Accuracy and limitations of planar thallium scintigraphy for identifying the involved coronary artery in patients with single-vessel disease: Findings in the ACME trial

This study compared the location of thallium-201 perfusion defects with the location of angiographically documented single-vessel coronary artery stenosis in 161 patients enrolled in the Veterans Administration Cooperative Study of Angioplasty Compared to Medical Therapy for Myocardial Ischemia. Planar myocardial perfusion imaging was undertaken in anterior, left anterior oblique, and lateral views. Each view was divided into three segments, thus providing nine segments for analysis. The ability of thallium-201 scintigraphy to predict the diseased coronary artery was assessed using a scoring system with probability ratios for discrimination. The mean diameter stenosis of all coronary artery lesions was greater than 80%. Nineteen patients (12%) had normal perfusion studies, six patients had an isolated segmental defect, and the remainder had defects in multiple segments (mean, 4.2 per patient). Left anterior descending stenosis was associated with significantly more frequent segmental defects in the septal segment of the left anterior oblique view and the anterior segment in the lateral view. The infrequent occurrence of segmental defects in the inferior segment of the lateral view with left anterior descending stenosis was significant (p<0.05). Sixty-four percent of patients with right coronary artery stenosis showed a segmental thallium defect in the inferior segment of the anterior view (p<0.05), while none of the patients with right coronary artery disease demonstrated a thallium defect in the anterolateral segment in the same view. The only segment that discriminated in favor of the circumflex stenosis was the posterior segment in the left anterior oblique projection (42%; p<0.01). Using probability ratios, the apical segment in the anterior view lacked predictive capability for any specific coronary artery stenosis. Scoring predicted one vessel in 105 of the 142 patients with perfusion defects. However, predictions were correct in only 45% of the patients overall and in only 26% of patients with circumflex coronary artery stenosis. Predictions of location were most frequently correct for patients with stenosis of the left anterior descending artery (62%). In summary, this study showed that thallium defects are rarely localized to a single segment and frequently involve multiple segments even in patients with single-vessel disease. Apical defects occur frequently with stenosis in all three coronary arteries and are least predictive of disease location. Although the location of planar thallium201 perfusion defects generally identified the coronary artery with stenosis, variability was high. A scoring system that integrated all segmental defects often failed to correctly identify the coronary artery with stenosis, especially when it involved the circumflex coronary artery. © 2001 by Cardiovascular Reviews & Reports, Inc.

Duke Scholars

Author Terry Ann Fortin Medicine, Cardiology