Клышников К.Ю., Овчаренко Е.А., Евтушенко А.В., Барбараш Л.С. Гидродинамические характеристики протеза клапана аорты с адаптивным динамическим каркасом. Сердечно-сосудистые заболевания. Бюллетень НЦССХ им. А.Н. Бакулева РАМН. 2023; 24 (1): 32–40. DOI: 10.24022/1810-0694-2023-24-1-32-40 HTML

Исследование посвящено оценке сохранения остаточного просвета армированного биопротеза сосудистого русла ксеногенного происхождения «КемАнгиоПротез» (ЗАО «НеоКор», Кемерово) при перегибе. Использованный в работе комплекс натурных и численных методов позволил определить механические свойства исследуемых объектов. В работе были использованы параметры шага спирали - 4 мм и толщины нити - 0.3-0.5 мм. Показано, что свойства материала сосудистой стенки анизотропны при сравнении продольного и поперечного направлений приложения нагрузки. Так, модули упругости составили 1.37 (0.90, 1.12, 1.44, 1.72) МПа против 0.80 (0.97, 1.23, 1.61, 2.15) МПа, соответственно, статистически значимо различаясь (p < 0.05). С помощью метода конечных элементов, использованного в работе на этапе подбора параметров армирующего слоя, показано, что остаточный просвет сосудистого протеза нелинейно зависит от особенностей армирования - количества нанесенных спиралей. Показано, что использование внешнего полимерного армирующего слоя позволяет снизить эффект перекрытия сосудистого протеза в случаях его изгиба, что характерно для инфраингвинальных реконструкций, в особенности при сравнении с исходным неармированным изделием. Дополнительно, введение усиления повышает радиальную жесткость протеза, что, потенциально, способно привести к снижению риска образования аневризм сосудистой стенки в отдаленном периоде.

The aim of the study was an in vitro hydrodynamic study of the developed prosthetic heart valve of the second generation, designed to carry out an implantation using «valve-in-valve» method. Material and methods. Prototypes of the developed prosthesis were studied under simulated physiological conditions of the heart using a Vivitro Labs pulse duplicator (Canada) in a comparative aspect with «UniLine» clinical commercial aortic valve bioprosthesis (Russia). Samples were tested by simulating sutureless implantation procedure. Results . The developed valves showed satisfactory hydrodynamic characteristics – for all cases of «implantation» from the position of the average trans-prosthetic gradient (6.1–11.1 mm Hg) and the effective orifice area (1.60–1.81 cm2 ). The analysis of the regurgitation fraction allowed us to determine the optimal sizes for implantation using «valvein-valve» method, which subsequently will form the basis of sizing guidelines for size selection. A qualitative analysis of the leaflet’s work demonstrated the presence of slight asymmetry for a number of prostheses – in case of mismatch of sizes when simulating «valve-in-valve» procedure. Conclusion . The tests demonstrate the viability of the developed design from the standpoint of hydrodynamic efficiency and determines the basic rules of selecting a prosthesis for reimplantation relative to the primary valve.

