Abstract Funding Acknowledgements Type of funding sources: None. Background Failure of the systemic right ventricle (SRV) is based on morphological differences between right and left ventricles (RVs and LVs). RV adaptation to systemic afterload includes increased circumferential (GCS) over longitudinal global myocardial strain (GLS) with an unknown impact on intracavitary blood flow distribution. This study aimed to explore the SRV pattern of hemodynamic forces (HFs). Methods 4D-Flow cardiovascular magnetic resonance data were acquired using a prototype sequence on a 1.5-T MAGNETOM Aera. The ratio between transverse (inferior-anterior, HFIA and septal-lateral, HFSL) and longitudinal (basal-apical, HFBA) HFs (RRMS) was calculated as in Figure 1, for systole and diastole. Results We enrolled 12 adults with SRV (6 D-transposition of great arteries after atrial switch operation and 6 L-transpositions) and 12 age-matched healthy subjects (41±12 vs 42±13,p = 0.89). SRVs reported comparable end-diastolic volumes (83±18 ml/m2), ejection fraction (60±8%) and GLS (−20.2±3.8%) to control RVs (75±13 ml/m2,p = 0.18; 64±5%,p = 0.25; −23±5.6%,p = 0.21). Differently, SRV mass (55±24 g/m2) and GCS (−18.9±7.8%) were greater than RVs (20±3 g/m2,p<0.001 and −12.4±4,p = 0.016) and comparable to control LVs (57±11 g/m2,p = 0.7 and −20.2±3.8%,p = 0.3). The 4D-Flow analysis showed that SRV systolic RRMS (0.98±0.31) was similar to LVs (0.94±0.27,p = 0.78) but lower than RVs (1.32±0.45,p = 0.04). This reflected a significantly increased HFBA with respect to RVs (0.338±0.150 vs. 0.162±0.097, p = 0.0025) and similar to LVs (0.462 ± 0.186, p = 0.087). Concomitantly, a moderate correlation was demonstrated between SRV systolic HFBA magnitude and GCS (r2=0.47,p = 0.013). During diastole, SRVs showed lower HFBA (0.173±0.086) than LVs (0.304±0.104,p = 0.0028), revealing a diastolic RRMS (0.74 ± 0.14) comparable to RVs (0.73 ± 0.17,p = 0.95) and significantly different from LVs (0.50 ± 0.19,p = 0.003). Conclusions In SRVs, RRMS is similar to LVs during systole, possibly as a result of increased GCS. Inversely, the SRV filling appears to be closely related to ventricular morphology as suggested by RRMS comparable to RVs during diastole.