Functional status as measured by NYHA classification. NYHA class categorizes patients by the severity of their heart failure symptoms. As the class increases, the degree of symptoms is more severe indicating worse functional status. Class I indicates no limitation of physical activity. Class II indicates slight limitation of physical activity. Class IIIA indicates marked limitation of physical activity where less than ordinary physical activity causes fatigue, palpitation, dyspnea, or angina pain. Class IIIB indicates marked limitation of physical activity where mild physical activity causes fatigue, palpitation, dyspnea, or angina pain. Class IV indicates inability to carry on any physical activity without discomfort.