[Thallium-201 re-injection: a new method for the identification of viable myocardium in patients with fixed deficits of myocardial uptake].

: Fixed defects on thallium-201 myocardial scintigraphy which have been traditionally interpreted as myocardial scar, may in fact be viable myocardium. This has been shown to be the case on 24 hour delayed imaging, positron emission tomography and repeat thallium imaging after coronary angioplasty or bypass surgery. We studied 25 suspected post myocardial infarction ischemia patients who had one or more fixed defects on exercise thallium scintigraphy. Immediately after the conventional delayed images, a second TI-201 injection of 1 mCi (re-injection) was given, followed by an additional set of images. After re-injection, 41% of fixed defects on the conventional delayed images showed increased thallium uptake as evidence of viable myocardium, and 46% of partially reversible defects on the conventional delayed images showed a concordant but increased uptake. Re-injection provided the only evidence for ischemia in 4 patients (16%) and documented ischemia in a new vascular territory in 3 patients (12%). Thus, we conclude that thallium re-injection is an improved technique for assessing myocardial viability in patients after myocardial infarction.