Significance of late redistribution thallium-201 imaging after rest injection for detection of viable myocardium

The aim of this study was to determine whether late redistribution imaging after rest injection of Tl-201 would provide further information on myocardial viability over conventional rest-early redistribution Tl-201 imaging. Methods: Twenty-nine patients with coronary artery disease and left ventricular dysfunction underwent rest, early (3-4 hr) and late (20-24 hr) redistribution Tl-201 and gated blood pool studies. In 14 patients with successful revascularization, gated blood pool study was repeated after the coronary intervention. Results: Nine of 29 patients showed early redistribution, and six additional patients showed further redistribution on the late images. Of 136 segments with initial Tl-201 defects, 18 showed early redistribution, and 10 showed late redistribution. When a threshold of 60% of peak activity was used as an index of myocardial viability, only a small fraction (3%) of the initial Tl-201 defects were additionally considered viable by the late images. In 14 patients who underwent revascularization, the positive (69%) and negative (87%) predictive Values of the early redistribution images for functional recovery were similar to those obtained by the late images (68% and 86%, respectively). Conclusion: Although tate redistribution after rest injection of Tl-201 occasionally occurs, most of the clinically relevant information on myocardial viability may be obtained by conventional rest-early redistribution Tl-201 imaging when the defect severity is considered an index of tissue viability.