Liu Yi, Dang Charles, Garcia Marisa, Gregersen Hans, Kassab Ghassan S
Department of Biomedical Engineering, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA.
Am J Physiol Heart Circ Physiol. 2007 Dec;293(6):H3290-300. doi: 10.1152/ajpheart.00666.2007. Epub 2007 Sep 14.
The stress and strain in the vessel wall are important determinants of vascular physiology and pathophysiology. Vessels are constrained radially by the surrounding tissue. The hypothesis in this work is that the surrounding tissue takes up a considerable portion of the intravascular pressure and significantly reduces the wall strain and stress. Ten swine of either sex were used to test this hypothesis. An impedance catheter was inserted into the carotid or femoral artery, and after mechanical preconditioning pressure-cross-sectional area relations were obtained with the surrounding tissue intact and dissected away (untethered), respectively. The radial constraint of the surrounding tissue was quantified as an effective perivascular pressure on the outer surface of the vessel, which was estimated as 50% or more of the intravascular pressure. For carotid arteries at pressure of 100 mmHg, the circumferential wall stretch ratio in the intact state was approximately 20% lower than in the untethered state and the average circumferential stress was reduced by approximately 70%. For femoral arteries, the reductions were approximately 15% and 70%, respectively. These experimental data support the proposed hypothesis and suggest that in vitro and in vivo measurements of the mechanical properties of vessels must be interpreted with consideration of the constraint of the surrounding tissue.
血管壁中的应力和应变是血管生理和病理生理的重要决定因素。血管在径向受到周围组织的约束。本研究的假设是，周围组织承担了相当一部分血管内压力，并显著降低了血管壁的应变和应力。选用10头雌雄不限的猪来验证这一假设。将阻抗导管插入颈动脉或股动脉，在进行机械预处理后，分别在周围组织完整和剥离（无束缚）的情况下获得压力-横截面积关系。周围组织的径向约束被量化为血管外表面的有效血管周围压力，估计为血管内压力的50%或更多。对于压力为100 mmHg的颈动脉，完整状态下的周向壁拉伸比比无束缚状态下低约20%，平均周向应力降低约70%。对于股动脉，降低幅度分别约为15%和70%。这些实验数据支持了所提出的假设，并表明在体外和体内测量血管力学性能时，必须考虑周围组织的约束。
