Matthews Peter B, Kim Brian, Azadani Ali N, Guy T Sloane, Guccione Julius M, Ge Liang, Tseng Elaine E
Department of Surgery, University of California at San Francisco Medical Center (UCSF), 94143-0118, USA.
J Heart Valve Dis. 2009 Nov;18(6):682-90.
Pulmonary autograft dilation can lead to aortic insufficiency requiring reoperation. Remodeling occurs when the pulmonary root is subjected to systemic pressure. It is unknown whether a regional variability of the material properties exists within the root, resulting in unequally distributed wall stress prior to remodeling after the Ross procedure. The study aim was to determine differences in regional pulmonary root material properties, and to identify changes in wall stress at both pulmonary and systemic pressure.
Five regions of the porcine pulmonary root--anterior and posterior artery, and each sinus--were subjected to displacement-controlled equibiaxial stretch testing. The stress-strain data recorded were used to determine stiffness at 35% strain. Separate finite element simulations of the root were performed using each of the five regional material properties. Tissue dilation and wall stress were compared at pulmonic and systemic pressures.
The pulmonary artery (PA) demonstrated tissue anisotropy, and was stiffer in the circumferential than the longitudinal direction (p < 0.001), whereas the sinuses demonstrated no differences in stiffness between the circumferential and longitudinal directions (p = 0.73). Overall, the PA was significantly more compliant than the sinuses, both circumferentially (p = 0.04) and longitudinally (p = 0.007). However, no regional differences in stiffness were found between the anterior and posterior PA (circumferential, p = 0.37; longitudinal, p = 0.06), or among the sinuses (circumferential, p = 0.22; longitudinal, p = 0.38) at 35% strain. Based on finite element simulations, the PA dilated from 35.14 +/- 1.67 cm to 45.98 +/- 2.56 cm, and the sinuses from 35.05 +/- 1.39 cm to 40.02 +/- 2.17 cm from pulmonic to systemic pressure. The maximum wall stress increased from 41.07 +/- 4.17 to 287.06 +/- 31.84 kPa in the PA, and from 55.87 +/- 4.38 to 295.64 +/- 32.97 kPa in the sinuses.
Significant inherent differences in compliance were demonstrated between the PA and pulmonary sinuses. These results suggest that the artery dilates more than the sinuses, but is subjected to equally large wall stresses when the systemic pressure is applied prior to remodeling.
肺动脉自体移植扩张可导致主动脉瓣关闭不全，需要再次手术。当肺动脉根部承受体循环压力时会发生重塑。目前尚不清楚根部材料特性是否存在区域差异，从而导致Ross手术后重塑前壁应力分布不均。本研究的目的是确定肺动脉根部区域材料特性的差异，并识别在肺动脉压力和体循环压力下壁应力的变化。
对猪肺动脉根部的五个区域——前动脉、后动脉和每个窦——进行位移控制的双轴拉伸试验。记录的应力-应变数据用于确定35%应变时的刚度。使用五个区域材料特性中的每一个对根部进行单独的有限元模拟。比较肺动脉压力和体循环压力下的组织扩张和壁应力。
肺动脉（PA）表现出组织各向异性，周向比纵向更硬（p < 0.001），而窦在周向和纵向的刚度没有差异（p = 0.73）。总体而言，无论是周向（p = 0.04）还是纵向（p = 0.007），PA都比窦更具顺应性。然而，在35%应变时，前、后PA之间（周向，p = 0.37；纵向，p = 0.06）或窦之间（周向，p = 0.22；纵向，p = 0.38）在刚度上未发现区域差异。基于有限元模拟，从肺动脉压力到体循环压力，PA从35.14±1.67 cm扩张到45.98±2.56 cm，窦从35.05±1.39 cm扩张到40.02±2.17 cm。PA的最大壁应力从41.07±4.17 kPa增加到287.06±31.84 kPa，窦的最大壁应力从55.87±4.38 kPa增加到295.64±32.97 kPa。
PA与肺窦之间在顺应性方面存在显著的固有差异。这些结果表明，动脉比窦扩张得更多，但在重塑前施加体循环压力时，承受的壁应力同样大。
