The role of oral dipyridamole stress gated SPECT in assessing the response of the left ventricle to stress: Re-evaluation of an old method

Introduction: We aimed to assess whether the vasodilator effect of oral dipyridamole on the left ventricular systolic function in patients with suspected CAD is different from that of intravenous (IV) dipyridamole using Tc-99m MIBI myocardial perfusion gated SPECT. Methods: Eighty-nine patients (17 male, 72 female; 61±10 years) were enrolled in this study. The patients underwent a dipyridamole stress test for the gating study. Forty-one patients were given oral dipyridamole (OD), and 48 patients were given intravenous dipyridamole (ID). Each group was divided into two subgroups according to whether they had normal or abnormal myocardial perfusion scintigraphy (MPS) findings (reversible perfusion defect). A two-day dipyridamole pharmacologic stress-rest Tc-99m MIBI myocardial perfusion gated SPECT protocol was performed in all patients. The LV ejection fraction (EF), end diastolic volume (EDV) and end systolic volume (ESV) were calculated from the gated data. Results: In the ID group, LV myocardial perfusion was normal in 28 cases and abnormal in 20 cases. In abnormal ID cases, a significant difference between rest and stress EDV was detected (P = 0.017). In the OD group, the LV myocardial perfusion was normal in 20 and abnormal in 21 cases. In the OD normal cases, the rest EF (P = 0.012) and EDV (P = 0.029) were significantly different from the stress cases. Conclusion: The effect of ID test continues during gated SPECT and results in LV diastolic dysfunction in patients with abnormal myocardial perfusion. Oral administration is also highly effective for detecting real myocardial ischemia that causes LV systolic and diastolic dysfunction.