| 摘要: | 本研究針對雙葉片主動脈人工心瓣St. Jude Medical(SJM),CarboMedics(CM)和 Edwards Tekna(modified Duromedics,DM)進行體外模擬之脈動流場量測。左心血管流模擬裝置符合幾何相似及動力相似。主動脈模型由石英玻璃管吹成一軸向對稱之主動脈竇,測試之心瓣裝置於主動脈之根部,模擬血液係採用黏滯係數.mu.=3.9cp之甘油混合溶液,液體之折射率接近石英玻璃管。測試邊界條件控制在符合生理脈動波形範圍,維持每分鐘70下心跳及每分鐘5升之血流流量。脈動流場量測採用二分量雷射測速儀(LDA),依流動方向分為五個量測斷面,均在動脈竇區內。 量測結果顯示,SJM,CM和DM雖同為雙葉片人工心瓣,然彼此呈現不相同流況,此由於幾何形狀差異、開啟角度差異及支移動方式不同。整體而言,SJM之紊流擾動最小,其次CM,DM具有較大的紊流擾動。三種心瓣均達到破壞血球及血小板界限,這與臨床上發現之併發症相符。
The pulsatile flow fields downstream the three aortic bileaflet mechanical valves: St. Jude Medical (SJM), CarboMedics (CM), Edwards Tekna (modified Duromedics, DM) were investigated in vitro. An experimental circulatory mock loop was used to simulate the left heart under the conditions of geometric and dynamic similarities. These tested valves were mounted on the base of a glass-made model aorta with symmetrical sinus. The blood analog fluid had a viscosity of 3.9 cp and had matching refractive index with the model aorta. Experimental parameters were set at the rate of 70 heart-beats and 5 liters of flow per minute. A two-component laser Doppler anemometer was used to measure the distributions of pulsatile velocities at five different axial locations inside the sinus of the aorta. Results show that although all the three valves are aortic bileaflet valves, they have different flow patterns, due to their different opening angles, shapes of leaflets and movements of hinges. Among these three valves, SJM has been found to have the smallest turbulent stress, CM has slightly higher whereas DM has the greatest stress. The levels of stress that these three valves generate are greater than the threshold for blood damage and thrombosis hence, resulting in the clinical complications. |
