Thallium-201 myocardial imaging: a comparison of the redistribution and rest images.

Forty-one patients with chest pain and suspected coronary artery disease underwent thallium-201 myocardial imaging, performed immediately following maximal treadmill exercise, also at "redistribution" 4--5 hr after exercise, and at rest 1 wk later. All had coronary angiography. All images in seven patients without coronary artery disease were normal. Twenty-seven of the 34 (79%) patients with coronary artery disease had new, exercise-induced image defects. The redistribution and rest images were identical in 15/27 (56%) patients (complete redistribution). In 10/27 (37%) patients with exercise-induced defects, some redistribution occurred but defect size on the redistribution image was larger than that on the rest images (incomplete redistribution). In 2/27 (7%) of patients with exercise-induced defects, redistribution was absent. The presence of prior myocardial infarction, regional abnormalities of left-ventricular contraction or the severity of coronary stenoses did not correlate with the presence or absence of redistribution. Overall image quality between the two studies was similar, although image collection times for the redistribution study were prolonged. We conclude that some redistribution (complete or incomplete) occurs in most patients with exercise-induced image defects. When both fixed and reversible perfusion defects are present, defect size was often larger in the redistribution image and may thus overestimate the extent of prior myocardial infarction.