Objective To elucidate the influence of two procedures aortic root remodeling using a straight tubular artificial vessel while preserving the aortic valve and the Florida sleeve procedure on the biomechanics of the aortic root.Methods Five finite element models of the aortic root were reconstructed using computed tomography angiography images,including two cases of aortic root remodeling(A1 and A2),two cases of the Florida sleeve procedure(B1 and B2),and one control group without aortic root pathology(C).Numerical simulations were performed to obtain the blood flow and pressure distribution result to assess the differences in the hemodynamics of the aortic root.Results There were no significant differences in the peak systolic velocity between the two procedures and the control.However,the flow velocity after aortic root remodeling was smoother,similar to the model of the control group,with a more stable average aortic pressure and wall shear stress.In the Florida sleeve procedure,high-speed blood flow affected the vessel wall,leading to various degrees of wall shear stress and pressure concentrations along the aortic wall.Conclusions After aortic root replacement with valve preservation,blood flow patterns in the reconstructed aortic root depended on postoperative changes in sinus geometry.Both surgical procedures showed favorable blood flow patterns;however,the flow pattern after aortic root remodeling was more stable than that after the Florida sleeve procedure.

Objective To investigate vascular remodeling and low-density lipoprotein(LDL)deposition,the growth and development trends of lateral branch plaques in bifurcated vessels,and the potential locations of subsequent plaque growth due to the presence of plaques.Methods An idealized model of bifurcated vessels was established and the distribution of wall shear stress before and after the growth of edge-branch plaques was obtained using computational fluid dynamics.Seven sections were intercepted in the areas of low shear stress:planes 1-3 were the low shear stress areas on the lateral branch before plaque formation,planes 4-5 were the proximal and distal edges of the plaque,and planes 6-7 were the lower shear stress areas of the plaque.Vascular remodeling and LDL deposition in the cross section were simulated.The growth and development trends of plaques are also discussed.Results Among planes 1-3,plane 2 produced obvious negative remodeling and the highest concentration of LDL deposition(102.266 mmol/L),thereby indicating that this was the initial location of the atherosclerotic plaque.Compared to plane 4,plane 5 produced more pronounced vascular remodeling,lumen narrowing,and the highest deposition concentration(110.17 mmol/L)after plaque formation,which indicated that the patch had a tendency for eccentric growth downstream.Compared to plane 6,plane 7(blood flow separation reattachment site)produced more negative remodeling and the highest deposition concentration(93.851 mmol/L),thereby indicating the possibility of new plaque formation near the reattachment point of blood flow separation.Conclusions Obvious vascular remodeling at low shear stress in the lateral branches leads to lumen stenosis and high LDL deposition,thus,forming atherosclerotic plaques.The lateral wall of the bifurcated blood vessels is the initial location of atherosclerotic plaque growth.After growth,the plaque tends to develop downstream,and subsequent plaques may form at the flow separation and reattachment points.

ObjectiveT o explore the influence of patch shape for intraventricular tunnel (IVT) construction on biomechanical performance of the double outlet right ventricle after correction. Methods Based on the idealized IVT model, a two-dimensional IVT patch was designed. Six groups of patch models with the rhombic long-to-short axis ratio of 1∶0.625, 1∶0.3, 1∶0.2, 1∶0.15, 1∶0.125, 1∶0.1 were established according to the difference between the long and short axis of the rhombus patch in the turning part, and finite element analysis method was used to numerically simulate the process of stitching, holding and propping up the patch into a three-dimensional (3D) IVT model. Results The maximum stresses on suture line of 6 patch models were mainly concentrated at acute-angle corners of the rhombus. As rhombic long-to-short axis ratio of the patch increased, the maximum stress of the IVT suture line first decreased and then increased, and the volume showed an increasing trend. The pressure difference between two ends of the tunnel first decreased and then increased. The patch with the long-to-short axis ratio of 1∶0.15 had a uniform surface stress distribution, and the maximum stress on the suture line was the smallest. Meanwhile the right ventricular volume was less encroached on, and the pressure difference at both ends of the tunnel was small. Conclusions The IVT shape can influence stresses of suture line, the right ventricle volume and the pressure difference of IVT with non-monotonic variations. The suture effect of the patch with the long-to-short axis ratio of 1∶0.15 is relatively better among the constructed models.

