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Background Whereas the risk factors for structural valve degeneration (SVD) of glutaraldehyde‐treated bioprosthetic heart valves (BHVs) are well studied, those responsible for the failure of BHVs fixed with alternative next‐generation chemicals remain largely unknown. This study aimed to investigate the reasons behind the development of SVD in ethylene glycol diglycidyl ether–treated BHVs. Methods and Results Ten ethylene glycol diglycidyl ether–treated BHVs excised because of SVD, and 5 calcified aortic valves (AVs) replaced with BHVs because of calcific AV disease were collected and their proteomic profile was deciphered. Then, BHVs and AVs were interrogated for immune cell infiltration, microbial contamination, distribution of matrix‐degrading enzymes and their tissue inhibitors, lipid deposition, and calcification. In contrast with dysfunctional AVs, failing BHVs suffered from complement‐driven neutrophil invasion, excessive proteolysis, unwanted coagulation, and lipid deposition. Neutrophil infiltration was triggered by an asymptomatic bacterial colonization of the prosthetic tissue. Neutrophil elastase, myeloblastin/proteinase 3, cathepsin G, and matrix metalloproteinases (MMPs; neutrophil‐derived MMP‐8 and plasma‐derived MMP‐9), were significantly overexpressed, while tissue inhibitors of metalloproteinases 1/2 were downregulated in the BHVs as compared with AVs, together indicative of unbalanced proteolysis in the failing BHVs. As opposed to other proteases, MMP‐9 was mostly expressed in the disorganized prosthetic extracellular matrix, suggesting plasma‐derived proteases as the primary culprit of SVD in ethylene glycol diglycidyl ether–treated BHVs. Hence, hemodynamic stress and progressive accumulation of proteases led to the extracellular matrix degeneration and dystrophic calcification, ultimately resulting in SVD. Conclusions Neutrophil‐ and plasma‐derived proteases are responsible for the loss of BHV mechanical competence and need to be thwarted to prevent SVD.

The cationic polymerization of isobutylene and its block copolymerization with styrene using DiCumCl/TiCl4/2,6-lutidine initiating system has been studied in open conditions. It was shown that a higher concentration of proton trap is required in open conditions as compared to the glove box technique in order to have good control over molecular weight and polydispersity. Polyisobutylenes with Mn ≤ 50,000 g mol−1 and low polydispersity (Đ ≤ 1.2) were prepared at [Lu] = 12 mM. The synthesis of poly(styrene-block-isobutylene-block-styrene) triblock copolymer (SIBS) in open conditions required the addition of proton trap into two steps, half at the beginning of the reaction and the second half together with styrene. Following this protocol, a series of triblock copolymers with different length of central polyisobutylene block (from Mn = 20,000 g mol−1 to 50,000 g mol−1) and side polystyrene blocks (Mn = 4000 g mol−1–9000 g mol−1) with low polydispersity (Đ ≤ 1.25) were synthesized. High molecular SIBS (Mn &gt, 50,000 g mol−1) with low polydispersity (Đ &lt, 1.3) containing longer polystyrene blocks (Mn &gt, 6000 g mol−1) demonstrated higher tensile strength (~13.5 MPa).

Objective: to study cellular and lipid infiltration, as well as the expression of tissue inhibitors of metalloproteinases (TIMP) types 1 and 2 in biological prosthetic heart valves (BPHVs) explanted due to dysfunction.Material and Methods. We examined 17 leaflets from 6 BPHVs, dissected from the aortic and mitral positions during valve replacement. For microscopic analysis, fragments of the BPHV leaflets were frozen and serial sections were made using a cryotome. In order to study cellular infiltration and the degree of degenerative changes in the prosthetic biomaterial, the sections were stained with Gill’s hematoxylin and eosin; Oil Red O stain was used to assess lipid deposition. Immunohistochemistry was used for cell typing and detection of TIMP-1/-2. The stained samples were analyzed by light microscopy.Results. Cellular and lipid infiltration of xenogeneic tissues was detected in all BPHV flaps studied. Recipient cells coexpressed pan-leukocyte and macrophage markers PTPRC/CD45 and CD68. Positive staining for TIMP-1/-2 co-localized with cell clusters but was absent in acellular sections.Conclusion. Cells infiltrating xenogeneic BPHV tissues express TIMP-1/-2. This suggests that BPHV immune rejection pathophysiology is partially similar to that of calcific aortic stenosis.

