Feasibility and Safety of Regadenoson Stress Perfusion Protocol in Pediatric Transplant Patients under General Anesthesia.

Background: Cardiac magnetic resonance with myocardial stress perfusion (stress CMR) is a non-invasive technique that offers assessment of myocardial function, perfusion, and viability. Regadenoson is a selective cardiac adenosine A2 receptor agonist with fewer side effects than adenosine and a favorable safety profile in older pediatric heart transplant recipients (PHTR). There are limited studies evaluating the hemodynamic response of regadenoson in pediatric patients under general anesthesia (GA).

Methods: We reviewed our experience with regadenoson stress CMR in PHTR under GA from 2020-2024 and compared to a non-GA group of PHTR who underwent regadenoson stress CMR from 2015-2022. Demographic and clinical data were recorded. Hemodynamic response and adverse events were reviewed. CMRs were reviewed for perfusion abnormalities and semi-quantitative analysis was performed using myocardial perfusion reserve index (MPRI).

Results: Forty-six PHTR underwent 53 stress CMRs under GA over the study period (mean age 7.8 years; range 3-19 years). All patients received endotracheal intubation and sevoflurane and were monitored during and after regadenoson administration per institutional protocol. Heart rate (HR) prior to regadenoson administration was 84±12 beats/min with a peak of 109±14 beats/min and average mean blood pressure (BP) was 63±12mmHg with a nadir of 45±8mmHg. Transient hypotension was observed in 33 (77%) scans, which resolved with phenylephrine. There were no other adverse events. Phenylephrine was used in 48 CMRs (91%) for blood pressure support at the discretion of anesthesia. Thirty-eight PHTR underwent 48 stress CMRs without sedation. CMRs were matched by time-since-transplant. The non-GA group was significantly older (mean age 15.8 years; p<0.001). GA patients had a larger percent decrease in mean BP compared to non-GA patients (27±17% vs 15±17%; p <0.001) with no difference in HR change. There were no significant differences in rates of qualitative perfusion defects, (11% vs 4%, p=0.18), late gadolinium enhancement or MPRI values between the two groups.

Conclusion: Regadenoson stress CMR is safe and feasible in PHTR under GA. While hypotension was frequently seen, it improved in all cases with phenylephrine. Semi-quantitative myocardial perfusion analysis by MPRI is feasible in these young patients, however further studies are needed to assess its clinical utility in this population.