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Do false positive thallium-201 scans lead to unnecessary catheterization? Outcome of patients with perfusion defects
R L Desmarais1, S Kaul, D D Watson
1Department of Medicine, University of Virginia Health Sciences Center, Charlottesville 22908.
Objectives:
We postulated that artifactually abnormal thallium-201 scans are well identified at the time of initial clinical interpretation by experienced readers and do not lead to unnecessary coronary angiography.
Background:
Exercise thallium-201 scintigraphy employing quantitative imaging techniques has yielded sensitivity and specificity values of 80% to 90%. There are image artifacts, such as breast shadows, and variants of normal that, if not correctly identified, can lead to a high false positive rate for detection of coronary artery disease.
Methods:
Data from 338 consecutive patients with one or more focal thallium-201 defects on quantitative planar images were reviewed. All patients had undergone symptom-limited exercise scintigraphy and were classified as having either artifactual or nonartifactual thallium-201 defects after review of clinical reports.
Results:
Of the 265 patients with defects judged to be nonartifactual on clinical readings, 167 underwent coronary angiography, which demonstrated significant coronary artery disease (> or = 50% stenosis) in 161 (96%) and normal findings in 6. Four of the latter six had documented prior myocardial infarction. The remaining 73 patients (85% female) had thallium-201 defects deemed to be artifactual on clinical readings, chiefly as a result of breast (66%) and diaphragmatic (8%) attenuation or variants of normal (26%). Only 4 (5%) of the 73 patients underwent subsequent coronary angiography; none had coronary artery disease. One had aortic stenosis and two had variant angina. Follow-up (mean 20 +/- 2 months) of the 69 patients in this group who did not undergo coronary angiography revealed no deaths and one nonfatal non-Q wave myocardial infarction.
Conclusions:
Artifactual defects on quantitative planar thallium-201 scintigraphy are well recognized by experienced interpreters and do not result in a high false positive rate leading to unnecessary cardiac catheterization. The incidence of coronary artery disease is high in patients with thallium-201 defects judged to be nonartifactual, and many patients with perfusion defects and angiographically normal coronary arteries have organic heart disease.