The significance of resting thallium-201 delayed SPECT for assessing viability of infarcted regions--comparison with exercise thallium-201 SPECT.

To clarify the clinical significance of resting thallium-201 (Tl) delayed SPECT for assessing the viability of infarcted regions, we studied resting Tl initial and delayed Tl SPECT one week after exercise (Ex) Tl SPECT in 38 patients (40 regions) with old myocardial infarction (OMI) and 35 patients (37 regions) with effort angina pectoris (EAP). Analysis of resting Tl and Ex Tl SPECT divided the patients with OMI into 3 groups. Twenty-three patients whose perfusion defect (PD) on resting delayed image was same as that of Ex delayed image were divided into 12 patients with Ex Tl redistribution (RD) (G1) and 11 patients without Ex Tl RD (G3). Fifteen patients showed a decrease of PD on resting delayed image compared with Ex delayed image (G2). Thirty-five patients with EAP were divided into 18 patients who had no PD on Ex delayed image (G1) and 17 patients whose PD did not disappear on Ex delayed image but disappeared on resting delayed image (G2). The increase of pulmonary artery wedge pressure on Ex was higher in G2 than in G1 of both OMI and EAP (OMI; G1 15 +/- 16 mmHg vs G2 27 +/- 7 mmHg; p less than 0.01, EAP; G1 12 +/- 7 mmHg vs G2 22 +/- 6 mmHg; p less than 0.05). The percent Tl uptake of the PD on Ex Tl initial images was lower in G2 than in G1 of both OMI and EAP (OMI: G1 63 +/- 7% vs G2 55 +/- 9%; p less than 0.05, EAP: G1 72 +/- 7% vs G2 65 +/- 9%; p less than 0.05). That of the PD on resting Tl delayed images was higher in G1 and G2 than in G3 of OMI (G1 78 +/- 7%, G2 74 +/- 8%, G3 41 +/- 10%; G1 vs G3, G2 vs G3 p less than 0.001). The prevalence of akinetic or dyskinetic wall motion on left ventriculography was higher in G2 than G1, and in G3 than G2 (G1 24.3%, G2 52.2%, G3 85.7%; p less than 0.001). Thus, in patients with OMI the decrease of Tl PD on resting Tl delayed images compared with Ex delayed images may indicate severe ischemia induced by stress as well as in patients with EAP, and furthermore the presence of viable muscle. On the other hand, the infarcted region without decrease of Tl PD on resting delayed images may lack viable muscle.