Understanding stages, ejection-fraction phenotypes and changing disease trajectories without forcing false equivalence.
Editorial note: Both supplied documents were published in 2026. However, they serve different purposes. The ESC document is a clinical practice guideline, whereas the Second Universal Definition is an expert consensus document and explicitly states that it is not a treatment guideline.
Key takeaways
- Heart failure can be classified along several different axes: disease stage, current ejection-fraction phenotype, clinical presentation, cause and trajectory over time.
- The 2026 ESC Guidelines use a fixed LVEF threshold: HFrEF is LVEF <50%, while HFpEF is LVEF ≥50% with additional objective evidence supporting the diagnosis.
- The Second Universal Definition recognises reduced, preserved and improved EF phenotypes but intentionally avoids imposing a universal numerical boundary between reduced and preserved EF.
- Both documents use the stages A, B, C and D, with substantial conceptual overlap.
- Stage and phenotype are complementary. A patient may simultaneously be described as stage C, HF with reduced EF, ischaemic in cause and clinically improving.
- Improved LVEF does not automatically mean that heart failure has resolved.
Why does heart failure classification appear confusing?
The apparent conflict arises because a single label cannot describe every clinically important aspect of heart failure.
Different classifications answer different questions:
| Clinical question | Classification needed |
|---|---|
| Does the person have risk factors, preclinical disease, symptomatic HF or advanced HF? | HF stage |
| What is the current ventricular phenotype? | LVEF-based phenotype |
| What caused the syndrome? | Aetiological classification |
| Is this new, chronic or decompensated HF? | Clinical-presentation classification |
| Is the patient improving, in remission, recovering or worsening? | Trajectory classification |
Therefore, stage A–D and HFrEF–HFpEF are not competing systems. They classify different dimensions of the same disease.
The main area of genuine difference between the documents is how they define the LVEF phenotypes.
What does the 2026 ESC framework classify?
The 2026 ESC Guidelines for the Management of Heart Failure were developed by the ESC Task Force, with special contribution from the Heart Failure Association and endorsement by the European Association for Cardio-Thoracic Surgery.
The guidelines classify heart failure principally by:
- disease stage;
- LVEF phenotype;
- clinical presentation;
- anatomical involvement; and
- clinical cause.
Classification by LVEF
The 2021 ESC classification contained three phenotypes:
- HFrEF: LVEF ≤40%;
- HF with mildly reduced EF: LVEF 41%–49%;
- HFpEF: LVEF ≥50%.
The 2026 ESC Guidelines remove HF with mildly reduced EF as a separate phenotype. They instead introduce two principal pathophysiological groups:
| ESC phenotype | 2026 definition |
|---|---|
| HFrEF | Symptoms and/or signs of HF with LVEF <50% |
| HFpEF | Symptoms and/or signs of HF with LVEF ≥50%, plus objective structural or functional abnormalities consistent with LV diastolic dysfunction or raised LV filling pressures, supported by raised natriuretic peptides |
This is a major change. A patient with symptomatic HF and an LVEF of 45% is now classified as having HFrEF under the 2026 ESC framework, rather than HF with mildly reduced EF.
However, the ESC acknowledges that 50% is an inherently imperfect dividing line. LVEF varies with imaging technique and interpretation and may be misleadingly high in conditions such as significant mitral regurgitation.
Importantly, HFpEF cannot be diagnosed from an LVEF of 50% or higher alone. Evidence supporting abnormal cardiac structure, function or filling pressures remains necessary.
(ESC Guidelines 2026, sections 3.1 and 3.3.1, pp.15–17.)
How does the ESC classify disease stage?
The ESC also uses four stages describing the development and progression of HF:
| Stage | ESC description |
|---|---|
| Stage A: At risk for HF | HF risk factors but no current or previous symptoms or signs, no structural cardiac changes and no elevated cardiac biomarkers |
| Stage B: Pre-HF | No current or previous symptoms or signs, but structural cardiac abnormalities, abnormal cardiac function, elevated natriuretic peptides or persistently elevated cardiac troponin |
| Stage C: Symptomatic HF | Current or previous symptoms and/or signs caused by a structural or functional cardiac abnormality |
| Stage D: Advanced HF | Severe symptoms, markedly impaired exercise capacity, severe cardiac dysfunction and recurrent HF events despite optimal therapy |
Only patients in stages C and D have symptomatic HF. Stages A and B identify people at risk of developing the clinical syndrome.
Once a patient has experienced symptomatic HF, subsequent improvement does not normally return them to stage B. The previous symptomatic disease remains clinically relevant.
