SEVERAL SYSTEMS have been proposed for
categorizing the degree of cardiovascular disability so
that one patient can be compared with another and so
that one patient's status can be monitored over time.1 4
The most often used classification system, formulated
by the Criteria Committee of the New York Heart
Association (table 1), classifies patients according
to the degree of symptoms resulting from ordinary
or less-than-ordinary activity. Although this widely
adopted system has been used to categorize the functional
status of patients in numerous clinical studies,
no information is available concerning how often clinicians
would disagree in their definitions of "ordinary"
or in their assessments of a patient's functional class,6
and few data are available regarding the system's correlation
with objective measures of exercise tolerance.
6' 7 In 1972, the Canadian Cardiovascular Society
proposed more detailed criteria (table 2), which
have been adopted by several studies, including the
National Heart, Lung and Blood Institute's Coronary
Artery Surgery Study.8 However, the Canadian
Cardiovascular Society system has not been evaluated
for its reproducibility or for its correlation with objective
measures of exercise tolerance.