Localization and quantification of ischemic myocardial areas in the postinfarct phase by dipyridamole 201thallium emission computerized tomography

In 41 patients with a history of an acute myocardial infarction, the location of myocardial ischemia was studied by 201Tl emission computed tomography immediately and 3 h after intravenous dipyridamole. Distant ischemia was distinguished from peri-infarctional ischemia by the presence of transient thallium defects in, or slow thallium washout from myocardium not supplied by the infarct-related coronary artery. Ischemia at a distance occurred in 13 patients and was always accompanied by peri-infarctional ischemia. Peri-infarctional ischemia without distant ischemia was observed in 15 patients. The occurrence of distant ischemia was found to be dependent on the severity of stenosis in non-infarct coronary vessels. 12 (86%) of 14 patients with non-infarct stenosis of 75% or greater had distant ischemia, but only 1 (4%) of 27 patients with a stenosis of less than 75% in another vessel. In the presence of distant ischemia, peri-infarctional ischemia was in 11 patients (85%) associated with collaterals supplying the infarct zone, whereas in 13 (87%) of the patients with peri-infarctional ischemia only, incomplete obstruction of the infarct-vessel was observed. It is concluded that, by the distinction between peri-infarctional and distant ischemia, the presence of a significant stenosis in non-infarct vessels can be non-invasively predicted from tomographic thallium scintigraphy with dipyridamole.