(ESC Guidelines 2026, section 3.3.2 and Figure 2, p.17.)
What does the Second Universal Definition classify?
The AHA/ACC/ESC/WHF Expert Consensus Document: Second Universal Definition of Heart Failure (2026) was produced by a joint international task force, in collaboration with the HFSA, the ESC Heart Failure Association and the Japanese Heart Failure Society.
It provides a standardised conceptual framework covering:
- the HF syndrome;
- stages of disease;
- LVEF phenotypes;
- causes of HF; and
- trajectories such as improvement, remission and recovery.
It is an expert consensus document, not a clinical practice guideline or clinical decision-support document.
How does it define the HF syndrome?
The Universal Definition describes HF as a clinical syndrome in which typical symptoms, examination findings and laboratory or imaging abnormalities indicating congestion or altered cardiac output are attributable to an underlying structural or functional cardiac abnormality.
Diagnosis depends on the accumulation of evidence rather than one isolated test.
Elevated natriuretic peptides or imaging evidence of congestion increase diagnostic certainty, but normal natriuretic peptide levels do not invariably exclude HF, particularly HFpEF with invasively demonstrated elevation of filling pressures.
(Second Universal Definition 2026, “Definition of HF Syndrome”, pp.e280–e281.)
What stages does it use?
The Universal Definition reaffirms stages A–D:
- Stage A: at risk but without symptoms, structural changes or elevated cardiac biomarkers.
- Stage B: pre-HF, with structural disease, functional abnormalities or elevated cardiac biomarkers but no current or previous symptoms.
- Stage C: current or previous symptomatic HF attributable to structural or functional cardiac abnormality.
- Stage D: advanced HF with severe symptoms, recurrent hospitalisation or refractory disease despite guideline-directed therapy.
These categories are very similar to the ESC stages because they arise from the same broader staging concept.
However, the detailed wording is not completely identical. The labels should therefore be attributed to the relevant document rather than assumed to be verbatim equivalents.
(Second Universal Definition 2026, Table 1, p.e281.)
How does the Universal Definition classify LVEF?
The Second Universal Definition recognises three clinically actionable groups:
- HF with reduced EF
- HF with preserved EF
- HF with improved EF
Unlike the ESC guideline, it does not specify one rigid numerical threshold separating reduced from preserved EF.
The document notes that:
- LVEF varies between imaging modalities and observers;
- normal values may vary with sex, age and ethnicity;
- an LVEF below 50% is unlikely to represent normal ventricular function;
- the clinically relevant threshold may differ according to the treatment or decision being considered.
Therefore, “reduced EF” in the Universal Definition should not automatically be translated as “LVEF <50%” in every context. That specific boundary belongs to the 2026 ESC guideline.
(Second Universal Definition 2026, “Classification of HF According to LVEF”, pp.e281–e282.)
The most important differences
| Feature | 2026 ESC Guidelines | Second Universal Definition |
|---|---|---|
| Document type | Clinical practice guideline | Expert consensus document |
| Principal purpose | Diagnosis and management of HF | Standardise definition, stages, phenotypes, causes and trajectories |
| Stage classification | Stages A–D | Stages A–D |
| LVEF groups | HFrEF and HFpEF | Reduced, preserved and improved EF |
| Fixed EF boundary | Yes: <50% versus ≥50% | No single universal boundary |
| HFmrEF | Removed as a separate phenotype | Not retained as a principal group |
| Improved EF | Recognised as an important descriptor | Explicit phenotype and part of the trajectory framework |
| Cause | Important for diagnosis and management | Formal universal classification of causes proposed |
| Treatment recommendations | Yes | No; treatment is deferred to clinical guidelines |
The difference in EF classification is not necessarily a clinical contradiction. The ESC requires operational categories for diagnosis and treatment recommendations. The Universal Definition seeks terminology that can remain applicable across populations, research settings and changing evidence.
Can the classifications be mapped directly?
Only partly.
The stages can be aligned broadly because both documents use the A–D structure. Nevertheless, the precise wording and criteria should still be checked against the relevant source.
The EF classifications cannot be mapped with complete precision:
- ESC HFrEF has a defined boundary of LVEF <50%.
- Universal “reduced EF” has no mandatory numerical boundary.
- ESC HFpEF requires LVEF ≥50% plus objective evidence supporting HF.
- Universal preserved EF also requires that the HF syndrome is established; preserved LVEF alone does not diagnose HF.
- Improved EF describes change over time and cannot be assigned from a single echocardiogram.
