Intrasaccular Flow Disruption devices – Way to the future

 Endovascular treatment for intracranial aneurysms is evolving at a rapid pace where new concepts keep evolving as we keep gaining both knowledge from the new scientific achievements and experience from the clinical data. One such major milestone is the evolution of Intrasaccular Flow Disruption (IFD) devices which are initially developed as a solution to the much complex Wide Neck Bifurcation Aneurysms (WNBA)[1]. But as we keep gaining experience, the scope of usage for IFDs are expanding in other scenarios making them a ray of hope for the future of endovascular treatment of intracranial aneurysms. Different devices were developed in this category like WEB (Microvention)[2], Artisse/LUNA (Medtronic)[3] and SEAL (Galaxy)[4] which are globular woven mesh devices designed to fill the aneurysm sac either partially or completely, Contour (Cerus)[5] which is designed to stay at the neck of the aneurysm and to divert blood flow away from aneurysm sac, Trenza (Stryker) and Medina (Medtronic) which are more like multifilament coils that can be deployed inside the aneurysm sac. The complexity of IFD design, different concepts of their development and the diversity of the technique required for their optimal deployment warrants extensive awareness and training in the operators. 

 Though the published clinical data suggest a lower complete occlusion rates with IFDs compared to Flow Diverters and Stent assisted coiling[1], computational flow dynamics (CFD) studies showed excellent flow disruption[6]. As the technique of IFD deployment plays a very significant role in the outcome and as more and more neurointerventionists gain experience in IFD deployment, the future of these devices looks promising. This video tries to analyze the technical aspects of IFD deployment to maximize the good outcome both in terms of complete occlusion of intracranial aneurysms and in terms of safety of the procedure. 

 One major advantage of IFDs is that they appear to be a good endovascular alternative when there are multiple intracranial aneurysms which are otherwise managed preferably with surgical clipping. Alternative techniques like simple coiling or assisted coiling like balloon or stent assisted coiling of multiple aneurysms may consume a significant amount of time, contrast dose and radiation dose. Multiple Flow diverters for multiple aneurysms increases the amount of metal in the cerebral vasculature necessitating more platelet suppression and higher risk of stent thrombosis. 

• Technical Key Points to remember for IFD deployment: 

1. Determining the size of the device is one of the most important factors that can determine the success of IFDs. Marginal oversizing may be necessary to achieve a tight apposition of the device to the inner wall of the aneurysm sac for effective flow disruption. This is especially important in the aneurysms whose cross section is far from circular shape, where oversizing ensures good apposition of the device to the whole circumference of the inner surface of the aneurysm sac. 

2. Recanalization of the aneurysm is more likely to happen with undersized IFDs. 

3. The angle of entry of microcatheter into the aneurysm sac is also a crucial factor that determines the outcome. Preshaped distal tip of the deployment microcatheter may improve the stability of the microcatheter tip inside the aneurysm sac while deploying IFDs but may compromise maneuverability. 

4. One should always consider the kickback of the microcatheter that can happen after disconnecting the push wire from the device. 

5. In scenarios where an important branch or perforator takes origin from the neck of the aneurysm sac, a little tilt or oblique placement of the IFD in the aneurysm sac should be considered. This maneuver is technically challenging especially as this is mostly dependent on the angle of entry of microcatheter tip into the sac which in turn is mostly dependent on the stability of microcatheter.

Finally, Dr Adnan Siddiqui very wisely suggested the philosophical difference between treating the disease and treating a manifestation of the disease in this video. He suggests that the aneurysm is a disease of the vessel wall and the flow dynamics inside, and the aneurysm sac as such is a manifestation. IFDs are designed to treat the sac and the flow dynamics which makes them a very reliable modality of treatment for intracranial aneurysms. But the technical complexity associated with their deployment makes them ‘not a first choice’ when it comes to aneurysm treatment. As the technology keeps advancing and the materials get more and more sophisticated, IFDs may evolve as the treatment of choice for a wide range of intracranial aneurysms.

References 

1. Chen CJ, Dabhi N, Snyder MH, Ironside N, Abecassis IJ, Kellogg RT, Park MS, Ding D. Intrasaccular flow disruption for brain aneurysms: a systematic review of long-term outcomes. Journal of Neurosurgery. 2021 Dec 24;137(2):360-72. 

2. Arthur AS, Molyneux A, Coon AL, Saatci I, Szikora I, Baltacioglu F, Sultan A, Hoit D, Almandoz JE, Elijovich L, Cekirge S. The safety and effectiveness of the Woven EndoBridge (WEB) system for the treatment of wide-necked bifurcation aneurysms: final 12-month results of the pivotal WEB Intrasaccular Therapy (WEB-IT) Study. Journal of neurointerventional surgery. 2019 Sep 1;11(9):924-30. 

3. Dmytriw AA, Salem MM, Yang VX, Krings T, Pereira VM, Moore JM, Thomas AJ. Endosaccular flow disruption: a new frontier in endovascular aneurysm management. Neurosurgery. 2020 Feb;86(2):170. 

4. Kraitem A, Gounis M, Vardar Z, King R, Langan E, Wolfe T, Badruddin A, Periera E, Follmer B, Rosqueta A, Zaidat O. O-028 the intrasaccular seal© device: improved flexibility and healing. Journal of NeuroInterventional Surgery. 2020 Aug 1;12(Suppl 1):A20-. 

5. Kraitem A, Gounis M, Vardar Z, King R, Langan E, Wolfe T, Badruddin A, Periera E, Follmer B, Rosqueta A, Zaidat O. O-028 the intrasaccular seal© device: improved flexibility and healing. Journal of NeuroInterventional Surgery. 2020 Aug 1;12(Suppl 1):A20-. 

6. Liebig T, Killer-Oberpfalzer M, Gal G, Schramm P, Berlis A, Dorn F, Jansen O, Fiehler J, Wodarg F. The safety and effectiveness of the Contour Neurovascular System (Contour) for the treatment of bifurcation aneurysms: the CERUS study. Neurosurgery. 2022 Mar 1;90(3):270-7. 

7. Mut F, Chung BJ, Chudyk J, Lylyk P, Kadirvel R, Kallmes DF, Cebral JR. Image-based modeling of blood flow in cerebral aneurysms treat