COMPARISON OF S-T SEGMENT HEART RATE SLOPE WITH EXERCISE THALLIUM IMAGING AND CONVENTIONAL S-T SEGMENT CRITERIA IN DETECTING CORONARY-ARTERY DISEASE - EFFECT OF EXERCISE LEVEL ON ACCURACY/

The S-T segment/heart rate (ST/HR) slope has been proposed as a more a ccurate electrocardiographic criterion for the diagnosis of coronary a rtery disease, but studies comparing the diagnostic value of the ST/HR slope with exercise thallium imaging are scant. The aims of this stud y were to assess the diagnostic accuracy of the ST/HR slope, conventio nal S-T segment criteria and exercise thallium imaging in detecting co ronary artery disease and to evaluate the effect of exercise level on the sensitivity and specificity of these three techniques. Ninety cons ecutive patients underwent treadmill testing and exercise thallium sin gle-photon emission computed tomography (SPECT) simultaneously, All 90 patients also underwent coronary angiography within 1 month of the ex ercise test, We found that exercise thallium SPECT had a significantly higher diagnostic accuracy than either the ST/HT slope or conventiona l S-T segment criteria (thallium imaging 82%, ST/HR slope 67%, convent ional S-T segment criteria 63%), The overall accuracy of the ST/HR slo pe was slightly but insignificantly greater than conventional S-T segm ent criteria (ST/HR slope 67%, conventional S-T segment criteria 63%; p = 0.639), In 50 patients with a lower exercise level, defined as not achieving 85% of their maximal predicted heart rate, the accuracy of the ST/HR slope was insignificantly greater (ST/HR slope 72%, conventi onal S-T segment criteria 66%; p = 0.517), In 40 patients with adequat e exercise, the accuracy rate was the same (60%) for both the ST/HR sl ope and conventional S-T segment criteria, We conclude that exercise t hallium imaging is more accurate than the ST/HR slope in diagnosing co ronary artery disease and that the accuracy of the ST/HR slope is marg inally better than conventional S-T segment criteria only in patients with a lower exercise level, and not in those with adequate exercise.