| Double outlet right ventricle（DORV）it is a complex cyanotic congenital heart disease,which mainly features that aortic and pulmonary arteries are completely or mostly originated in the right ventricle,and ventricular septal defect（VSD）is the only outlet of the left ventricle.The main treatment method is DORV correction surgery,which uses bovine pericardial patch to establish an intraventricular tunnel（IVT）from VSD to the aortic valve orifice.At present,some patients will experience patch tearing and distortion after the traditional patch（circle,ellipse,notch）is used to establish IVT,which can cause complications such as residual fistula and obstruction of the left and right ventricular outflow tracts,affecting the left and right ventricles and the ejection function of the ventricle.Therefore,a modular patch was designed in this study.The finite element numerical simulation method was used to analyze the different biomechanical performance caused by three-dimensional IVT composed of two-dimensional patch structures with different shapes,so as to provide a scientific theoretical basis for making a more reasonable operation plan of personalized IVT patch.The main research contents and methods of this article are as follows:（1）Based on the patient’s CT image,an idealized parametric myocardial model was established.According to the principle that the perimeter of the patch is equal to the length of the suture edge,the traditional patch model（1 group）and the modular patch（6 groups）models were established.The method of structural mechanics was used to simulate the surgical process of DORV correction surgery,and to obtain the maximum stress of the suture edge and the volume of IVT.Hemodynamic analysis on the calculated 16 groups of IVT models were performed,and the pressure difference between two ends of IVT（△P）and blood flow velocity were obtained,to explore the mechanical effects of patches of different shapes on the IVT.（2）According to the aortic valve diameter of 7.5 mm,9.75 mm and 12 mm,the idealized parameterized myocardial models of Type A,B and C for children of different ages were established.Based on the above three idealized IVT models,18 sets of patch models with different ratios of the long and short axis of the rhombus in the turning part were established.The finite element numerical simulation method was used to simulate the surgical process and prognosis results of DORV surgery,the maximum stress of the suture margin,IVT volume,△P and blood flow velocity and other parameters were obtained,to explore the influence of the rhomboid long and short axis of the turning part of the modular patch on IVT trend.The research results show that:（1）In the three-dimensional IVT models with different patch shapes,the stress of the traditional patch is mainly concentrated at the inflection point of the seam edge,and the stress of the modular patch is concentrated at the seam of the acute edge of the diamond.In the traditional patch,the middle and downstream parts of the circular patch are folded in,which is easy to cause the obstruction of the left ventricular outflow tract.The remaining 9 groups of models have redundancy on both sides of the VSD.The volume change rate of the IVT formed by the patch with the notch-shaped long and short axis ratio of 0.5:1 is the smallest;the maximum stress of the suture edge is relatively small,which is 3.224MPa;and △P is the smallest,which is 3.92 mm Hg;at the same time,the peak blood flow velocity in IVT is the smallest;and it is not prone to left ventricular outflow tract obstruction.This model is of the best suture effect among the traditional patches.The stress of the suture edge of the modular patch decreases first and then increases.Among them,the stress with a ratio of long and short axis of 1:0.15 is the smallest,which is 3.121 MPa;its volume change rate is small,its minimum ΔP is 3.66 MPa,and the peak blood flow velocity in the IVT is the smallest;the suture effect of the modular patch is relatively good,and it is better than the patch with the notch shape of0.5:1 in the traditional patch.（2）Compared with traditional patches,modular patches can improve the structure of three-dimensional IVT and present good biomechanical properties.With the increase of the ratio of length to short axis,the maximum stress and △P of Type A,Type B and Type C show a gradual decrease;Type A and Type C show a decreasing trend in volume,Type B shows a trend of decrease first and then increase.When the length of the long and short axis of Type A patch is 1:0.225,the stress at the suture edge is 1.42 MPa,the volume change rate is 26.7%,the △P is 8.07 mm Hg,and the blood flow velocity is 1.602 m/s.When the long and short axis of the Type B patch increases as 1:0.15,the stress at suture edge is 1.446 MPa,the volume change rate is 5.2%,the △P is 4.46 mm Hg,and the blood flow velocity is 1.195 m/s.When the length of the long and short axis of the Type C patch is 1:0.125,the stress at the suture edge is 1.59 MPa,the volume change rate is 35.2%,the △P is 4.88 mm Hg,and the blood flow velocity is 1.260 m/s.After the above ratios of Type A,Type B,and Type C,the change rate of each biomechanical parameter is less than 5% with the increase of the ratio of long and short axis,and the probability of eddy flow is greatly reduced.Conclusion: Compared with the traditional patch,modular patch can improve the structure of three-dimensional IVT,and has good biomechanical properties in reducing the stress of suture edge,invasion of right ventricle,pressure difference between two ends of IVT and blood flow velocity in IVT.Synthesizing the results of the 18 groups of models of A,B and C,the stress on the suture edge is relatively small,and the invasion of the right ventricle is small when the ratio of the length and the short axis of the patch in the turning part is increased to 1:0.125;The change rate of△P is less than 5%,the vortex at the entrance of the IVT is gradually reduced,the suture effect is better,and the incidence of postoperative complications and secondary operations can be reduced. |
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