Incomplete redistribution in delayed thallium-201 single photon emission computed tomographic (SPECT) images: An overestimation of myocardial scarring

• Published in: Journal of the American College of Cardiology Vol. 12; no. 4; pp. 955 - 963
• Main Authors: Cloninger, Karen G., DePuey, E.Gordon, Garcia, Ernest V., Roubin, Gary S., Robbins, Wendy L., Nody, Agatha, DePasquale, Eugene E., Berger, Harvey J.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01-10-1988; Elsevier Science
• Subjects: Adult; Aged; Angioplasty, Balloon; Biological and medical sciences; Cardiology. Vascular system; Cardiomyopathies - diagnostic imaging; Cardiomyopathies - therapy; Cicatrix - diagnostic imaging; Coronary Disease - diagnostic imaging; Coronary heart disease; Diagnosis, Differential; Electrocardiography; Exercise Test; Female; Heart; Humans; Male; Medical sciences; Middle Aged; Myocardial Infarction - diagnostic imaging; Thallium Radioisotopes; Time Factors; Tomography, Emission-Computed; Radionuclide study; Human; Infarct; Scar; Coronary artery; Myocardium; Cuffed tube; Cardiovascular disease; Instrumental dilatation; Coronary heart disease; Positron emission tomography; Percutaneous route
• ISSN: 0735-1097; 1558-3597
• DOI: 10.1016/0735-1097(88)90461-5

To determine if incomplete redistribution at 4 h in exercise tomographic thallium-201 studies is always due to a myocardial scar, 141 patients were evaluated before and after a total of 160 successful percutaneous transluminal coronary angioplasty procedures. Thallium studies were analyzed using polar “bull's-eye” maps. For both immediate and delayed images, abnormalities were quantified as a thallium score by calculating a standard deviation-weighted sum of pixels > 2.5 SD below gender-matched normal limits. One hundred forty-four of 160 studies indicated abnormalities before angioplasty. Of these 144, incomplete redistribution occurred in 111 (77%): 16 (14%) in patients with and 95 (86%) in patients without prior Q wave myocardial infarction. After angioplasty, improvement in delayed image score occurred in 8 (50%) of 16 patients with prior infarction and 72 (76%) of 95 patients without prior infarction (p < 0.05). After angioplasty, delayed images were normal in 1 (6%) of 16 patients with prior infarction and 32 (34%) of the 95 without (p < 0.05). Before angioplasty. delayed image scores were positively correlated with scores in the immediate postexercise images in patients with (r = 0.84) and those without (r = 0.69) prior infarction.
To determine if additional delayed images could help differentiate scar from ischemia, an 8 to 24 h delayed image was obtained in each of 40 other patients with incomplete redistribution at 4 h. Of 28 patients with prior infarction, 15 had no redistribution and 13 had further redistribution at 8 to 24 h. Of 12 patients without prior infarction, 1 had no redistribution, 7 had further redistribution and 4 had complete redistribution.
Thus, 4 h delayed thallium image defects frequently do not signify myocardial infarction. Their severity is proportional to immediate poststress abnormalities. Additional imaging at 8 to 24 h is recommended in patients with incomplete redistribution and no evidence of prior infarction.