Ability of the exercise electrocardiogram test to detect ischemia in stable coronary artery disease patients with ST-segment depression on the resting electrocardiogram.
BACKGROUND
The appearance of ST-segment depression on the exercise electrocardiogram (ETT) generally indicates myocardial ischemia. Disorders 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 indicator of ischemia in patients with a resting electrocardiographic ST depression, presumably caused by coronary disease.


METHODS
We studied 882 patients 1 to 6 months after a hospitalization for myocardial infarction or unstable angina as part of the Multicenter Study of Myocardial Ischemia. An ETT and thallium-201 perfusion scan were performed in all patients. For the purpose of this study, the perfusion scan was considered the "gold standard" for ischemia. We correlated the ETT ST-segment responses with the perfusion scan in a group with a normal electrocardiogram baseline ST segment (NO ST DEP group) and in a group with resting electrocardiographic ST depression > or =0.5 mm (ST DEP group).


RESULTS
Although the frequency of ischemia by perfusion 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 than the NO ST DEP group (p = 0.056). Baseline characteristics of the two groups probably account for these differences. The overall diagnostic accuracy is similar (58% vs 56%) in the two groups.


CONCLUSIONS
We conclude that in a stable population with known coronary disease, the presence of ST depression on the resting electrocardiogram does not impair the detection of ischemia by the ETT, but may be associated with a higher false-positive rate.
Kalaria
V G
VG
Division of Cardiology, University of Rochester, NY, USA.
Dwyer
E M
EM
D000328:Adult; D000368:Aged; D000789:Angina, Unstable / Q000175:diagnosis; D003327:Coronary Disease / Q000175:diagnosis*; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis; D017202:Myocardial Ischemia / Q000175:diagnosis*; D011446:Prospective Studies; D012015:Reference Standards; D012680:Sensitivity and Specificity; D013794:Thallium Radioisotopes
D013794:Thallium Radioisotopes