Prognostic significance of regional myocardial ischemia of the ventricular septum assessed by thallium-201 exercise testing

Use of exercise thallium (Tl-201) myocardial imaging for diagnosis of coronary artery disease (CAD) is well established. Recently, Tl-201 perfusion imaging has been shown to have important prognostic value in patients with CAD.^1-3 Studies have consistently shown that the presence of transient Tl-201 defects, indicating ischemic viable myocardium, predicts cardiac events.^1-3 We previously reported that among patients presenting for evaluation of chest pain without known previous myocardial infarction (MI), the total number of transient Tl-201 defects is superior to other clinical, exercise, angiographic and radionuclide data for predicting cardiovascular death or nonfatal MI.¹ This suggests that the extent of ischemic viable myocardium is an important determinant of the risk of a cardiac event. However, whether specific regional abnormalities of myocardial perfusion carry prognostic value is unknown. Previous studies indicate that left anterior descending (LAD) CAD may have a worse outcome than disease in other arteries^4,5 but regional ischemia determined by Tl-201 imaging has not been investigated for independent prognostic value. Therefore, our previously described cohort of patients¹ was reevaluated to test the hypothesis that regional myocardial schemia has independent prognostic value.