Effect of bucladesine calcium combined with metoprolol on heart rate variability and cardiac function prognosis in heart failure patients with chronic arrhythmias

Background Heart failure (HF) with chronic arrhythmias is associated with autonomic dysfunction and poor outcomes. Heart rate variability (HRV) reflects autonomic dysfunction and predicts outcomes in HF. This study investigated whether adding bucladesine calcium to metoprolol improves HRV and cardiac function compared with metoprolol alone. Methods This single-center retrospective observational study included 87 patients with HF and chronic arrhythmia treated between January 2023 and April 2024. Patients received metoprolol tartrate alone (control group, n = 41) or bucladesine calcium combined with metoprolol (observation group, n = 46) for 12 weeks. The primary outcome was change from baseline in HRV time-domain parameters. Between-group differences were compared with 95% confidence intervals. Exploratory sensitivity and multivariable-adjusted analyses were performed. Results Baseline characteristics were comparable between groups. The combination group showed significantly greater improvements in ΔSDNN [mean difference 13.63 ms, 95% CI (4.17, 23.09), P = 0.005] and ΔRMSSD [8.94 ms, (2.80, 15.08), P = 0.005]. ΔLF/HF showed a borderline difference ( P = 0.043). ΔLVEF was significantly greater [4.86%, (1.31, 8.41), P = 0.008], as was ΔCO ( P = 0.019), while ΔLVEDd did not differ significantly ( P = 0.395). The overall response rate was numerically higher (89.1% vs. 78.0%) but not statistically significant ( P = 0.266). Adverse event rates were comparable. After multivariable adjustment, ΔSDNN ( P = 0.037) and ΔRMSSD ( P = 0.042) remained significant, while ΔLVEF became borderline ( P = 0.062). Conclusion Adding bucladesine calcium to metoprolol was associated with greater improvements in HRV time-domain parameters and LVEF, though effects were attenuated after covariate adjustment.