[Computer modeling of the area of carotid endarterectomy with patches of various forms]. / Sposob komp'yuternogo modelirovaniya zony klassicheskoi karotidnoi endarterektomii s primeneniem zaplat razlichnoi formy.

OBJECTIVE: To describe geometric models of carotid artery bifurcation and computer modeling of carotid endarterectomy (CEA) with patches of various configurations. MATERIAL AND METHODS: The method was demonstrated on a reconstructed model of intact vessel based on preoperative CT of the affected vessel in a certain patient. Blood flow is modeled by computational fluid dynamics using Doppler ultrasound data. Risk factors were assessed considering hemodynamic parameters of vascular wall associated with WSS. RESULTS: We studied hemodynamic results of 10 virtual CEA with patches of various shapes on the example of a reconstructed intact artery in a particular patient. Patch implantation is aimed at prevention of carotid artery narrowing since simple suture without a patch can reduce circumference of the artery by 4-5 mm. This result adversely affects blood flow. On the other hand, too wide a patch creates aneurysm-like deformation of internal carotid artery bulb. It is not optimal due to a large recirculation zone. It was found that patch width approximately equal to 3 mm ensures an optimal hemodynamic result. Deviations from this median value, both upward and downward, impair hemodynamics while the absence of a patch results the worst result. CONCLUSION: The proposed computer modeling technique is able to provide a personalized patch selection for CEA with low risk of restenosis in long-term follow-up period.

First Experience of Sutureless Redo on Mitral Valve Using Valve-in-Valve Technique: Two-Stage Implantation on a Large Animal.

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.

[The renin-angiotensin-aldosterone system as a potential target for therapy in patients with calcific aortic stenosis: a literature review].

Calcific aortic valve stenosis (CAVS) is a serious socio-economic problem in developed countries because this disease is the most common indication for aortic valve replacement. Currently, there are no methods for non-invasive treatment of CAVS. Nevertheless, it is assumed that effective drug therapy for CAVS can be developed on the basis of modulators of the renin-angiotensin-aldosterone system (RAAS), which is involved in the pathogenesis of this disease. The purpose of this paper is to compile and analyze current information on the role of RAAS in the CAVS pathophysiology. Recent data on the effectiveness of RAAS inhibition are reviewed.

[Infective Endocarditis Causing Native and Prosthetic Heart Valve Dysfunction].

Infective endocarditis (IE) is the disease that has high inhospital mortality. Heart valves dysfunction - both native and prosthetic - is the primary IE complication requiring a surgical intervention. The IE causes and its course have been discussed in this review. In particular, the role of concomitant infectious foci in the formation and development of IE have been considered, the mechanisms of mutual transition of subacute and acute clinical forms have been described. Modern diagnostic principles and methods based on the Duke criteria system have been mentioned, as well as the difficulties that follow the patient's clinical status evaluation. The normobiotic microbiota participation, as well as the possibilities for their identification using blood culture and PCR technique, have been closely reviewed. According to modern researches and publications, there have been made the conclusion about the contribution of obligate anaerobic bacteria, fungi and viruses to the development of endocarditis. There have been described the hypothesis about the presumptive strategy for the cardiac dysfunction formation as a result of the IE causative agents cells metabolic activity based on a literature data analysis in the article: vegetation formed by Staphylococcus aureus can lead to the heart valve stenosis, and the influence of hyaluronidases, collagenases on a heart valve structure can lead to regurgitation. The pathogens cells ability to avoid the human immune system response is caused by the biofilms, fibrin vegetations formation and the enzymes production - cytotoxins (streptolysins, leukocidin, etc.). It has been suggested that the mediators of inflammation and leukocyte cells participate in the destruction of native and prosthetic tissues due to an IE pathogens inaccessibility for immunocompetent cells.

[Influence of suture material on the development of postoperative complications in vascular surgery and their prevention]. / Vliianie shovnogo materiala na razvitie posleoperatsionnykh oslozhnenii v sosudistoi khirurgii i puti ikh profilaktiki.

Postoperative complications in vascular surgery may be partly provoked by suture material. Analysis of the mechanisms of these complications may be useful for their prevention. Mechanisms of suture-induced thrombosis and neointimal hyperplasia, possible strategies for prevention of postoperative complications including those allowing drug deliveries directly to the vascular anastomosis area are discussed in the article. According to the literature data, heparin is the most optimal drug for modifying suture material and prevention of thrombosis and neointimal hyperplasia. Heparin delivery to the vascular anastomosis site will reduce the risk of thrombosis by inhibiting the activity of thrombin. Complex of heparin and antithrombin III increases inhibitory effect of antithrombin against thrombin. In addition, heparin is able to reduce proliferation of vascular smooth muscle cells through inhibition of the synthesis of extracellular matrix proteases involved in migration and proliferation of cells. Thus, heparin delivery to the vascular injury site may be used to prevent thrombosis and myoproliferative response. Moreover, this strategy prevents complications associated with systemic administration of anticoagulants.

[Evolution of transcatheter aortic valve implantation: from planning to robotic systems]. / Évoliutsiia transkateternoi implantatsii aortal'nogo klapana.

