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.