Cardiovascular magnetic resonance normal values for pulmonary arteries and ventricular volumes in paediatric patients with transposition of the great arteries after arterial switch operation

Funding Acknowledgements Type of funding sources: None. Background The anatomy of the pulmonary arteries (PA) in patients with transposition of the great arteries (TGA) after arterial switch operation (ASO) with Lecompte manoeuvre is different compared to healthy subjects and stenoses of the PA are known to occur. Cardiovascular magnetic resonance (CMR) imaging is an excellent imaging modality to assess PA anatomy in TGA patients. However, disease specific normal values for PA size do not exist. Furthermore, the impact of pulmonary artery size, age and gender on ventricular volumes and function is unknown. Therefore, we sought to establish disease specific normative ranges for PA dimensions as well as biventricular volumes and function. Methods 70 CMR scans of paediatric patients with TGA after ASO with Lecompte manoeuvre (mean age 12.3 ± 3.6 years; range 5-18 years; 57 males) were included. Cine CMR sequences as well as contrast-enhanced magnetic resonance angiography (CE-MRA) data were used to measure pulmonary artery dimensions. Right and left PA were each measured at three locations during its course around the aorta. Ventricular volumes, mass and ejection fraction were measured from a stack of short axis cine images. Results Mean systolic and diastolic diameters of the MPA were 15.0 ± 2.3 mm (10.5 ± 2.7 mm/m²) / 13.2 ± 2.9 mm (9.2 ± 2.9 mm/m²) and mean cross-sectional MPA area was 286.7 ± 81.7 mm². Mean systolic and diastolic diameters for the RPA and LPA at the narrowest point were: RPA 10.5 ± 2.8 mm (7.8 ± 2.4 mm/m²) / 8.1 ± 2.2 mm (6.0 ± 1.9 mm/m²); LPA 8.4 ± 2.8 mm (6.2 ± 2.1 mm/m²) / 7.4 ± 2.3 mm (5.4 ± 1.6 mm/m²). Mean values for biventricular volumes, ejection fraction and mass were as follows: 1) left ventricular (LV) end-diastolic volume (EDV) 89.0 ± 20.3 ml/m² and end-systolic volume (ESV) 35.1 ± 11.7 ml/m², 2) right ventricular (RV) EDV 76.4 ± 15.4 ml/m² and ESV 32.4 ± 9.1 ml/m², 3) LV and RV ejection fraction 61.1 ± 6.5 % / 58.9 ± 6.1 % and 4) LV and RV mass 59.6 ± 15.2 g/m² / 23.3 ± 7.4 g/m². Separate centile charts for boys and girls for PA dimensions as well as biventricular volumes, mass and ejection fraction were created. Conclusion We established disease specific CMR normal values for the PA dimensions as well as for ventricular volumes, mass and ejection fraction in paediatric patients with TGA after ASO. Our data will improve CMR image interpretation and may serve as a reference in future studies.