Rest or redistribution thallium myocardial imaging for resting myocardial perfusion: a detailed comparison with...

Redistribution thallium-201 (201T1) imaging is the most common method of assessing resting myocardial perfusion. However, the equivalence of a redistribution image and a separate rest injection is unclear. Although the presence of a defect on rest imaging has normally been equated with the presence of a myocardial infarction, it has recently been shown that a significant proportion of fixed defects on exercise-redistribution 201T1 actually represent areas of viable myocardium. This study was a detailed comparison of rest and redistribution imaging in 30 patients undergoing routine exercise 201T1 scanning for the assessment of coronary artery disease. A small dose (15 MBq) of 201T1 was administered at rest following the imaging in three standard planar views. Similar stress images were acquired using a further 50-55 MBq of 201T1 administered at peak effort. Redistribution images were acquired 3-4 h later and equilibrium blood pool ventriculography performed using in vivo labelling with 600 MBq 99Tcm-pertechnetate. Of 150 abnormal segments on the exercise scans, 74 (49%) were identified as being reversible on the redistribution scans and 58 (39%) on the rest images. Only 39 (53%) of these reversible defects were identified on both the redistribution and rest scans. Only 41% of the fixed defects on the redistribution images (32% of fixed defects on the rest images) had abnormal wall motion. Therefore, rest and redistribution images are not equivalent. Both rest and redistribution images significantly overestimate myocardial infarction. This may have significant effects on patient selection for revascularization procedures and therefore all patients having perfusion scintigraphy should also have additional assessment of regional wall motion to allow accurate classification of the functional status of myocardial segments.