Thallium-201 single-photon emission computed tomography with intravenous dipyridamole to diagnose coronary artery disease

To determine the ability of thallium-201 single-photon emission computed tomography (SPECT) after dipyridamole infusion (0.71 mg/kg body weight) to detect coronary disease and predict individual coronary stenoses, 76 patients unable to exercise adequately underwent thallium-201 SPECT and quantitative analysis with bull's eye polar maps immediately after dipyridamole infusion and again 4 hours later. Bull's eye maps were compared with files compiled from gender-matched normal patients who had less than 5% probability of coronary artery disease while undergoing exercise thallium-201 SPECT. All patients underwent coronary arteriography. Test sensitivity in detecting coronary disease (>50% diameter stenosis of any vessel) was 89%, with sensitivities of 73% to 82% in detecting stenoses of individual vessels. Specificity for coronary artery disease was 47% (83% to 88% for individual vessels). However, 5 of the 8 patients with false-positive thallium-201 SPECT had 30% to 40% stenoses. The results, from a comparison of patients who underwent dipyridamole infusion with patients who exercised, indicate that dipyridamole infusion is a satisfactory alternative to exercise for thallium-201 SPECT. Coronary stenosis of less than 50% is a frequent cause of scan abnormalities.