lead parameters, echocardiographic indicators, and clinical outcomes evaluation were recorded at multiple time points. Univariable analysis of variance and Mann-Whitney U-tests for repeated measures were used to assess the effects of the LBBP upgrade. Results: At the follow-up of 12 months, for PICM patients, left ventricular ejection fraction (LVEF) significantly increased from 36.6 ± 7.2% at Pre-LBBP to 51.3 ± 8.7% after LBBP upgrade (P < 0.001), and left ventricular end-diastolic diameter (LVEDD) significantly decreased from 61.5 ± 6.4mm at Pre-LBBP to 55.2 ± 6.5mm after LBBP upgrade (P < 0.001), besides, New York Heart Association (NYHA) classification improved from 3.16 ± 0.82 at Pre-LBBP to 1.76 ± 0.88 after LBBP upgrade (P < 0.001), but they all failed to restore the level of the initial status before RVP (LVEF: 51.3 ± 8.7% vs 60.3 ± 7.6%, P < 0.001) (LVEDD: 55.2 ± 6.5mm vs 49.7 ± 6.1mm, P < 0.001) (NYHA:1.76 ± 0.88 vs 1.11±0.31, P < 0.001). Furthermore, for PICM patients, the number of moderate-to-severe heart failure (HF) (NYHA III-IV) and diuretics used after the LBBP upgrade also could not restore the level before RVP (P = 0.002 and P = 0.004). At the follow-up of 12 months, Non-PICM patients after the LBBP upgrade had no significant improvement in LVEF, LVEDD, NYHA classification (LVEF: P = 0.521; LVEDD: P = 0.383; NYHA classification: P = 0.279) and no difference compared with Pre-RVP (LVEF: P = 0.559; LVEDD: P = 0.952; NYHA classification: P = 0.942). Conclusion: LBBP upgrade effectively improved the cardiac function and clinical outcomes in PICM patients but failed to restore the functional levels before RVP. For Non-PICM patients, the cardiac function and clinical outcomes after the LBBP upgrade had no significant difference when compared to Pre-RVP and Pre-LBBP.