Heart failure with mid-range ejection fraction and the effect of β-blockers after acute myocardial infarction

There is currently an ongoing debate about the 'grey area' of heart failure with mid-range ejection fraction (HFmrEF). We evaluated characteristics, prognosis, and the effect of β-blockers on clinical outcomes in patients with HFmrEF after acute myocardial infarction (AMI). We included a total of 10,785 patients and divided them into three groups: EF 40-49% (HFmrEF; n = 2717; reference); EF < 40% (reduced EF [HFrEF]; n = 1194); and EF ≥ 50% (preserved EF [HFpEF]; n = 6874). The primary outcome was 2-year all-cause mortality. HFmrEF was intermediate between HFrEF and HFpEF for baseline characteristics. The risk of all-cause mortality was lower for HFmrEF patients compared to HFrEF patients (adjusted hazard ratio [HR] 0.710; 95% confidence interval [CI] 0.544-0.927; P = 0.012). However, HFmrEF patients tended to be at higher risk for 2-year all-cause mortality than HFpEF patients (adjusted HR 1.235; 95% CI 0.989-1.511; P = 0.090). β-blockers were associated with reductions in all-cause mortality for the entire cohort (adjusted HR 0.760; 95% CI 0.592-0.975; P = 0.031). β-blockers were effective in patients with HFrEF (adjusted HR 0.667; 95% CI 0.471-0.944; P = 0.022), tended to be effective in patients with HFmrEF (adjusted HR 0.665; 95% CI 0.426-1.038; P = 0.072), but not effective in patients with HFpEF (adjusted HR 0.852; 95% CI 0.548-1.326; P = 0.478; interaction P = 0.026). In conclusion, clinical profiles and prognosis of patients with post-AMI HFmrEF are largely intermediate between HFrEF and HFpEF. β-blockers reduced or tended to reduce 2-year all-cause mortality in patients with HFrEF or HFmrEF, respectively, but not those with HFpEF after AMI.