Objective: to justify the design of a self-expanding transcatheter aortic valve prosthesis based on a biomaterial stabilized with ethylene glycol diglycidyl ether using numerical simulation and a series of field experiments with working prototypes to determine the consistency of the proposed design solutions.Material and methods. Numerical computer models of a developed aortic valve prosthesis intended for transcatheter implantation, as well as prototypes of the most promising concepts for a series of field tests, were used in the work. Computer 3D models were subjected to numerical analysis in the Abaqus/CAE environment (Dassault Systemes, France) based on the finite element method with iterative design optimization and repeated numerical experiments. Physical prototypes of the transcatheter prosthesis were subjected to a series of mechanical tests for axial and radial compression, as well as tests on a Vivitro hydrodynamic stand (Vivitro Labs, Canada) under simulated normal flow. All studies were carried out in a comparative aspect with a similar transcatheter aortic valve prosthesis (control), the CoreValve™ bioprosthesis (Medtronic, Inc., USA).Results. Computer simulation demonstrates the stress-strain state values that do not significantly exceed the critical levels (628 and 756 MPa versus the threshold value 1080 MPa) for two basic concepts of support frames. The fatigue strength based on the calculation of the mean and alternating stresses corresponding to normo- and hypertensive states based on the Goodman diagrams, did not reveal any evidence that the threshold values (destruction area after 200 million cycles) were exceeded. The hydrodynamic characteristics of working prototypes made on the basis of computer models correspond to the testing data of CoreValve™ clinical bioprosthesis: the effective orifice area was 1.97 cm2, the mean transprosthetic gradient was 8.9 mm Hg, the regurgitant volume was 2.2–4.1 mL per cycle depending on the prototype model.Conclusion. Generally, experiments carried out showed the consistency of the concepts, including from the point of view of implementation of the leaflet apparatus based on xenogeneic tissues treated with ethylene glycol diglycidyl ether.

We report here finite element analysis of the mechanical behavior of aortic valve implant support frames. The material fatigue strength and the effects of annealing on the frames were assessed. The von Mises stresses arising during production processing in the lamellae of the end sections were found to have amplitudes close to the critical (ultimate tensile strength). Annealing reduced the maximum stress by 14.8–23.3% compared to non–annealed samples. Annealed support frames are expected to display more satisfactory material fatigue strength characteristics under the same alternating cyclic stresses.

The goal of this study was to assess the patency rate for a reinforced vascular bioprosthesis with KemAngioProsthesis xenogenic cells (JSC NeoСor, Kemerovo) during its mechanical deformation. The complex of natural and numerical methods used in the work made it possible to determine the mechanical properties of the test objects. We used a pitch of the helix of 4 mm and a thickness of the thread of 0.3–0.5 mm. It is shown that the material properties of the vascular wall are anisotropic compared to the longitudinal and transverse directions under loading. Thus, the elastic moduli were 1.37 (0.90, 1.12, 1.44, and 1.72) MPa versus 0.80 (0.97, 1.23, 1.61, and 2.15) MPa, respectively; the statistical analysis showed significant differences of these moduli among layers (p < 0.05). Using the finite element method to select parameters for the reinforcing lining it was found that the patency rate for a vascular prosthesis depends nonlinearly on the number of spirals. It has been shown that the external polymeric reinforcing lining during its mechanical deformation can offer satisfying patency rates and outcomes, which is typical of infra-inguinal reconstructions, especially when compared to the original unreinforced product. Additionally, the introduction of reinforcement increases the radial stiffness of the prosthesis, which can potentially lead to a decrease in the risk of vascular wall aneurysms in the long term.

This paper describes an approach based on machine learning technology that is of particular interest for the localization and characterization of both single focal stenoses and multivessel multifocal lesions. Due to the complexity of analyzing large amounts of data for the cardiac surgeon, we pay special attention to the analysis, training, and comparison of popular neural networks that classify and localize foci of stenosis on coronary angiography data. From the complete coronarography dataset collected at the Research Institute for Complex Issues of Cardiovascular Diseases, we retrospectively select data of 100 patients. For the automated analysis of the medical data, the paper considers in detail three models (SSD MobileNet V1, Faster-RCNN ResNet-50 V1, and Faster-RCNN NASNet), which differ in their architecture, complexity, and the number of weights. The models are compared in terms of their basic efficiency characteristics: accuracy, training time, and prediction time. The test results show that the training and prediction times are directly proportional to the complexity of the models. In this regard, Faster-RCNN NASNet exhibits the lowest prediction time (the average processing time for one image is 880 ms), while Faster-RCNN ResNet-50 V1 has the highest prediction accuracy. The latter model reaches the mean average precision (mAP) level of 0.92 on the validation dataset. On the other hand, SSD MobileNet V1 is the fastest model, capable of making predictions with a prediction rate of 23 fps.

