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Increased IMPEDE-FX Embolization Plug Packing Volume Reduces Sac Wall Strain In Idealized 3d-printed Aortic Models
Baqir J. Kedwai, BHSc, Joshua T. Geiger, MD, Daniel J. Lehane, BA, Sam Najjar, Michael C. Stoner, MD, Doran S. Mix, MD.
University of Rochester Medical Center, Rochester, NY, USA.
OBJECTIVES: The IMPEDE-FX Embolization Plug (Shape Memory Medical, Santa Clara, CA, USA) is a polyurethane-based, self-expanding polymer with demonstrated hemostatic properties. The objective of this study was to evaluate the effect of IMPEDE-FX plugs on wall strain using ultrasound elastography (USE) in a 3D-printed aortic aneurysm model.
METHODS: An idealized abdominal aortic aneurysm model was designed as an axisymmetric cylinder with a 5 cm sphere in the center. A 3.4 cm diameter GORE TAG Conformable Thoracic Stent Graft was deployed in the model. The model was connected to a flow circuit and subjected to pulsatile water flow. In stepwise fashion, embolization plugs were deployed to packing volumes of 100% (16 plugs), 150% (24) and 250% (40) of the sac volume. Packing volumes were calculated based on the volume of a fully expanded plug in free space. Axial images of the aortic model were captured at five, ten and fifteen minutes for each condition with USE. The maximum mean principal strain (ɛ
p) of the model wall was measured at each time interval using a finite element mesh technique that evaluated frame-to-frame displacement of the images over one cardiac cycle. The principal strains were divided by the circuit’s pulse pressure to produce a pressure-normalized wall strain measurement (ɛ
p/PP).
RESULTS: The hemodynamic circuit was operated at a flow rate of 3.33 L/min, a stroke volume of 47.7 mL per pulse, and pulse pressures ranging from 7.7 to 8.4 kPa. Across all conditions, the ɛ
p/PP decreased by an average of 9.5% between the ten and fifteen-minute intervals as plugs reached full expansion. Additionally, higher packing volumes trended towards decreased wall strain. The 100% packing condition had a 41% increase in ɛ
p/PP from baseline at fifteen minutes. The 250% condition had a 1.3% decrease in ɛ
p/PP at the same interval. The percent change in ɛ
p/PP at each packing volume is illustrated in Figure 1.
CONCLUSIONS: These data suggest that higher packing volumes of the IMPEDE-FX Embolization Plug reduce maximum mean principal wall strain in an idealized abdominal aortic aneurysm model. Further studies should explore the effects of a wider range of packing volumes on wall strain.
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