NITINOL EMBOLIC PROTECTION FILTERS: DESIGN INVESTIGATION BY COMPUTATIONAL TOOLS

Clinical procedures are getting less and less invasive and the medical market is a continuing success story for the application of shape memory alloy products. Nitinol superelastic effect is exploited in many applications such as peripheral stenting procedures to treat stenotic vessels. However, the effectiveness to treat carotid artery stenoses (Carotid Artery Stenting, CAS) compared with its surgical counterpart, carotid endarterectomy (CEA) is still a matter of concern. Neurological deficits may develop in patients undergoing CAS due to distal embolization. Design, development, and usage of embolic protection devices (EPDs), such as embolic protection filters, appear to have a significant impact on the success of CAS. Unfortunately, some drawbacks, such as filtering failure, inability to cross tortuous high-grade stenoses, malpositioning and vessel injury are still present and require design improvement. Consequently, there is a significant need for design tools as well as for careful engineering investigations and design analyses of such SMA devices. Computer models have shown the capability to provide useful information to understand the mechanics of cardiovascular devices, e.g. stents, and to improve device design. The present study aims to investigate the embolic protection filter design by computational tools.
We first developed a parametrical Computer-Aided Design (CAD) model of an embolic filter based on micro-CT scans of the Angioguard (Cordis, J&J) EPD by means of the open source pyFormex software (http://pyformex.berlios.de). Second, we used the Finite Element Method (Abaqus) to simulate the deployment of the nitinol filter as it exits the delivery catheter. Comparison of the simulations with micro-CT images of the real device exiting the catheter showed excellent correspondence. 
We conclude that the proposed methodology offers a useful tool to evaluate and to compare current or new designs of EPD's. Further investigation will include the vessel wall apposition and the interaction of the filter with the blood flow.