Implantation of polymeric heart valves can solve the problems of existing valve substitutes – mechanical and biological. Objective : to comprehensively assess the hemocompatibility of styrene-isobutylene-styrene (SIBS) triblock copolymer, synthesized by controlled cationic polymerization in comparison with expanded polytetrafluoroethylene (ePTFE) used in clinical practice. Materials and methods . SIBS-based films were made by polymer solution casting method; in vitro biocompatibility assessment was performed using cell cultures, determining cell viability, cell adhesion and proliferation; tendency of materials to calcify was determined through in vitro accelerated calcification; i n vivo biocompatibility assessment was performed by subcutaneous implantation of rat samples; hemocompatibility was determined ex vivo by assessing the degree of hemolysis, aggregation, and platelet adhesion. Results . The molecular weight of synthesized polymer was 33,000 g/mol with a polydispersity index of 1.3. When studying cell adhesion, no significant differences (p = 0.20) between the properties of the SIBS polymer (588 cells/mm 2 ) and the properties of culture plastics (732 cells/mm 2 ) were discovered. Cell adhesion for the ePTFE material was 212 cells/mm 2 . Percentage of dead cells on SIBS and ePTFE samples was 4.40 and 4.72% (p = 0.93), respectively, for culture plastic – 1.16% (p < 0.05). Cell proliferation on the ePTFE surface (0.10%) was significantly lower (p < 0.05) than for the same parameters for SIBS and culture plastic (62.04 and 44.00%). Implantation results (60 days) showed the formation of fibrous capsules with average thicknesses of 42 μm (ePTFE) and 58 μm (SIBS). Calcium content in the explanted samples was 0.39 mg/g (SIBS), 1.25 mg/g (ePTFE) and 93.79 mg/g (GA-xenopericardium) (p < 0.05). Hemolysis level of red blood cells after contact with SIBS was 0.35%, ePTFE – 0.40%, which is below positive control (p < 0.05). Maximum platelet aggregation of intact platelet-rich blood plasma was 8.60%, in contact with SIBS polymer – 18.11%, with ePTFE – 22.74%. Conclusion . In terms of hemocompatibility properties, the investigated SIBS polymer is not inferior to ePTFE and can be used as a basis for development of polymeric prosthetic heart valves.

Background.  Tissue-engineered vascular grafts can be reinforced by a biostable or biodegradable polymer sheath. A combination of electrospinning, routinely used for fabrication of biodegradable tubular grafts, and the layer-by-layer coating allows forming a polymeric sheath ensuring long-term integrity and high biocompatibility of the vascular grafts after the implantation. Aim To evaluate mechanical properties and in vivo performance of biodegradable small-diameter vascular grafts with a reinforcing sheath. Methods.  Tubular grafts (4 mm diameter) were fabricated from poly(3-hydroxybutyrate-co3-hydroxyvalerate) and poly(e-caprolactone) by emulsion electrospinning with the incorporation of vascular endothelial growth factor (VEGF) into the inner third of the graft and basic fibroblast growth factor (bFGF) along with stromal cell-derived factor-1α (SDF-1α) into the outer two thirds of the graft wall. Poly(e-caprolactone) sheath was formed by the layer-by-layer coating. Upon graft fabrication, scanning electron microscopy was performed to assess the grafts’ surface, tensile testing allowed evaluating mechanical properties. The samples were implanted into the ovine carotid artery (n = 5 animals) for 12 months with the subsequent histological examination. Results.  Sintering temperature of 160°C during the extrusion allowed effective and delicate merging of poly(e-caprolactone) coating with the outer surface of the poly(3hydroxybutyrate-co-3-hydroxyvalerate)/poly(e-caprolactone) tubular graft. The thickness of poly(e-caprolactone) fiber was 380–400 μm, the increment of the reinforcing filament was 1 mm. The reinforcing sheath led to a 3-fold increase in durability and elastic modulus of the vascular grafts. At the 12-months follow-up, the grafts reported retained integrity. No signs of inflammation or calcification were found. Conclusion.  The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(e-caprolactone) vascular grafts with hierarchically incorporated growth factors and the reinforced poly(e-caprolactone) spiral sheath demonstrated improved mechanical properties while retaining integrity and high biocompatibility after the long-term implantation into the ovine carotid artery.

Since its introduction in 2002, transcatheter aortic valve implantation (TAVI) has evolved dramatically and is now standard of care for intermediate risk patients with aortic stenosis. The development of innovative transcatheter heart valves and refinement of technical skills have contributed to the decrease in complication rates associated with TAVI. Increased experience, smaller sheaths, rigorous pre-procedural planning and improved vascular closing techniques have resulted in markedly lower rates of vascular complications. The next step was the simplification of the procedure, which contributed to a further decrease in complications, reduced procedural time, and shorter hospital stay. Change-over from general anaesthesia to conscious sedation, refusal from predilatation, and use of the radial approach instead of the contralateral femoral approach are all instrumental in achieving optimal results. Prospects for development include visual assist systems and robotic systems that can potentially optimize the transcatheter aortic valve implantation process, improve safety and effectiveness of the procedure.

