Original ArticleHemodynamic Effect of Flow Diverter and Coils in Treatment of Large and Giant Intracranial Aneurysms
Introduction
Large and giant intracranial aneurysms (≥10 mm) have worse outcomes compared with small aneurysms when using conventional endovascular treatment. Flow diverter (FD) devices are increasingly used for treating these aneurysms.1, 2, 3, 4 Rather than mechanically excluding the aneurysm from the circulation, the FD is designed to create a low-flow hemodynamic state within the aneurysm that would favor its thrombosis and ultimate occlusion and remodeling. However, under the condition of inflow stream into the aneurysm, and when patients are under dual-antiplatelet therapy, use of the FD barely provides immediate thrombosis and occlusion of the aneurysm. During this time, some clinical complications, such as delayed aneurysm rupture and flow persistency, have been reported.1, 2, 3, 4, 5, 6, 7, 8 To avoid these complications, our medical center usually places a few coils in addition to the Tubridge FD in an attempt to further protect the dome and dampen the inflow effect on the aneurysmal wall.
The Tubridge is a new type of FD device developed by MicroPort Medical Company (Shanghai, China). Animal experiments and preliminarily clinical experience have shown that the Tubridge FD is a safe and effective device for treatment of large and giant internal carotid artery (ICA) aneurysms.4, 9, 10 Understanding the hemodynamic effect within an aneurysmal sac after the Tubridge FD deployment is essential. Computational fluid dynamics (CFD) is an efficient method to understand how the FD affects aneurysmal hemodynamics for successful treatment, as well as the inevitable complications.11, 12, 13
This study evaluated the independent hemodynamic effect of the Tubridge FD, as well as the combined hemodynamic effect of the Tubridge FD and loose packing coils in treatment of large and giant ICA aneurysms, using CFD simulations, the virtual Tubridge FD deployment method, and porous medium modeling.
Section snippets
Patients
Between June 2013 and May 2015, 10 patients were treated by a single Tubridge FD and loose packing coils (bare) in our department. All of these patients were enrolled in a multicenter, randomized, and controlled clinical trial that aimed to assess the clinical safety and effectiveness of the Tubridge FD in treatment of unruptured large/giant ICA aneurysms.9 The Institutional Review Board of our hospital approved this study, and written informed consent was obtained from all of the patients.
Angiographic Results
Six aneurysms were treated by the Tubridge FD and loose packing coils. Immediate postoperative angiographic results showed residual aneurysm in all of the aneurysms. During follow-up, 4 aneurysms (cases 1, 2, 4, and 6) were completely occluded, 1 aneurysm (case 5) showed residual neck, and 1 aneurysm (case 3) still showed residual aneurysm (see Table 1, Figure 1). None of the patients had any procedure-related morbidity or mortality.
Hemodynamic Results
Before treatment, aneurysmal flow patterns were similar in all
FD Treatment for Large and Giant Aneurysms
Large and giant aneurysms (≥10 mm) present a challenge for classic endovascular treatment. The FD device appears to be an effective therapeutic option, but large and giant size still represents added risks.1, 2, 3 A large multicenter study of pipeline FD therapy retrospectively studied 793 patients with 906 aneurysms in 17 centers and found that the complication rates with Pipeline treatment are comparable with those of other endovascular treatment options such as stent-assisted coiling.3 But
Limitations
A limitation of the present study is the small sample size. A larger series is required to assess the clinical safety and effectiveness of the Tubridge FD. Our follow-up time range is 5–12 months. Continued follow-up of the participants in this study will be helpful to further verify our results. To our knowledge, well-defined data about the sufficient coil packing degree are not available, and the exact efficacy of adjunctive coiling in different FDs treatment of large and giant aneurysms
Conclusions
On the basis of the CFD method, adjunctive coiling with the Tubridge FD placement may significantly reduce intra-aneurysmal flow velocity and WSS, promoting thrombosis formation and occlusion of aneurysms. CFD simulations can help operators understand the variation in intra-aneurysmal hemodynamics and choose a safer treatment for patients. Further studies with refined CFD modeling and in vitro experiments are needed to confirm these results.
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This work was supported by the National Natural Science Foundation of China (81301003, 81171079, 81471167, 81371315, and 81220108007); Special Research Project for Capital Health Development (2014-1-1071); and Youth Fund of Beijing Neurosurgical Institute (2014-001).
LJ and JZ contributed equally to the preparation of the manuscript and data collection. JL performed statistical analysis. YZ and XY conceived and designed the research. SW designed the research and did the CFD simulation. NP, HM, and JZ designed in-house software and developed virtual stent-deployment technique.
Conflict of interest statement: The authors declare that they have no conflict of interest.