What is Heart Failure?
Heart failure is a complex clinical syndrome characterized by symptoms and signs resulting from structural or functional impairment of the heart's ability to fill with or eject blood. 1
Core Definition
Heart failure occurs when the heart cannot pump sufficient blood to meet the body's metabolic needs or accommodate systemic venous return 2. This is not simply a weakened heart—it encompasses any cardiac abnormality that impairs ventricular filling or ejection 1, 3.
Key Diagnostic Components
The modern definition requires three elements for diagnosis 4:
- Clinical symptoms and/or signs (dyspnea, fatigue, peripheral edema, pulmonary congestion)
- Structural and/or functional cardiac abnormality (documented by imaging or hemodynamics)
- Objective evidence through either:
- Elevated natriuretic peptides (BNP or NT-proBNP), OR
- Objective evidence of pulmonary or systemic congestion
Important Distinction: Pre-Heart Failure States
Not all cardiac dysfunction equals heart failure. The guidelines distinguish between 1, 3:
- Stage A (At Risk for HF): Risk factors present (hypertension, diabetes, obesity, cardiotoxic exposure) but no structural disease, biomarker elevation, or symptoms
- Stage B (Pre-HF): Structural heart disease OR elevated biomarkers OR elevated filling pressures, but no symptoms—this is not yet heart failure
- Stage C (Heart Failure): Current or prior symptoms WITH structural/functional abnormality—this is actual heart failure
- Stage D (Advanced HF): Severe symptoms at rest despite optimal therapy
Classification by Ejection Fraction
Heart failure is further categorized by left ventricular ejection fraction (LVEF) 1, 3, 4:
- HFrEF (reduced EF): LVEF ≤40%
- HFmrEF (mildly reduced EF): LVEF 41-49%
- HFpEF (preserved EF): LVEF ≥50%
- HFimpEF (improved EF): Baseline LVEF ≤40% that improves by ≥10 points to >40%
This classification matters because treatment responses and prognosis differ significantly across these categories.
Clinical Impact
Heart failure affects approximately 7 million U.S. adults and accounts for 14% of all deaths 5. It represents the leading cause of hospitalization in patients over 65 years 6, with incidence reaching 20% in those over 75 years old. The 5-year mortality remains approximately 50% despite modern therapies 2.
Common Pitfalls
Do not confuse asymptomatic structural heart disease with heart failure—patients in Stage B have cardiac abnormalities but are not yet in heart failure and should not be labeled as such 1. This distinction is critical for accurate communication, appropriate treatment selection, and avoiding unnecessary alarm for patients.