Reduced Regadenoson Dose Using Heart Rate-Targeted Titration in Paediatric Stress Perfusion CMR

Background Weight-based regadenoson dosing for paediatric stress perfusion cardiac magnetic resonance (CMR) achieves coronary vasodilation but may result in excessive drug exposure in some patients. We evaluated feasibility, safety, and diagnostic performance of heart rate-targeted regadenoson titration as an individualised alternative to fixed based dosing. Methods We performed a retrospective analysis of 31 consecutive regadenoson stress perfusion CMR studies (29 technically successful) in paediatric patients with known or suspected coronary artery disease (2015-2025). Regadenoson was administered incrementally targeting ≥20% heart rate increase. Outcomes included achieved doses, haemodynamic responses, adverse events, image quality, and positivity rate. Results were compared with published weight-based dosing protocols. Results Mean age was 11.8±4 years (range 3-18) and weight 50.4±21 kg (range 14.9-91.8). Complete dosing data were available for 21/29 studies. Target heart rate response was achieved in all 29 studies (100% success) with median dose 3.2 mcg/kg (range 1.6-8), representing 60% reduction compared with standard 8 mcg/kg protocols. Among patients >50 kg, 83% achieved adequate stress with ≤160 mcg (≤40% of standard 400 mcg adult dose). Mean heart rate increased 42% (range 16-77%). Transient blood pressure reductions ≥10 mmHg occurred in 9 patients. All studies yielded diagnostic-quality images. Stress-inducible perfusion defects were identified in 7/29 studies (24%). No major adverse events occurred. Conclusions Heart rate-targeted regadenoson titration for paediatric stress perfusion CMR is feasible, achieving diagnostic-quality images with substantially reduced drug exposure. Consistent haemodynamic responses and positivity rates comparable to published series suggest adequacy of pharmacological stress, though prospective validation with quantitative perfusion measurement is required.