Duration of Adenosine-Induced Myocardial Hyperaemia: Insights from Quantitative 13N-Ammonia Positron Emission Tomography Myocardial Perfusion Imaging

Aims This study aimed to assess the impact of adenosine on quantitative myocardial blood flow (MBF) in a rapid stress-rest protocol compared with a rest-stress protocol using 13N-ammonia positron emission tomography (PET) myocardial perfusion imaging (MPI) and to gain insights into the time dependency of such effects. Methods and results Quantitative MBF at rest (rMBF) and during adenosine-induced stress (sMBF) and myocardial flow reserve (MFR) were obtained from 331 retrospectively identified patients who underwent 13N-ammonia PET MPI for suspected chronic coronary syndrome and who all exhibited no perfusion defects. Of these, 146 (44.1%) underwent a rapid stress-rest protocol with a time interval (Delta tstress-rest) of 20 +/- 4 min between adenosine infusion offset and rest imaging, as per clinical routine. The remaining 185 (55.9%) patients underwent a rest-stress protocol and served as the reference. Groups did not differ regarding demographics, risk factors, medication, left ventricular function, and calcium scores. rMBF was significantly higher in the stress-rest vs. the rest-stress group [0.80 (interquartile range 0.66-1.00) vs. 0.70 (0.58-0.83) mLmin-1g-1, P < 0.001], and, as sMBF was identical between groups [2.52 (2.20-2.96) vs. 2.50 (1.96-3.11), P = 0.347], MFR was significantly lower in the stress-rest group [3.07 (2.43-3.88) vs. 3.50 (2.63-4.10), P = 0.007]. There was a weak correlation between Delta tstress-rest and rMBF (r = -0.259, P = 0.002) and between Delta tstress-rest and MFR (r = 0.163, P = 0.049), and the proportion of patients with abnormally high rMBF was significantly decreasing with increasing Delta tstress-rest. Conclusion Intravenously applied adenosine induces a long-lasting hyperaemic effect on the myocardium. Consequently, rapid stress-rest protocols could lead to an overestimation of rMBF and an underestimation of MFR.