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Dipyridamole-induced ST segment depression during thallium-201 imaging in patients with coronary artery disease:
1Department of Medicine, University of Vermont, College of Medicine, Burlington.
Insights
Dipyridamole-induced ST depression in coronary artery disease patients is linked to good coronary collateral vessels and increased rate-pressure product, suggesting mechanisms for "coronary steal" and heightened myocardial oxygen demand.
Area of Science:
- Cardiology
- Diagnostic Imaging
- Clinical Medicine
Background:
- Dipyridamole-thallium-201 myocardial scintigraphy is used to assess coronary artery disease.
- ST segment depression during dipyridamole stress testing can occur in patients with coronary artery disease.
- The determinants of dipyridamole-induced ST depression are not fully understood.
Purpose of the Study:
- To investigate the angiographic and hemodynamic factors associated with dipyridamole-induced ST segment depression.
- To identify predictors of ST depression during dipyridamole stress testing in patients with known coronary artery disease.
Main Methods:
- 41 patients with coronary artery disease underwent dipyridamole-thallium-201 scintigraphy.
- Stepwise multivariate logistic regression analyzed angiographic findings, hemodynamic changes, and thallium-201 results.
- Coronary collateral vessels, multivessel disease, heart rate, blood pressure, and rate-pressure product were assessed.
Main Results:
- ST depression occurred in 34% of patients.
- Good coronary collateral vessels (p<0.02) and increased rate-pressure product (p<0.02) were significant predictors of ST depression.
- Good collateral vessels were more frequent in patients with ST depression (79% vs 22%).
- Rate-pressure product increased significantly more in patients with ST depression.
Conclusions:
- Dipyridamole-induced ST depression is associated with good coronary collateral vessels, potentially via "coronary steal".
- Increased rate-pressure product, reflecting higher myocardial oxygen demand, also predicts ST depression.
- These factors may explain the limited prognostic value of dipyridamole-induced ST depression.
Abstract:
To examine the angiographic and hemodynamic determinants of dipyridamole-induced ST segment depression in patients with coronary artery disease, 41 patients with angiographically documented coronary disease who underwent dipyridamole-thallium-201 myocardial scintigraphy were studied. Dipyridamole-induced ST depression occurred in 14 (34%) of the 41 patients. Stepwise multivariate logistic regression was performed to compare the predictive value of angiographic findings (good coronary collateral vessels, jeopardized collateral vessels, multivessel disease), hemodynamic changes (changes in heart rate, systolic pressure, diastolic pressure and rate-pressure product), thallium-201 results (perfusion defect, thallium-201 redistribution) and demographic data (age, gender, medications). Only the presence of good coronary collateral vessels (p less than 0.02) and increases in rate-pressure product after dipyridamole infusion (p less than 0.02) were significant multivariate predictors of dipyridamole-induced ST depression. Good collateral vessels were more common in the group with ST depression (11 [79%] of 14) than they were in the group without ST depression (6 [22%] of 27; p less than 0.001). Rate-pressure product increased 2,835 +/- 1,648 beats/min.mm Hg in the group with ST depression compared with 1,179 +/- 1,417 beats/min.mm Hg in patients without ST depression (p less than 0.005). In conclusion, dipyridamole-induced ST segment depression in patients with coronary artery disease appears to be related to 1) the presence of good coronary collateral vessels, which may act by facilitating "coronary steal", and 2) increases in rate-pressure product, reflecting increased myocardial oxygen demand. These observations may explain the lack of prognostic value of dipyridamole-induced ST segment depression described in previous reports.