Accordingly, we sought to expand on previous modeling to determine disease prevalence, treatment distribution, and survival outcomes for patients with severe AS aged ≥60 years. Using a mixed methodology of meta-analysis and stochastic simulation, our analysis estimates the number of patients with severe AS eligible for AVR across 37 countries comprising the International Monetary Fund's 2015 advanced economies index. Key Words: aortic valve ◼ aortic valve stenosis ◼ heart valve prosthesis ◼ transcatheter aortic valve replacement ◼ meta-analysis Background-In

Certain styrenic thermoplastic block copolymer elastomers can be processed to exhibit anisotropic mechanical properties which may be desirable for imitating biological tissues. The ex-vivo hemocompatibility of four triblock (hard–soft–hard) copolymers with polystyrene hard blocks and polyethylene, polypropylene, polyisoprene, polybutadiene or polyisobutylene soft blocks are tested using the modified Chandler loop method using fresh human blood and direct contact cell proliferation of fibroblasts upon the materials. The hemocompatibility and durability performance of a heparin coating is also evaluated. Measures of platelet and coagulation cascade activation indicate that the test materials are superior to polyester but inferior to expanded polytetrafluoroethylene and bovine pericardium reference materials. Against inflammatory measures the test materials are superior to polyester and bovine pericardium. The addition of a heparin coating results in reduced protein adsorption and ex-vivo hemocompatibility performance superior to all reference materials, in all measures. The tested styrenic thermoplastic block copolymers demonstrate adequate performance for blood contacting applications.

ObjectiveThe study aims were (1) to identify the community prevalence of moderate or greater mitral or tricuspid regurgitation (MR/TR), (2) to compare subjects identified by population screening with those with known valvular heart disease (VHD), (3) to understand the mechanisms of MR/TR and (4) to assess the rate of valve intervention and long-term outcome.MethodsAdults aged ≥65 years registered at seven family medicine practices in Oxfordshire, UK were screened for inclusion (n=9504). Subjects with known VHD were identified from hospital records and those without VHD invited to undergo transthoracic echocardiography (TTE) within the Oxford Valvular Heart Disease Population Study (OxVALVE). The study population ultimately comprised 4755 subjects. The severity and aetiology of MR and TR were assessed by integrated comprehensive TTE assessment.ResultsThe prevalence of moderate or greater MR and TR was 3.5% (95% CI 3.1 to 3.8) and 2.6% (95% CI 2.3 to 2.9), respectively. Primary MR was the most common aetiology (124/203, 61.1%). Almost half of cases were newly diagnosed by screening: MR 98/203 (48.3%), TR 69/155 (44.5%). Subjects diagnosed by screening were less symptomatic, more likely to have primary MR and had a lower incidence of aortic valve disease. Surgical intervention was undertaken in six subjects (2.4%) over a median follow-up of 64 months. Five-year survival was 79.8% in subjects with isolated MR, 84.8% in those with isolated TR, and 59.4% in those with combined MR and TR (p=0.0005).ConclusionsModerate or greater MR/TR is common, age-dependent and is underdiagnosed. Current rates of valve intervention are extremely low.

A bi-directional, layered microstructure in cylinder forming block copolymers results from the local balance of shear and extensional flow during slow injection moulding.

Styrene-based block copolymers are promising materials for the development of a polymeric heart valve prosthesis (PHV), and the mechanical properties of these polymers can be tuned via the manufacturing process, orienting the cylindrical domains to achieve material anisotropy. The aim of this work is the development of a computational tool for the optimization of the material microstructure in a new PHV intended for aortic valve replacement to enhance the mechanical performance of the device. An iterative procedure was implemented to orient the cylinders along the maximum principal stress direction of the leaflet. A numerical model of the leaflet was developed, and the polymer mechanical behavior was described by a hyperelastic anisotropic constitutive law. A custom routine was implemented to align the cylinders with the maximum Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts principal stress direction in the leaflet for each iteration. The study was focused on valve closure, since during this phase the fibrous structure of the leaflets must bear the greatest load. The optimal microstructure obtained by our procedure is characterized by mainly circumferential orientation of the cylinders within the valve leaflet. An increase in the radial strain and a decrease in the circumferential strain due to the microstructure optimization were observed. Also, a decrease in the maximum value of the strain energy density was found in the case of optimized orientation; since the strain energy density is a widely used criterion to predict elastomer's lifetime, this result suggests a possible increase of the device durability if the polymer microstructure is optimized. The present method represents a valuable tool for the design of a new anisotropic PHV, allowing the investigation of different designs, materials, and loading conditions. Keywordspolymeric heart valve; heart valve prosthesis; computational modeling