Biomedical Engineering Center, Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
PLoS One. 2009 Dec 2;4(12):e8105. doi: 10.1371/journal.pone.0008105.
Treatment of arterial bifurcation lesions using drug-eluting stents (DES) is now common clinical practice and yet the mechanisms governing drug distribution in these complex morphologies are incompletely understood. It is still not evident how to efficiently determine the efficacy of local drug delivery and quantify zones of excessive drug that are harbingers of vascular toxicity and thrombosis, and areas of depletion that are associated with tissue overgrowth and luminal re-narrowing.
We constructed two-phase computational models of stent-deployed arterial bifurcations simulating blood flow and drug transport to investigate the factors modulating drug distribution when the main-branch (MB) was treated using a DES. Simulations predicted extensive flow-mediated drug delivery in bifurcated vascular beds where the drug distribution patterns are heterogeneous and sensitive to relative stent position and luminal flow. A single DES in the MB coupled with large retrograde luminal flow on the lateral wall of the side-branch (SB) can provide drug deposition on the SB lumen-wall interface, except when the MB stent is downstream of the SB flow divider. In an even more dramatic fashion, the presence of the SB affects drug distribution in the stented MB. Here fluid mechanic effects play an even greater role than in the SB especially when the DES is across and downstream to the flow divider and in a manner dependent upon the Reynolds number.
The flow effects on drug deposition and subsequent uptake from endovascular DES are amplified in bifurcation lesions. When only one branch is stented, a complex interplay occurs - drug deposition in the stented MB is altered by the flow divider imposed by the SB and in the SB by the presence of a DES in the MB. The use of DES in arterial bifurcations requires a complex calculus that balances vascular and stent geometry as well as luminal flow.
药物洗脱支架（DES）治疗动脉分叉病变是目前常见的临床实践，但药物在这些复杂形态中的分布机制尚未完全了解。目前还不清楚如何有效地确定局部药物输送的疗效，并量化药物过多的区域，这些区域预示着血管毒性和血栓形成，以及药物耗尽的区域，这些区域与组织过度生长和管腔再变窄有关。
我们构建了模拟血流和药物输送的支架部署动脉分叉的两相计算模型，以研究当主支（MB）使用 DES 治疗时调节药物分布的因素。模拟预测了分叉血管床中广泛的血流介导的药物输送，其中药物分布模式不均匀，对相对支架位置和管腔血流敏感。MB 中的单个 DES 与侧支（SB）侧壁上的大逆行管腔血流相结合，可在 SB 管腔壁界面上提供药物沉积，除非 MB 支架位于 SB 分流器的下游。更戏剧性的是，SB 的存在会影响支架 MB 中的药物分布。在这里，流体力学效应的作用比在 SB 中更为重要，尤其是当 DES 横跨并位于血流分压器的下游，并且其方式取决于雷诺数。
在分叉病变中，药物沉积和随后从血管内 DES 吸收的血流效应会被放大。当只有一个分支被支架支撑时，就会发生复杂的相互作用 - 支架 MB 中的药物沉积会受到 SB 中血流分压器的影响，而 SB 中的药物沉积则会受到 MB 中 DES 的影响。DES 在动脉分叉处的使用需要一种复杂的计算方法，该方法需要平衡血管和支架的几何形状以及管腔血流。
