In-vitro assessment of endovascular aortic repair grafts influence on limb occlusion and ischemia using particle image velocimetry
Sina G. Yazdi
Dept of Mechanical Engineering, University of Canterbury
Time & Place
Tue, 18 Jun 2019 13:45:00 NZST in E14 (Lecture Theatre), Engineering CORE
Aortic dissection, aneurysms, and occlusive diseases are common vascular diseases which affect normal hemodynamics in the aorta. Endovascular aortic repair (EVAR) using grafts is a common treatment to restore normal hemodynamics. During EVAR surgery, a graft is inserted from femoral and delivered via a sheath to the lesion area. However, various complications such as endoleaking, dislocation, or limb occlusion have been reported for EVAR. Various experimental and numerical studies have been conducted to explore the effect of grafts on hemodynamics after EVAR. However, the risk of limb occlusion and stenosis due to graft extension to iliac branches has not been addressed in experimental or numerical studies.
In this study, it was hypothesized that the compliance mismatch between the graft and parent artery causes hemodynamic disturbances at the distal edge of the graft. Therefore, the potential for the graft to cause limb occlusion was assessed. A compliant transparent silicone phantom was fabricated using a lost-core casting method. A circulatory mimicking loop was developed to run the fluid and generate a physiological flow waveform. Planar Particle Image Velocimetry was utilized to capture fluid dynamics in the replica. The result showed a low velocity region at the graft trailing edge wall. The low velocity boundary layer thickness decreased downstream of the graft. A flow recirculation was initiated and increased in size during the mid-acceleration at the low velocity region. Shear stresses fluctuated at the trailing edge of the graft which is a risk factor for intimal thickening followed by graft or limb occlusion. It was concluded that this hemodynamic behaviour was due to the graft and parent artery compliance mismatch.