In Vitro Pulsatile Flow Visualization on Extracardiac Conduits for The Right Ventricular Outflow Tract Reconstruction: Qualitative Considerations

心外管道重建右室流出道的體外脈動流暢可視化定性研究

袁師敏(Shi-Min Yuan) ； 常謙(Qian Chang) ； 郭一如(Yi-Ru Guo) ； 郭加強(Jia-Qiang Guo)

《The Kaohsiung Journal of Medical Sciences》 14卷5期 (1998/05) Pp. 258-265

https://doi.org/10.6452/KJMS.199805.0258

摘要

心外同種帶瓣管道重建右室流出道 (RVOT)是複雜先天性心臟病外科治療的重要手段之一。手術近期效果良好，而遠期效果欠滿意，且遠期失敗的血行力學因素不詳，體外脈動流場可視化未見報道。建立簡易右心循環模擬裝置，設置生理條件，應用直徑 0.18mm 之聚苯乙烯粒子作為示綜劑，觀察正常肺循環系統模型、含各種瓣膜及不含瓣膜之心外管道重建 RVOT 之肺動脈閉鎖模型的流場特點。正常肺循環流場以軸流為主，伴有小範圍的流動紊亂，舒張期右心室內出現單個渦旋。心外管道重建 RVOT 之肺動脈閉鎖模型中，右心室內出現雙渦旋，主肺動脈中出現二次流，兩分支中二次流較正常肺循環模型者增強。心外管道流場：含正常生物瓣時，其近段為二次流動，遠段變為軸流；含狹窄生物瓣時，全段均為二次流，其強度隨瓣膜狹窄程度的加重而增強。心外管道帶雙葉陶瓷碟瓣無論收縮、舒張期，心外管道中機械瓣均處于最大開啟位，即重度關閉不全，減速期心外管道內可見重度返流。實驗畢，見雙葉碟瓣軸窩內嵌入示綜粒子，致卡瓣“不含瓣膜之心外管道重建 RVOT 使心外管道產生返流。重建 RVOT 之心外管道內，含正常或異常瓣膜時，均可發生異常流動。當前系統阻力條件下，雙葉碟瓣置換術后，軸窩內若附0.18mm 以上大小之微血栓，即有致卡瓣之傾向。證實了含生物瓣之心外管道的優點。不含瓣膜之心外管道重建 RVOT 使管道內出現返流，流體能耗增大，臨床應盡量避免應用。

並列摘要

Valved homograft conduits play an important role in the right ventricular outflow tract (RVOT) reconstruction for the surgical treatment of complex congenital heart disease. An excellent immediate rather than long-term outcome could be obtained. The hemodynamics for late failure, however, remained unclear. In vitro pulsatile flow visualization was not conducted before.
A simplified right heart duplicator system was set up and driven under physiologic conditions. Polystyrene of 0.18mm in diameter was applied as the tracing particle. Flow characteristics of models of normal pulmonary circulation as well as pulmonary artery atresia with the RVOT reconstructed utilizing valved and non-valved extracardiac conduits were observed.
Flow patterns in the normal pulmonary circulatory model were mainly of axial flow associated with small scope of flow disturbances. A single vortex in the right ventricle was noted in diastole. In the pulmonary artery atresia model, a couple of vortexes were found in the right ventricle, a secondary flow in the main pulmonary artery, and a stronger secondary flow than in the normal pulmonary circulatory model in the two branches in both systole and diastole. A secondary flow was found in the proximal, an axial flow was observed in the distal portion of the extracardiac conduit with normal bioprosthetic valves and a secondary flow was observed in the entire conduit with stenotic bloprosthetic valves. The secondary flow intensity became stronger with the development of the stenosis. Severe insufficiency occurred in the bileaflet ceramic tilting-disc prosthesis during the entire cardiac circle, i.e., the prosthesis was in a maximum open position. Severe reverse flow could be found in the extracardiac conduit in the deceleration phase. Concavity of the crank shaft was found by examination to be filled with tracing particles and the prosthesis became stuck. Model of RVOT reconstruction with non-valved conduit yielded reverse flow inside the extracardiac conduit as well.
Secondary flow may occur in normal or diseased extracardiac conduit for RVOT reconstruction. If micro-thrombus of over 0.18mm in diameter attached in the concave of the crank shaft of a bileaflet tilting-disc prosthesis under a condition of resistance as occurred in the present study, the prosthesis may become stuck. Model of RVOT reconstruction with non-valved extracardiac conduit yielded reverse flow inside the conduit, of which the flow pattern was of greater energy consumption. Thus, a non-valved conduit should be avoided in clinical practice as far as possible.

並列關鍵字

extracardiac conduit ； flow visualization ； hear valves