Study On The Biomechanical Mechanism And Surgical Planning Of The Influence Of Ascending Aortic Root Geometry On Aortic Insufficiency

Surgical options for aortic root treatment comes from clinical experience. Understanding the biomechanical mechanism is needed to guide the evidence-based surgical decision in order to avoid neoaortic valve regurgitation. Using computational simulation investigated the surgical treatment of aortic root so as to know the postoperative influence of the geometric configurations of aortic root, such as sinotubular junction and sinus diameter, the position of the coronary sinus orifice, on neoaortic insufficiency. For this purpose, the structural finite element and two dimensional fluid structural interaction method were used in a controlled situation, and aortic valve function was quantified in terms of geometric orifice area, maximum leaflet stress, changes in aortic annulus diameter, Leaflet summit displacement, as well as leaflet contact pressure. This study proposed surgical planning solutions and offered the theoretical support for the design and test of prosthetic valve.Concrete research content includes following several aspects: first of all, the classification and treatment of aortic valve regurgitation, simulation and in vitro modeling of aortic root, biomechanical mechanism are presented as background. Secondly, six geometric modeling method, tissue properties, numerical analysis method, evaluation parameters of mechanical behaviors for aortic root, and experimental method in vitro are presented as the theory basis researching biomechanics mechanism of aortic root. And then, using the structural finite element model investigated the effects of shell element and composite element contain of shell and beam element on simulation results, and the effects of varying the sinotubular junction and sinus diameters on neoaortic performance. Next, using two dimensional fluid structural interaction model investigated the effects of varying the sinotubular junction and sinus diameters on neoaortic performance, and the effect of the position of the coronary sinus orifice on aortic leaflet coaptation after the surgical treatment of aortic root. Finally, software solutions, design and implementation of programmer, and an example in application for surgical planning software are presented.There are some significant results as follows. First of all, the effect of varying the sinotubular junction and sinus diameters on neoaortic performance after the surgical treatment of aortic root was investigated using structural finite element method. It was evident that increasing these diameters within a range of 20% can increase the leaflet contact pressure for the aortic root, and vice versa. This may be one reason why neoaortic valve insufficiency occurs long after the surgical treatment of aortic root has been performed in patients with aortic valve disease. Secondly, the effect of varying the sinotubular junction and sinus diameters on neoaortic performance after the surgical treatment of aortic root was investigated using two dimensional fluid structure interaction simulation method. For the surgical treatment of aortic root, aortic valve closure function can be affected by various sinotubular junction and sinus diameter. Compared with the sinus diameters, sinotubular junction diameters have less effect on the performance of aortic valve closure, when the diameter difference is within a range of 20%. So surgical planning might give sinus diameter more consideration. And then, the effect of the position of the coronary sinus orifice on aortic leaflet coaptation after the surgical treatment of aortic root was investigated. The position of the coronary sinus orifice affects the pressure distribution on the aortic root. The pressure difference between none, left, and right coronary sinus leads to the risk of a leaflet mismatch. The model with the coronary sinus orifice located on the bottom of the sinus developed higher local pressure on the maximum diameter position of the sinus compared to the model with the coronary sinus orifice located in the middle of the sinus. The higher local pressure creates symmetrical deformation of the three leaflets, and decreases the risk of leaflet mismatch in coaptation. Finally, preliminary surgical planning software was developed geometrical configuration of aortic root.The research results may be used to guide the evidence-based surgical decision for aortic root easily and scientifically, and offer the detailed pathological information for the patient, in order to avoid medical dispute.