Azadani Ali N, Chitsaz Sam, Matthews Peter B, Jaussaud Nicolas, Leung James, Ge Liang, Tseng Elaine E
Department of Surgery, University of California at San Francisco Medical Center (UCSF), San Francisco, CA 94143-0118, USA.
J Heart Valve Dis. 2012 Jul;21(4):527-34.
Significant dilation of the pulmonary autograft after the Ross operation is problematic and requires reoperation. Autograft remodeling occurs in response to the immediate rise in pressure and consequent wall stress. The stress-strain response of the pulmonary root plays an important role in understanding the structural and functional changes of the autograft following the Ross procedure. At present, limited data are available on the mechanical properties of fresh human pulmonary roots; hence, the study aim was to determine the regional mechanical properties of human pulmonary roots.
Eighteen fresh healthy specimens of human pulmonary root were obtained from the California Transplant Donor Network (Oakland, CA, USA). Five regions of the pulmonary root--anterior and posterior pulmonary artery (PA), and each of the three sinuses--were subjected to displacement-controlled equibiaxial stretch testing within 24 h of cross-clamp time. Comparisons between the different regions of the pulmonary root were made based on tissue stiffness at physiologic stress. Histologic analyses were also performed of the fibrous structures of the PA and sinuses.
Human PA and sinuses demonstrated a nonlinear response to loading, with no directional dependency to biaxial loading. The anterior PA was significantly more compliant than the posterior PA and the three sinuses in both circumferential and longitudinal directions (p < 0.04). However, there was no significant difference between the stiffness of the posterior PA and that of the three sinuses (p > 0.43), or among the three sinuses (p > 0.30) in the two directions. A tight, more dense weave of elastin was found in the anterior PA than in either the posterior PA or the sinuses.
Significant inherent differences in compliance were demonstrated among different regions of the human pulmonary root. These regional differences may impact upon pulmonary autograft remodeling following the Ross operation, and also influence late autograft dilation.
Ross手术后肺动脉自体移植物出现明显扩张是个问题，需要再次手术。自体移植物重塑是对压力即刻升高及随之而来的壁应力的反应。肺动脉根部的应力应变反应在理解Ross手术后自体移植物的结构和功能变化中起重要作用。目前，关于新鲜人肺动脉根部力学性能的数据有限；因此，本研究的目的是确定人肺动脉根部的局部力学性能。
从美国加利福尼亚移植供体网络（加利福尼亚州奥克兰）获取18个新鲜健康的人肺动脉根部标本。在阻断时间24小时内，对肺动脉根部的五个区域——肺动脉前后壁（PA）以及三个窦中的每一个——进行位移控制的双轴拉伸试验。根据生理应力下的组织硬度对肺动脉根部不同区域进行比较。还对PA和窦的纤维结构进行了组织学分析。
人PA和窦对加载呈现非线性反应，对双轴加载无方向依赖性。在周向和纵向，前PA均显著比后PA及三个窦更具顺应性（p < 0.04）。然而，后PA与三个窦的硬度在两个方向上无显著差异（p > 0.43），三个窦之间也无显著差异（p > 0.30）。在前PA中发现的弹性蛋白编织比后PA或窦更紧密、更密集。
人肺动脉根部不同区域之间存在明显的固有顺应性差异。这些区域差异可能影响Ross手术后肺动脉自体移植物的重塑，也会影响晚期自体移植物扩张。
