Friday, March 31, 2023
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Why does the literature sometimes refer to WHO functional class and sometimes to NYHA functional class? What is the difference?
The functional classification is the measure of the limits imposed on a patient by a disease. It is a critical element of the assessment of patients with pulmonary arterial hypertension (PAH). Functional classification is strongly predictive of mortality,[1] and is an important factor in the choice of PAH therapy.[2]
The New York Heart Association (NYHA) put forward a formal functional classification system for patients with cardiac disease in 1928. This system has been updated numerous times, most recently in 1994. [3] (Please see table below.[4]) Since then, despite its ambiguities and documented interobserver variability, NYHA functional class has maintained a seemingly hallowed place in the clinical description of patients with chronic cardiovascular diseases; it is commonly used as an endpoint in clinical studies of investigational therapies.
In 1998, the World Health Organization (WHO) convened an expert panel in Evian, France, to rework the diagnostic classification system for patients with pulmonary hypertension. As part of that effort, the NYHA functional classification system was revised to reflect the unique physiology of pulmonary hypertension. The WHO functional classification system[5] recognizes the importance of near syncope and syncope in the symptom complex of these patients. Syncope is generally thought to carry a grave prognosis in patients with PAH. For this reason, PAH patients who have experienced a syncopal episode are generally assigned to WHO functional class IV (although this is not explicitly stated in the WHO functional classification system).
In practice, the two classification systems are used interchangeably when characterizing patients with PAH. So long as one recognizes the importance of syncope when assessing these patients, and classifies them accordingly, one can use either "NYHA" or "WHO" functional classification.
A. New York Heart Association functional classification Class 1: No symptoms with ordinary physical activity. Class 2: Symptoms with ordinary activity. Slight limitation of activity. Class 3: Symptoms with less than ordinary activity. Marked limitation of activity. Class 4: Symptoms with any activity or even at rest. B. World Health Organization functional assessment classification Class I: Patients with PH but without resulting limitation of physical activity. Ordinary physical activity does not cause undue dyspnea or fatigue, chest pain, or near syncope. Class II: Patients with PH resulting in slight limitation of physical activity. They are comfortable at rest. Ordinary physical activity causes undue dyspnea or fatigue, chest pain, or near syncope. Class III: Patients with PH resulting in marked limitation of physical activity. They are comfortable at rest. Less than ordinary activity causes undue dyspnea or fatigue, chest pain, or near syncope. Class IV: Patients with PH with inability to carry out any physical activity without symptoms. These patients manifest signs of right-heart failure. Dyspnea and/or fatigue may even be present at rest. Discomfort is increased by any physical activity. Table reprinted with permission from Rubin LJ. Diagnosis and management of pulmonary arterial hypertension: ACCP Evidence-Based Clinical Practice Guidelines. Introduction. Chest. 2004;126:7S-10S.