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.

[Calcification Patterns of the Components of the Cardiovascular System and Their Substitutes: Composition, Stucture and Localization of Calcific Deposits].

Calcification of cardiovascular tissues and biological substitutes results in abnormal biomechanics, causing stenosis or tissues ruptures. Therefore, the understanding of calcification pathways will facilitate the development of strategies for calcification risk reduction. Even though calcification pathways have been studied since the mid-80s and are widely described in the medical literature, there is no consensus on the cause-and-effect relationships in this pathological process. The current review covers the composition, structural aspects and specific localization of calcific deposits in native heart valves and blood vessels, bioprosthetic heart valves treated with glutaraldehyde. Moreover, experimental data on the composition of in vivo and in vitro calcification are presented. These characteristics of calcific deposits provide new insights in the calcification pathways. According to the results of the literature review, one may conclude that cell death, microfracture of the surrounding tissues with the overall biochemical imbalance may potentiate the calcification process. Moreover, the progression of calcification process is associated with the accumulation of mechanical stress.

[Elucidation of the Tubular Leaflet Geometry of the Aortic Heart Valve Prosthesis by Finite Element Analysis].

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.

[Screening analysis of proteolytic enzymes and their inhibitors in the leaflets of epoxy-treated bioprosthetic heart valves explanted due to dysfunction]. / Skriningovyi analiz proteoliticheskikh fermentov i ikh ingibitorov v stvorkakh époksiobrabotannykh bioproteznykh klapanov serdtsa, éksplantirovannykh po prichine disfunktsii.

Bioprosthetic heart valves (BHVs) are known for their lower thrombogenicity rates and excellent hemodynamic parameters similar to native valves. However, the lifespan of these medical devices is limited to 15 years due to the structural valve degeneration. One of the mechanisms underlying functional impairment and calcification of BHVs includes proteolytic degradation of biomaterials. However, proteases found in xenogeneic BHVs tissue remain poorly studied. In this study using the dot blot assay, we have performed a screening analysis of proteolytic enzymes and their inhibitors in the leaflets of five BHVs explanted due to their dysfunction. Five aortic valves (AVs) explanted due to calcific aortic valve disease were studied as a comparison group. The results of the study have demonstrated that at least 17 proteases and 19 of their inhibitors can be found in BHVs. In the AVs 20 proteases and 21 their inhibitors were identified. Small quantitative differences were noted between proteomic profiles of the BHVs and AVs. Matrix metalloproteinases (MMPs) were expressed in BHVs and AVs at comparable levels, but the level of tissue inhibitors of metalloproteinases-1/-2 and RECK protein in implant tissues was lower than in natural valves. Probably, excessive activity of MMPs cannot be counterbalanced by their inhibitors in BHVs and therefore MMPs can degrade prosthetic biomaterial. Moreover, the detection of a wide range of proteolytic enzymes and their inhibitors in the degenerated BHVs suggests the existence of several pathophysiological pathways that can lead to structural valve degeneration.

Mechanism of Vascular Injury in Transcatheter Aortic Valve Replacement.

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 Systèmes, 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.

Prognostic Model of Typical Complications Caused by Transcatheter Aortic Valve Replacement.

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.

Modeling of transcatheter aortic valve replacement: Patient specific vs general approaches based on finite element analysis.

BACKGROUND: There are two main methods used for transcatheter aortic valve replacement (TAVR) FEA modeling for medical devices development: patient specific and general approaches. Advantages and disadvantages of both approaches have never been compared in a single study. METHOD: Here we propose a bioinformatic algorithm to evaluate the accuracy of patient specific and generalized FEA approaches with regards to proximity configuration of the implanted stent reconstructed by computed tomography. In addition, in this study we also assessed the impact of the level of detail on FEA accuracy in the patient specific approach. RESULTS: Our results demonstrate that in certain cases, the generalized approach can ensure the same accuracy as the patient specific approach. Therefore, considering high cost effectiveness of the generalized approach, we identify it as more feasible in the context of TAVR. Furthermore, we suggest that high level of detail can improve the reproducibility of modeling results in the patient specific approach. CONCLUSIONS: Our findings may help medical engineers to better understand the peculiarities of both approaches and therefore make the right decision when choosing a particular approach for computer modeling. Future studies are required to validate our observations.

Computer-aided design of the human aortic root.

The development of computer-based 3D models of the aortic root is one of the most important problems in constructing the prostheses for transcatheter aortic valve implantation. In the current study, we analyzed data from 117 patients with and without aortic valve disease and computed tomography data from 20 patients without aortic valvular diseases in order to estimate the average values of the diameter of the aortic annulus and other aortic root parameters. Based on these data, we developed a 3D model of human aortic root with unique geometry. Furthermore, in this study we show that by applying different material properties to the aortic annulus zone in our model, we can significantly improve the quality of the results of finite element analysis. To summarize, here we present four 3D models of human aortic root with unique geometry based on computational analysis of ECHO and CT data. We suggest that our models can be utilized for the development of better prostheses for transcatheter aortic valve implantation.