Assessing Early Cardiac Outflow Tract Adaptive Responses Through Combined Experimental-Computational Manipulations.

Mechanical forces are essential for proper growth and remodeling of the primitive pharyngeal arch arteries (PAAs) into the great vessels of the heart. Despite general acknowledgement of a hemodynamic-malformation link, the direct correlation between hemodynamics and PAA morphogenesis remains poorly understood. The elusiveness is largely due to difficulty in performing isolated hemodynamic perturbations and quantifying changes in-vivo. Previous in-vivo arch artery occlusion/ablation experiments either did not isolate the effects of hemodynamics, did not analyze the results in a 3D context or did not consider the effects of varying degrees of occlusion. Here, we overcome these limitations by combining minimally invasive occlusion experiments in the avian embryo with 3D anatomical models of development and in-silico testing of experimental phenomenon. We detail morphological and hemodynamic changes 24 hours post vessel occlusion. 3D anatomical models showed that occlusion geometries had more circular cross-sectional areas and more elongated arches than their control counterparts. Computational fluid dynamics revealed a marked change in wall shear stress-morphology trends. Instantaneous (in-silico) occlusion models provided mechanistic insights into the dynamic vessel adaptation process, predicting pressure-area trends for a number of experimental occlusion arches. We follow the propagation of small defects in a single embryo Hamburger Hamilton (HH) Stage 18 embryo to a more serious defect in an HH29 embryo. Results demonstrate that hemodynamic perturbation of the presumptive aortic arch, through varying degrees of vessel occlusion, overrides natural growth mechanisms and prevents it from becoming the dominant arch of the aorta.