Objective To explore the biomechanical mechanism of aortic insufficiency (AI) after single aortic valve replacement (SAVR) in children and propose the corresponding countermeasures. Methods The idealized aortic valve model and postoperative growth model were constructed. By changing the length of leaflet free edge, leaflet height as well as improving the design with a concave structure, the effects of different structure dimensions on movement synchronization and closing performance of the aortic valve after surgery were compared. Results The closure of the replacement leaflet lagged behind the autologous leaflet, which fitted 2 mm below free edge of the replacement leaflet. AI occurred 6 years after operation. Increasing leaflet height could not improve the postoperative effect and would increase the maximum stress of the leaflet. Increasing free edge length by 10% could improve the postoperative outcomes, while increasing free edge length by 15% would cause the leaflet to be too long, hence resulting in a poor fit of the aortic valve. Compared with the traditional structure, the concave structure was more beneficial for closing performance of the aortic valve, and it could effectively reduce the maximum stress by 20% with the best effect. Conclusions The leaflet movement will be out of synchronization after SAVR, the point of convergence will be shifted, and AI will appear 6 years after surgery. It is recommended to use a concave structure with free edge length increased by 10%, while increasing leaflet height is not recommended.

To solve the problem of stent malapposition of intravascular stents, explore the design method of intravascular body-fitted stent structure and to establish an objective apposition evaluation method, the support and apposition performance of body-fitted stent in the stenotic vessels with different degrees of calcified plaque were simulated and analyzed. The traditional tube-mesh-like stent model was constructed by using computational aided design tool SolidWorks, and based on this model, the body-fitted stent model was designed by means of projection algorithm. Abaqus was used to simulate the crimping-expansion-recoil process of the two stents in the stenotic vessel with incompletely calcified plaque and completely calcified plaque respectively. A comprehensive method for apposition evaluation was proposed considering three aspects such as separation distance, fraction of non-contact area and residual volume. Compared with the traditional stent, the separation distances of the body-fitted stent in the incompletely calcified plaque model and the completely calcified plaque model were decreased by 21.5% and 22.0% respectively, the fractions of non-contact areas were decreased by 11.3% and 11.1% respectively, and the residual volumes were decreased by 93.1% and 92.5% respectively. The body-fitted stent improved the apposition performance and was effective in both incompletely and completely calcified plaque models. The established apposition performance evaluation method of stent considered more geometric factors, and the results were more comprehensive and objective.
Constriction, Pathologic/surgery* ; Humans ; Plaque, Atherosclerotic ; Stents

Objective To establish a method for non-invasive calculation of fractional flow reserve (FFRCT) with the shape resistance of coronary artery stenosis as boundary condition, and to verify the accuracy of this method. Methods CT angiography images of 16 patients with coronary artery disease were reconstructed; the mathematical model of shape resistance was established by considering the minimum cross-sectional area and the length of stenosis of coronary artery stenosis, the induced pressure difference as the boundary condition was applied to calculate FFRCT (named as shape resistance method ). The values of clinical FFR were taken as the gold standard, previous diameter method and volume method were taken as control method, and accuracy of shape resistance method was investigated from the aspects of mean error rate, accuracy rate, sensitivity rate, positive prediction rate and negative prediction rate. Results The mean error rate of calculated FFRCT by the diameter method, volume method and shape resistance method were 11.76%, 10.46%, 4.82%, the accuracy rates were 85%, 65%, 90%, the sensitivity rates were 87.5%, 66.7%, 87.5%, the positive prediction rate were 75%, 25%, 87.5%, respectively, while the negative prediction rates were all 91.6%. Conclusions The established shape resistance method is better than the diameter method and volume method from the aspects of mean error rate, accuracy rate, sensitivity rate and positive prediction rate; the FFRCT based on the shape resistance method and clinical FFR have good consistency, and this work may provide a new way for the calculation and application of FFRCT.

