What are the different levels of heart failure?

Heart Failure Classification Systems

Heart failure is classified using two complementary systems: the ACC/AHA staging system (Stages A-D) that tracks disease progression, and the NYHA functional classification (Classes I-IV) that assesses symptom severity. 1

ACC/AHA Staging System (Disease Progression)

This staging system is unidirectional—patients advance from one stage to the next and cannot regress, though progression can be slowed or stopped with treatment. 1, 2

Stage A: At Risk for Heart Failure

• Patients have risk factors but no structural heart disease and no symptoms 1, 3
• Risk factors include: hypertension, coronary artery disease, diabetes mellitus, obesity, metabolic syndrome, exposure to cardiotoxic agents (chemotherapy, alcohol abuse), family history of cardiomyopathy, or history of rheumatic fever 3, 2
• These patients have never had heart failure 1

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

• Patients have structural heart disease but remain asymptomatic 1, 3
• Structural abnormalities include: reduced left or right ventricular ejection fraction, left ventricular hypertrophy, chamber enlargement, wall motion abnormalities, valvular heart disease, elevated filling pressures, or elevated cardiac biomarkers 3, 4
• These patients have never experienced heart failure symptoms 1

Stage C: Symptomatic Heart Failure

• Patients have current or past symptoms of heart failure with underlying structural heart disease 1, 3
• This represents the bulk of patients with clinical heart failure 1
• Symptoms include dyspnea, fatigue, reduced exercise tolerance, and fluid retention 1, 5

Stage D: Advanced/Refractory Heart Failure

• Patients have severe symptoms that interfere with daily life despite optimized medical therapy 1, 3
• Characterized by recurrent hospitalizations despite guideline-directed management 3, 4
• These patients require consideration for: mechanical circulatory support, continuous inotropic infusions, cardiac transplantation, or palliative care/hospice 1, 3, 2

NYHA Functional Classification (Symptom Severity)

This classification complements the staging system and is used primarily for patients in Stage C or D to assess functional capacity. 1 The NYHA class can fluctuate over time with treatment or disease progression, unlike the ACC/AHA stages. 1

Class I: No Limitation

• No limitation of physical activity—ordinary physical activity does not cause undue fatigue, palpitations, dyspnea, or anginal pain 3, 5

Class II: Slight Limitation

• Slight limitation of physical activity—comfortable at rest, but ordinary physical activity results in fatigue, palpitations, dyspnea, or anginal pain 3, 5

Class III: Marked Limitation

• Marked limitation of physical activity—comfortable at rest, but less-than-ordinary activity causes fatigue, palpitations, dyspnea, or anginal pain 3, 5

Class IV: Severe Limitation

• Unable to carry out any physical activity without discomfort—symptoms of heart failure are present even at rest, and any physical activity increases discomfort 3, 5

Classification by Left Ventricular Ejection Fraction (LVEF)

Heart failure is further classified based on ejection fraction, which has therapeutic and prognostic implications. 1, 6, 4

HFrEF: Heart Failure with Reduced Ejection Fraction

• LVEF ≤40% 1, 6, 4
• Also called systolic heart failure 1
• Most randomized controlled trials have enrolled these patients, and efficacious therapies have been demonstrated only in this group 1

HFmrEF: Heart Failure with Mildly Reduced Ejection Fraction

• LVEF 41-49% 1, 6, 4
• These patients fall into a borderline or intermediate group with characteristics similar to HFpEF 1

HFpEF: Heart Failure with Preserved Ejection Fraction

• LVEF ≥50% 1, 6, 4
• Also called diastolic heart failure 1
• Diagnosis is challenging because it largely involves excluding other noncardiac causes of symptoms 1
• To date, efficacious therapies have not been clearly identified 1

HFimpEF: Heart Failure with Improved Ejection Fraction

• Baseline LVEF ≤40%, with a ≥10-point increase from baseline and second measurement >40% 6, 4
• These patients may be clinically distinct from those with persistently preserved or reduced EF 1

Acute Heart Failure Classifications (Context-Specific)

Killip Classification (Acute Myocardial Infarction)

Used to provide a clinical estimate of circulatory derangement in acute MI: 1, 5

• Stage I: No heart failure—no clinical signs of cardiac decompensation 1, 5
• Stage II: Heart failure—rales, S3 gallop, pulmonary venous hypertension with wet rales in lower half of lung fields 1, 5
• Stage III: Severe heart failure—frank pulmonary edema with rales throughout lung fields 1, 5
• Stage IV: Cardiogenic shock—hypotension (SBP <90 mmHg), oliguria, cyanosis, sweating 1, 5

Forrester Classification (Acute Myocardial Infarction)

Describes clinical and hemodynamic status based on perfusion and pulmonary capillary wedge pressure (PCWP): 1, 5

• Class 1: Normal perfusion and normal PCWP 1
• Class 2: Poor perfusion and low PCWP (hypovolemic) 1
• Class 3: Near-normal perfusion and high PCWP (pulmonary edema) 1
• Class 4: Poor perfusion and high PCWP (cardiogenic shock) 1

Critical Clinical Caveats

Poor Correlation Between Symptoms and Cardiac Function

• There is a poor relationship between symptoms and severity of cardiac dysfunction 1
• Patients with very low ejection fraction may be asymptomatic, while those with preserved LVEF may have severe disability 1
• This discordance may be explained by alterations in ventricular distensibility, valvular regurgitation, pericardial restraint, cardiac rhythm abnormalities, and noncardiac factors (peripheral vascular function, skeletal muscle physiology, pulmonary dynamics) 1

Symptoms Should Not Solely Guide Therapy Titration

• Symptoms alone should not guide optimal titration of neurohormonal inhibitors (ACE inhibitors, ARBs, beta-blockers, aldosterone antagonists) 1
• These drugs impact mortality in a manner not closely related to symptoms 1
• Patients should be titrated to the optimal, tolerated dose regardless of symptom improvement 1

Prognostic Value of NYHA Classification

• The NYHA classification remains an independent predictor of mortality despite its limitations 3
• Mortality varies significantly: Class II (7-15%), Class III (12-26%) 5
• Patients should be regularly reassessed as they may move between classes with treatment 3

Diagnostic Utility of Natriuretic Peptides

• BNP <100 pg/mL or NT-proBNP <400 pg/mL: Chronic heart failure unlikely 1, 5
• BNP 100-400 pg/mL or NT-proBNP 400-2000 pg/mL: Uncertain diagnosis 1, 5
• BNP >400 pg/mL or NT-proBNP >2000 pg/mL: Chronic heart failure likely 1, 5

ECG Screening Value

• If the ECG is completely normal, heart failure (especially with systolic dysfunction) is unlikely (<10%) 1, 5