Dipyridamole myocardial perfusion single photon emission computed tomography in patients with slow coronary flow

Several studies have indicated that the velocity of contrast dye increases after intravenous dipyridamole infusion in patients with a slow-flow pattern (SFP). In this study we compared the results of coronary arteriography and exercise myocardial perfusion single photon emission computed tomography (SPECT) in patients with SFP. We also investigated the changes in myocardial perfusion in patients with abnormal exercise myocardial perfusion SPECT by using a pharmacological stress test with dipyridamole.

This study included 60 patients who revealed SFP in their coronary arteriograms. Slow coronary flow diagnoses were made using the frame count method. A single day rest-exercise technetium-99m hexakis-2-methoxy-isobutyl isonitrile (Tc-99m MIBI; Du Pont Pharma SA, Belgium) SPECT was performed in all patients. Patients who had reversible perfusion defect (RPD) on the exercise SPECT were evaluated with dipyridamole myocardial perfusion scintigraphy. RESULTS Patients with SFP revealed both higher frame counts in native coronary arteries and higher mean frame counts. The coronary frame count was 26.4 +/- 3.5 in control patients and 64.40 +/- 16.64 in patients with SFP, respectively (P < 0.001). Exercise perfusion SPECT showed RPD in 17 patients (group 1), but was normal in 43 others (group 2). There were no statistically significant differences between groups 1 and 2 in frame counts. Myocardial perfusion was normalized in all 17 patients of group 1 after dipyridamole infusion.

In patients with SFP perfusion, changes may improve with dipyridamole infusion. This study indicates that this improvement can be shown by dipyridamole SPECT. Furthermore, no correlation was observed between the time needed to fill a native coronary artery and RPD of the myocardium.