針對單一心室心臟缺陷(Single Ventricle Heart Defects, SVHD)的病患，為了改善血流動力以及減少心臟的負荷，Fontan等人提出了緩解性(Palliative)的手術，逐步經由手術而將含氧血與缺氧血分開，其最終階段為全腔靜脈動脈吻合術(Total Cavopulmonary Connection, TCPC)，目的是將體、肺循環完全分離。但重建後心房前負載(Preload)不足，上、下腔靜脈回流壓力增高，而導致許多併發症產生，例如:房性心律不整(Atrial Arrhythmias)、肝水腫(Hepatic Congestion)、蛋白質流失症(Protein Losing Enteropathy)等。本研究擬建立一特殊仿生循環測試台以模擬TCPC血流動力特徵，並加入右心輔助器以探討如何改善TCPC血流動力特性。本研究探討右心輔助器在不同的輔助頻率與血泵射血時間點對於上、下腔靜脈與肺循環的血液動力改善功效，並討論最佳的輔助參數設定。實驗結果顯示改變血泵射血時間點，對於輔助成效沒有太大的影響。然而，隨著輔助頻率的增快，靜脈回流壓力隨之降低，而肺動脈、左心房壓力與心輸出量也隨之增加，顯示右心輔助器可有效地改善原本病態的TCPC循環特性。當輔助頻率為100BPM時，靜脈回流壓力降低73%、肺動脈壓力增加40%、左心房壓力增加85%、心輸出量增加了21%。本研究結果證明右心輔助器的置入可減少靜脈回流壓力以及增加肺部灌流壓力，進而增加左心室的前負荷，改善TCPC循環所伴隨的倂發症，使病患回復至正常人的血液循環動力特性。

SUMMARY
The hemodynamic characteristics associated with congenital single ventricular heart disease can be improved by the palliative Fontan operation. Despite that total cavopulmonary connection (TCPC) of the Fontan procedure can separate the oxygenated and deoxygenated blood circulation, the elevated venous return pressure and decreased atrial preload may lead to long-term complications including arrhythmias, protein losing enteropathy, hepatic congestion, ventricular dysfunction and diminished exercise capacity, etc. As a result, in order to survive the TCPC-induced complications, the patient must undergo heart transplantation or be implanted with right ventricular assist device (RVAD). To explore the RVAD-intervened TCPC hemodynamic alteration, a mock circulation loop (MCL) has been constructed. In this in-vitro study, we adopted a valved pulsatile blood pump as the RVAD and examined the pressure and flowrate associated with the RVAD-assisted right and left lungs and the atrial preload and cardiac output of the left ventricle. The aim of this investigation is two-fold. First, we explore if RVAD insertion in TCPC flow may recover heart toward the desired bi-ventricular circulation physiology. Second, we would like to decide the critical parameters associated with the RVAD device design. Unlike the systemic counterpulsation support, the assist phase relative to heart rhythm is immaterial to the improvement of venous return pressure decrease and pulmonary circulation renormalization. The results show that the RVAD assist frequency is most influential. For example, with 1:1 assist ratio of the RVAD, the superior vena cava (SVC) and inferior vena cava (IVC) pressures can be decreased 32.8%, pulmonary artery pressure increased 40%, left atrium pressure increased 58.3% and cardiac output increased 17%, indicating that RVAD insertion in the TCPC circuit can bring back the bi-ventricular circulation physiology as expected.

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