Institute for Medical Engineering and Science, Massachusetts Institute of Technology , Cambridge, Massachusetts.
Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School , Boston, Massachusetts.
Am J Physiol Heart Circ Physiol. 2018 Nov 1;315(5):H1182-H1193. doi: 10.1152/ajpheart.00199.2018. Epub 2018 Aug 10.
Management of aortic dissections (AD) is still challenging, with no universally approved guideline among possible surgical, endovascular, or medical therapies. Approximately 25% of patients with AD suffer postintervention malperfusion syndrome or hemodynamic instability, with the risk of sudden death if left untreated. Part of the issue is that vascular implants may themselves induce flow disturbances that critically impact vital organs. A multilayer mesh construct might obviate the induced flow disturbances, and it is this concept we investigated. We used preintervention and post-multilayer flow modulator implantation (PM) geometries from clinical cases of type B AD. In-house semiautomatic segmentation routines were applied to computed tomography images to reconstruct the lumen. The device was numerically reconstructed and adapted to the PM geometry concentrically fit to the true lumen centerline. We also numerically designed a pseudohealthy case, where the geometry of the aorta was extracted interpolating geometric features of preintervention, postimplantation, and published representative healthy volunteers. Computational fluid dynamics methods were used to study the time-dependent flow patterns, shear stress metrics, and perfusion to vital organs. A three-element Windkessel lumped parameter module was coupled to a finite-volume solver to assign dynamic outlet boundary conditions. Multilayer flow modulator not only significantly reduced false lumen blood flow, eliminated local flow disturbances, and globally regulated wall shear stress distribution but also maintained physiological perfusion to peripheral vital organs. We propose further investigation to focus the management of AD on both modulation of blood flow and restoration of physiologic end-organ perfusion rather than mere restoration of vascular lamina morphology. NEW & NOTEWORTHY The majority of aortic dissection modeling efforts have focused on the maintenance of physiological flow using minimally invasive placed grafts. The multilayer flow modulator is a complex mesh construct of wires, designed to eliminate flow disruptions in the lumen, regulate the physiological wall stresses, and enhance endothelial function and offering the promise of improved perfusion of vital organs. This has never been fully proved or modeled, and these issues we confirmed using a dynamic framework of time-varying arterial waveforms.
主动脉夹层（AD）的管理仍然具有挑战性，在可能的手术、血管内或药物治疗中，没有普遍认可的指南。大约 25%的 AD 患者术后会出现灌注不良综合征或血流动力学不稳定，如果不治疗，有猝死的风险。部分问题在于血管植入物本身可能会引起严重影响重要器官的血流紊乱。多层网结构可能会避免诱导的流动干扰，这正是我们研究的概念。我们使用了来自 B 型 AD 临床病例的术前和多层血流调节剂植入物（PM）后的几何形状。应用内部半自动分割例程对 CT 图像进行重建，以重建管腔。该装置被数值重建，并适当地适配于 PM 几何形状，与真腔中心线同心。我们还数值设计了一个假健康案例，其中主动脉的几何形状是通过插值术前、植入后的几何特征以及已发表的代表性健康志愿者的特征来提取的。计算流体动力学方法用于研究时变流型、剪切应力指标和重要器官的灌注。一个三元件风箱集中参数模块与有限体积求解器耦合，以分配动态出口边界条件。多层血流调节剂不仅显著降低了假腔血流，消除了局部血流紊乱，全局调节了壁面剪切应力分布，而且维持了外周重要器官的生理灌注。我们建议进一步研究，将 AD 的管理重点放在调节血流和恢复生理终末器官灌注上，而不仅仅是恢复血管层形态。
新的和值得注意的是，大多数主动脉夹层建模工作都集中在使用微创放置的移植物来维持生理血流。多层血流调节剂是一种复杂的线网结构，旨在消除管腔中的流动干扰，调节生理壁应力，增强内皮功能，并提供改善重要器官灌注的承诺。这从未被完全证明或建模，我们使用时变动脉波形的动态框架确认了这些问题。
