Heart Failure Definitions: AHA and ESC
ESC Definition (Most Recent - 2016)
Heart failure is a clinical syndrome characterized by typical symptoms (breathlessness, ankle swelling, fatigue) that may be accompanied by signs (elevated jugular venous pressure, pulmonary crackles, peripheral edema) caused by a structural and/or functional cardiac abnormality, resulting in reduced cardiac output and/or elevated intracardiac pressures at rest or during stress. 1
Key Diagnostic Components Required by ESC:
- Symptoms typical of heart failure: breathlessness at rest or on exercise, fatigue, tiredness, ankle swelling 1
- Signs typical of heart failure: tachycardia, tachypnea, pulmonary rales, pleural effusion, raised jugular venous pressure, peripheral edema, hepatomegaly 1
- Objective evidence of structural or functional cardiac abnormality at rest: cardiomegaly, third heart sound, cardiac murmurs, abnormality on echocardiogram, raised natriuretic peptide concentration 1
The ESC emphasizes that demonstration of an underlying cardiac cause is central to the diagnosis, as this is usually a myocardial abnormality causing systolic and/or diastolic ventricular dysfunction, though abnormalities of valves, pericardium, endocardium, heart rhythm, and conduction can also cause heart failure 1.
AHA/ACC Definition (Universal Definition - 2021)
The American Heart Association, in collaboration with international societies, defines heart failure as a clinical syndrome with symptoms and/or signs caused by a structural and/or functional cardiac abnormality and corroborated by elevated natriuretic peptide levels and/or objective evidence of pulmonary or systemic congestion. 2
Critical Distinction from ESC:
The AHA/ACC universal definition explicitly requires either elevated natriuretic peptides OR objective evidence of congestion as corroborating evidence, making it slightly more stringent than the ESC definition 2. This represents an evolution from earlier definitions that relied more heavily on clinical assessment alone.
Classification Systems Both Societies Use
By Ejection Fraction (Consensus):
Both societies classify heart failure based on left ventricular ejection fraction (LVEF):
- HFrEF (Heart Failure with Reduced EF): LVEF ≤40% 1, 2
- HFmrEF (Heart Failure with Mid-range EF): LVEF 41-49% 1, 2
- HFpEF (Heart Failure with Preserved EF): LVEF ≥50% 1, 2
The 2016 ESC guidelines introduced the HFmrEF category to stimulate research into this "grey area" population that was previously poorly defined 1.
By Stage (AHA/ACC Staging System):
The AHA/ACC uses a four-stage progression system 2:
- Stage A (At Risk for HF): Patients at risk but without structural heart disease or symptoms
- Stage B (Pre-HF): Structural heart disease present but no symptoms
- Stage C (Symptomatic HF): Structural heart disease with current or prior symptoms
- Stage D (Advanced HF): Refractory heart failure requiring specialized interventions
By Functional Status (Both Societies):
Both use the NYHA (New York Heart Association) functional classification 1:
- Class I: No limitation; ordinary physical activity does not cause symptoms
- Class II: Slight limitation; comfortable at rest but ordinary activity causes symptoms
- Class III: Marked limitation; comfortable at rest but less than ordinary activity causes symptoms
- Class IV: Unable to carry out any physical activity without discomfort; symptoms present even at rest
Important Nuances and Evolution
Preclinical Recognition:
Both societies recognize that asymptomatic structural or functional cardiac abnormalities are precursors of heart failure and that recognition is important because starting treatment at the precursor stage may reduce mortality 1. This represents a shift toward earlier intervention.
Diastolic vs Systolic Terminology:
The ESC explicitly states that diastolic and systolic heart failure should not be considered as separate entities, as most patients have evidence of both types of dysfunction 1. The terminology has evolved from "systolic/diastolic HF" to the more precise "HFrEF/HFpEF" classification 1.
Diagnostic Certainty:
A critical caveat: a normal ECG makes heart failure, especially due to LV systolic dysfunction, unlikely 1. Conversely, low-normal natriuretic peptide concentrations in an untreated patient make heart failure unlikely 1. These negative predictive values are clinically useful for ruling out the diagnosis.