Gradual loading ameliorates maladaptation in computational simulations of vein graft growth and remodelling

Vein graft failure is a prevalent problem in vascular surgeries, including bypass grafting and arteriovenous fistula procedures in which veins are subjected to severe changes in pressure and flow. Animal and clinical studies provide significant insight, but understanding the complex underlying coupled mechanisms can be advanced using computational models. Towards this end, we propose a new model of venous growth and remodelling (G&R) based on a constrained mixture theory. First, we identify constitutive relations and parameters that enable venous adaptations to moderate perturbations in haemodynamics. We then fix these relations and parameters, and subject the vein to a range of combined loads (pressure and flow), from moderate to severe, and identify plausible mechanisms of adaptation versus maladaptation. We also explore the beneficial effects of gradual increases in load on adaptation. A gradual change in flow over 3 days plus an initial step change in pressure results in fewer m...

静脉移植物失败是血管外科领域的常见问题，涵盖旁路移植术与动静脉瘘手术——此类手术中静脉会承受压力与血流的剧烈变化。动物实验与临床研究虽已提供诸多重要见解，但借助计算模型可进一步厘清其背后复杂的耦合作用机制。为此，我们提出一种基于约束混合理论的静脉生长与重塑（G&R）新模型。首先，我们确定了能使静脉适应血流动力学（haemodynamics）中等扰动的本构关系与参数。随后我们固定这些关系与参数，将静脉置于从中度到重度的一系列复合载荷（压力与血流）环境中，并明确了静脉产生适应性改变与适应不良的合理机制。此外，我们还探究了载荷逐步升高对静脉适应过程的有益影响。为期3天的血流渐进式变化联合初始阶跃式压力变化，可使更少的……