Itatani Keiichi, Miyaji Kagami, Tomoyasu Takahiro, Nakahata Yayoi, Ohara Kuniyoshi, Takamoto Shinichi, Ishii Masahiro
Department of Cardiovascular Surgery, Kitasato University School of Medicine, Sagamihara, Japan.
Ann Thorac Surg. 2009 Aug;88(2):565-72; discussion 572-3. doi: 10.1016/j.athoracsur.2009.04.109.
In the extracardiac Fontan operation, larger conduits are used when considering the patients' growth rate. However, larger conduits may cause inefficient flow due to turbulence or stagnation, resulting in late problems such as thrombosis or stenosis. Our objective was to reveal the physiologic effects of respiration and exercise using numerical models, based on the energy loss and flow stagnation, and to determine optimal conduit size.
For the Fontan operation, a conduit from 14 to 22 mm was created based on angiographic data from 17 Fontan patients (mean age, 36.0 months; mean body surface area, 0.53 m(2)). Respiratory-driven flow of the superior and inferior vena cava was determined at rest and during exercise on two levels (0.5 and 1.0 W/kg) by magnetic resonance imaging flow studies. Flow stagnation was defined as the volume of the region where flow velocity was less than 0.01 m/second at both the expiratory and inspiratory phases.
In larger conduits, backward flow at the expiratory phase was prominent. Energy loss was small even during exercise, but the change was slightly larger between 14 and 16 mm than other conduit sizes (14 mm, 5.759 mW; 16 mm, 4.881 mW; and 22 mm, 4.199 mW during 1.0 W/kg exercise). Stagnation volume at the expiratory phase increased with an increase of conduit size (14 mm, 9.20% vs 22 mm, 33.9% conduit volume at rest).
Fontan circulation is a low-energy system even during exercise. Larger conduits were proven to have redundant spaces, thus 16 and 18 mm conduits were optimal.
在心脏外Fontan手术中，考虑到患者的生长速度会使用更大的管道。然而，更大的管道可能会由于湍流或停滞导致血流效率低下，从而引发诸如血栓形成或狭窄等晚期问题。我们的目的是基于能量损失和血流停滞情况，使用数值模型揭示呼吸和运动的生理效应，并确定最佳管道尺寸。
对于Fontan手术，根据17例Fontan患者（平均年龄36.0个月；平均体表面积0.53 m²）的血管造影数据创建了直径从14至22毫米的管道。通过磁共振成像血流研究确定了上腔静脉和下腔静脉在静息状态以及两个运动水平（0.5和1.0 W/kg）时的呼吸驱动血流。血流停滞定义为呼气和吸气阶段流速均小于0.01米/秒的区域体积。
在较大的管道中，呼气阶段的逆流较为明显。即使在运动期间能量损失也较小，但在14至16毫米之间的变化略大于其他管道尺寸（1.0 W/kg运动时，14毫米为5.759毫瓦；16毫米为4.881毫瓦；22毫米为4.199毫瓦）。呼气阶段的停滞体积随管道尺寸的增加而增加（静息时，14毫米为管道体积的9.20%，22毫米为33.9%）。
即使在运动期间，Fontan循环也是一个低能量系统。已证明较大的管道存在多余空间，因此16毫米和18毫米的管道是最佳选择。
