Seong Jaehoon, Wakhloo Ajay K, Lieber Baruch B
Department of Biomedical Engineering, University of Miami, 1251 Memorial Drive, Coral Gables, FL 33146, USA.
J Biomech Eng. 2007 Dec;129(6):863-72. doi: 10.1115/1.2800787.
Endovascular coiling is an acceptable treatment of intracranial aneurysms, yet long term follow-ups suggest that endovascular coiling fails to achieve complete aneurysm occlusions particularly in wide-neck and giant aneurysms. Placing of a stentlike device across the aneurysm neck may be sufficient to occlude the aneurysm by promoting intra-aneurysmal thrombosis; however, conclusive evidence of its efficacy is still lacking. In this study, we investigate in vitro the efficacy of custom designed flow divertors that will be subsequently implanted in a large cohort of animals. The aim of this study is to provide a detailed database against which in vivo results can be analyzed. Six custom designed flow divertors were fabricated and tested in vitro. The design matrix included three different porosities (75%, 70%, and 65%). For each porosity, there were two divertors with one having a nominal pore density double than that of the other. To quantify efficacy, the divertors were implanted in a compliant elastomeric model of an elastase-induced aneurysm model in rabbit and intra-aneurysmal flow changes were evaluated by particle image velocimetry (PIV). PIV results indicate a marked reduction in intra-aneurysmal flow activity after divertor implantation in the innominate artery across the aneurysm neck. The mean hydrodynamic circulation after divertor implantation was reduced to 14% or less of the mean circulation in the control and the mean intra-aneurysmal kinetic energy was reduced to 29% or less of its value in the control. The intra-aneurysmal wall shear rate in this model is low and implantation of the flow divertor did not change the wall shear rate magnitude appreciably. This in vitro experiment evaluates the characteristics of local flow phenomena such as hydrodynamic circulation, kinetic energy, wall shear rate, perforator flow, and changes of these parameters as a result of implantation of stentlike flow divertors in an elastomeric replica of elastase-induced saccular aneurysm model in rabbit. These initial findings offer a database for evaluation of in vivo implantations of such devices in the animal model and help in further development of cerebral aneurysm bypass devices.
血管内栓塞是治疗颅内动脉瘤的一种可接受的方法，然而长期随访表明，血管内栓塞尤其在宽颈和巨大动脉瘤中无法实现动脉瘤的完全闭塞。在动脉瘤颈部放置类似支架的装置可能足以通过促进瘤内血栓形成来闭塞动脉瘤；然而，其疗效的确凿证据仍然缺乏。在本研究中，我们在体外研究定制设计的血流导向装置的疗效，随后将其植入一大群动物体内。本研究的目的是提供一个详细的数据库，以便分析体内结果。制作了六个定制设计的血流导向装置并在体外进行测试。设计矩阵包括三种不同的孔隙率（75%、70%和65%）。对于每种孔隙率，有两个分流器，其中一个的标称孔密度是另一个的两倍。为了量化疗效，将分流器植入兔弹性蛋白酶诱导的动脉瘤模型的顺应性弹性体模型中，并通过粒子图像测速法（PIV）评估瘤内血流变化。PIV结果表明，在无名动脉中穿过动脉瘤颈部植入分流器后，瘤内血流活动显著减少。分流器植入后的平均流体动力循环降至对照中平均循环的14%或更低，瘤内平均动能降至对照中其值的29%或更低。该模型中的瘤内壁面剪切率较低，血流导向装置的植入并未明显改变壁面剪切率大小。这项体外实验评估了局部流动现象的特征，如流体动力循环、动能、壁面剪切率、穿支血流，以及在兔弹性蛋白酶诱导的囊状动脉瘤模型的弹性体复制品中植入类似支架的血流导向装置后这些参数的变化。这些初步发现为评估此类装置在动物模型中的体内植入提供了一个数据库，并有助于脑动脉瘤旁路装置的进一步开发。
