16 What are the stratification data for risk from
exercise tests in patients with angina? Which
patterns of response warrant referral for
angiography?
Vic Froelicher
The best evidence available on these questions is found in the
two studies that used the appropriate statistical techniques to find
the risk markers that were independently and statistically
associated with the time to cardiovascular events. Both studies
were performed in large populations (>3000 patients with
probable coronary disease) and had five year follow-up. The
Veteran’s Affairs (VA) study was performed only in men and the
risk factors identified were a history of congestive heart failure
(CHF) or digoxin administration, an abnormal systolic blood
pressure (SBP) response, limitation in exercise capacity, and ST
depression.^1 The DUKE study included both genders and has
been reproduced in the VA as well as other populations.^2 It
includes exercise capacity, ST depression and whether or not
angina occurred. The DUKE score has been included in all of the
major guidelines in the form of a nomogram that calculates the
estimated annual mortality due to cardiovascular events.
In general, an estimate more than 1 or 2% is high risk and
should lead to a cardiac catheterisation that provides the “road
map” for intervention. Certainly a clinical history consistent with
congestive heart failure raises the annual mortality of any patient
with angina and this is not considered in the DUKE score.
Exercise capacity has been a consistent predictor of prognosis and
disease severity. This is best measured in METs (multiples of
basal oxygen consumption). In clinical practice this has been
estimated from treadmill speed and grade but future studies may
show the actual analysis of expired gases to be more accurate.
Numerous studies have attempted to use equations to predict
severe angiographic disease rather than prognosis but these have
not been as well validated.^3
RReeffeerreenncceess
1 Morrow K, Morris CK, Froelicher VF et al. Prediction of cardiovascular
death in men undergoing noninvasive evaluation for CAD. Ann Int Med
1993; 111188 : 689–95.