Topoleski L D, Salunke N V
Department of Mechanical Engineering, UMBC 21250, USA.
Z Kardiol. 2000;89 Suppl 2:85-91. doi: 10.1007/s003920070105.
This paper summarizes the results from mechanical testing of atherosclerotic plaques performed in the Cardiovascular Mechanics Laboratory and the Laboratory for Implantable Materials at UMBC. The motivation for our work is that balloon angioplasty, stenting, and roto-ablation are mechanical processes that are designed to permanently alter the shape of an occluded arterial lumen. The mechanisms of permanent plaque deformation are not known. Therefore, to study the mechanical behavior of plaques, we performed mechanical tests on atherosclerotic lesions with different compositions and investigated differences in the materials' mechanical responses. Atherosclerotic plaque specimens were subjected to two main types of loading: multiple cyclic compression and stress-relaxation. The multiple-cycle test protocol was two fifteen-cycle loading phases that were separated by a 10-15 minute unloaded "rest" period. The compressive stress-relaxation test protocol was a series of three consecutive loadings (called phases I, II, and III). Each phase consisted of a 25% compression that was achieved in less than 1 second, a 10 minute relaxation period, and a 10 minute unloaded "rest" period between loadings. In the multiple cycle compressive loading, plaques exhibited three distinct types of behavior, which corresponded to the plaque compositions. Calcified plaques showed behaviors distinct from other plaque types and healthy vessels. In contrast to the cyclic compression results, plaque types could not be distinguished solely on the basis of stress relaxation behavior. Calcified and fibrous plaques had similar behavior, and therefore histology was used for definite identification. Calcified plaques have unique mechanical properties, and therefore interventions like angioplasty, roto-ablation, and stenting may require protocols specific for calcified lesions. The optimum protocols for calcified plaques may be quite different from plaques with other compositions. It is essential to learn more about the mechanical behavior of all plaque types to increase the success rate of occlusive atherosclerosis treatments.
本文总结了在马里兰大学巴尔的摩县分校心血管力学实验室和可植入材料实验室对动脉粥样硬化斑块进行力学测试的结果。我们开展这项工作的动机在于，球囊血管成形术、支架植入术和旋切术都是旨在永久性改变闭塞动脉管腔形状的机械过程。永久性斑块变形的机制尚不清楚。因此，为了研究斑块的力学行为，我们对不同成分的动脉粥样硬化病变进行了力学测试，并研究了材料力学响应的差异。动脉粥样硬化斑块标本承受两种主要类型的载荷：多次循环压缩和应力松弛。多循环测试方案是两个15次循环的加载阶段，中间间隔10 - 15分钟的无载荷“休息”期。压缩应力松弛测试方案是一系列连续的三次加载（称为阶段I、II和III）。每个阶段包括在不到1秒内达到25%的压缩、10分钟的松弛期以及两次加载之间10分钟的无载荷“休息”期。在多次循环压缩加载中，斑块表现出三种不同类型的行为，这与斑块成分相对应。钙化斑块表现出与其他斑块类型和健康血管不同的行为。与循环压缩结果相反，仅根据应力松弛行为无法区分斑块类型。钙化斑块和纤维斑块具有相似的行为，因此使用组织学进行明确识别。钙化斑块具有独特的力学性能，因此像血管成形术、旋切术和支架植入术等干预措施可能需要针对钙化病变的特定方案。钙化斑块的最佳方案可能与其他成分的斑块有很大不同。了解所有斑块类型的力学行为对于提高闭塞性动脉粥样硬化治疗的成功率至关重要。
