Heart disorders can limit a person's ability to perform physical activities. One way to evaluate the severity of a heart disorder is to determine how limited this ability is.
Doctors may use the New York Heart Association (NYHA) functional class system to make this evaluation:
However, this system is not foolproof, because even serious heart disorders may cause no symptoms if people reduce their activity level to compensate for the disorder.
Last full review/revision October 2012 by Lyall A. J. Higginson, MD