Abstract
PURPOSE: This study sought to investigate the presence of residual myocardial hyperemia on the recovery phase in patients undergoing stress CMR. MATERIAL AND METHODS: 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 (MBF(rest)), stress (MBF(stress)) and recovery (MBF(recovery)) and MPR indices (MPR(stress/rest) and MPR(stress/recovery)) were calculated using automated pixel-wise quantitative myocardial perfusion mapping. RESULTS: A total of 30 patients (22 males, mean age of 62.7 ± 1 years) were included in the analysis. Global MBF(rest) and MBF(stress) 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 (MBF(recovery) of 0.92 ± 0.3 mL/g/min) and statistically differed from MBF(rest) (p < 0.01), suggesting residual myocardial hyperemia. This resulted in an abnormally low MPR(stress/recovery) (2.43 ± 0.7) with respect to MPR(stress/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). CONCLUSION: Despite the use of euphylline to counteract the vasodilator effect, MBF does not completely revert to resting values and MBF(recovery) cannot be used as a substitute for MBF(rest) when regadenoson is used. Consequently, a rest/stress protocol is advised for quantitative CMR perfusion to obtain accurate MBF and MPR parameters.