Flow Diverter Effect on Cerebral Aneurysm Hemodynamics: an in Vitro Comparison of Telescoping Stents and the Pipeline

Introduction: Flow diverting devices and stents can be used to treat cerebral aneurysms too difficult to treat with coiling or craniotomy and clipping. However, the hemodynamic effects of these devices have not been studied in depth. The objective of this study was to quantify and understand the fluid dynamic changes that occur within bifurcating aneurysms when treated with different devices and configurations. Methods: Two physical models of bifurcating cerebral aneurysms were constructed: an idealized model and a patient-specific model. The models were treated with four device configurations: a single low-porosity Pipeline embolization device (PED) and one, two, and three high-porosity Enterprise stents deployed in a telescoping fashion. Particle image velocimetry was used to measure the fluid dynamics within the aneurysms; pressure was measured within the patient-specific model. Results: The PED resulted in the greatest reductions in fluid dynamic activity within the aneurysm for both models. However, a configuration of three telescoping stents reduced the fluid dynamic activity within the aneurysm similarly to the PED treatment. Pressure within the patient-specific aneurysm did not show significant changes among the treatment configurations; however, the pressure difference across the untreated vessel side of the model was greatest with the PED. Conclusion: Treatment with stents and a flow diverter led to reductions in aneurysmal fluid dynamic activity for both idealized and patient-specific models. While the PED resulted in the greatest flow reductions, telescoping high-porosity stents performed similarly and may represent a viable treatment alternative in situations where the use of a PED is not an option. © 2013 Springer-Verlag Berlin Heidelberg

An in Vitro Study of Pulsatile Fluid Dynamics in Intracranial Aneurysm Models Treated With Embolic Coils and Flow Diverters

Although coil embolization is one of the most effective treatments for intracranial aneurysms (ICAs), the procedure is often unsuccessful. For example, an ICA may persist after coil embolization if deployed coils fail to block the flow of blood into the aneurysm. Unfortunately, the specific flow changes that are effected by embolic coiling (and other endovascular therapies) are poorly understood, which creates a barrier to the design and execution of optimal treatments in the clinic. We present an in vitro pulsatile flow study of treated basilar tip aneurysm models that elucidates relationships between controllable treatment parameters and clinically important post-treatment fluid dynamics. We also compare fluid dynamic performance across embolic coils and more recently proposed devices (e.g., the Pipeline Embolization Device) that focus on treating ICAs by diverting rather than blocking blood flow. In agreement with previous steady flow studies, coil embolization-reduced velocity magnitude at the aneurysmal neck by greater percentages for a narrow-neck aneurysm, and reduced flow into aneurysms by greater percentages at lower parent vessel flow rates. However, flow diversion reduced flow into a wide-neck aneurysm more so than coil embolization, regardless of flow conditions. Finally, results also showed that for the endovascular devices we examined, treatment effects were generally less dramatic under physiologic pulsatile flow conditions as compared to steady flow conditions. The fluid dynamic performance data presented in this study represent the first direct in vitro comparison of coils and flow diverters in aneurysm models, and provide a novel, quantitative basis to aid in designing endovascular treatments toward specific fluid dynamic outcomes. © 2012 IEEE