Anne-Marie Koop

5 213 Table 1. Acquisition parameters of the CMR protocol. Echo time (ms) 1.286 Repetition time (ms) 9.226 Radiofrequency pulse (ms) 0.300 Flip angle (degrees) 10 Spectral width (Hz) 75,757 Echo position (%) 20 Acquisition matrix 256 x 128 Reconstructed matrix 256 x 256 In-plane resolution (µm) 117x117 Averages 8 Frames per heart beat 15 Slice thickness (mm) 1 Navigator points 256 Acquisition time per slice (s) 120 DISCUSSION This protocol provides a reproducible method for PAB in mice and the subsequent assessment of cardiac remodelling and functional adaptation using CMR. PAB differs from other models of increased RV pressure load because it involves absolute and static increase of afterload without the presence of other triggers. RV pressure load in models of hypoxia, monocrotaline, shunt, or a combination of these inducers are based on remodelling of the pulmonary vasculature. This remodelling is driven by endothelial damage, inflammation, cytokine migration, and vasoconstriction. The degree of these processes differs per model, therefore the degree of pressure load differs subsequently. In contrast to these models, PAB induces fixed RV afterload and is therefore reproducible and not affected by therapeutic interventions. This allows for the study of interventions targeting the pressure-loaded RV without affecting the RV afterload. This model of PAB in mice shows a significant gradient across the PAB and enables evaluation of this substantial pressure load. Dimensional evaluation by echocardiography is challenging due to the triangular shape of the RV wrapped around the LV, and its position immediately behind the sternum 41,42 . Echocardiography, both 2D and 3D, has shown to be inferior compared to CMR 51,52 . In pediatric cohorts with congenital heart diseases, echocardiographic volumetry shows lower reliability and systematic underestimation compared to