A comparative analysis of bench-top performance assessment of distal protection filters in transient flow conditions.

Siewiorek, Gail M; Wholey, Mark H; Finol, Ender A

PURPOSE To compare the performance in vitro of 6 distal protection filters (DPFs) on the basis of filtration ability and effects on pressure gradient and vascular impedance in a flow model of the internal carotid artery (ICA). METHODS Six DPFs (Accunet, Angioguard, FilterWire, Gore Embolic Filter, NAV6, and SpiderFX) were evaluated in a physiologically realistic flow loop. A blood analog was heated to body temperature and circulated by a pulsatile pump outputting a time-varying flow rate representative of the ICA. The ICA flow model was a highly curved tube representing a challenging site for filter deployment. The DPFs were deployed at the apex of the curved segment, and 2 sizes of microspheres (143 and 200 µm) were injected to simulate embolization. The capture efficiency, pressure gradient, normalized pressure gradient, and vascular impedance were calculated. RESULTS The Gore filter had high capture efficiency (143 µm: 99.97%; 200 µm: 100.00%) with relatively small increases in pressure gradient (143 µm: +27%; 200 µm: +20%) and vascular impedance (143 µm: +23.4%; 200 µm: +6.1%) after particles were injected. Spider had the lowest capture efficiency (143 µm: 1.50%; 200 µm: 19.34%, p<0.0005), while NAV6 (143 µm: +916%, p<0.0005) and Accunet (200 µm: +179%, p<0.0005) yielded the largest pressure gradient increases. CONCLUSION A bench-top flow apparatus exhibiting physiologically realistic conditions was developed by combining pulsatile flow and a body temperature blood analog. Using microspheres larger than the pore size of most of the DPFs, the device-wall apposition has an important effect on the overall filter performance and the global fluid dynamics in the flow model.