Heart Failure With Mid-Range (Borderline) Ejection Fraction: Clinical Implications and Future Directions.

Heart failure (HF) with borderline ejection fraction was first defined in 2013 in the American College of Cardiology/American Heart Association guidelines as the presence of the typical symptoms of HF and a left ventricular ejection fraction (LVEF) of 41% to 49%. In 2016, the European Society of Cardiology specified HF with mid-range ejection fraction (HFmrEF) as LVEF of 40% to 49%. This range of LVEF is less well studied compared with HF with preserved ejection fraction (HFpEF) and HF with reduced ejection fraction (HFrEF). Although there are effective, guideline-directed medical therapies for patients with HFrEF, no therapies thus far show measurable benefit in HFpEF. Patients with HFmrEF have a clinical profile and prognosis that are closer to those of patients with HFpEF than those of HFrEF, with certain distinctions. Whether these patients represent a unique and dynamic HF group that may benefit from targeted therapies known to be beneficial in patients with HFrEF, such as neurohormonal blockade, requires further study. This review summarizes what is known about the clinical epidemiology, pathophysiology, and prognosis for patients with HFmrEF and how these features compare with the more well-studied HF groups. Although recommended treatments currently focus on aggressive management of comorbidities, we summarize the studies that identify a potential signal for beneficial therapies. Future studies are needed to not only better characterize the HFmrEF population but to also determine effective management strategies to reduce the high cardiovascular morbidity and mortality burden on this phenotype of patients with HF.