The impact of regimented aminophylline use on extracardiac radioisotope activity in patients undergoing regadenoson stress SPECT myocardial perfusion imaging: A substudy of the ASSUAGE trial

In patients undergoing regadenoson stress SPECT myocardial perfusion imaging (MPI), the impact of the regimented administration of aminophylline on the cardiac-to-extracardiac photon activity ratio is unknown. This is a substudy of the ASSUAGE trial (NCT01250496); a double-blinded, randomized, placebo-controlled clinical trial which investigated the attenuation of regadenoson-related adverse effects using 75 mg of intravenous aminophylline vs placebo, administered 90 seconds following Tc-99m-tetrofosmin injection in patients undergoing regadenoson stress SPECT-MPI. In subjects with normal MPI enrolled in the trial, we sampled from the antero-posterior planar projection of the post-stress scintigraphic data the mean photon activity in the myocardium, liver, bowel, and lungs. The mean cardiac-to-extracardiac activity ratios were compared between patients randomized to aminophylline vs placebo. We studied 158 eligible subjects, randomized to receive aminophylline (n = 86) or placebo (n = 72). The means of photon activity ratios of the heart-to-liver, heart-to-bowel, heart-to-lungs, inferior wall of the heart-to-liver, and inferior wall of the heart-to-bowel were not statistically different between those who received aminophylline vs placebo (P values > .30). Only the time lapse between stress Tc-99m-tetrofosmin injection and stress SPECT acquisition independently correlated with higher heart-to-liver and heart-to-bowel activity ratios (P values a parts per thousand currency sign .01). Patients' body mass index independently correlated with lower heart-to-lung ratio (P = .009). The regimented intravenous aminophylline use following regadenoson stress does not significantly improve the cardiac-to-extracardiac photon activity ratio in patients undergoing regadenoson stress Tc-99m-tetrofosmin SPECT-MPI.