The dynamic coupling of stent degradation and vessel remodeling can influence not only the structural morphology and material property of stent and vessel, but also the development of in-stent restenosis. The research achievements of biomechanical modelling and analysis of stent degradation and vessel remodeling were reviewed; several noteworthy research perspectives were addressed, a stent-vessel coupling model was developed based on stent damage function and vessel growth function, and then concepts of matching ratio and risk factor were established so as to evaluate the treatment effect of stent intervention, which may lay the scientific foundation for the structure design, mechanical analysis and clinical application of biodegradable stent.
Biomechanical Phenomena ; Constriction, Pathologic ; Humans ; Stents

This study aims to explore the effect of aortic sinus diameter on aortic valve opening and closing performance in the case of no obvious disease of aortic valve and annulus and continuous dilation of aortic root. A total of 25 three-dimensional aortic root models with different aortic sinus and root diameters were constructed according to the size of clinical surgical guidance. The valve sinus diameter S is set to 32, 36, 40, 44 and 48 mm, respectively, and the aortic root diameter is set to 26, 27, 28, 29 and 30 mm, respectively. Through the structural mechanics calculation with the finite element software, the maximum stress, valve orifice area, contact force and other parameters of the model are analyzed to evaluate the valve opening and closing performance under the dilated state. The study found that aortic valve stenosis occurs when the = 32 mm, = 26, 27 mm and = 36 mm, = 26 mm. Aortic regurgitation occurs when the = 32, 36 and 40 mm, = 30 mm and = 44, 48 mm, = 29, 30 mm. The other 15 models had normal valve movement. The results showed that the size of the aortic sinus affected the opening and closing performance of the aortic valve. The smaller sinus diameter adapted with the larger root diameter and the larger sinus diameter adapted with the smaller root diameter. When the sinus diameter is 40 mm, the mechanical performance of the valve are good and it can well adapt with the relatively large range of aortic root dilation.
Aorta ; anatomy & histology ; Aortic Valve ; physiology ; Aortic Valve Insufficiency ; physiopathology ; Aortic Valve Stenosis ; physiopathology ; Humans

Based on the noninvasive detection indeices and fuzzy mathematics method, this paper studied the noninvasive, convenient and economical cardiovascular health assessment system. The health evaluation index of cardiovascular function was built based on the internationally recognized risk factors of cardiovascular disease and the noninvasive detection index. The weight of 12 indexes was completed by the analytic hierarchy process, and the consistency test was passed. The membership function, evaluation matrix and evaluation model were built by fuzzy mathematics. The introducted methods enhanced the scientificity of the evaluation system. Through the Kappa consistency test, McNemer statistical results ( = 0.995 > 0.05) and Kappa values (Kappa = 0.616, < 0.001) suggest that the comprehensive evaluation results of model in this paper are relatively consistent with the clinical, which is of certain scientific significance for the early detection of cardiovascular diseases.
Cardiovascular Diseases ; diagnosis ; Cardiovascular System ; Fuzzy Logic ; Humans ; Models, Cardiovascular ; Research

Valve transplantation is often used in the treatment of aortic valve insufficiency. However, after surgery, the reconstructed aortic roots have an expansion phenomenon, in which the lack of valve height causes the aortic valve to close again. In this paper, the effects of different aortic valve height design on valve opening and closing performance were studied. The optimal surgical plan was obtained by numerical simulation, providing technical support and theoretical basis. In this paper, six groups of three-dimensional geometric models with a valve height increment of ± 0.5 mm were established with a root diameter of 26.0 mm and a valve height of 14.0 mm. Through the structural mechanics calculation and analysis of the parameters such as maximum stress, valve area and contact force of the model, reasonable geometrical dimensions are obtained. The study found that the maximum stress values of the six groups of models ranged from 640 to 690 kPa, which was consistent with the results of the literature; the three-group models with valve heights of 13.5 mm, 14.0 mm, and 14.5 mm were within a reasonable range. The contact force value of the 6 groups of leaflets increased with the increase of valve height. Studies have shown that the height of the aortic valve has an effect on the aortic valve closure performance. A valve height that is too small or too large will reduce the aortic systolic valve area and affect the aortic function.
Aortic Valve ; physiology ; surgery ; Aortic Valve Insufficiency ; surgery ; Heart Valve Prosthesis ; Humans ; Models, Cardiovascular