Calcification of biomaterials used in prosthetic heart valves has been a challenging issue in cardiovascular surgery. The objective of this work is to compare the efficiency of polyvinyl alcohol (PVA) and tannic acid (TA) modification of xenomaterials, pre-stabilized with glutaraldehyde (GA) and ethylene glycol diglycidyl ether (EGDE), in reducing calcification. Analysis of mechanical properties evaluated under uniaxial tension, showed a significant increase in the tensile strength of the test samples compared to the control (unmodified) samples (p < 0.05). Additional treatment of GA-fixed tissue with PVA and TA significantly reduced the amount of calcium in the samples implanted into rats for a 60-day follow-up (p < 0.05). The level of calcification of samples prestabilized with EGDE and treated with PVA and TA did not differ from the control group (p = 0.063). Cumulative analysis of the study results demonstrated that the GA-fixed biomaterial modified with PVA and TA can reduce calcium-binding activity and increase strength. This indicates the prospects for clinical application of the proposed treatment methods. This being said, the issue of long-term body response requires further study of the long-term stability of the modified biomaterial under physiologic blood flow conditions.

The study of blood flow in vascular bioprostheses is a rather complicated task, since the shape of the inner surface of the bioprosthesis is variable, due to xenogenic origin. Because of this, vortex zones can occur inside the vascular bioprosthesis. In addition, the flow structure may contain sections where the flow velocity is abnormally high. It is all the more difficult to assess the nature of the course when using this vascular bioprosthesis as a shunt. A numerical comparison of the blood flow in a bioprosthesis connected to the main vascular bed using the «end-to-end» and «end-to-side» methods (bypass) taking into account the heart rate and blood pressure was performed. It is shown that, due to the nonlinearity of the initial bioprosthesis geometry, the implantation method affects the blood flow. Because of this, vortex zones arise and, with certain combinations of parameters, the effects of «separation» of vortices.

A biocompatible thermoelastoplastic, poly(styrene-block-isobutylene-block-styrene), was incorporated with carbon nanotubes. The resulting nanocomposites containing 1, 2, and 4% filler were analyzed by optical microscopy and scanning electronic microscopy, and their strength, elastic-strain properties, contact angle with water, and electrical conductivity were evaluated. Partial heterogeneity in the nanofiller distribution in the macromolecular matrix was revealed. With an increase in the nanotube concentration, the tensile strength increases nonlinearly and the extension ability decreases. Statistically significant differences in the contact angle between the control samples and samples containing 4% carbon nanoparticles were revealed (94.1°± 1.7°and 84.4°± 2.3°, respectively). The electrical conductivity of the samples increases with an increase in the content of nanoparticles. The possibility and conditions of preparing the new promising material for cardiovascular surgery were determined.

This review discusses works on the use of artificial neural networks for processing numerical and textual data. Application of a number of widely used approaches is considered, such as decision support systems; prediction systems, providing forecasts of outcomes of various methods of treatment of cardiovascular diseases, and risk assessment systems. The possibility of using artificial neural networks as an alternative approach to standard methods for processing patient clinical data has been shown. The use of neural network technologies in the creation of automated assistants to the attending physician will make it possible to provide medical services better and more efficiently.

The aim of the study was to develop a prognostic model based on statistical discriminant analysis to assess the risk of postoperative disturbance of cardiac conduction and paraprosthetic regurgitation after transcatheter aortic valve replacement. Materials and Methods Clinical data of 10 patients implanted with CoreValveTM prostheses (Medtronic Inc., USA) were used to develop prognostic models. To that end, we analyzed changes in hemodynamic and functional parameters provided by echocardiography in the pre- and postoperative periods. Results We observed significant positive changes in the severity of left ventricular myocardial hypertrophy; on the contrary, volume indicators did not significantly change, which might be associated with the concentric type of left ventricular hypertrophy. The discriminant analysis made it possible to determine major (preoperative) morphological and functional indicators associated with the two most common complications of the procedure: left bundle branch block and paraprosthetic regurgitation. Left ventricular posterior wall thickness, interventricular septal thickness, left atrium dimension, and myocardial mass are the critical factors that determine the development of these complications. Conclusion In the prognostic model, the proposed weighting coefficients allow one to assess the risk of postoperative complications; however, the presence of false-positive results requires further refinement of these coefficients within the linear equation.

