Definition of Heart Failure with Reduced Ejection Fraction (HFrEF)
Heart Failure with Reduced Ejection Fraction (HFrEF) is defined as symptomatic heart failure with a left ventricular ejection fraction (LVEF) ≤40%. 1, 2
Core Diagnostic Criteria
HFrEF requires the presence of three essential components:
- Typical symptoms including breathlessness, ankle swelling, fatigue, exertional intolerance, and fluid retention 1
- Clinical signs such as elevated jugular venous pressure, pulmonary crackles, peripheral edema, S3 gallop rhythm, orthopnea, and hepatojugular reflux 1
- Documented LVEF ≤40% measured by echocardiography, radionuclide technique, or cardiac magnetic resonance imaging 1
Distinction from Other Heart Failure Types
The classification by ejection fraction creates three distinct categories:
- HFrEF: LVEF ≤40% 1, 2
- HFmrEF (Heart Failure with Mid-Range EF): LVEF 40-49% (previously called the "grey area") 1
- HFpEF (Heart Failure with Preserved EF): LVEF ≥50% 1
Clinical Significance of the HFrEF Definition
This specific LVEF cutoff of ≤40% is critically important because only patients meeting this criterion have demonstrated mortality and morbidity benefits from evidence-based pharmacological and device therapies in randomized controlled trials. 1, 2
The distinction matters for treatment decisions:
- Guideline-directed medical therapy (GDMT) including ACE inhibitors/ARBs/ARNIs, beta-blockers, mineralocorticoid receptor antagonists, and SGLT2 inhibitors has proven efficacy only in HFrEF 1, 3
- Device therapies such as implantable cardioverter-defibrillators and cardiac resynchronization therapy are indicated specifically for HFrEF patients with LVEF ≤35% 4, 3
- No therapies have yet demonstrated mortality benefit in HFpEF, making the distinction between HFrEF and HFpEF therapeutically crucial 1
Underlying Pathophysiology
HFrEF results from structural and/or functional cardiac abnormalities causing:
- Impaired ventricular systolic function leading to reduced cardiac output 1
- Elevated intracardiac pressures at rest or during stress 1
- Pathological left ventricular remodeling and progressive dilatation 5
The most common causes include myocardial abnormalities, though valvular disease, pericardial disease, endocardial abnormalities, and rhythm/conduction disturbances can also produce HFrEF 1
Important Clinical Caveats
A critical pitfall is assuming all patients with low EF have HFrEF—the diagnosis requires both the reduced EF AND clinical symptoms/signs of heart failure. 1
- Patients with asymptomatic systolic LV dysfunction (LVEF ≤40% without symptoms) represent a precursor stage to HFrEF, not HFrEF itself 1
- Recognition of this asymptomatic stage is important because initiating treatment at this precursor stage may reduce mortality 1
- Some patients previously diagnosed with HFrEF may experience improvement in EF to >40% with treatment—these patients with "HF with improved EF" may represent a clinically distinct subgroup 1