ABILITY OF THE EXERCISE ELECTROCARDIOGRAM TEST TO DETECT ISCHEMIA IN STABLE CORONARY-ARTERY DISEASE PATIENTS WITH ST-SEGMENT DEPRESSION ON THE RESTING ELECTROCARDIOGRAM
Vg. Kalaria et Em. Dwyer, ABILITY OF THE EXERCISE ELECTROCARDIOGRAM TEST TO DETECT ISCHEMIA IN STABLE CORONARY-ARTERY DISEASE PATIENTS WITH ST-SEGMENT DEPRESSION ON THE RESTING ELECTROCARDIOGRAM, The American heart journal, 135(5), 1998, pp. 901-906
Background The appearance of ST-segment depression on the exercise ele
ctrocardiogram (ETT) generally indicates myocardial ischemia. Disorder
s that produce ST-segment depression on the resting electrocardiogram
can confound the results of the ETT. The purpose of this study was to
assess the reliability of exercise ST-segment depression as an indicat
or of ischemia in patients with a resting electrocardiographic ST depr
ession, presumably caused by coronary disease. Methods We studied 882
patients 1 to 6 months after a hospitalization for myocardial infarcti
on or unstable angina as part of the Multicenter Study of Myocardial I
schemia. An ETT and thallium-201 perfusion scan were performed in all
patients. For the purpose of this study, the perfusion scan was consid
ered the ''gold standard'' for ischemia. We correlated the ETT ST-segm
ent responses with the perfusion scan in a group with a normal electro
cardiogram baseline ST segment (NO ST DEP group) and in a group with r
esting electrocardiographic ST depression greater than or equal to 0.5
mm (ST DEP group). Results Although the frequency of ischemia by perf
usion scan was similar in the ST DEP group (48%) to that in the NO ST
DEP group (40%), the ST DEP group had a significantly higher (p = 0.03
) sensitivity (54%) in detecting ischemia than the NO ST DEP group (35
%). The ST DEP group, however; had a lower (58% vs 74%) specificity th
an the NO ST DEP group (p = 0.056). Baseline characteristics of the tw
o groups probably account for these differences. The overall diagnosti
c accuracy is similar (58% vs 56%) in the two groups. Conclusion We co
nclude that in a stable population with known coronary disease, the pr
esence of ST depression on the resting electrocardiogram does not impa
ir the detection of ischemia by the ETT, but may be associated with a
higher false-positive rate.