The Evaluation of Caffeine Effects in Myocardial Blood Flow, Myocardial Flow Reserve and Hemodynamic Change by ^99mTc-sestamibi Dynamic SPECT/CT

Introduction: Quantitative coronary blood flow could be collected by dynamic single-photon emission computed tomography/ computed tomography (Dynamic SPECT/CT) for CAD diagnosis in previous studies. However, it is little known about the relationship between caffeine and Dynamic SPECT/CT. The purpose of this study is to investigate the role of caffeine on Dynamic SPECT/CT in suspected CAD or with abnormal CT angiography (CTA) patients.

Methods: Totally 56 patients was enrolled with suspected CAD (31 patients) or abnormal CT angiography (CTA) (25 patients) who were referred by cardiologists. They divided into 3 groups randomly: (1) Caffeine abstinence for 72 hours before study; (2) <24 hours Caffeine intake (one tablet, about 200 mg) before study; (3) >24 hours Caffeine intake before study. Rest (13 mCi ^99mTc-sestamibi; MIBI)/dipyridomale-stress (30 mCi MIBI) Dynamic SPECT/CT one day protocol performed on a dedicated Siemens Symbia-T2 SPECT/CT system. The quantitative data was analyzed by MyoFloQ software. Disease vessels (>50% stenosis) were defined on CTA or PCI. Statistical analysis was performed with commercially available soft ware (SPSS) and P <0.05 was considered statistically significant.

Results: In this study, we have developed the caffeine testing model using before imaging. We found the level of serum theophylline has positive correlation to the serum caffeine level. The theophylline level rose to the peak at 24 hour after caffeine intake. Caffeine blunted hemodynamic effects (heart rate response, HRR) during dipyridamole pharmacologic stress and also reduced stress MBF and MFR by dipyridamole-induced hyperemia. Interesting, caffeine has no influence in rest MBF. Interesting, caffeine has “only” no reduced sMBF in disease vessels, as compared with non-disease vessels.

Conclusions: Caffeine reduces HRR, stress MBF and MFR by Dipyridamole-induced hyperemia. Therefore, we concluded that caffeine should be prohibited at least 24 hours before Dynamic SPECT/CT exam to avoid false positive result. Since the high cost of caffeine test, it is also possible to replace the caffeine test by serum theophylline level. Caffeine has no reduced sMBF in disease vessels, as compared with non-disease vessel. It might be associated with impaired adenosine-mediated vasodilation in atherosclerotic coronary arteries. However, it maybe need more studied for evaluated it.