Residual myocardial hyperemia in regadenoson stress/rest quantitative perfusion cardiac magnetic resonance

This study sought to investigate the presence of residual myocardial hyperemia on the recovery phase in patients undergoing stress CMR. Fifty patients with clinical indication for stress CMR underwent quantitative perfusion imaging in resting conditions, after regadenoson-induced hyperemia (400 mcg, 5 mL), and 10 min after recovery with euphylline. Studies showing hypoperfusion due to ischemia and/or prior myocardial infarction were excluded. Global myocardial blood flow during rest (MBFrest), stress (MBFstress) and recovery (MBFrecovery) and MPR indices (MPRstress/rest and MPRstress/recovery) were calculated using automated pixel-wise quantitative myocardial perfusion mapping. A total of 30 patients (22 males, mean age of 62.7 ± 1 years) were included in the analysis. Global MBFrest and MBFstress were 0.83 ± 0.2 mL/g/min and 2.1 ± 0.6 mL/g/min, respectively. After recovery with euphylline, myocardial perfusion did not return to the resting values (MBFrecovery of 0.92 ± 0.3 mL/g/min) and statistically differed from MBFrest (p < 0.01), suggesting residual myocardial hyperemia. This resulted in an abnormally low MPRstress/recovery (2.43 ± 0.7) with respect to MPRstress/rest (2.56 ± 0.7) (p = 0.03). A linear mixed-effects model accounting for repeated measures revealed statistically significant group differences over time in global MBF (mean difference 0.1, 95% CI 0.02-0.17, p = 0.01) and global MPR (mean difference -0.13, 95% CI -0.25 to -0.02, p = 0.02). Despite the use of euphylline to counteract the vasodilator effect, MBF does not completely revert to resting values and MBFrecovery cannot be used as a substitute for MBFrest when regadenoson is used. Consequently, a rest/stress protocol is advised for quantitative CMR perfusion to obtain accurate MBF and MPR parameters.