School of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30332, USA.
Am J Physiol Heart Circ Physiol. 2010 Feb;298(2):H395-405. doi: 10.1152/ajpheart.00040.2009. Epub 2009 Nov 13.
Calcific aortic valve (AV) disease has a high prevalence in the United States, and hypertension is correlated to early onset of the disease. The cause of the disease is poorly understood, although biological and remodeling responses to mechanical forces, such as membrane tension, have been hypothesized to play a role. The mechanical behavior of the native AV has, therefore, been the focus of many recent studies. In the present study, the dynamic deformation characteristics of the AV leaflet and the effects of hypertension on leaflet deformation are quantified. Whole porcine aortic roots were trimmed and mounted in an in vitro pulsatile flow loop and subjected to normal (80/120 mmHg), hypertensive (120/160 mmHg), or severe hypertensive (150/190 mmHg) conditions. Local valve leaflet deformations were calculated with dual-camera photogrammetry method: by tracking the motion of markers placed on the AV leaflets in three dimensions and calculating their spatial deformations. The results demonstrate that, first, during diastole, high transvalvular pressure induces a stretch waveform which plateaus over the diastolic duration in both circumferential and radial directions. During systole, the leaflet stretches in the radial direction due to forward flow drag forces but compresses in the circumferential direction in a manner in agreement with Poisson's effect. Second, average diastolic and systolic stretch ratios were quantified in the radial and circumferential directions in the base and belly region of the leaflet, and diastolic stretch was found to increase with increasing pressure conditions.
钙化性主动脉瓣 (AV) 疾病在美国的发病率很高，高血压与疾病的早期发病有关。尽管已经假设生物和对机械力（如膜张力）的重塑反应可能起作用，但该疾病的病因仍不清楚。因此，天然 AV 的力学行为一直是许多最近研究的重点。在本研究中，量化了 AV 瓣叶的动态变形特征以及高血压对瓣叶变形的影响。整个猪主动脉根部经过修剪并安装在体外脉动流回路中，并承受正常（80/120mmHg）、高血压（120/160mmHg）或严重高血压（150/190mmHg）条件。局部瓣叶变形通过双摄像头摄影测量法计算：通过跟踪放置在 AV 瓣叶上的标记在三维空间中的运动并计算它们的空间变形。结果表明，首先，在舒张期间，高跨瓣压在舒张期间在圆周和径向方向上产生拉伸波形，其达到平台。在收缩期间，由于前向流阻力，瓣叶在径向方向上拉伸，但在圆周方向上压缩，这种方式与泊松效应一致。其次，量化了瓣叶基底部和中部的径向和圆周方向的舒张和收缩拉伸比，发现舒张拉伸随压力条件的增加而增加。
