Body Surface ST Mapping in Isoproterenol Stress Test in the Ischemic Heart Disease

ST segment mapping was performed on 15 patients with ischemic heart disease and 5 control subjects before and after isoproterenol (ISP) infusion. ST mapping was recorded using 87 leads according to Yamada. ISP was injected at a rate of 0.02g/kg/min for 5 minutes. In ischemic heart disease, ST map developed negative areas in the left anterior chest wall extending from mid line to left axillar line after ISP. The ST depression appeared gradually during infusion of ISP and completed by 5 minutes. This distribution of ST depression was different from that of left ventricular hypertrophy, or of complete left bundle branch block which spared mid anterior chest. Typical precordial ST depression were not found in patients without ischemic heart disease. Maximal ST depression was between 0.07mV and 0.53mV. The point of maximal ST depression corresponded to one of the conventional chest lead in 6 of 15 cases. In other 9 cases, the point of maximal ST depression did not correspond to the conventional chest lead and was mostly located superiorly to V3-V5. ST depression correlated well with the maximal ST depression (r=0.90). ST depression at V5 correlated less well with ST depression (r=0.70). On 201 Tl stress scan, a reversible large perfusion defect was detected in 2 out of 5 patients with marked ST depression. These findings suggested that ISP induced ST map changes are useful in diagnosis of myocardial ischemia.