[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.

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.