The Effects of Dipyridamole on Left Ventricular Function Evaluated by Stress-Rest Gated 201Tl Myocardial Perfusion SPECT

Abstract

Background: Gated myocardial perfusion SPECT simultaneously evaluates myocardial perfusion at tracer injection and ventricular function at imaging. Stress imaging is usually performed immediately after tracer injection with 201Tl, but 30 to 60 min later with (superscript 99m)Tc tracers. Therefore, 201Tl gated SPECT seems to have more chance to detect the functional changes caused by stress procedures. The purpose of this study was to evaluate the effects of dipyridamole on left ventricular function by stress-rest gated 201Tl myocardial perfusion SPECT. The results were correlated with the coronary angiographic findings. Methods: The study retrospectively included 150 patients who underwent dipyridamole 201Tl gated SPECT and coronary angiography within 3 months. Post-stress and 4-h rest images were obtained and left ventricular ejection fraction (LVEF) was calculated by automated software (QGS 3.0). Summed stress score (SSS), summed rest score (SRS) and summed difference score (SDS) were used for describing perfusion abnormalities. The patients were further divided into three groups according to the difference of LVEF (△ LVEF) between post-stress and rest images. Group A: △LVEF≥5%, group B: 5%＞△LVEF＞-5%, group C: △LVEF≤-5%. The patients were thought to have signify significant coronary artery disease (CAD) when coronary angiography showed≥70% stenoses in at least one vessel. Results: There were 43 patients (29%) in group A, 63 (42%) in group B, and 44 (29%) in group C. SSS of the three groups were 9.77±9.90, 12.05±10.37 and 17.07±11.89 (group A, B and C); SRS were 6.28±7.88, 6.03±6.64 and 7.02±7.33; and SDS were 3.49±4.53, 6.02±7.72 and 10.05±10.37. The SSS and SDS of group C were significantly higher than those of group A and B (P＜0.05), but SRS was not significantly different between the three groups. Significant CAD was noted in 21 patients (49%) for group A, 38 (62%) for group B, and 36 (82%) for group C. Chi-square test for trend showed significant difference (P＜0.01) between the three groups of patients. Conclusions: Dipyridamole may cause transient increase or decrease of LVEF. In addition, the dipyridamole-induced decrease of LVEF shown on post-stress and rest gated 201Tl SPECT was significantly correlated to myocardial ischemia and significant CAD.