Assessment of Human Fetal Left Heart Hemodynamics during Prenatal Development
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The hemodynamic forces and wall shear stresses (WSS) play an important role during the fetal heart development. Abnormal levels of flow-driven shear stress can deteriorate the proper functioning of the cells responsible for the growth and remodeling of the heart and lead to congenital heart defects (CHDs). Hypoplastic left heart syndrome (HLHS) is a critical CHD with severely underdeveloped left ventricle and responsible for 25-40% of all neonatal cardiac deaths. To characterize the main differences between the healthy and HLHS fetal hearts in terms of morphology, flow behavior, and WSS levels, will help to understand the mechanobiological development of the human fetal hearts. The comparison of healthy and HLHS fetal hearts is important to understand the embryonic development of HLHS. Computational fluid dynamics (CFD) modeling is performed to elucidate the flow behavior and WSS levels in the heart chambers. First, the model geometries are generated using the medical images. Then, the flow domain is discretized in spatial and time domains for solving the governing fluid flow equations. Inlet flow conditions are determined using the Doppler ultrasound velocity measurements. The analyses cover the range of gestational week 16 and week 34. HLHS hearts have higher peak flow rates at the valves compared to the control hearts. The turbulent activity in the left side of the heart is higher than the right side. For the control hearts, there is a balance between the left and right sides of the heart, which is preserved during the development. The ratio of the cross-sectional area between the left and right sides of the heart is about 57.5% to 42.5% for the control hearts. HLHS significantly reduces the cross-sectional area of the left side of the heart. For HLHS hearts, the ratio between the left and right sides becomes about 30% to 70%. The average WSS levels significantly increase at the left side of the HLHS hearts. This study indicates the critical importance of the altered inflow hemodynamics during the human fetal heart development. CFD analysis can be used to predict the initiation and growth of CHDs. The presence of CHDs significantly changes the biomechanical environment in the fetal hearts.