Fluid dynamics and mass transport in lower limb vessels: Effects on restenosis

Abstract

Lower limb vessels suffer from peripheral artery disease (PAD), a common manifestation of atherosclerosis, presenting a prevalence increasing with age. In order to limit the morbidity, the diminished quality of life, and the mortality in the population affected by PAD, both open surgical (i.e., vein-graft placement) and endovascular procedures (i.e., angioplasty and stenting) are currently adopted as revascularization approaches. Despite the improvements in diagnostics and the available revascularization techniques for the treatment of PAD, restenosis remains a major clinical limitation, conditioned by disease severity and anatomical location. The causes of this adverse event, leading to severe lumen renarrowing in around 30%–40% of cases, are still not fully understood. The altered hemodynamic forces, which are balanced by the dynamic structural vessel changes after treatment, have been recognized as an important promoting factor favoring the inward vessel remodeling of the treated lower limb vessels. These forces can be quantified through computational fluid dynamics (CFD) simulations. Specifically, through the numerical solution of the governing equations of fluid motion, complex patient-specific treated anatomies can be investigated, giving insights on the role of blood flow-related phenomena in the operative and postoperative periods. Additionally, CFD simulations enable the analysis of mass transport phenomena and thus can be successfully used during the process of design and investigation of drug-eluting systems, such as drug-coated balloons, endovascular mini-invasive devices more frequently used in the treatment of PAD, and of restenosis because of the antiproliferative drug activity on the cells of the vessel wall. The present chapter reviews the existing state-of-the-art CFD and drug transport models of femoro-popliteal arteries, with particular attention to vessels treated with drug-coated balloons, stents, or vein grafts, and affected by restenosis. Moreover, future perspectives on the modeling of hemodynamics and mass transport in lower limb vessels are presented.