Twenty-four-hour quantitative thallium imaging for predicting beneficial revascularization.

To determine the utility of 24-h thallium single-photon emission tomographic imaging for the assessment of myocardial viability, 40 patients with persistently decreased uptake on 3-h delayed imaging after exercise were studied before and after bypass surgery (n = 34) or coronary angioplasty (n = 6). Wall motion improvement after revascularization was also analysed in 23 patients with respect to the segments with and without 24-h redistribution. Of a total of 113 segments without redistribution at 3-h imaging after exercise, 62 (55%) demonstrated redistribution at 24 h. After revascularization 57 (92%) of these 62 segments revealed improvement of thallium uptake. On the other hand 40 (78%) of the 51 segments with persistently decreased thallium uptake until 24 h did not show improvement of uptake after revascularization. Of the 15 segments with > 50% relative thallium uptake and without redistribution on 24-h images, ten showed improvement of thallium uptake after revascularization. Hence higher uptake even without 24-h redistribution may indicate viability. Regional wall motion improved in 22 of 23 segments with redistribution on 24-h images, and did not improve after revascularization in 19 of 22 segments without redistribution at 24 h. These data suggest that 24-h late imaging with quantitative analysis may provide reliable information about reversible myocardial ischaemia in segments that demonstrate a fixed perfusion abnormality on conventional 3-h delayed imaging.