The value of exercise electrocardiography and exercise thallium-201 myocardial perfusion scanning in determining the presence of single vessel coronary artery obstruction.

In 39 patients with single vessel coronary artery disease and no previous myocardial infarction, exercise thallium-201 myocardial perfusion scanning and 12 lead exercise electrocardiography (ECG) were compared to see how reliably each method identified the site of coronary artery obstruction. Significant (greater than or equal to 70% diameter) stenosis was present in the left anterior descending (LAD) coronary artery in 21 patients, in the right coronary artery (RCA) in 14 patients and in the left circumflex (LCX) in four patients. Thallium defects on the scan in the septal (SEPT), anteroseptal (ANT SEPT) and anterior (ANT) segments correlated (P less than 0 . 0005) with LAD disease and defects in the inferior (INF), posteroinferior (POST INF), and posterior (POST) segments correlated (P less than 0 . 0005) with RCA or LCX disease. Exercise induced ST segment elevation in VI and/or AVL correlated with LAD disease. The site of ischaemic ST depression did not correlate with disease in any vessel. ST segment depression in leads L2, 3, AVF (67%) and in leads V4--6 (67%) was most sensitive for detecting patients with LAD disease and ST depression in leads V4--6 was most sensitive (56%) for detecting patients with RCA or LCX disease but neither differentiated LAD from RCA/LCX disease.