Predicting Iliac Artery Deformation in Response to Guidewire Insertion Using Computational Simulations

Abstract

Background: Abdominal aortic aneurysm (AAA) rupture has an associated mortality of 90%. AAAs are repaired when they meet size criteria, become symptomatic, or rupture. Use of aortic diameter as the primary criterion in the decision to intervene fails to take into consideration that AAAs rupture at sizes below operative thresholds or reach extreme size without rupture. We have previously shown that AAAs rupture at sites of low wall shear stress (WSS) where flow recirculation and intraluminal thrombus (ILT) tend to be more abundant. This study examined the fate of ILT deposition in AAA growth. We hypothesized that AAA expansion would be associated with increasing ILT deposition in sites of flow recirculation.Methods: A total of six patients with serial images of AAA growth over three time points were studied. Aortic measurements and sites of ILT deposition were recorded. Three-dimensional AAA geometry was generated from computed tomography angiography images. Predicted aortic blood flow velocity, localized pressure variation, and WSS profiles were correlated with AAA growth and ILT deposition. This study was carried out with biomedical ethics approval.Results: AAA growth was associated with increasing ILT deposition in most cases. The site of maximal ILT deposition strongly correlated with regions of flow recirculation and low WSS but did not correlate with the region of maximal aortic expansion. Interestingly, in some cases, the recirculation zone changed location with AAA growth, and this was associated with similar change in location of ILT deposition.Conclusions: This study has shown that ILT increases with increasing AAA size in most aneurysms and that deposition of ILT occurs at sites with low WSS and flow recirculation. An understanding of the alterations in WSS in pulsatile flow and its effect on vascular endothelium will lead to a better understanding of AAA development and growth and may ultimately lead to better prediction of AAA rupture potential.

Prediction of advanced endovascular stent graft rotation and its associated morbidity and mortality

“…insertion of the delivery system by partially straightening the iliac artery. 18 However, as the burden of atherosclerotic disease increases, the iliac artery becomes less compliant. 19,20 As a result, the artery retains higher levels of torsion that would normally be negated by the extrastiff guidewire.…”

Analysis of Iliac Artery Geometric Properties in Fenestrated Aortic Stent Graft Rotation

“…It has been previously shown that a stiff guidewire alters iliac artery anatomy and could, therefore, modify its geometric properties. [34][35][36] How much the guidewire deforms the iliac artery depends on the local mechanical properties of the vessel wall. The guidewire tends to straighten out the iliac artery, which would serve to decrease the net torsion in the vessel from what was measured based on preoperative CT imaging; however, it is known that regions of iliac artery calcification increase the local vessel wall stiffness, 37,38 which would reduce the impact of the guidewire on vessel deformation.…”