Invasive coronary angiography remains the gold standard for diagnosing coronary artery disease, which may be complicated by both, patient-specific anatomy and image quality. Deep learning techniques aimed at detecting coronary artery stenoses may facilitate the diagnosis. However, previous studies have failed to achieve superior accuracy and performance for real-time labeling. Our study is aimed at confirming the feasibility of real-time coronary artery stenosis detection using deep learning methods. To reach this goal we trained and tested eight promising detectors based on different neural network architectures (MobileNet, ResNet-50, ResNet-101, Inception ResNet, NASNet) using clinical angiography data of 100 patients. Three neural networks have demonstrated superior results. The network based on Faster-RCNN Inception ResNet V2 is the most accurate and it achieved the mean Average Precision of 0.95, F1-score 0.96 and the slowest prediction rate of 3 fps on the validation subset. The relatively lightweight SSD MobileNet V2 network proved itself as the fastest one with a low mAP of 0.83, F1-score of 0.80 and a mean prediction rate of 38 fps. The model based on RFCN ResNet-101 V2 has demonstrated an optimal accuracy-to-speed ratio. Its mAP makes up 0.94, F1-score 0.96 while the prediction speed is 10 fps. The resultant performance-accuracy balance of the modern neural networks has confirmed the feasibility of real-time coronary artery stenosis detection supporting the decision-making process of the Heart Team interpreting coronary angiography findings. ispartof: SCIENTIFIC REPORTS vol:11 issue:1 ispartof: location:England status: published

Currently, transcatheter aortic valve implantation (TAVI) represents the most efficient treatment option for patients with aortic stenosis, yet its clinical outcomes largely depend on the accuracy of valve positioning that is frequently complicated when routine imaging modalities are applied. Therefore, existing limitations of perioperative imaging underscore the need for the development of novel visual assistance systems enabling accurate procedures. In this paper, we propose an original multi-task learning-based algorithm for tracking the location of anatomical landmarks and labeling critical keypoints on both aortic valve and delivery system during TAVI. In order to optimize the speed and precision of labeling, we designed nine neural networks and then tested them to predict 11 keypoints of interest. These models were based on a variety of neural network architectures, namely MobileNet V2, ResNet V2, Inception V3, Inception ResNet V2 and EfficientNet B5. During training and validation, ResNet V2 and MobileNet V2 architectures showed the best prediction accuracy/time ratio, predicting keypoint labels and coordinates with 97/96% accuracy and 4.7/5.6% mean absolute error, respectively. Our study provides evidence that neural networks with these architectures are capable to perform real-time predictions of aortic valve and delivery system location, thereby contributing to the proper valve positioning during TAVI.

A three-dimensional unsteady periodic flow of blood in xenogenic vascular bioprostheses is simulated by computational fluid dynamics methods. The geometry of the computational domain is based on microtomographic scanning of bioprostheses. To set a variable pressure gradient causing an unsteady flow in the prostheses, personal-specific data of the Doppler echography of the blood flow of a particular patient are used. A comparative analysis of the velocity fields in the flow areas corresponding to three real samples of bioprostheses with multiple stenoses is carried out. In the zones of stenosis and outside of them, the distribution of the near-wall shear stress, which affects the risk factors for thrombosis in the prostheses, is analyzed. An algorithm for predicting the hemodynamic effects arising in vascular bioprostheses is proposed; the algorithm is based on the numerical modeling of the blood flow in these prostheses.

The study is devoted to numerical modeling of transcatheter aortic valve implantation (TAVI) from the position of prognostic value in comparison with clinical data. The finite element method implemented in the Abaqus/CAE software and the reconstruction of three-dimensional models based on the computer microtomography of the CoreValve bioprosthesis of a size of 29 mm and the patient-specific data of functional studies (multispiral tomography) were used in the work. The study included three variations in the modeling of the aortic valve prosthesis procedure, which determine the level of detalization of the numerical experiment. All stages of the TAVI process were reproduced: the crimp of the prosthesis, the movement of the delivery system, the interaction of the guide - guidewire with the elements of the “prosthesis-root” of the aorta system, implantation itself. In silico experiment demonstrated significant quantitative and qualitative agreement with the data of intraoperative fluorography and computed tomography after the TAVI procedure. It is shown that the inclusion of additional elements – the guidewire and catheter of the delivery system into the “aortic root” has a positive effect on the convergence of the data with the clinical results. The analysis of the stress-strain state of the elements interacting in the experiment demonstrated a significant contribution to the analyzed parameters of the prosthetic motion stage along the guidewire as part of the delivery system catheter. Nevertheless, a comparison with the results of the clinical evaluation of the TAVI procedure revealed a number of differences in the response of the model of the bioprosthesis at the later stages of modeling, which requires further researches of a level of detalization. The approach is extremely promising both for practitioners and for research work of prosthetic designers, it can be applied in further R&D tasks.

—A numerical evaluation was performed to assess the efficiency of reinforcement of small-diameter vascular grafts made of polymeric materials. Based on the finite-element analysis, an algorithm was developed to find the optimal parameters for the reinforcing layer and to evaluate its stress–strain state under conditions of longitudinal bending simulation. The findings may be useful for industrial and laboratory trials in studies of the strengthening properties of similar products.

