Pharmacologic stress imaging. Pharmacologic stress imaging has increasingly been employed as an alternative to exercise imaging for detection of coronary artery disease and risk stratification particularly in patients who are unable to perform adequate exercise. Sensitivity and specificity of thallium 201 scintigraphy using intravenous dipyridamole infusion as a stress for coronary artery disease detection average 85% and 91%, respectively. Dipyridamole imaging is also useful for differentiating between ischemia and scar and identifying patients who have an increased risk for subsequent cardiac events. Dipyridamole imaging is particularly useful for preoperative risk stratification in patients undergoing surgery for peripheral vascular or aortic disease. Dipyridamole imaging is also useful for identifying residual myocardial ischemia after myocardial infarction and detecting restenosis after coronary angioplasty. Adverse side effects of dipyridamole are promptly reversed by aminophylline. Dipyridamole stress can also be employed in association with echocardiography for detection of ischemia-induced regional wall motion abnormalities. 