What are the classifications of heart failure based on ejection fraction, clinical severity, and NYHA functional class?

Heart Failure Classification

Heart failure is classified using three complementary systems: ACC/AHA stages (A through D), left ventricular ejection fraction categories (HFrEF, HFmrEF, HFpEF), and NYHA functional class (I through IV), with the 2022 ACC/AHA/HFSA guidelines providing the definitive framework for all three classification schemes 1.

Classification by ACC/AHA Stage

The staging system emphasizes disease progression and is not reversible—once a patient advances to a higher stage, they remain in that stage even if symptoms resolve 1:

• Stage A (At-Risk for HF): Patients with risk factors (hypertension, diabetes, obesity, atherosclerotic disease, family history of cardiomyopathy, cardiotoxic agent exposure) but no structural heart disease, elevated biomarkers, or symptoms 1

• Stage B (Pre-HF): No current or prior HF symptoms, but evidence of:

  • Structural heart disease (reduced EF, ventricular hypertrophy, chamber enlargement, wall motion abnormalities, valvular disease)
  • Elevated filling pressures by invasive or noninvasive measures
  • Elevated BNP or persistently elevated troponin (excluding acute coronary syndrome, chronic kidney disease, pulmonary embolus, myopericarditis) 1

• Stage C (Symptomatic HF): Structural heart disease with current or previous HF symptoms. Critical point: A patient who becomes asymptomatic with treatment remains Stage C and requires continued guideline-directed medical therapy 1

• Stage D (Advanced HF): Marked symptoms interfering with daily life and recurrent hospitalizations despite optimized guideline-directed medical therapy 1

Classification by Left Ventricular Ejection Fraction

The 2022 guidelines establish clear LVEF thresholds that differ from prior classifications 1, 2:

• HFrEF (HF with Reduced EF): LVEF ≤40%

  • This threshold is based on randomized controlled trials demonstrating survival benefit with therapies in this population
  • Most evidence-based therapies with mortality reduction target this group 1, 2

• HFmrEF (HF with Mildly Reduced EF): LVEF 41-49%

  • Represents a dynamic category—patients typically transition either improving from HFrEF or deteriorating toward HFrEF
  • One measurement is inadequate; serial LVEF assessments and trajectory evaluation are essential 1, 2
  • Diagnosis requires symptoms/signs plus objective evidence of cardiac dysfunction (elevated natriuretic peptides or evidence of elevated filling pressures) 1, 2

• HFpEF (HF with Preserved EF): LVEF ≥50%

  • Represents at least 50% of the HF population with increasing prevalence
  • Diagnosis is challenging and requires symptoms/signs plus objective measures of cardiac dysfunction beyond just normal EF 1, 2

Important Caveat on LVEF Classification

The trajectory of LVEF over time matters more than a single measurement, particularly for HFmrEF patients 1, 2. The guidelines emphasize evaluating the cause and direction of EF changes rather than relying on one time point.

NYHA Functional Classification

The NYHA system characterizes symptoms and functional capacity in patients with Stage C or D heart failure 1:

• Class I: No limitation of physical activity; ordinary activity does not cause symptoms
• Class II: Slight limitation of physical activity; comfortable at rest but ordinary activity causes symptoms
• Class III: Marked limitation of physical activity; comfortable at rest but less than ordinary activity causes symptoms
• Class IV: Unable to carry out any physical activity without symptoms; symptoms present at rest

Key Characteristics of NYHA Classification

• Subjective assessment by clinician with limited reproducibility, but remains an independent predictor of mortality 1
• Can change over time with treatment—unlike ACC/AHA stages which are permanent 1
• Widely used to determine eligibility for treatments and devices in clinical practice 1
• Despite substantial overlap in objective measures between classes (research shows 63-88% overlap in various parameters), it retains prognostic value 3

Clinical Application Note

A Stage C patient who becomes asymptomatic with treatment is classified as NYHA Class I but remains Stage C 1. This distinction is crucial because it mandates continuation of guideline-directed medical therapy regardless of symptom resolution.

Integration of Classification Systems

These three classification schemes serve complementary purposes 1, 2:

• ACC/AHA stages guide prevention strategies and track irreversible disease progression
• LVEF categories determine specific pharmacologic therapies with proven mortality benefit
• NYHA class assesses current symptom burden and functional status for device eligibility and monitoring treatment response

The 2022 guidelines emphasize that proper classification requires all three systems, as they provide different but essential information for optimizing patient management and prognosis 1, 2.