Classification of EF 45-50%
An ejection fraction of 45-50% is classified as heart failure with mildly reduced ejection fraction (HFmrEF), not HFpEF. 1
Definitive EF Classification Thresholds
According to the 2022 AHA/ACC/HFSA guidelines, the classification is straightforward:
Therefore, an EF of 45-50% falls squarely within the HFmrEF range (41-49%), with only EF values of exactly 50% or higher qualifying as HFpEF. 1, 2
Clinical Implications of This Classification
Why This Distinction Matters
The HFmrEF category represents patients on a dynamic trajectory—they may be improving from HFrEF or deteriorating toward it. 1 A single EF measurement at one time point is inadequate; you must evaluate the trajectory of LVEF over time and identify the underlying cause. 1
Diagnostic Requirements Beyond EF
For HFmrEF diagnosis, you need more than just the EF number and symptoms: 1, 2
- Elevated natriuretic peptides (BNP >35 pg/mL or NT-proBNP >125 pg/mL) 2
- Echocardiographic evidence of elevated filling pressures (E/e' ≥15) or diastolic dysfunction 1, 2
- Structural heart disease (increased left atrial volume index or LV mass index) 1
Treatment Approach
Patients with HFmrEF should be treated similarly to HFrEF patients, as evidence suggests therapies effective in HFrEF (beta blockers, ACE inhibitors/ARBs, mineralocorticoid receptor antagonists, SGLT2 inhibitors) also benefit HFmrEF patients. 3, 4, 5
Critical Caveat
If a patient's EF improves from <40% to 45-50%, they are classified as HFimpEF (heart failure with improved EF), not HFmrEF. 1 These patients should continue HFrEF treatment despite the improved EF, as discontinuation can lead to deterioration. 1 The guideline explicitly notes uncertainty about how to treat patients who improve from HFmrEF (41-49%) to ≥50%. 1