Introduction Flow diversion has successfully treated aneurysm patients for more than a decade. Multiple devices with design variations in composition and braid structure have been released over this time with the primary goal of intraneurysmal flow reduction. Computational fluid dynamics (CFD) studies have been the most commonly used method to evaluate the effect of different pore structures on intraneurysmal flow. The goal of this study was to use CFD analysis to compare the flow diversion behavior of the second-generation release of the Surpass flow diverter (Surpass Evolve, Stryker Neurovascular) with the latest generation Pipeline device (Pipeline Flex Embolization Device with Shield, Medtronic Neurovascular).
Methods Evolve and Pipeline flow diverters were deployed in silicone replicas of two patient-specific aneurysms (figure 1). The ‘treated’ replicas were scanned at a voxel resolution of 10.3 microns with a micro-CT scanner. Image slices encompassing the aneurysm neck were segmented. The centerline of each wire in the aneurysm neck region was manually traced and used to design the flow diverter covering the neck. The devices were manually registered and embedded in the aneurysm neck wall, i.e., the effect of wall apposition was not considered here. CFD was conducted in Fluent (ANSYS, Canonsburg, PA) by generating a volumetric mesh comprised of 2–4.5 Million polyhedral cells. An instantaneous, pulsatile, axisymmetric velocity profile was imposed at the cervical carotid entrance and pressures at the middle cerebral, anterior cerebral, and posterior communicating outlets were set to atmospheric. The kinetic energy of flow (velocity-squared) was averaged over the aneurysm volume at about 200 time-points over the cardiac cycle and used to compare the relative flow diversion efficacy of the two devices.
Results The figure 1 shows the streamlines near systole color-coded by velocity for all 6 cases. A progressive qualitative reduction (from red to blue color) can be seen in the inflow ‘jet’ as well as intraneurysmal velocities from the Control (no device) to Pipeline to Evolve cases. The plots quantifying the kinetic energy with each device clearly show that the intraneurysmal flow activity with the Evolve device was less than with the Pipeline device.
Conclusion The Evolve device produced greater reduction in intraneurysmal flow as compared to the Pipeline device in this computational study. In vivo studies are required to evaluate the endothelialization and biological efficacy of the devices.
Disclosures C. Sadasivan: 1; C; Stryker Neurovascular, Vascular Simulations Inc. 2; C; Vascular Simulations Inc. 4; C; Vascular Simulations Inc. 6; C; Vascular Simulations Inc. B. Kovarovic: None. R. Ghosh: None. D. Fiorella: 1; C; Stryker Neurovascular, Medtronic Neurovascular. 2; C; Stryker Neurovascular, Medtronic Neurovascular. 4; C; Vascular Simulations Inc.
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