Failure properties of intraluminal thrombus in abdominal aortic aneurysm under static and pulsating mechanical loads
Failure properties of intraluminal thrombus in abdominal aortic aneurysm under static and pulsating mechanical loads
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DOI：
10.1016/j.jvs.2008.01.036
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发表时间：
2008-07-01
影响因子：
4.3
通讯作者：
Swedenborg, Jesper
中科院分区：
文献类型：
--
作者：
Gasser, T. Christian;Gorgulu, Goray;Swedenborg, Jesper
目的：有研究表明，腔内血栓（ILT）的机械失效可能在腹主动脉瘤（AAA）破裂中起关键作用，在本研究中，对这一假设进行了研究。提出了一种体外实验方法，该方法提供了ILT组织在静态和脉动机械载荷下的层特异性失效数据。总共从开放择期AAA修复术期间采集的8个ILT的管腔、内侧和近腔层制备了112个骨形测试样本。在37 ℃和pH 7.0下，在补充有胎牛血清、L-抗坏血酸和抗生素的Dulbecco改良Eagle培养基（DMEM）中进行三种不同类型的机械实验，表示为对照试验、极限强度试验和疲劳试验。详细地说，疲劳测试是加载ILT组织的实验。在三个不同的负荷水平下，以1.0 Hz的固有频率进行脉动的方式。ILT的极限强度（腔层、内侧层和腔外层分别为156.5 kPa、92.0 kPa和47.7 kPa）和参考刚度（腔层、内侧层和腔外层分别为62.88 kPa、47.52 kPa和41.52 kPa）从内到外连续降低。ILT组织在60%极限强度的脉冲载荷下在不到1小时内失效，而约40%极限强度的载荷水平在13.9小时内未导致失效。ILT组织易受疲劳失效的影响，且强度随载荷循环次数显著降低。因此，经过合理的时间脉冲加载后，ILT的强度远低于其极限强度，并且当与有限元（FE）研究的应力预测相比时，这表明体内疲劳失效的可能性。ILT内的失效可能向其后面的弱化血管壁传播，并可能在此后引发AAA失效。
Objectives: It has been suggested that mechanical failure of intraluminal thrombus (ILT) could play a key role in the rupture of abdominal aortic aneurysms (AAAs), and in the present study, this hypothesis has been investigated. An in vitro experimental approach has been proposed, which provides layer-specific failure data of ILT tissue under static and pulsatile mechanical loads.Methods. In total, 112 bone-shaped test specimens are prepared from luminal, medial, and abluminal layers of eight ILTs harvested during open elective AAA repair. Three different types of mechanical experiments, denoted as control test, ultimate strength test, and fatigue test were performed in Dulbecco's modified eagle's medium (DMEM) supplemented with fetal calf serum, L-ascorbic acid, and antibiotics at 37 degrees C and pH 7.0. In detail, fatigue tests, which are experiments, where the ILT tissue is loaded. in pulsatile manner, were carried out at three different load levels with a natural frequency of 1.0 Hz.Results. ILT's ultimate strength (156.5 kPa, 92.0 kPa, and 47.7 kPa for luminal, medial, and abluminal layers, respectively) and referential stiffness (62.88 kPa, 47.52 kPa, and 41.52 kPa, for luminal, medial, and abluminal layers, respectively) continuously decrease from the inside to the outside. ILT tissue failed within less than 1 hour under pulsatile loading at a load level of 60% ultimate strength, while a load level of about 40% ultimate strength did not cause failure within 13.9 hours.Conclusions. ILT tissue is vulnerable against fatigue failure and shows significant decreasing strength with respect to the number of load cycles. Hence, after a reasonable time of pulsating loading ILT's strength is far below its ultimate strength, and when compared with stress predictions from finite element (FE) studies, this indicates the likelihood of fatigue failure in vivo. Failure within the ILT could propagate towards the weakened vessel wall behind it and could initialize AAA failure thereafter.