Exercise-induced ST-T changes and severity of myocardial ischemia in single-vessel coronary artery disease

The purpose of this study was to evaluate how exercise-induced ST-T changes reflect the severity of myocardial ischemia in 66 patients with singlevessel disease (SVD) who underwent stress thallium scans. Quantitative assessment of myocardial ischemia was performed with thallium ischemic score (TIS) derived from circumferential profile analysis. Circumferential profiles of the initial and 4 hr redistribution myocardial image were generated for each of three views (ANT, LAO 45, LAO 70) and TIS was obtained as the average of the area between the initial and 4 hr redistribution profile for each view. In 66 patients with SVD, TIS were compared with coronary angiographic findings. TIS was correlated well with the severity of coronary artery stenosis. In addition, TIS was also correlated well with lung thallium uptake in 46 LAD disease. Therefore, these data proved that TIS was useful for the evaluation of the severity of myocardial ischemia. In 46 LAD disease, TIS, being as the indicator of the severity of myocardial ischemia, was compared precisely with results of stress electrocardiograms to evaluate how exercise-induced ST-T changes reflect the severity of myocardial ischemia. Patients with negative U wave had the highest mean TIS and those with horizontal or down sloping ST depression of 1.0 mm or more had higher mean TIS than those with slow upsloping ST depression of 1.5 mm or more, but there were no significant differences between these groups and those without ST-T change and the mean TIS was not different significantly between V2-6 ST depression group and V2-6, II, III, aVF ST depression group. In conclusion, these results indicated that exercise-induced ST-T changes reflect the severity of myocardial ischemia in some degree but also has a limitation in evaluation of the severity of myocardial ischemia. (author)