Search for promising polymer materials as a base for cusps of leaflet heart valve prostheses is a topical problem from the viewpoint of limited durability of fixed biological material. For this purpose, styrene-isobutylene-styrene (SIBS) triblock copolymer was prepared by controlled cationic polymerization. The synthesized SIBS is characterized by the number-average molecular mass Mn = 33 000 and narrow monodisperse molecular-mass distribution (Mw/Mn = 1.3). The ultimate strength of the polymer film was lower than that of xenopericard and ePTFE in the longitudinal direction by a factor of 3.30 and 6.36, respectively (p < 0.05); it was lower than that of ePTFE in the transverse direction by a factor of 4.58 (p < 0.05) and did not differ significantly (p = 0.65) from that of xenopericard in the transverse direction. The relative elongation and Young’s modulus of the SIBS film exceeded those of ePTFE and xenopericard in the longitudinal direction by a factor of 3.00 and 5.68 and in the transverse direction by a factor of 6.50 and 3.86, respectively (p < 0.05). The contact angle for different sides of the SIBS film was 101.6° ± 2.9°/104.4° ± 0.9°. According to the data of atomic force microscopy, the height difference on the SIBS surface usually did not exceed 1 µm, with separate pits of 20–40 µm size. The results of studying the physical properties of the surface and the mechanical properties determining the primary biocompatibility factors in comparison with control materials show that SIBS polymers are promising for making leaflet heart valve prostheses.

Polymeric heart valves seem to be an attractive alternative to mechanical and biological prostheses as they are more durable, due to the superior properties of novel polymers, and have the biocompatibility and hemodynamics comparable to tissue substitutes. This study reports a comprehensive assessment of a nanocomposite based on the functionalised graphene oxide and poly(carbonate-urea)urethane with the trade name “Hastalex” in comparison with GORE-TEX, a commercial polymer routinely used for cardiovascular medical devices. Experimental data have proved that GORE-TEX has a 2.5-fold (longitudinal direction) and 3.5-fold (transverse direction) lower ultimate tensile strength in comparison with Hastalex (p

The paper describes the features of in silico simulation of fluid flows of variable viscosity in the study of prosthetic heart valves. Computer modeling and its verification were performed on the example of the bioprosthesis "UniLine" (Russia) used in modern cardio-surgical practice. A spatial model of the object of investigation was obtained by the method of computer microtomography, followed by the reconstruction of the primitive grid in two-dimensional sections. In the numerical experiment, the immersed boundary method was used. Herein the interaction of a solid and a liquid as well as the impact of mechanics of deformation of the elements of the prosthesis, such as the winged apparatus, were taken into account. Verification of the calculation algorithm was performed in the pulsating flow setup in conditions of simulating the physiological parameters of hydrodynamics similar to those used in silico. In general, the results of the simulation are consistent with the quantitative and qualitative data of the hydrodynamic experiment. Thus, in the numerical simulation, a pressure gradient of 3.0 ± 1.1 mmHg was obtained, an effective orifice area of 2.8 cm2, a regurgitation volume of 0.1 ml/min. The experimental evaluation has shown the similar indicators: 6.5 ± 3.6 mmHg, 2.3 ± 0.6 cm2, 3.1 ± 1.7 ml/min, respectively. The described method demonstrates its promise and can be used in design and research tasks.

Arterial aneurysms represent a significant cause of morbidity and mortality worldwide; therefore, there is a growing need for the rapid and precise tool or method enabling to predict aneurysm emergence. The objective of this study was to develop a computer-aided method for aneurism prediction. Here we utilized a computer-based approach to establish a non-invasive, high-resolution and rapid method for the prediction of aneurysm-prone arterial segments based on combining microcomputed tomography (microCT) scanning with finite element analysis (FEA). We performed a microCT image binarization and designed a computing algorithm for FEA mesh construction, followed by application of gradient mapping and stress modeling to identify thin-walled high-stress areas responsible for the development of aneurysms. The fidelity of our computing algorithm for FEA mesh construction was similar to the commercially available software. The maximum possible error of our approach did not exceed that of either microCT or clinically available multislice computed tomography angiography scanning. Our computational approach revealed thin-walled arterial segments under a high stress, therefore potentially predicting aneurysm-prone sites. Here we demonstrate our approach for the prediction of arterial segments under a high risk of aneurysm occurrence, which should be further validated in pre-clinical models to be translated into the clinical practice.

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.

We examined a fiber formation from pristine and modified single-walled carbon nanotube (SWCNT) films using a recently developed wet pulling technique. Crucial phenomena in the wet pulling process are a folding of a solvent soaked SWCNT film due to the liquid surface tension and fiber densification during the solvent evaporation. It is shown that electrical characteristics of the as-produced fibers are determined by the type of the liquid employed in their formation, which defines the SWCNT packing degree. The obtained specific strength (0.6–0.8 N/tex), toughness (up to 127 J/g) and specific conductivity (0.5–1.2 kS·m2/kg) are in many cases comparable with published data for fibers produced by more resource-consuming methods. These, in combination with the simplicity of our method and high piezoresistive gauge factor of 14 (for untwisted fibers at a 1% elongation), make SWCNT fibers promising components in future applications of stretchable electronics and robotics.

