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Quantitative thallium imaging findings in patients with normal coronary angiographic findings and in clinically
Insights
Abnormal exercise thallium imaging findings are common in patients with normal coronary angiography. Subcritical coronary stenoses may contribute, but often other factors cause these discrepancies, suggesting potential underestimation of coronary obstruction.
Area of Science:
- Cardiology
- Nuclear Medicine
- Diagnostic Imaging
Background:
- Exercise thallium imaging is a key diagnostic tool for coronary artery disease.
- Interpreting "abnormal" findings requires clear criteria based on normal reference ranges.
- Discrepancies between imaging and angiography can impact patient management.
Purpose of the Study:
- To compare computer-quantified exercise thallium images in clinically normal subjects and patients with chest pain but normal angiography.
- To identify factors contributing to abnormal thallium findings in patients with angiographically normal coronary arteries.
Main Methods:
- Analysis of exercise thallium images from 45 healthy individuals (Group I) and 44 patients with chest pain and normal coronary angiography (Group II).
- Computer quantification of thallium uptake and clearance, adjusted for peak exercise heart rate.
- Comparison of imaging results with clinical characteristics and coronary stenosis severity.
Main Results:
- 45% of patients in Group II (normal angiography) exhibited "abnormal" exercise thallium imaging findings.
- Subcritical coronary stenoses (0-49%) were more frequent in Group II patients with abnormal thallium results (35% vs 4%).
- Subcritical stenoses did not fully explain the observed abnormalities, indicating other contributing factors.
Conclusions:
- Abnormal exercise thallium findings are frequent in patients with angiographically normal coronary arteries.
- Subcritical coronary stenoses partially explain these findings, suggesting potential underestimation of coronary obstruction.
- Establishing robust criteria for exercise thallium imaging requires careful consideration of both clinically and angiographically normal populations.
Abstract:
Computer-quantified exercise thallium images in 45 clinically normal subjects (group I) and in 44 patients with chest pain and no significant coronary artery disease by angiography (group II) were compared. Group II patients were older and more frequently female, had ST-segment depression by electrocardiography, and included 8 with subcritical (0 to 49%) stenoses. When normality was defined by the range of thallium imaging values in the clinically normal subjects, and after correcting clearance for peak exercise heart rate, 20 of 44 patients (45%) in group II had "abnormal" findings. The only difference between the 20 patients with abnormal findings and the 24 with normal findings in group II was a greater frequency of subcritical (less than 50%) coronary stenoses in the abnormal group, 7 (35%) vs 1 (4%) (p less than 0.05). However, this does not explain most of the abnormalities of thallium imaging in group II. Thus, abnormal thallium findings in subjects with normal angiographic findings are frequently seen and are partially related to the presence of subcritical coronary stenoses, suggesting an underestimation of coronary obstruction. Furthermore, clinically and angiographically normal subjects may differ substantially, and both sets of normal subjects should be considered when establishing criteria for abnormality in exercise thallium imaging.