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Transcatheter aortic valves (TAV) are symmetrically designed, but they are often not deployed inside cylindrical conduits with circular cross-sectional areas. Many TAV patients have heavily calcified aortic valves, which often result in deformed prosthesis geometries after deployment. We investigated the effects of deformed valve annulus configurations on a surgical bioprosthetic valve as a model for TAV. We studied valve leaflet motions, stresses and strains, and analog hydrodynamic measures (using geometric methods), via finite element (FE) modeling. Two categories of annular deformations were created to approximate clinical observations: (1) noncircular annulus with valve area conserved, and (2) under-expansion (reduced area) compared to circular annulus. We found that under-expansion had more impact on increasing stenosis (with geometric orifice area metrics) than noncircularity, and that noncircularity had more impact on increasing regurgitation (with regurgitation orifice area metrics) than under-expansion. We found durability predictors (stress/strain) to be the highest in the commissure regions of noncircular configurations such as EllipMajor (noncircular and under-expansion areas). Other clinically relevant performance aspects such as leaflet kinematics and coaptation were also investigated with the noncircular configurations. This study provides a framework for choosing the most challenging TAV deformations for acute and long-term valve performance in the design and testing phase of device development. [ABSTRACT FROM AUTHOR]

Fiber and matrix‐dominant properties of fiber‐reinforced polymer composites are important in many structural applications. Pre‐mixing the polymer matrix with nanoparticles could enhance the through‐thickness or matrix‐dominant properties. Surface treatment of fiber reinforcements with nanoparticles, on the other hand, could improve the in‐plane or fiber‐dominated properties of laminated composites, as well as interfacial adhesion. In this article, a novel low‐cost manufacturing method, combining surface treatment of fibers with matrix modification techniques, was devised to incorporate nanoparticles for the simultaneous reinforcement of matrix and fibers without increasing the viscosity of the epoxy matrix. Several graphene‐based nanomaterials, including graphene oxide (GO) and its thermally reduced version (rGO), graphene nanoplatelets (GNPs), and multi‐walled carbon nanotubes (MWCNTs) were employed to modify the epoxy matrix and the surface of glass fibers. Unmodified and modified epoxy and fibers were used for fabricating multiscale glass fiber‐reinforced composites following the vacuum‐assisted resin transfer molding process. The composites obtained combined improvements in both the fiber and matrix‐dominant properties, resulting in superior composites. We investigated the morphological, rheological and mechanical properties of the glass fiber‐reinforced multiscale composites. The results from testing for tensile properties and interlaminar shear strength (ILSS) of the glass fiber‐reinforced composites indicate that the introduction of GNPs, GO, rGO, and MWCNTs enhanced mechanical properties. The fracture surfaces of the fiber‐reinforced composites were examined by scanning electron microscopy and we used the micrographs to explain the tensile and ILSS results. POLYM. COMPOS., 40:E1732–E1745, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this computational modelling work, we explored the mechanical roles that various glycosaminoglycans (GAGs) distributions may play in the porcine ascending aortic wall, by studying both the transmural residual stress as well as the opening angle in aortic ring samples. A finite element (FE) model was first constructed and validated against published data generated from rodent aortic rings. The FE model was then used to simulate the response of porcine ascending aortic rings with different GAG distributions prescribed through the wall of the aorta. The results indicated that a uniform GAG distribution within the aortic wall did not induce residual stresses, allowing the aortic ring to remain closed when subjected to a radial cut. By contrast, a heterogeneous GAG distribution led to the development of residual stresses which could be released by a radial cut, causing the ring to open. The residual stresses and opening angle were shown to be modulated by the GAG content, gradient, and the nature of the transmural distribution.

In aortic valve-sparing surgery, the native valve of the patient is left in place but may need correction of its dimensions in order to regain full competence. A sizer was designed that can simultaneously measure the leaflet height and free edge length. A prototype was built and successfully used in porcine hearts of various sizes. The sizer is easy to use and provides dependable measurement of the aortic leaflet dimensions. Moreover, it represents a new resource on which surgeons may draw on to perform aortic valve-sparing surgery, with a better outcome for the patients.

Background and Aim of the Study: By increasing the longitudinal stress in the ascending aorta, downward movement of the aortic root might promote the proximal transverse tears seen in aortic dissections. The study aim was to evaluate the influence of five common cardiac conditions on the magnitude of aortic root displacement in cardiac patients., Methods: Aortic root contrast injections were analyzed in 90 patients (mean age 68 years) to measure downward motion of the root perpendicular to the plane of the sinotubular junction (STJ)., Results: Displacement of the aortic root ranged from 0 to 14 mm (mean 4.8 mm). Patients with aortic insufficiency (AI) showed increased aortic root movement (7.3 versus 4.3 mm, p = 0.003), whereas those with left ventricular hypokinesis (3.7 versus 5.5 mm, p = 0.014) or with myocardial hypertrophy (3.8 versus 5.1 mm, p = 0.073) exhibited reduced downward movement. These variables were independent, and correlated with the magnitude of aortic root motion. A stress analysis of the aortic root, arch and branches of the arch determined that the longitudinal stress approximately 2 cm above the STJ, in the outer curve of the aorta, was increased by 32% in patients with AI compared to patients without AI., Conclusion: Patients with cardiac conditions associated with increased aortic root motion such as AI may be at greater risk of aortic dissection because of increased longitudinal stress in the ascending aorta. Therefore, AI should be used as an indicator and aortic root displacement monitored to prevent the risk of aortic dissection.