The aim of the study was to determine the potential mechanism of vascular complications due to "catheter-vascular wall" interaction in transcatheter aortic valve replacement using experimental and numerical analysis. Materials and methods A series of full-scale bench tests and numerical simulations were carried out using the CoreValve commercial transfemoral delivery system for aortic valve bioprosthesis (Medtronic Inc., USA). Full-scale tests were carried out using a phantom of the vascular system (a polymeric silicone model of Transcatheter Aortic Valve; Trandomed 3D Inc., China) with simulation of all stages of delivery system movement along the vascular bed. They involved introduction into the common femoral artery, movement along the abdominal and thoracic parts of the aorta, the aortic arch, and positioning the system to the implantation site. The force arising from the passage of the delivery system was assessed using sensors of a Z50 universal testing machine (Zwick/Roell, Germany). Numerical simulation of transcatheter valve replacement procedure was carried out in a similar way with allowance for the patient-specific anatomy of the recipient's aorta using the finite element method in the Abaqus/CAE environment (Dassault Systemes, France). Results It was found that in the process of the delivery system passing through the vascular system, there occurred force fluctuations associated with catheter bending and its interaction with the aortic wall in the region of its arch. For example, in the initial straight portions, the pushing force was 3.8-7.9 N; the force increased to the maximum (11.1 and 14.4 N with and without the prosthesis) with bending of the distal portion of the catheter. A similar increase was observed when performing numerical simulation with high-quality graphic visualization of stress on the "spots" of contact between the catheter and the vascular wall with an increase in stress to 0.8 MPa. Conclusion Numerical and full-scale bench tests prove the significant effect of the properties of delivery system catheter for transcatheter aortic valve replacement on the interaction with the aortic walls.

Transcatheter heart valve prosthesis implantation (TCHVPI) is a complex method whose results depend on each of the components of the biotechnological system, such that complications cannot always be avoided. New medical technologies, namely robot systems (RS) and visual guidance systems (VGS) have been developed to counter these problems and make the procedure less dependent on the human factor. This review discusses the main current and potential VGS and RS technologies; the role of their integration is discussed and the main requirements for next-generation TCHVPI RS are evaluated.

Purpose To evaluate forces distribution, local stresses and deformation of mitral annuloplasty rings in response to annuloplasty. Methods Seguin (St. Jude Medical), Physio I (Edwards LifeScience), Memo 3D (Sorin) and Future SG (Medtronic) MAR of size 30 mm were included in the study. The study group included 4 males patients aged 52–68 years who underwent isolated mitral valve annuloplasty for ischemic mitral regurgitation. All surgeries were performed by the same experienced operator according to the standardized protocol. The mechanical properties of the similar set of MAR were evaluated under uniaxial compression by 15% in the longitudinal and transverse directions on the Testing Machines Z5.0 (Zwick/Roell). Biomechanics was assessed with MSCT. The MAR frame models at the initial state and at the ventricular ejection and atrial systole phases were obtained from DICOM-data using computer tomography Sensation Somatom 64 (Siemens). The models were compared using the innovative numerical algorithm in MatLab (Mathworks) by forming pairs for “systole – diastole”, “initial state – diastole” for all four types of MAR. We compared the mobility of the implanted devices and changes in the physiological saddle shape geometry of the mitral annulus in response to annuloplasty. We performed the quantitative analysis of the movement of each point of the reconstructed model between two states with the subsequent calculation of the required forces based on the finite element analysis. Results Future CG MAR has the greatest longitudinal and transverse stiffness (18.1N and 4.8N, respectively), whereas Memo 3D demonstrates the lowest values (2.3N and 1.5N). The rest two models show intermediate values of 4.2 - 11.3 N to 2.0 - 4.3N. The comparative analysis of MAR before and after implantation shows that Physio demonstrates the most pronounced deviations from normal physiological shape with significant annular compression along the intercommissural diameter by 1.36 mm resulted in a rounded annulus shape. None significant geometrical deformity among the other prosthetic rings. MEMO 3D demonstrates an average deformation by 0.18 mm across all zones, Seguin - 0.42 mm, Future CG - 0.34 mm. The force distribution analysis demonstrated the least forces of MEMO 3D, whereas the largest ones (up to 1.5N) are shown by Future SG, leading to the induction of locally elevated stress in surrounding tissues, potentially triggering the development of paravalvular fistulae. Conclusion Preliminary results demonstrate that the use of flexible rings with initially mobile structure allows preserving the native mitral annulus mobility after annuloplasty and reducing the stress (forces) acting on the surrounding tissues. The presented non-invasive method for estimating the stress of mitral annulus is crucial for advanced clinical practice as it allows further studying of the underlying pathologic mechanisms of developing paravalvular fistulae.

