Department of Cardiovascular Surgery, Kitasato University School of Medicine, Sagamihara, Japan.
J Thorac Cardiovasc Surg. 2011 Jul;142(1):127-35. doi: 10.1016/j.jtcvs.2010.11.033. Epub 2011 Feb 1.
In the era of the staged Fontan operation, small pulmonary artery index (<250 mm(2)/m(2)) has not affected the early or midterm results. The lower limit of pulmonary artery index, however, has not yet been determined. We created numeric models of the Fontan circulation to investigate the lower limit of the pulmonary artery size.
The extracardiac Fontan geometries with pulmonary artery index, ranging from 50 to 200 mm(2)/m(2) with every 10-mm(2)/m(2) increase, were created from the postoperative angiographic data of 17 patients. The superior and inferior vena caval flow rates at rest and on 2 exercise levels (0.5 and 1.0 W/kg) were given by magnetic resonance imaging flow studies. Respiration-driven transient flow analysis was performed with a finite element solver. Energy loss and mean inferior vena caval pressure were obtained from the results.
Energy loss and mean inferior vena caval pressure were prominently increased in small pulmonary artery index models, especially during exercise. The pulmonary artery indices sufficient for mean inferior vena caval pressure less than 17 mm Hg were 80 mm(2)/m(2) at rest, 100 mm(2)/m(2) during 0.5-W/kg exercise, and 110 mm(2)/m(2) during 1.0-W/kg exercise. With the increase of pulmonary arterial resistance, mean inferior vena caval pressure increased, but the flow pattern did not change.
A small pulmonary artery causes a high pressure gradient and a high energy loss. The lower limit of pulmonary artery index, considering the exercise tolerance, was 110 mm(2)/m(2).
在分期 Fontan 手术时代，小肺动脉指数（<250mm²/m²）并未影响早期或中期结果。然而，肺动脉指数的下限尚未确定。我们建立了 Fontan 循环的数值模型，以研究肺动脉大小的下限。
从 17 例患者的术后血管造影数据中创建了肺动脉指数范围从 50 到 200mm²/m²的体外心脏 Fontan 几何图形，每 10mm²/m²增加一次。磁共振成像流量研究给出了静息和两种运动水平（0.5 和 1.0 W/kg）下上腔静脉和下腔静脉的流速。使用有限元求解器进行呼吸驱动瞬态流量分析。从结果中获得能量损失和平均下腔静脉压力。
在小肺动脉指数模型中，能量损失和平均下腔静脉压力明显增加，尤其是在运动期间。足以使平均下腔静脉压力小于 17mmHg 的肺动脉指数在静息时为 80mm²/m²，在 0.5-W/kg 运动时为 100mm²/m²，在 1.0-W/kg 运动时为 110mm²/m²。随着肺动脉阻力的增加，平均下腔静脉压力增加，但流量模式没有改变。
小肺动脉导致高压力梯度和高能量损失。考虑到运动耐量，肺动脉指数的下限为 110mm²/m²。
