Alteration of intraaneurysmal hemodynamics by placement of a self-expandable stent

Laboratory investigation

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  • 1 Division of Interventional Neuroradiology, University of California, Los Angeles Medical Center and David Geffen School of Medicine, Los Angeles, California; and
  • 2 Department of System Design Engineering, Keio University Faculty of Science and Technology, Yokohama, Japan
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Object

Development of a flexible self-expanding stent system and stent-assisted coiling technique facilitates endovascular treatment of wide-necked brain aneurysms. The hemodynamic effect of self-expandable stent placement across the neck of a brain aneurysm has not been well documented in patient-specific aneurysm models.

Methods

Three patient-specific silicone aneurysm models based on clinical images were used in this study. Model 1 was constructed from a wide-necked internal carotid artery–ophthalmic artery aneurysm, and Models 2 and 3 were constructed from small wide-necked middle cerebral artery aneurysms. Neuroform stents were placed in the in vitro aneurysm models, and flow structures were compared before and after the stent placements. Flow velocity fields were acquired with particle imaging velocimetry.

Results

In Model 1, a clockwise, single-vortex flow pattern was observed in the aneurysm dome before stenting was performed. There were multiple vortices, and a very small fast flow stream was newly formed in the aneurysm dome after stenting. The mean intraaneurysmal flow velocity was reduced by ~ 23–40%. In Model 2, there was a clockwise vortex flow in the aneurysm dome and another small counterclockwise vortex in the tip of the aneurysm dome before stenting. The small vortex area disappeared after stenting, and the mean flow velocity in the aneurysm dome was reduced by 43–64%. In Model 3, a large, counterclockwise, single vortex was seen in the aneurysm dome before stenting. Multiple small vortices appeared in the aneurysm dome after stenting, and the mean flow velocity became slower by 22–51%.

Conclusions

The flexible self-expandable stents significantly altered flow velocity and also flow structure in these aneurysms. Overall flow alterations by the stent appeared favorable for the long-term durability of aneurysm embolization. The possibility that the placement of a low-profile self-expandable stent might induce unfavorable flow patterns such as a fast flow stream in the aneurysm dome cannot be excluded.

Abbreviations used in this paper: ICA = internal carotid artery; MCA = middle cerebral artery; OphA = ophthalmic artery; PIV = particle imaging velocimetry.

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Contributor Notes

Address correspondence to: Satoshi Tateshima, M.D., Division of Interventional Neuroradiology, Department of Radiological Sciences, Ronald Reagan University of California Los Angeles Medical Center, 757 Westwood Plaza, Suite 2129A, Los Angeles, California 90095-7437. email: stateshima@mednet.ucla.edu.
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