Classification of Heart Failure by Ejection Fraction
Heart failure is classified into three distinct categories based on left ventricular ejection fraction (LVEF): HFrEF (LVEF ≤40%), HFmrEF (LVEF 41-49%), and HFpEF (LVEF ≥50%), with each category requiring different diagnostic criteria and therapeutic approaches. 1, 2
The Three Primary Heart Failure Categories
Heart Failure with Reduced Ejection Fraction (HFrEF)
HFrEF is defined as LVEF ≤40% and represents the category with the most robust evidence for mortality-reducing therapies. 2, 3, 4
This phenotype typically presents with left ventricular dilation and systolic dysfunction, most commonly caused by ischemic heart disease or dilated cardiomyopathy. 1, 3
Four-pillar guideline-directed medical therapy (ARNI/ACE-inhibitor, beta-blocker, mineralocorticoid receptor antagonist, and SGLT2 inhibitor) has proven mortality benefit in this population. 3
Heart Failure with Mildly Reduced Ejection Fraction (HFmrEF)
HFmrEF is defined as LVEF 41-49% and represents a heterogeneous group that includes patients with improving HFrEF or deteriorating HFpEF. 1, 2
This category was specifically created to distinguish patients on a dynamic trajectory—serial LVEF measurements are essential because a single measurement is inadequate to determine whether the patient is improving or worsening. 2, 5
Patients with HFmrEF share more clinical features with HFrEF than HFpEF, particularly the high prevalence of ischemic heart disease, and should be treated with the same four-pillar GDMT as HFrEF. 3, 5
Beyond LVEF, HFmrEF diagnosis requires elevated natriuretic peptides (BNP >35 pg/mL or NT-proBNP >125 pg/mL) and/or echocardiographic evidence of structural heart disease such as elevated E/e′ ≥15, increased left atrial volume index, or increased left ventricular mass index. 1, 2, 3
Heart Failure with Preserved Ejection Fraction (HFpEF)
HFpEF is defined as LVEF ≥50% and now accounts for more than 50% of all heart failure cases, with outcomes comparable to HFrEF. 1
Patients with HFpEF typically lack left ventricular dilation but exhibit increased wall thickness, left atrial enlargement, and elevated filling pressures reflecting diastolic dysfunction. 1, 3, 6
The diagnosis requires symptoms and signs of heart failure plus elevated natriuretic peptides and/or objective evidence of elevated filling pressures (E/e′ ≥15 or invasive hemodynamic confirmation). 1, 3
HFpEF is more common in women, older adults, and patients with cardiometabolic diseases including hypertension, diabetes, obesity, and chronic kidney disease. 1
Until recently, treatment was limited to symptom management with diuretics and comorbidity control, but SGLT2 inhibitors have now demonstrated reduced cardiovascular death and heart failure hospitalizations in this population. 1, 3
Additional Important Category: Heart Failure with Improved Ejection Fraction (HFimpEF)
HFimpEF is defined as prior LVEF ≤40% with subsequent measurement >40%, representing patients whose ejection fraction has improved with therapy. 2, 3
These patients must continue full four-pillar GDMT indefinitely because abrupt discontinuation leads to relapse of heart failure and left ventricular dysfunction. 2, 3
When a patient's EF improves from <40% to 45-50%, this is classified as HFimpEF rather than HFmrEF, and HFrEF-directed therapy should be maintained. 2
Critical Diagnostic Principles Across All Categories
Transthoracic echocardiography must be performed first to measure LVEF, as this measurement categorizes the heart failure phenotype and directs all subsequent therapy. 3
Natriuretic peptide measurement (BNP or NT-proBNP) is required to confirm the diagnosis and stratify prognosis—markedly elevated values confer diagnostic certainty. 1, 3
The Universal Definition of Heart Failure requires symptoms and/or signs of heart failure caused by structural/functional cardiac abnormalities plus either elevated natriuretic peptides OR objective evidence of cardiogenic pulmonary or systemic congestion. 1, 3
Common Pitfalls and How to Avoid Them
Never rely on a single LVEF measurement for definitive therapeutic decisions—ejection fraction can vary by 5-10% depending on imaging modality, interpretation method, and clinical status, so repeat imaging is required. 1, 2, 3
Do not assume HFpEF is synonymous with diastolic dysfunction—while diastolic dysfunction is a hallmark, subtle systolic abnormalities are often present and the syndrome is multifactorial. 1, 6
Avoid misclassifying patients with LVEF 45-50% as HFpEF—this range falls within HFmrEF (41-49%), and only values ≥50% meet criteria for HFpEF. 2
Do not discontinue GDMT when LVEF improves above 40%—maintain therapy to prevent relapse, as these patients have HFimpEF and remain at high risk. 2, 3
Screen for reversible etiologies (coronary ischemia, significant valvular disease, thyroid dysfunction) because their identification may fundamentally alter management and prognosis. 3