Aortic arch

Abstract: Intravascular pressures, distributions of blood oxygen, dye-dilution curves, cineradiography, and electromagnetic flowmeters in major vessels suggest a highly directional flow oE systemic and pulmonary venous blood through reptilian hearts. The lacertilian right aortic arch contains blood from the pulmonary, and the left from the pulmonary or sometimes both pulmonary and systemic veins. Traces made of the pressure and blood flow show that the lacertilian and chelonian cava venosum and pulmonale are functionally distinct. Atrioventricular valves probably prevent regurgitation during ventricular systole and form an obstruction between the cava arteriosum and venosum during ventricular filling. The muscular ridge approaches the ventral ventricular wall at systole forming a functional ventricular septum. Low pulmonary vascular resistance favors pulmonary ejection before systemic. In Pseudemys the balance between pulmonary and systemic resistance causes a left-to-right shunt during respiration and a right-to-left shunt during diving; the latter probably reduces the expenditure of cardiac energy during hypoxia. Pressure traces and cineradiography indicate separation of systemic and pulmonary venous returns in alligators. The left ventricle perfuses both aortic arches and the right the pulmonary arch. Right ventricular pressure may exceed pulmonary pressure during ejection suggesting an impedance in the pulmonary outflow tract. Pulmonary resistance in crocodilians may increase during diving, instituting a right-to-left shunt.

Abstract: Morphogenesis of the "immature symmetric embryonic aortic arches" into the "mature and asymmetric aortic arches" involves a delicate sequence of cell and tissue migration, proliferation, and remodeling within an active biomechanical environment Both patient-derived and experimental animal model data support a significant role for biomechanical forces during arch development The objective of the present study is to quantify changes in geometry, blood flow, and shear stress patterns (WSS) during a period of normal arch morphogenesis Composite three-dimensional (3D) models of the chick embryo aortic arches were generated at the Hamburger-Hamilton (HH) developmental stages HH18 and HH24 using fluorescent dye injection, micro-CT, Doppler velocity recordings, and pulsatile subject-specific computational fluid dynamics (CFD) India ink and fluorescent dyes were injected into the embryonic ventricle or atrium to visualize right or left aortic arch morphologies and flows 3D morphology of the developing great vessels was obtained from polymeric casting followed by micro-CT scan Inlet aortic arch flow and cerebral-to-lower body flow split was obtained from 20 MHz pulsed Doppler velocity measurements and literature data Statistically significant variations of the individual arch diameters along the developmental timeline are reported and correlated with WSS calculations from CFD CFD simulations quantified pulsatile blood flow distribution from the outflow tract through the aortic arches at stages HH18 and HH24 Flow perfusion to all three arch pairs are correlated with the in vivo observations of common pharyngeal arch defect progression The complex spatial WSS and velocity distributions in the early embryonic aortic arches shifted between stages HH18 and HH24, consistent with increased flow velocities and altered anatomy The highest values for WSS were noted at sites of narrowest arch diameters Altered flow and WSS within individual arches could be simulated using altered distributions of inlet flow streams Thus, inlet flow stream distributions, 3D aortic sac and aortic arch geometries, and local vascular biologic responses to spatial variations in WSS are all likely to be important in the regulation of arch morphogenesis

Abstract: Catastrophic ascending aorta aneurysm (AsAA) dissection and rupture can be prevented by elective surgical repair, but identifying individuals at risk remains a challenge. Typically the decision to operate is based primarily on the overall aneurysm size, which may not be a reliable indicator of risk. In this study, AsAA inflation and rupture was simulated in 27 patient-specific finite element models constructed from clinical CT imaging data and tissue mechanical testing data from matching patients. These patients included n = 8 with concomitant bicuspid aortic valve (BAV), n = 10 with bovine aortic arch (BAA), and n = 10 with neither BAV nor BAA. AsAA rupture risk was found to increase with elevated systolic wall stress and tissue stiffness. The aortic size index was sufficient for identifying the patients with the lowest risk of rupture, but unsuitable for delineating between patients at moderate and high risk. There was no correlation between BAV or BAA and AsAA rupture risk; however, the AsAA morphology was different among these patients. These results support the use of mechanical parameters such as vessel wall stress and tissue stiffness for AsAA presurgical evaluation.