NYHA classification
The New York Heart Association classification is a simple four-step ladder for describing how much heart failure limits a person's daily life. Rather than measuring the heart directly, it asks a practical question: how much activity can you do before symptoms stop you?
Class I means no limitation — ordinary activity causes no breathlessness or fatigue. Class II means slight limitation, with symptoms during ordinary exertion such as climbing stairs. Class III means marked limitation, with symptoms during less-than-ordinary activity such as walking on the flat, though the person is comfortable at rest. Class IV means symptoms at rest or with any activity. A patient's class can move up or down as their condition worsens or responds to treatment.
The NYHA class is widely used to track progress, guide therapy intensity, and qualify patients for certain treatments and trials. Its weakness is subjectivity: it depends on the patient's report and the clinician's judgment, and two assessors may disagree. It is therefore best used alongside objective measures such as ejection fraction, natriuretic peptides, and exercise testing.
NYHA class describes current symptoms and can change week to week; it differs from the ACC/AHA stages A to D, which describe disease progression and, once reached, do not move backward.