Exercise testing is an importnat diagnostic and prognostic procedure in the assessment of patients with ischemic heart disease. But standard ST-segment depression criteria was not high enough to estimate coronary srtery disease. Recently, the heart rate adjustment of ST segment depression, ST segment/heart rate slope and index, have been proposed as a more accurate criteria for diagnosing significant coronary artery disease. The objective of this study was to compare the discriminating power of proposed ST segment/heart rate slope and index with that of a standard method of assessing exercise-induced ST segment depression for estimating coronary artery disease.

Sixty nine patients with ischemic heart disease were studied with exercise treadmill testing and coronary angiography. Computer-measured ST-segment amplitudes were obtained and analysis of the heart rate-adjusted ST segment depression(ST/HR slope and △ST/HR index) was done. The sensitivity, specificity, and extent of coronary artery disease on each criteria were compared.

1) The sensitivity of △ST/HR index partition of 1.6uV/beats/min was slightly higher(83%) and the specificity of ST/HR slope partition of 2.4uV/beats/min was higher(87%) than the standard exercise electrocardiographic criteria. 2) Early onset of ischemic ST-segment depression, profound ST-segment depression(≥2mm), and downsloping ST-segment were associated with more extensive coronary artery disease. 3) On ST/HR slope, no CAD was 1.7±0.26uV/beats/min, one vessel disease was 2.6±0.34 uV/beats/min, two vessel disease was 2.7±1.36uV/beats/min, one vessel disease was 2.8±0.35uV/beats/min, and on △ST/HR index, no CAD was 1.8±0.38uV/beats/min, one vessel disease was 2.8±1.36uV/beats/min, two vessel disease 3.4±1.44uV/beats/min, and three vessel disease was 3.7±2.95uV/beats/min. The increment of ST/HR slope and △ST/HR index were associated with the coronary artery disease and its severity, but the correlations were not high enough.

The heart rate adjustment of ST segment depression was not high enough for improved detection of coronary artery disease, compared with standard ST-segment depression criteria. But these indexes can be improved the clinical usefulness of the treadmill exercise test for coronary aretry disease.