Heart Rate Adjustment of ST Segment Depression as a Myocardial Ischemia Index of Coronary Artery Disease

ABSTRACT

BACKGROUND: 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. METHODS: 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 big up tri, Delta ST/HR index) was done. The sensitivity, specificity, and extent of coronary artery disease on each criteria were compared. RESULTS: 1) The sensitivity of big up tri, Delta 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(> or =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 big up tri, Delta 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 big up tri, Delta ST/HR index were associated with the coronary artery disease and its severity, but the correlations were not high enough. CONCLUSION: 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.