What are the stages of heart failure according to American College of Cardiology (ACC)/American Heart Association (AHA) guidelines?

ACC/AHA Heart Failure Staging System

The ACC/AHA classifies heart failure into four progressive stages (A through D) based on structural heart disease and symptom presence, where patients advance through stages but cannot spontaneously regress, and each stage requires specific evidence-based interventions to prevent progression and reduce mortality. 1

The Four Stages Defined

Stage A: At Risk for Heart Failure

• No structural heart disease and no symptoms, but presence of risk factors that predispose to heart failure development 1, 2
• Includes patients with:
  • Hypertension 1, 2
  • Coronary artery disease 1, 2
  • Diabetes mellitus 1, 2
  • Metabolic syndrome and obesity 1, 2
  • Exposure to cardiotoxic agents 2
  • Family history of cardiomyopathy 1
  • Atherosclerotic disease 1

Stage B: Pre-Heart Failure (Structural Heart Disease Without Symptoms)

• Structural heart disease present but no current or prior heart failure symptoms 1, 2
• Corresponds to NYHA Class I (no limitation of physical activity) 1
• Includes patients with:
  • Left ventricular systolic dysfunction (LVEF ≤40%) 2, 3
  • Left ventricular hypertrophy 1, 4
  • Previous myocardial infarction 4, 3
  • Asymptomatic valvular disease 1, 2
  • Wall motion abnormalities 2
  • Elevated filling pressures or cardiac biomarkers 2

Stage C: Symptomatic Heart Failure

• Structural heart disease with current or past symptoms of heart failure 1
• Encompasses NYHA Classes I through IV 1:
  • Class I: No limitation; ordinary activity doesn't cause symptoms 2
  • Class II: Slight limitation; ordinary activity causes dyspnea/fatigue 1, 2
  • Class III: Marked limitation; less than ordinary activity causes symptoms 1, 2
  • Class IV: Unable to perform any activity without symptoms; symptoms at rest 1, 2
• Symptoms include dyspnea, fatigue, reduced exercise tolerance 1

Stage D: Advanced/Refractory Heart Failure

• Refractory heart failure requiring specialized interventions despite optimized medical therapy 1, 5
• Corresponds to NYHA Class IV 1
• Characterized by:
  • Recurrent hospitalizations 1, 2
  • Symptoms that interfere with daily life 2
  • Cannot be safely discharged without specialized interventions 1
  • Progressive decline primarily driven by heart failure syndrome 5

Critical Staging Principles

Unidirectional Progression

• Patients advance through stages but cannot spontaneously regress to earlier stages 1, 4
• A Stage C patient who becomes asymptomatic with treatment remains Stage C and requires continued Stage C therapies 4
• Progression can only be slowed or stopped by treatment, not reversed 1, 4
• This mirrors cancer staging systems where disease stage reflects irreversible structural changes 4

Relationship to NYHA Classification

• The ACC/AHA staging system complements but does not replace the NYHA functional classification 1
• NYHA classification gauges symptom severity and can change frequently with treatment 1
• ACC/AHA stages reflect disease progression and structural changes that are more permanent 1
• A Stage C patient may fluctuate between NYHA Classes I-IV but remains Stage C 1

Prognostic Significance

Mortality Risk by Stage

• 5-year survival decreases progressively: Stage 0 (99%), Stage A (97%), Stage B (96%), Stage C (75%), Stage D (20%) 6
• Progression from one stage to the next is associated with reduced survival and increased natriuretic peptide concentrations 1
• Mean BNP levels increase by stage: Stage 0 (26 pg/mL), Stage A (32 pg/mL), Stage B (53 pg/mL), Stage C (137 pg/mL), Stage D (353 pg/mL) 6

Population Prevalence

• In community cohorts of adults ≥45 years: 32% Stage 0,22% Stage A, 34% Stage B, 12% Stage C, 0.2% Stage D 6
• 56% of adults ≥45 years are in Stage A or B, representing a massive at-risk population requiring intervention before symptom development 6

Stage-Specific Treatment Imperatives

Stage A Management

• Control hypertension, diabetes, and dyslipidemia 2
• Smoking cessation and alcohol moderation 2
• Regular exercise and weight management 2
• Avoid cardiotoxic agents 2

Stage B Management (Critical Intervention Point)

• ACE inhibitors for all patients with LVEF ≤40% (Class I, Level A evidence) to prevent symptomatic heart failure and reduce mortality 4, 3
• Beta-blockers for all patients with LVEF ≤40% (Class I, Level B-R evidence) to prevent symptomatic heart failure 4, 3
• ARBs as alternative for ACE inhibitor-intolerant patients 3
• ICD for patients ≥40 days post-MI with LVEF ≤30% for primary prevention of sudden cardiac death 4, 3
• Avoid thiazolidinediones in patients with LVEF <50% due to increased heart failure risk 3
• Avoid nondihydropyridine calcium channel blockers (diltiazem, verapamil) with LVEF <50% due to negative inotropic effects 3

Stage C Management

• All Stage A and B interventions 2
• Diuretics for fluid retention in addition to ACE inhibitors and beta-blockers 1
• SGLT2 inhibitors for HFrEF 2
• Treatment of underlying conditions for HFpEF 2

Stage D Management

• Mechanical circulatory support 1, 2
• Continuous inotropic infusions 1, 2
• Heart transplantation 1, 2
• Palliative and hospice care integration 2, 5

Common Pitfalls to Avoid

• Do not downgrade a patient's stage based on symptom improvement with treatment—once structural disease develops (Stage B) or symptoms occur (Stage C), the patient remains at that stage 1, 4
• Do not delay Stage B interventions waiting for symptoms to develop—the staging system was specifically designed to capture the opportunity to prevent mortality by intervening before symptoms appear 4
• Do not confuse NYHA class with ACC/AHA stage—a Stage C patient in NYHA Class I still requires full Stage C therapies 1
• Do not miss the Stage B diagnosis—structural heart disease is objectively measurable and represents "a point of no return" requiring specific evidence-based therapies 4, 3