Abstract Body (Do not enter title and authors here): Introduction Anomalous aortic origin of a coronary artery (AAOCA) can result in sudden cardiac death in the young and risk stratification is challenging. Though dobutamine stress cardiac MRI (DS-CMR) is feasible in pediatric patients, exercise stress CMR (ES-CMR) has lower rates of adverse events, higher diagnostic accuracy, and the ability to better reflect the physiologic changes occurring with exercise. No studies have evaluated ES-CMR in the pediatric population. We aim to describe our institution’s experience with ES-CMR using supine bicycle ergometry in patients with AAOCA.

Methods We retrospectively reviewed the medical records of AAOCA patients who underwent ES-CMR at our institution between 2011 and 2024 for demographic, clinical presentation, cardiopulmonary exercise test (CPET) and ES-CMR data. The exercise-based portion of the CMR consisted of supine cycle ergometry utilizing a ramp protocol, immediately after which perfusion imaging was performed. We used descriptive statistics for data analysis.

Results Of 38 patients who underwent ES-CMR, the median age was 16 years (range 13-24) and 68% were male. Diagnoses included anomalous right coronary artery (N=28), anomalous left coronary artery (N=8), and single coronary artery (N=1 single right, N=1 single left). Median maximal heart rate (HR) during ES-CMR was 160 bpm (range 130-190, median 80% predicted) with a median maximal HR during patients’ most recent CPET of 187 bpm (range 160-203, median 97% predicted). No patients had perfusion defects at rest or with exercise stress, or evidence of myocardial scarring. There were no adverse events.

Discussion We demonstrate for the first time the use of ES-CMR in a cohort of pediatric and young adult patients with AAOCA. ES-CMR can provide a unique modality to assess for ischemia at rest and stress as a means of risk stratification and simulate physiologic changes occurring with exercise stress in a single study. Although maximum heart rates during supine cycle ergometry are lower than those reached during CPET, they are similar to those reached during DS-CMR. ES-CMR can be a helpful and safe diagnostic tool in patients with AAOCA.