NYHA Classification of Heart Failure
The NYHA (New York Heart Association) functional classification is a four-class system that grades heart failure symptom severity based on physical activity limitations, ranging from Class I (no limitation) to Class IV (symptoms at rest). 1
The Four NYHA Classes
The classification system stratifies patients as follows 1:
Class I: No limitation of physical activity. Ordinary physical activity does not cause undue breathlessness, fatigue, or palpitations. 1
Class II: Slight limitation of physical activity. Comfortable at rest, but ordinary physical activity results in undue breathlessness, fatigue, or palpitations. 1
Class III: Marked limitation of physical activity. Comfortable at rest, but less than ordinary physical activity results in undue breathlessness, fatigue, or palpitations. 1
Class IV: Unable to carry on any physical activity without discomfort. Symptoms at rest can be present. If any physical activity is undertaken, discomfort is increased. 1
Clinical Context and Limitations
The NYHA classification is a subjective assessment by healthcare providers that can change frequently over short periods of time. 1 This system has been used to select patients in nearly all randomized heart failure treatment trials and therefore determines which patients benefit from evidence-based therapies. 1
Important Caveats
Symptom severity correlates poorly with ventricular function. 1 Patients with mild symptoms (NYHA II) may still have relatively high absolute risk of hospitalization and death. 1
Symptoms can change rapidly. A stable patient with mild symptoms can become suddenly breathless at rest with onset of an arrhythmia, and an acutely unwell patient with pulmonary edema may improve rapidly with diuretic administration. 1
The NYHA system poorly discriminates between Classes I and II. Recent studies demonstrate substantial overlap (60-93%) in objective measures including NT-proBNP levels, 6-minute walk distance, and quality of life scores between these classes. 2, 3, 4
Relationship to ACC/AHA Staging System
The NYHA classification is intended to complement, not replace, the ACC/AHA staging system (Stages A-D). 1, 5 The ACC/AHA stages represent disease progression that typically does not reverse, while NYHA class reflects current symptom status that can fluctuate with treatment. 1
For example, a patient in ACC/AHA Stage C (structural heart disease with prior or current HF symptoms) remains Stage C even if treatment renders them NYHA Class I (asymptomatic). 1
Clinical Assessment Requirements
Guidelines recommend documenting NYHA class at every patient visit, though this should be supplemented with objective measures. 1 Acceptable quantitative assessments include 1:
- NYHA functional class
- Kansas City Cardiomyopathy Questionnaire (KCCQ)
- Minnesota Living with Heart Failure Questionnaire (MLHFQ)
- 6-minute walk test
- Peak oxygen consumption (VO2) or VE/VCO2 slope
When symptoms worsen, a documented plan of care must be established, which may include medication uptitration, device therapy consideration, lifestyle modifications, or referral for advanced therapies. 1
Treatment Implications
All patients with HFrEF should receive guideline-directed medical therapy (ACE inhibitors/ARBs, beta-blockers, mineralocorticoid receptor antagonists) regardless of NYHA class, as these therapies provide similar relative mortality reductions across all functional classes. 5 The absolute benefit increases with higher NYHA class, but even asymptomatic patients (Class I) have measurable mortality risk. 5
NYHA Class IV corresponds to ACC/AHA Stage D (advanced heart failure) and requires evaluation for mechanical circulatory support, cardiac transplantation, or palliative care. 5