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Exercise tomographic thallium-201 imaging in patients with severe coronary artery disease and normal
T F Christian1, T D Miller, K R Bailey
1Mayo Clinic, Rochester, Minnesota.
Insights
Exercise thallium-201 imaging offers minimal added value over clinical and ECG data for detecting severe coronary artery disease in patients with normal resting ECGs. The high cost of this imaging may not justify its routine use.
Area of Science:
- Cardiology
- Diagnostic Imaging
- Preventive Medicine
Background:
- Coronary artery disease (CAD) diagnosis often relies on clinical assessment and electrocardiography (ECG).
- Exercise stress testing is a common diagnostic tool for CAD.
- Thallium-201 scintigraphy is used to assess myocardial perfusion.
Purpose of the Study:
- To evaluate the incremental value of exercise thallium-201 scintigraphy.
- To compare its effectiveness against clinical and ECG variables for detecting three-vessel or left main coronary artery disease (CAD).
- To assess the cost-effectiveness of thallium-201 imaging in patients with normal resting ECGs.
Main Methods:
- Prospective cohort study of 411 patients with normal resting ECGs.
- Patients underwent exercise thallium-201 scintigraphy followed by coronary angiography.
- Logistic regression analysis was used to identify predictors of severe CAD using clinical, ECG, and thallium-201 variables.
Main Results:
- Clinical variables (diabetes, sex, age, angina) and exercise parameters (heart rate-blood pressure product, ST depression) independently predicted severe CAD.
- Thallium-201 redistribution added minimal information, reclassifying only 3% of patients.
- The cost per additional reclassification was $20,550; event-free survival was high across risk groups.
Conclusions:
- Thallium-201 scintigraphy provides limited incremental value beyond clinical and exercise ECG data for identifying severe CAD in patients with normal resting ECGs.
- The high cost associated with thallium-201 imaging may not be justified for routine use in this patient population.
- Clinical and exercise ECG variables are effective in risk stratification for severe CAD when resting ECGs are normal.
Objective:
To assess the incremental value and cost-effectiveness of exercise tomographic thallium-201 imaging compared with clinical and exercise electrocardiographic variables for detecting three-vessel or left main coronary artery disease in patients with normal at-rest electrocardiograms.
Design:
Prospective cohort study.
Participants:
411 patients (77 [19%] had three-vessel or left main disease) with normal at-rest electrocardiograms who underwent exercise tomographic thallium-201 studies and subsequently had coronary angiography.
Measurements:
Clinical, exercise, and thallium-201 variables; univariate followed by multivariate logistic regression analysis to determine predictors of three-vessel or left main disease (clinical variables; clinical and exercise electrocardiographic variables; and clinical, exercise, and thallium-201 variables). Patients were classified by each of these models into low-, intermediate-, and high-risk groups.
Setting:
A tertiary referral center.
Results:
Among the clinical variables, diabetes mellitus, sex, age, and typical angina were independently associated with severe coronary disease (46% of patients were correctly classified into low- or high-risk groups). The peak exercise heart rate-blood pressure product and the magnitude of the exercise-induced ST depression added independent information to clinical variables. Among the thallium variables, the change in the global thallium-201 score (a measure of redistribution) added independent information to clinical and exercise variables, resulting in only 3% of the patients being reclassified regarding their predicted risk for severe coronary disease. The cost per additional reclassification was estimated to be $20,550. Twenty-one cardiac events occurred (7 cardiac deaths and 14 myocardial infarctions) after thallium study (follow-up, 2.8 +/- 1.0 years). Event-free survival was 94% to 97% regardless of the predicted probability of developing three-vessel or left main coronary artery disease by any model.
Conclusions:
When the at-rest electrocardiogram is normal, thallium-201 scintigraphy adds little information to clinical and exercise variables in identifying patients with severe coronary artery disease. The high cost of this information may not justify the routine use of sophisticated imaging for this purpose.
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