The STICH trial and its 10-year extension highlighted the benefits of coronary artery bypass grafting (CABG) in stable multivessel coronary artery disease for patients with heart failure (HF) and reduced ejection fraction (HFrEF). In 2014, the European Society of Cardiology’s heart failure guidelines introduced a new HF phenotype based on ejection fraction, categorizing as midrange ejection fraction (HFmrEF) those with EF between 40-49%. Evidence on CABG outcomes in patients with HFmrEF remains limited. The STICH study included only patients with HFrEF (EF<35%), and previous observational studies did not separately analyze this HFmrEF group.

In this study, a retrospective analysis of the Veterans Health Affairs (VHA) national registry from 2010 to 2019 was conducted to evaluate CABG outcomes in patients with stable ischemic heart disease. Patients were categorized into preserved EF (control group), HFmrEF (EF >40% and <55%), and HFrEF. All-cause mortality and the need for new hospitalization for HF and/or recurrent myocardial infarction were compared between groups using a Cox model and recurrent events analysis, respectively. Among 6533 patients, 1715 (26.3%) had HFmrEF, and 566 (8.6%) had HFrEF; the remaining 4252 (65.1%) with normal EF comprised the control group. Patients with HFrEF were more likely to have diabetes mellitus (59%), insulin therapy (36%), and a history of myocardial infarction (31%). Anemia was significantly more prevalent in HFrEF patients (49%), along with lower serum albumin (mean 3.6 mg/dL). Compared with the control group, a significantly higher mortality risk was observed in the HFmrEF (HR = 1.3) and HFrEF (HR = 1.5) groups. HFmrEF patients were also at higher risk of myocardial infarction (HR = 1.2; p = 0.04), and the risk of HF-related hospitalization was significantly higher in HFmrEF (HR = 4.1) and HFrEF patients (HR = 7.2).

The authors conclude that heart failure in patients with moderately reduced ejection fraction has a negative impact on survival after CABG compared with patients with preserved EF. Furthermore, these patients experience higher rates of myocardial infarction and the need for readmission due to HF.

COMMENTARY:

Ischemic heart disease accounts for nearly 70% of all HF cases, and one-third of coronary artery disease patients have HF. From these data alone, the significance of identifying any factor that can alter prognosis in these ischemic heart disease patients with reduced EF is evident. Age, left ventricular EF, the number and type of affected vessels, myocardial viability, associated mitral disease, revascularization quality, and adherence to medical therapy, among other factors, influence CABG outcomes. The STICH trial previously demonstrated that patients with EF <35% assigned to CABG had lower rates of cardiovascular mortality and HF readmissions than those in the medical therapy group, with these results extending over a 10-year follow-up. Separately, there is sufficient literature indicating that CABG offers superior survival outcomes compared with percutaneous intervention (PCI) in patients with HFrEF (LVEF <40%). However, it is worth recalling the disappointing results of PCI compared with medical therapy in the recent REVIVED study in patients with severe stable coronary artery disease and severe left ventricular dysfunction (LVEF <35%).

This study by Deo et al. provides invaluable, novel insights into this subgroup of HFmrEF patients, confirming a worse prognosis after CABG compared with patients with preserved EF. Until now, there has been limited and conflicting evidence in this relatively new HFmrEF category. Another noteworthy aspect of this study is its analysis of a large, homogeneous cohort (99% male) of CABG patients appropriately categorized into three EF-based groups. This careful classification reduces the heterogeneity found in traditional studies analyzing this HFmrEF subgroup.

Three critical aspects are highlighted in these findings: first, revascularized HFmrEF patients present a higher risk of myocardial infarction, HF-related hospitalizations, and reduced survival compared with those with preserved EF. Five-year survival was 74% in the HFmrEF group, compared with 82% for normal EF patients and 65% for HFrEF patients—figures lower than those reported in previous clinical trials. This discrepancy between “real-world” data and clinical trials’ outcomes persists. Second, nearly 80% of patients received at least three grafts, but only 6% had more than one arterial graft, reflecting an extremely low use of multiple arterial grafts. Third, only 30% of HFmrEF and HFrEF patients were prescribed optimal HF medical therapy at discharge, mainly due to a lack of angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, or aldosterone antagonists. With new evidence, the inclusion of empagliflozin is now standard in these patients’ pharmacological regimen, though it was not included in this series as it predates 2019.

To conclude, improving clinical outcomes in ischemic heart disease patients with HF requires two priorities: 1) multiple arterial grafting (bilateral internal mammary artery or a combination of internal mammary and radial artery grafts), which benefits long-term results; 2) optimal medical therapy from the start of postoperative care and throughout follow-up, as recommended by major HF management guidelines. There are no excuses; the difficult part of our job is not to fulfill our duty, but to know about it.

REFERENCE:

Deo SV, Sundaram V, Sahadevan J, Selvaganesan P, Mohan SM, Rubelowsky J, Josephson R, et al. Outcomes of coronary artery bypass grafting in patients with heart failure with a midrange ejection fraction. J Thorac Cardiovasc Surg. 2023 Jan;165(1):149-158.e4. doi: 10.1016/j.jtcvs.2021.01.035.