Fluid Dynamic Study of a Compliant Model for an Inferior Vena Cava Filter

Open Access
Author:
Fox, Evan M
Area of Honors:
Bioengineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Keefe B Manning, Thesis Supervisor
  • Peter J Butler, Honors Advisor
  • William O Hancock, Faculty Reader
Keywords:
  • deep vein thrombosis
  • pulmonary embolism
  • inferior vena cava filter
  • particle image velocimetry
Abstract:
Deep vein thrombosis afflicts a reported 1 in 1000 persons, resulting in severe medical consequences for many as the thrombus may dislodge to form a pulmonary embolism. If undiagnosed, this can cause impaired oxygenation, heart strain, or sudden death due to occlusion of blood flow in all cases. Multiple iterations of inferior vena cava (IVC) filters were developed to prevent such emboli from reaching the lungs. Yet, complications remain due to induced thrombus formation, intimal hyperplasia, perforation through the IVC, and filter fracture. The goal of this study was to examine flow phenomena around a Bard G2 Express IVC filter in an effort to identify areas likely to cause complications. A mock venous circulatory flow loop was constructed which features a compliant model for the vena cava. Clinically observed flow rates were matched for both resting (2.7 lpm) and exercise (5.5 lpm) conditions. The outlet pressure of the IVC was maintained at 11 mmHg. Particle image velocimetry (PIV) was used to measure the flow with high spatial resolution for the unoccluded, filtered, and occluded IVC. Multiple planes were taken to assess the three-dimensionality in the flow. Data concerning the flow impact following implantation of the filter and clot was recorded. Standard deviations were high for this study (median 28.8% of the velocity magnitude in the exercising midline right iliac). For the first time, three-dimensional characteristics were characterized in a PIV study concerning an IVC filter; both sets of conditions demonstrated asymmetric flow and jets altered direction between planes (especially in the resting, unoccluded case). Regions of recirculation were characteristic of all flows, especially under resting conditions. Wakes were present in both the filtered and occluded experiments, which could promote thrombus growth downstream of the filter or clot. Yet, the asymmetries may aid in the development of larger shear forces on the thrombus, facilitating thrombolysis.