基于文丘里效应的自身动力性Fontan循环的数值模拟和验证

Right ventricle bypass (Fontan) operation is the sole treatment strategy for functional single ventricle, however, its mortality and morbidity still remains the highest among congenital heart disease surgery. The underlying cause lies in lack of right ventricular power source. Results of our previous researches and foreign studies indicate that the key is to provide a pumping power resource at the level of the cavopulmonary connection by boosting a pressure of about 2-5 mmHg with maintaining low CVP pressure(5-<15 mmHg) stat simultaneously. The essence of Venturi effect and ejector pump is a high-energy flow stream driving a low-energy flow with reduction of upstream flow pressure. A hypothesis based on it ,a Gore-Tex conduit is connected between the ascending aortic artery and the right pulmonary artery(RPA) at the level of the cavopulmonary connection with the help of high-energy systemic circulation. A clip is applied to the RPA end of the conduit to produce a high-velocity nozzle and boost Fontan power with low CVP . According to the hypothesis, following researches will be carried out: （1）Construction and numerical simulation of 3-dimensional model of extracardiac Fontan operation; 2) Numerical simulation of the best design of nozzle in.3-dimensional model,including diameter and angle; 3) To verify the best design of nozzle on a canine Fontan circulation ; 4) To verify the middle term patency of the nozzle on a Glenn animal model . These researches will provide theories foundation and application perspective for a self-powering Fontan and bi-ventricular Fontan physiology.

右心室旷置（Fontan）手术是功能性单心室的唯一治疗方案，但并发症和死亡率仍居先心病首位，根本原因在于Fontan循环缺少右心室动力供应。前期工作和国外研究显示如何在腔肺连接水平供给动力源，保持腔静脉低压状态(5∽15 mmHg)同时提升2∽5mmHg动力是关键。文丘里效应和喷射泵的本质是高能量流体驱动低能量流体，同时降低上游压力。假设：借助高能量体循环，管道连接升主动脉和腔肺连接水平的右肺动脉，近右肺动脉端部分钳闭造成高速喷嘴，以提升Fontan动力和保持腔静脉低压。围绕假设，展开研究：（1）构建和数值模拟心外管道Fontan手术三维模型；（2）三维模型上数值模拟探讨喷嘴最佳设计：口径和角度；（3）犬自身动力性Fontan循环模型上验证喷嘴最佳设计；（4）犬自身动力性双向腔肺吻合术（Glenn）模型上验证喷嘴的中期通畅性。为形成自身动力性、双心室Fontan生理提供理论基础和应用前景。

功能性单心室是一类结构复杂的先天性心脏病，严重危害患儿生命。右心室旷置术（Fontan手术）是目前唯一的纠治方式，但因术后肺循环缺乏心室泵血作用，患者远期预后较差，常合并蛋白丢失、肝功能异常、心律失常等并发症，严重者出现心肺供能衰竭，甚至需要心肺移植。近十年，国外提出了一些右心室辅助装置，用于改善Fontan术后肺循环缺乏供能的情况，但是存在应用条件苛刻、结构复杂、手术操作难度大等问题，难以应用于临床。本项目结合医学与计算流体力学，提出基于文丘里效应的自身动力性Fontan循环，利用左心系统提供的高速血流驱动上、下腔静脉血液回流。在体外计算流体力学模拟实验中，该管道能有效地为腔静脉血流供能，在不提高肺动脉压力的前提下仍能提高肺血流。该特性有利于缓解进行性腔静脉压力升高，并促进肺血管发育。在中长期大动物实验中，自身动力性Fontan循环不仅为肺循环供能，还能在肺动脉内形成搏动性血流。搏动血流可维持正常的血管内皮功能，避免血管内皮增生、血管重构等作用，有效降低并发症发病率。本项目研究结果证明：基于文丘里效应的自身动力性Fontan循环能产生类似右心室的泵血作用，可以为肺循环供能，从而降低术后并发症发生率。该研究为自身动力性Fontan循环提供理论基础和应用前景。