Consequently, a clinician should not mechanically convert every Universal reduced-EF label into ESC HFrEF without knowing the actual LVEF and clinical context.
How should both frameworks be applied?
A practical approach is:
Establish the clinical question → Are you describing risk, established HF, current ventricular phenotype, cause or trajectory?
Determine the HF stage → Apply stages A–D using symptoms, previous HF history, structural or functional abnormalities and biomarkers.
If symptomatic HF is present, establish the current phenotype → Under the ESC: apply the <50% or ≥50% threshold and confirm the additional evidence required for HFpEF.
Apply the Universal phenotype separately → Record reduced, preserved or improved EF without assuming an unsupported numerical equivalence.
Add cause and trajectory where known → For example, ischaemic cause, improved EF, remission or worsening HF.
If essential information is missing → Record that the phenotype or trajectory cannot yet be classified rather than guessing.
How can the same patient receive different but valid labels?
| Clinical scenario | ESC classification | Universal classification | Interpretation |
|---|---|---|---|
| Hypertension and diabetes, no cardiac abnormality or symptoms | Stage A | Stage A | At risk, but does not have HF |
| Asymptomatic LV hypertrophy with elevated natriuretic peptides | Stage B/pre-HF | Stage B/pre-HF | Preclinical cardiac disease, not symptomatic HF |
| Current HF symptoms, LVEF 45% | Stage C HFrEF | Stage C, likely reduced-EF phenotype | ESC supplies the definite <50% threshold; the Universal document does not |
| Previous symptomatic HF with LVEF rising from 30% to 45% | Stage C HFrEF with improved LVEF | Stage C, HF with improved EF | Stage reflects previous symptoms; improved EF describes trajectory |
| HF symptoms, LVEF 55%, raised filling pressures and structural abnormalities | Stage C HFpEF | Stage C, preserved-EF phenotype | The clinical syndrome and objective evidence establish HF; EF alone would be insufficient |
Improvement, remission and recovery are not interchangeable
Both documents recognise that LVEF may change over time.
The ESC describes improved LVEF as:
- an absolute LVEF increase of at least 10 percentage points; and
- a resulting LVEF above 40%.
The Universal Definition similarly describes HF with improved EF as previous reduced EF followed by an increase of at least 10 percentage points to an LVEF above 40%.
However, the Universal document goes further by distinguishing:
- Improvement: LVEF improves, but structural, biomarker or clinical abnormalities may persist.
- Remission: LVEF has normalised, symptoms are minimal and biomarkers are stable, but vulnerability to relapse remains.
- Recovery: sustained normalisation of cardiac structure, function, biomarkers and symptoms over extended follow-up.
Recovery is therefore a much stronger claim than improved EF. A normal follow-up LVEF alone is insufficient to establish it.
(ESC Guidelines 2026, section 3.3.1, pp.16–17; Second Universal Definition 2026, “Trajectories of HF”, pp.e284–e285.)
Common classification mistakes
- Diagnosing HF solely because LVEF is below 50%.
- Diagnosing HFpEF from a preserved LVEF without objective evidence of cardiac dysfunction or raised filling pressures.
- Applying HFrEF or HFpEF labels to an asymptomatic stage A or B patient.
- Continuing to use HFmrEF as a principal 2026 ESC phenotype.
- Assuming that Universal “reduced EF” always means LVEF <50%.
- Moving a previously symptomatic patient from stage C back to stage B after symptoms improve.
- Describing improved EF as recovery based on one follow-up echocardiogram.
- Treating disease stage, LVEF phenotype and clinical trajectory as alternative labels when they provide complementary information.
Practical summary
The most useful way to document HF in 2026 is multidimensional.
A complete clinical description might read:
Stage C heart failure, current ESC HFrEF phenotype with LVEF 45%, improved from 30%, ischaemic in cause, presently clinically compensated.
Each component adds different information:
- Stage C records the history of symptomatic HF.
- HFrEF describes the current ESC LVEF phenotype.
- Improved from 30% describes the trajectory.
- Ischaemic identifies the cause.
- Clinically compensated describes the present clinical state.
The ESC and Universal frameworks should therefore be used together where helpful. The goal is not to choose one label over another, but to identify exactly which dimension of heart failure each label is describing.
Primary sources
- 2026 ESC Guidelines for the Management of Heart Failure. European Society of Cardiology; 2026. doi:10.1093/eurheartj/ehag100.
- Walsh MN et al. AHA/ACC/ESC/WHF Expert Consensus Document: Second Universal Definition of Heart Failure (2026). Circulation. 2026;154:e279–e293. doi:10.1161/CIR.0000000000001455.