2. Definition of HF

HF is a complex clinical syndrome in which abnormal heart function results in, or increases the subsequent risk of,

• HF with reduced ejection fraction (HFrEF): LVEF ≤ 40%.

This recognizes the uncertainty that often occurs in the measurement of LVEF, the evolving landscape of current clinical trials enrolling patients with different LVEF cutoffs, and evolving ways to evaluate cardiac function. Echocardiography is the most accessible method to evaluate LVEF in Canada. Estimates of ejection fraction (EF) might vary because of patient or technical factors, as well as therapy or clinical deterioration. The previously stated EF cut points recognize that there is a large body of evidence related to treatment for patients with HFrEF and emerging evidence for patients with HFpEF and HFmEF. HFmEF might represent many different phenotypes, including patients transitioning to and from HFpEF. The term “recovered EF” has also been added to the literature,^[5] referring to patients who previously had HFrEF and now have an EF > 40%. These patients might eventually be classified in the HFmEF or HFpEF group but deserve recognition because despite their recovered imaging parameters, they might still carry additional risk for adverse clinical events. Uncertainty exists on strategies for management of individuals with HFmEF including surveillance, treatment, and prognosis.

2.1 Ejection fraction terminology

This guideline uses the following terms:

• HF with preserved ejection fraction (HFpEF): LV ejection fraction (LVEF) ≥ 50%;
• HF with a mid-range ejection fraction (HFmEF): LVEF 41%-49%;

2.2 Symptoms terminology

Symptoms are described using the New York Heart Association (NYHA) functional class I-IV (Table 1).