The ST segment/heart rate slope as a predictor of coronary artery disease: Comparison with quantitative thallium imaging and conventional ST segment criteria

The ST segment shift relative to exercise-induced increments in heart rate, the ST/heart rate slope ( ST HR slope), has been proposed as a more accurate ECG criterion for diagnosing significant coronary artery disease (CAD). Its clinical utility, with the use of a standard treadmill protocol, was compared with quantitative stress thallium (TI) and standard treadmill criteria in 64 unselected patients who underwent coronary angiography. The overall diagnostic accuracy of the ST HR slope was an improvement over TI and conventional ST criteria (81%, 67%, and 69%). For patients failing to reach 85% of their age-predicted maximal heart rate, its diagnostic accuracy was comparable with TI (77% and 74%). Its sensitivity in patients without prior myocardial infarctions was equivalent to that of thallium (91% and 95%). The ST HR slope was directly related to the angiographic severity (Gensini score) of CAD in patients without a prior infarction ( r = 0.61, p < 0.001). The ST HR slope was an improved ECG criterion for diagnosing CAD and compared favorably with TI imaging.