Comparative Outcomes of Heart Failure with Preserved vs. Mildly Reduced Ejection Fraction After Off-Pump Coronary Artery Bypass: A Single-Center Retrospective Study.

Background/Objectives: Heart failure (HF) phenotype based on left ventricular ejection fraction (LVEF) may be associated with outcomes after coronary revascularization, but data comparing patients with HF with preserved EF (HFpEF) and HF with mildly reduced EF (HFmrEF) undergoing coronary artery bypass grafting (CABG) remain limited. We compared clinical outcomes and longitudinal echocardiographic changes between patients with HFpEF and HFmrEF undergoing isolated off-pump CABG (OPCAB). Methods: We retrospectively analyzed 362 patients with HF who underwent isolated OPCAB between 2012 and 2020, including 273 with HFpEF (LVEF ≥ 50%) and 89 with HFmrEF (LVEF 41-49%). Overall survival was analyzed using Cox regression, and composite cardiovascular adverse events (CCAEs) and their individual components were analyzed using Fine-Gray models. Inverse probability of treatment weighting (IPTW) was used to reduce measured baseline confounding. Longitudinal echocardiographic changes were evaluated using linear mixed-effects models. Results: Patients with HFmrEF had higher baseline NT-proBNP levels and more adverse echocardiographic features than those with HFpEF. In IPTW-weighted analyses, HFmrEF was associated with all-cause mortality (HR, 3.09; 95% CI, 1.39-6.89; p = 0.006), HF readmission (sHR, 5.72; 95% CI, 2.12-15.45; p < 0.001), and CCAEs (sHR, 2.67; 95% CI, 1.37-5.19; p = 0.004). A significant group-by-time interaction was observed for LVEF (p < 0.001), with an early postoperative increase in LVEF in the HFmrEF group. Conclusions: In patients with HF undergoing isolated OPCAB at a single center, HFmrEF was associated with poorer long-term outcomes than HFpEF, although an early postoperative increase in LVEF was observed. These associations may partly reflect differences in baseline HF severity rather than EF category alone.