Assessment of viable myocardium within infarct zone by exercise thallium-201 scintigraphy.

The viability of the myocardial regions corresponding to pathologic Q waves was evaluated. Thirty-four patients with prior myocardial infarction underwent serial thallium-201 scintigraphy during treadmill exercise testing. On the delayed images, 8 of the initial 85 segmental defects (8 patients, 9%) showed total redistribution (RD) and 11 (6 patients, 13%) showed partial RD. In contrast, 66 segments showed persistent defect. The segments with total RD were more likely to be associated with normal or hypokinetic wall motion than the segments with persistent defect (p less than 0.05). Six of the 38 segments (13%) with collateral vessels showed total RD and 10 (21%) showed partial RD. However, 35 of 38 segments (92%) without collateral vessels showed persistent defect. There was a significant difference (p = 0.02) in myocardial thallium uptake patterns when the segments with and without collateral vessels were compared. It is concluded that (1) exercise-induced thallium RD may occur in patients with prior myocardial infarction, and myocardial infarct regions with total RD are highly associated with good contractility; these suggest the presence of viable but jeopardized myocardium within the infarct zone, and (2) collateral vessels may play a role in limiting infarct size.