The most commonly-used nomenclature for classifying degrees of heart failure severity is that developed by the New York Heart Association in 1964.* Patients with mild heart failure are classified in this four-tier system as those who show symptoms when they exert themselves. The remaining tiers match the increasing physical limitations of patients as their heart failure worsens. In overview, the NYHA classes are:
- Class I Patient is comfortable with ordinary physical activity, but elevated activity causes symptoms, such as fatigue and shortness of breath.
- Class II Patient is comfortable at rest, but ordinary physical activity causes symptoms.
- Class III Even light activity causes patient fatigue, heart palpitation, or shortness of breath.
- Class IV Patient shows symptoms at rest, and any physical activity only increases the discomfort.
*”Diseases of the Heart and Blood Vessels: Nomenclature and Criteria for Diagnosis. 6th ed.” The Criteria Committee of the New York Heart Association. Boston, Mass: Little Brown, 1964.