Heart Failure With Midrange Ejection Fraction-What Is It, If Anything?

The patient cohort with left ventricular ejection fractions (LVEFs) of 41%-49%, which has been defined as heart failure with midrange ejection fraction (HFmrEF), represent a significant proportion of the heart failure (HF) population. Despite the clear cutoffs established by different society guidelines, confusion remains regarding the exact significance of midrange LVEF within the HF syndrome. Patients with LVEF 41%-49% represent a heterogeneous group of patients sharing pathophysiologic mechanisms, biomarker profiles, comorbidities, and clinical characteristics with patients with preserved and reduced LVEF. In this clinical review, we discuss the underlying pathophysiologic mechanisms that culminate in the clinical syndrome of HF and contribute to the disparities observed between HFpEF, HFrEF, and HFmrEF. We highlight differences and similarities in clinical characteristics and imaging features between HFpEF and HFrEF in an effort to disentangle the heterogeneous group of patients with midrange LVEF, but ultimately we conclude that LVEF should be seen as simply one important element of a continuum throughout the HF syndrome, and that although is useful, it is an oversimplification, because HF syndrome is more of a continuum. The underlying pathophysiology, etiology, and comorbidities of patients presenting with HF is becoming ever more important as the limitations of a classification solely based on LVEF are being better recognised, and as patient-specific personalisation of care is becoming ever more important.