本研究為探討主動脈側血泵(Para-aortic Blood Pump;簡稱PABP) 反脈動循環輔助下之冠狀動脈流場特性，特建構一套循環測試平台(Mock Circulation Test Rig)以利實驗進行。本測試台依據混合循環模式(Hybrid Circulation Model)做系統及組件設計，包含了(1)由矽膠所製作可顯示脈動流場之波傳現象與對流效應的人體主要動脈系統，(2)可提供心肌內層、中層及外層流量量測的冠狀動脈系統，以及(3)區塊參數法所架構的體循環系統與肺循環系統。實驗中將血液循環分成健康狀態、心衰竭狀態以及反脈動輔助之情況作血動力特徵模擬，依照血動力指標，以心肌耗氧指標(Tension Time Index, TTI)，心肌養分供需比例(Endocardial Viability Ratio, EVR)，平均主動脈收縮壓(Mean Systolic Pressure, MSP)，平均主動脈舒張壓(Mean Diastolic Pressure, MDP)，心搏量(Stroke Volume, SV)，卸載後主動脈壓(Unloading Aortic Pressure, AoPun)，左心室壓力－體積關係圖(Left Ventricle Pressure Volume Loop, LV P-V Loop)，心輸出量(Cardiac Output, CO)，心室收縮功(Stroke Work, SW)，冠狀動脈灌流量(Coronary Perfusion, CoPerf)以及新心肌養分供需比例(New Endocardial Viability Ratio, EVRnew)作為反脈動輔助之指標參數進行性能分析。實驗發現將血泵充氣時間點設置在主動脈瓣關閥的時間點上時，會產生最佳的舒張強化(Diastolic Augmentation)效果。而血泵的洩氣時間點則可視選擇最小的心肌脈動耗氧量或最大的心輸出增加量為輔助目標，將其設置在左心室開始收縮射血前或後的區間內。當在心室收縮射血前做反脈動卸載輔助時，血動力指標中的MDP增加27%~39%，EVR達30%~45%與CO達5%，並減少TTI與MSP，分別達3%~5%與6%~10%之多，對於CoPerf增加達到3%~12%；若於心室收縮射血後做反脈動卸載輔助，除了EVR外其餘血動力指標都有明顯上升，而CO則有最佳接近15%的增益，CoPerf增加量達23%~33%，MDP平均增加45%，EVRnew達30%~45%，TTI降低8%，MSP有稍微增加的趨勢。以CO與CoPerf而言，延後反脈動卸載時間都有幫助。越往後卸載，對於冠狀動脈逆流負作用越少，也代表淨增加量越多，對於心肌養分供應最充足。波強度分析法亦被應用來分析不同血泵卸載時間的脈動波與流場特性。實驗發現反脈動舒張強化的效果確實增強心肌灌流量也伴隨著波強度增加。以收縮卸載時間的不同，越靠近主動脈開閥（無論前或後），主動脈舒張末期壓力差、收縮卸載導致的反向膨脹波或者是左心室射血所誘導出的正向壓縮波的強度均會減小。本研究發現最佳收縮卸載時機為左心室射血瞬間，於此時間卸載不僅可降低單位心輸出量所耗之心室收縮功，也可減少冠狀動脈逆流現象。

In order to study the coronary flow characteristics under counter-pulsatile support, a special mock circulation loop was constructed. This mock loop, designed using a hybrid 1-D flow and lumped parameter model concept, comprises 1) silicone-rubber artificial arteries that can simulate pulse wave transport and flow convection; 2) a 3-layered coronary flow module that can produce phasic coronary flow characteristics subjected to intra-myocardial compression/relaxation effect; and 3) the connected systemic and pulmonary segments represented by lumped resistors and compliance chambers. Hemodynamics associated with healthy, heart failure and PABP supported conditions were simulated. The indices used to quantify the counter-pulsatile effectiveness include tension time index (TTI), endocardial viability ratio (EVR), mean systolic pressure (MSP), mean diastolic pressure (MDP), stroke volume (SV), stroke work (SW), unloading aortic pressure (AoPun), left ventricular pressure-volume loop (LV P-V Loop), cardiac output (CO), coronary perfusion (CoPerf), and new endocardial viability ratio (EVRnew). Optimal pump inflation time was found at the aortic valve closure instant, which achieved the best diastolic augmentation performance. Pump deflation time, however, can be set before or after aortic valve opening, depending on whether minimal myocardial oxygen consumption or maximal cardiac output and/or coronary perfusion enhancement is desired. Pump deflation prior to aortic valve opening can achieve gains in: MDP 27-39%, EVR 30-45%, CO 5%, CoPerf 3-12%, and reductions in: TTI 3-5% and MDP 6-10%. Deflation after LV ejection, however, can result in increase in: CO15%, CoPerf 23-33%, MDP 45%, EVRnew 30-45%, and reductions in TTI 8%. It was found that delaying deflation time into early systole could be beneficial to both cardiac output and coronary perfusion enhancement. The more the deflation time is delayed, the more effective the reduction in coronary blood steal. Wave intensity (WI) analysis was also performed to analyze the pulse wave and the flow characteristics associated with different PABP deflation timings. The results show that myocardial perfusion assist was positively proportional to the augmenting WI. In aorta, the backward decompression wave generated during unloading can help heart ejection but the WIs behaved differently for pre-systole and post-systole deflation timings. Both PABP-produced backward decompression WI and heart-generated forward compression WI would reduce for delayed deflation timings due to wave cancellation. The present mock loop experiment found that the optimal PABP deflation time locates at the instant of heart ejection, for which the LV SV and coronary regurgitation can be greatly reduced.

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