The New York Heart Association (NYHA) functional class helps to classify congestive heart failure patients based on their symptoms.
Class I: No symptoms of heart failure.
Class II: Symptoms of heart failure with moderate exertion, such as ambulating two blocks or two flights of stairs.
Class III: Symptoms of heart failure with minimal exertion, such as ambulating one block or one flight of stairs, but no symptoms at rest.
Class IV: Symptoms of heart failure at rest.
Note that the NYHA functional class differs from the ACC/AHA Heart Failure Classification system in that the former allows movement from one class to the other, while the ACC/AHA classification does not (see below).