Abstract
The introduction of heart failure (HF) with mid-range ejection fraction (HFmrEF) as a distinct phenotype has achieved its aim of stimulating research into the underlying characteristics, pathophysiology and treatment of HF patients with left ventricular ejection fraction of 40-49 %. Comparison of clinical characteristics, comorbidities, outcomes and prognosis among patients with HF with preserved ejection fraction, HFmrEF and HF with reduced ejection fraction allowed consideration of HFmrEF as an intermediate phenotype, which often resembles HF with reduced ejection fraction more than HF with preserved ejection fraction. The latest findings suggest that patients with HFmrEF seem to benefit from therapies that have been shown to improve outcomes in HF with reduced ejection fraction.