Background Prosthetic heart valves fabricated from pericardium preserved in EGDE (ethylene glycol diglycidyl ether) may be a promising option for patients with valvular heart disease. Purpose To assess morphological changes in the failed PeriCor and UniLine bioprostheses and to determine the underlying mechanisms contributing to their dysfunction. Methods 17 patients with EGDE-treated mitral bioprosthetic valves (PeriCor group, n=11, UniLine group= 6). undergoing repeat mitral valve replacement were included in the study. The median age of patients at the time of the primary replacement was 59 (54; 64) and 57 (55, 65) years, respectively. All cases of calcifications, spontaneous perforations, leaflet tears and ruptures, pannus growth, bioprosthetic leaflet fusion were assessed using microscopy and micro-computed tomography. The contribution of degenerative changes leading to the failure of bioprostheses was estimated with the Chi-square test. Results Pannus growth was observed in 53.8% of all explanted bioprostheses. Its overgrowth was abundant covering the leaflets and the stent struts and resulted in decreased effective orifice area and subsequent stenosis. Bioprosthetic leaflet fusion was observed only in the PeriCor group and accounts for 70%. Of them, 93% of cases of leaflet fusion was accompanied by the ruptures in the opposite commissural zones and subsequent leaflet perforations. The signs of calcification were reported in 57.6% of cases. Of them, 50% of cases had calcified stent frame tissue covering and 35% - pannus. Interestingly, calcification was not the main cause leading to the valve failure in 53.3% of cases. Conclusion Modes of bioprosthetic valve dysfunction include primary tissue degeneration, calcification and pannus growth. Primary tissue degeneration, pannus growth and commissural fusions account for a larger percentage in the modes of dysfunctions for EGDE-treated xenoaortic bioprostheses rather than calcification. Our findings suggest that preservation methods play one of the key roles in the dysfunction pattern.

Sutureless implantation of the mitral valve bioprosthesis using the valve-in-valve method was performed on a large animal (sheep). According to the results of a two-stage implantation (primary implantation of a xenopericardial 26-mm framed bioprosthesis and reimplantation of the developed 23-mm bioprosthesis), minor changes in quantitative indicators were revealed: an increase in the transprosthetic gradient by 1.3 mm Hg and a decrease in the area of the mitral orifice by 21.6%. Considerable reduction in the intervention time by 18 min was achieved (by 40% in comparison with the primary prosthesis). The absence of adverse events in the animal and complications in the post-operative period, as well as physiological hemodynamic indicators indicate the safety of the developed medical device.

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.С момента своего появления в 2002 г. транскатетерная имплантация аортального клапана претерпела значительные изменения и теперь является стандартом лечения пациентов с аортальным стенозом с промежуточным хирургическим риском. Развитие инновационных транскатетерных клапанов сердца и совершенствование технических навыков способствовали уменьшению частоты осложнений, связанных с транскатетерной имплантацией аортального клапана. Увеличение опыта, снижение профиля доставки, тщательное планирование процедуры и улучшенные устройства ушивания места доступа привели к значительно более низкому уровню сосудистых осложнений. Следующим этапом развития стало упрощение процедуры, что способствовало дальнейшему уменьшению осложнений, сокращению времени процедуры и пребывания в больнице. Переход от общей анестезии к седации, отказ от предилатации, использование лучевого доступа вместо контралатерального бедренного – это важный шаг в оптимизации результатов транскатетерной имплантации аортального клапана. Перспективами развития являются системы визуального ассистирования и роботизированные системы, которые могут потенциально оптимизировать процесс транскатетерной имплантации аортального клапана, повысить безопасность и эффективность процедуры.

