Study Of Histological And Computational Fluid Dynamics For Congenital Supravalvular Aortic Stenosis

Objective: Congenital supravalvular aortic stenosis(SVAS)is a rare condition.The choice of surgical methods is still controversial and the long-term effect is uncertain.In the first part of this study,we studied the histological characteristics of lesions to clarify the relationship between pathological morphology and pathogenesis.The second part compared multiple hemodynamic parameters before and after surgery based on two patients.Using the technology of virtual surgery,we explored the differences of intra-aortic hemodynamics among three common surgical procedures.Method: We observed the histological characteristics of the stenosed aorta or pulmonary artery in children by HE and EVG staining in part I.In part II,we collected preoperative computed tomography(CT)and post-operative magnetic resonance imaging(MRI)data of2 children.Three-dimensional reconstruction and computational hemodynamic simulation were performed.In the third part,one typical case of SVAS was recruited.After three-dimensional reconstruction,virtual Mc Goon,Doty and Brom operations were performed with computer-aided design software.The hemodynamic simulation of preoperative and virtual operation was then carried out.Results: In the first part,the histological results showed that the arterial wall of the lesion was obviously thickened,especially the middle layer.The layers of elastic lamellae in arterial media increased abnormally;each layer,however,had become thinner and showed decreased elastin content.In the second part,we found that the presence of supravalvular stenosis not only caused abnormal increase in the flow velocity,but also caused unstable blood flow in the region of ascending aorta and aortic arch.Uneven distribution of wall shear stress(WSS)was detected.Surgery could effectively restore the steady blood flow and uniform distribution of wall shear stress.The blood flow ratio of the innominate artery(IA),the left common carotid artery(LCCA)and the coronary artery(CA)decreased after surgery.In the third part,SVAS could be effectively relieved after three kinds of virtual surgery,and the abnormal high-speed blood flow disappeared.The distribution of WSS was related to the configuration of postoperative aorta.The blood flow distribution ratio of the IA,the LCCA and left subclavian artery(LSA)changed after operation,but there was no significant difference among the operations.Preoperative coronary flow was 7.56%and increased to 7.99% in Mc Goon,8.55% in Doty and 8.89% in Brom after surgery.The energy loss after each operation was greatly reduced,and the energy efficiency after Mc Goon operation was higher than that of other operations.Conclusion: Congenital SVAS is an obstructive disease of left ventricular outflow tract caused by genetic abnormalities.The abnormal thickening of vessels in the lesion leads to narrow lumen and unstable blood flow in the aorta.Surgery can effectively relieve SVAS and restore the stable blood flow and uniform WSS distribution.The three common surgical procedures all significantly reduce the energy loss and improve energy efficiency.The blood flow distribution of the main branches of aorta changes after surgery.According to the individual anatomical characteristics of the patient,the blood flow of coronary artery may increase or decrease to certain extent.