ABSTRACT
Heart failure (HF) research and guidelines have primarily focused on two major groups defined by left ventricular ejection fraction (LVEF)—HF with preserved ejection fraction (HFpEF) and HF with reduced ejection fraction (HFrEF). This chapter discusses two groups of patients with HF that have not been clearly addressed in the existing evidence base. HF with recovered ejection fraction (HFrecEF) refers to the subset of HF patients with low LVEF that subsequently improved to normal or near-normal LVEF. Heart failure with midrange EF (HFmrEF) refers to the subset of patients with HF and an LVEF in the border zone between HFpEF and HFrEF, currently defined as LVEF between 40% and 49%. This chapter reviews the characteristics, clinical course, and treatments of HFrecEF and HFmrEF. The topics discussed include the reliability of LVEF measurements, predictors of LVEF recovery, transitions in LVEF across categories including HFmrEF, and the heterogeneity of phenotypes within HFrecEF and within HFmrEF.