Aim: to evaluate the biomechanical remodeling of polymer grafts modified with vascular endothelial growth factor (VEGF) after implantation into rat abdominal aorta.Materials and methods. Vascular grafts of2 mmdiameter were fabricated by electrospinning from polycaprolactone (PCL) and a mixture of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) and PCL. The grafts were modified with VEGF by biphasic electrospinning. Morphology of the grafts was assessed by scanning electron microscopy. Physico-mechanical properties of PCL and PHBV/PCL grafts were estimated using uniaxial tensile test and physiological circulating system equipped with state-of-theart ultrasound vascular wall tracking system. Physico-mechanical testing of PCL/VEGF and PHBV/PCL/VEGF was performed before and after implantation into rat abdominal aorta for 6 months. The modeling of coronary artery bypass grafting (CABG) was performed by finite element analysis for modified grafts.Results. Durability of PCL and PHBV/PCL grafts did not differ from that of human internal mammary artery; however, elasticity and stiffness of these grafts were higher compared to internal mammary artery. Viscoelastic properties of the grafts were comparable to those of native blood vessels. Modification of the grafts with VEGF reduced material stiffness. Six months postimplantation, PCL/VEGF and PHBV/PCL/VEGF were integrated with aortic tissue that induced changes in the physico-mechanical properties of the grafts similar to the native vessel. Biomechanical modeling confirmed the functioning of modified grafts in bypass position for CABG.Conclusion. PCL/VEGF and PHBV/PCL/VEGF grafts have satisfactory physico-mechanical properties and can be potentially used in the reconstruction of blood vessels.

The aim of the investigation is to assess the possibility of predicting the outcome of transcatheter aortic valve prosthesis implantation in real clinical practice on the basis of patient-specific modeling. Material and Methods. Modeling of transcatheter bioprosthesis implantation was carried out based on clinical data of a patient aged 72 years. Multispiral computed tomography (CT) was performed before and after the operative intervention. Reconstruction of aorta and valvular apparatus geometry was done on the basis of obtained slices using computer-aided design (CAD). With the help of microcomputer tomography and a series of projection images and mathematical algorithms a 3D-model of the frame was reconstructed, on which a 3D-mesh from 17,000 cubic (C3D8)-elements was built. Simulation of the system component interaction was conducted using a finite element method involving a number of successive steps: preliminary balloon dilatation — frame compression in the catheter — releasing the frame from the catheter. To evaluate the accuracy of modeling results compared to the CT data of the patient with the implanted bioprosthesis a proprietary algorithm was developed using MATLAB R2014a software (The MathWorks, USA). Arrays of points corresponding to the center of the supporting frame beams, obtained in 11 orthogonal sections, were used as input data. Results. Peculiarities of patient-specific approach to modeling the implantation of transcatheter CoreValve bioprothesis by means of the developed bioinformation algorithm has been analyzed. We managed to achieve a high convergence of simulation and CT data for the frame inflow area (the difference of the simulation results for the first three layers did not exceed 4%). Comparison of the results in terms of the annulus area has also demonstrated a high convergence: the identity amounted to more than 90% for the inflow and middle zones of the supporting frame. Conclusion. The highest level of detail, including calcium conglomerates modeling, as well as a comprehensive description of nonlinear elements of the system under study accurately reproduces the process of implantation of the transcatheter aortic valve prosthesis.

Samples of commercial and noncommercial xenopericardial grafts of different origin and processing are analyzed. A full-scale test of uniaxial stretching of the material was used to evaluate the features of physical and mechanical properties of the samples, and a computer finite element method simulation was used to evaluate the degree of the object compression. The results were analyzed in terms of the capacity of selected pericardial grafts to serve as a valve apparatus of a transcatheter heart valve prosthesis.

In this study, we incorporated carbon nanotubes (CNTs) into poly(styrene-block-isobutylene-block-styrene) (SIBS) to investigate the physical characteristics of the resulting nanocomposite and its cytotoxicity to endothelial cells. CNTs were dispersed in chloroform using sonication following the addition of a SIBS solution at different ratios. The resultant nanocomposite films were analyzed by X-ray microtomography, optical and scanning electron microscopy, tensile strength was examined by uniaxial tension testing, hydrophobicity was evaluated using a sessile drop technique, for cytotoxicity analysis, human umbilical vein endothelial cells were cultured on SIBS&ndash, CNTs for 3 days. We observed an uneven distribution of CNTs in the polymer matrix with sporadic bundles of interwoven nanotubes. Increasing the CNT content from 0 wt% to 8 wt% led to an increase in the tensile strength of SIBS films from 4.69 to 16.48 MPa. The engineering normal strain significantly decreased in 1 wt% SIBS&ndash, CNT films in comparison with the unmodified samples, whereas a further increase in the CNT content did not significantly affect this parameter. The incorporation of CNT into the SIBS matrix resulted in increased hydrophilicity, whereas no cytotoxicity towards endothelial cells was noted. We suggest that SIBS&ndash, CNT may become a promising material for the manufacture of implantable devices, such as cardiovascular patches or cusps of the polymer heart valve.

This paper presents the analysis of relationships between geometrical parameters of the tubular leaflet apparatus and its functional characteristics. In addition, the degree of the influence of deformation of different zones of leaflets on its ability to perform its function is evaluated in this work. The outcomes of this study could be helpful in developing new models of the transcatheter prosthetic heart valves leaflet apparatus or analyzing existing in-clinical transcatheter aortic valve implantation prostheses.