Background The current study highlights potential benefits of using ePTFE, a polymeric material, as the main component suitable for fabrication of prosthetic heart valves. Novel polymeric materials seem to be promising for replacing biological elements commonly used in medical products for cardiovascular surgery. High biocompatibility and mechanical properties prolong their lifespan during direct blood contact. Nevertheless, it is necessary to conduct a series of specific tests to determine their properties and benefits of their application. Despite well-known biological properties of ePTFE, there are few studies assessing it as a material for heart valve leaflets. Aim To evaluate the mechanical properties of the commercially available sample of ePTFE and to conduct a numerical experiment assessing its potential for the application. Methods The polymer properties (Gore & Associates Inc., USA) were evaluated under uniaxial tension in two mutually perpendicular directions to determine the degree of anisotropy of the material. A xenopericardial patch (ZAO “NeoCor”, Russia), routinely used for the fabrication of bioprosthetic leaflets, was taken as the control sample. The spatial model of the investigated material was carried out in CAD SolidWorks 2016 (Dassault Systemes, USA). Numerical modeling of the samples was performed with the finite element method using the orthotropic material model in the Abaqus/CAE (Dassault Systemes, USA). Results There are significant difference found in the mechanical properties of the studied materials: the tension at stretching of ePTFE in the longitudinal and transverse directions differed from xenopericardium by 1.9 and 7.5 times, respectively (p < 0.05). The elongation before rupture of ePTFE in direction I and direction II was greater than that of xenopericardium (2.39 vs. 1.9 times, respectively). Numerical modeling demonstrated insignificant qualitative differences in the valve opening while applying pressure equal to normal physiological pressure and low pressure. In addition, the zones of high stress in commissural racks, which are critical zones for fatigue resistance, have been identified, albeit require additional in vitro research. Conclusion Mechanical properties of ePTFE suggests it to be a promising polymeric material suitable for fabrication of flexible leaflets of the heart valve prosthesis. It has similar leaflet functioning, compared with the xenopericardium sample, routinely used in manufacturing. ePTFE is more resistant to rupture, which confirms its greater fatigue strength. However, it requires further study by advanced methods.

Aim : to evaluate the manipulative properties of the system being developed for cardiac valve re-operation on an in vitro bovine heart model. Material and methods. The prototype of the prosthesis being developed, mounted on the implant holder, as well as the dilatation balloon of its own design, were used as the objects of the study. The bioprosthesis «UniLine» of 21 mm size for the aortic position was chosen as the target site of implantation, which was established by the «classical» suture method. After that, the implantation of the tested device was carried out as a «valve in valve» and the quality of the installation and the combined operation of all the components of the re-prosthesis system were evaluated. Results. The test implantation demonstrated the consistency of the proposed method on the basis of balloon seamless fi xation, as well as high ergonomic characteristics: the average time of seamless implantation of the developed prototype on an in vitro animal heart model was 3 minutes versus the implantation of the «UniLine» bioprosthesis – 11 min, Implantation provided a reliable prosthesis The breaking force was 12.9 N, which is equivalent to a pressure of 279 mm Hg.

Insufficiency of the valvular apparatus of the lower-limb veins is one of the main causes of the development of chronic venous insufficiency. This disease is commonly prevalent in developed countries including Russia and is an urgent and socially significant problem. Insufficiency of the venous valves may be corrected by a wide variety of approaches and methods however they all are not universal or have low efficacy and in some cases cannot be applied at all. This article is dedicated to the review of the existing methods of surgical correction of valvular insufficiency of lower-limb veins, as well as a review of the studies of the most promising trend of this problem, i.e. prosthetic repair of venous valves.