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Abnormal nondefect zone myocardial thallium washout ratio in patients with reversible thallium defects and normal
1Department of Internal Medicine, University of Cincinnati, OH 45267-0542.
Insights
Thallium myocardial defects in patients without coronary artery stenosis may indicate noncoronary heart disease. A lower thallium washout ratio in these patients suggests conditions beyond simple artifacts, aiding diagnosis.
Area of Science:
- Cardiology
- Nuclear Medicine
- Diagnostic Imaging
Background:
- Thallium myocardial perfusion defects in patients without significant coronary artery stenosis are often attributed to imaging artifacts.
- Differentiating true perfusion abnormalities from artifacts is crucial for accurate diagnosis and patient management.
Purpose of the Study:
- To investigate the cause of thallium myocardial defects in patients with normal coronary angiograms.
- To assess the utility of thallium washout ratios in differentiating noncoronary heart disease from artifacts.
Main Methods:
- Retrospective analysis of 323 patients undergoing dipyridamole thallium myocardial imaging.
- Coronary angiography performed to assess for luminal diameter stenosis (>20%).
- Calculation of time-standardized regional thallium washout ratios (dipyridamole vs. baseline).
Main Results:
- 10 out of 159 patients with perfusion abnormalities had normal coronary angiograms and no ECG evidence of infarction or left bundle branch block.
- These patients exhibited a significantly lower regional thallium washout ratio compared to controls (1.57 +/- 0.40 vs. 2.27 +/- 0.92, p=0.041).
- Nine of the 10 patients had independent evidence of noncoronary heart disease, including left ventricular hypertrophy.
Conclusions:
- Thallium myocardial defects in patients with normal coronary arteriograms may represent noncoronary heart disease rather than artifacts.
- Regional thallium washout ratios can assist in differentiating noncoronary heart disease from soft tissue artifacts in these specific patient groups.
Abstract:
Thallium myocardial defects in patients with no angiographic coronary artery stenosis have been attributed to attenuation effects and other artifacts. Of 323 patients having thallium myocardial imaging following dipyridamole infusion, 10 of 159 patients with a segmental perfusion abnormality were found to have no luminal diameter stenosis greater than 20% on coronary angiography and no electrocardiographic (ECG) evidence of myocardial infarction or left bundle branch block. A time-standardized regional thallium washout ratio was calculated as thallium myocardial counts with dipyridamole to counts without dipyridamole. In comparison to 10 age-matched control patients with no evidence of cardiac disease and no myocardial thallium defect, study patients had a lower regional myocardial thallium washout ratio from both the defect and nondefect (1.57 +/- 0.40 versus 2.27 +/- 0.92, p = 0.041) zones. Nine of the 10 study patients had independent evidence of noncoronary heart disease, including echocardiographic or ECG evidence of left ventricular hypertrophy in six patients. In patients with thallium defects and normal coronary arteriograms, a time-standardized regional thallium myocardial washout ratio for the nondefect zone may aid in the differentiation of patients with noncoronary heart disease from those with soft tissue artifacts.
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