Elsevier

World Neurosurgery

Volume 89, May 2016, Pages 199-207
World Neurosurgery

Original Article
Hemodynamic Effect of Flow Diverter and Coils in Treatment of Large and Giant Intracranial Aneurysms

https://doi.org/10.1016/j.wneu.2016.01.079Get rights and content

Background

This study aimed to investigate the hemodynamic changes induced by a flow diverter (FD) and coils in the treatment of internal carotid artery aneurysms, as well as to evaluate the effect of this treatment by using angiographic follow-up data.

Methods

Six large and giant aneurysms were treated by the Tubridge FD and loose packing coils between June 2013 and May 2015. Patient-specific models were constructed and analyzed using a computational fluid dynamics (CFD) method. The virtual FD deployment method was used to implant the Tubridge stent into a 3-dimensional digital subtraction angiographic image of the aneurysms, and the coils were simulated by a porous medium model.

Results

Tubridge FD alone can significantly reduce the intra-aneurysmal flow velocity (0.17 ± 0.05 m/s–0.11 ± 0.06 m/s, P < 0.001) and wall shear stress (WSS, 1.39 ± 0.29 Pa–0.77 ± 0.34 Pa, P = 0.001) and increase the low wall shear area (LSA, 6.38% ± 1.49%–34.60% ± 28.90%, P = 0.047). Coils, as a supplementary measure, further reduced the velocity (0.11 ± 0.06 m/s–0.08 ± 0.05 m/s, P = 0.03) and WSS (0.77 ± 0.34 Pa–0.47 ± 0.35 Pa, P = 0.04) and increased the LSA (34.60% ± 28.90%–63.33% ± 34.82%, P = 0.044). Aneurysm with sustained strong inflow after treatment (case 3, 25% reduction in velocity, 12% reduction in WSS, and 16% increment in LSA) showed partial patency, whereas others with a weaker inflow jet (mean 56% reduction in velocity, 74% reduction in WSS, and 1081% increment in LSA) showed complete occlusion at follow-up.

Conclusions

On the basis of using 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.

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.

References (25)

  • R.J. Damiano et al.

    Finite element modeling of endovascular coiling and flow diversion enables hemodynamic prediction of complex treatment strategies for intracranial aneurysm

    J Biomech

    (2015)
  • J. Fan et al.

    Morphological-hemodynamic characteristics of intracranial bifurcation mirror aneurysms

    World Neurosurg

    (2015)
  • F. Briganti et al.

    Endovascular treatment of cerebral aneurysms using flow-diverter devices: a systematic review

    Neuroradiol J

    (2015)
  • F. Alghamdi et al.

    The Silk flow-diverter stent for endovascular treatment of intracranial aneurysms

    Expert Rev Med Devices

    (2015)
  • D.F. Kallmes et al.

    International retrospective study of the pipeline embolization device: a multicenter aneurysm treatment study

    AJNR Am J Neuroradiol

    (2015)
  • Y. Zhou et al.

    A novel flow-diverting device (Tubridge) for the treatment of 28 large or giant intracranial aneurysms: a single-center experience

    AJNR Am J Neuroradiol

    (2014)
  • N. Lin et al.

    Use of coils in conjunction with the pipeline embolization device for treatment of intracranial aneurysms

    Neurosurgery

    (2015)
  • M. Chow et al.

    Delayed spontaneous rupture of a posterior inferior cerebellar artery aneurysm following treatment with flow diversion: a clinicopathologic study

    AJNR Am J Neuroradiol

    (2012)
  • B. Turowski et al.

    Early fatal hemorrhage after endovascular cerebral aneurysm treatment with a flow diverter (SILK-Stent): do we need to rethink our concepts?

    Neuroradiology

    (2011)
  • Z. Kulcsar et al.

    Intra-aneurysmal thrombosis as a possible cause of delayed aneurysm rupture after flow-diversion treatment

    AJNR Am J Neuroradiol

    (2011)
  • Y. Zhou et al.

    Parent artery reconstruction for large or giant cerebral aneurysms using a Tubridge flow diverter (PARAT): study protocol for a multicenter, randomized, controlled clinical trial

    BMC Neurol

    (2014)
  • Q. Huang et al.

    Hemodynamic changes by flow diverters in rabbit aneurysm models: a computational fluid dynamic study based on micro-computed tomography reconstruction

    Stroke

    (2013)
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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.

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