Open access Review Stroke Vasc Neurol: first published as 10.1136/svn-2020-000347 on 25 March 2020. Downloaded from Advances in endovascular aneurysm management: flow modulation techniques with braided mesh devices Jessica K Campos ,1 Barry Cheaney II ,2 Brian V Lien,1 David A Zarrin,3 Chau D Vo,4 Geoffrey P Colby,5 Li- Mei Lin ,6 Alexander L Coon 6 To cite: Campos JK, ABSTRACT FLOW DIVERSION (FD) EMBOLISatiON Cheaney II B, Lien BV, et al. Flow diverters and flow disruption technology, alongside The concept of FD stems from the lessons Advances in endovascular nuanced endovascular techniques, have ushered in a aneurysm management: flow learnt in the development of stent-assisted new era of treating cerebral aneurysms. Here, we provide modulation techniques with coiling. The association of denser coil packing braided mesh devices. Stroke an overview of the latest flow modulation devices and with better angiographical and clinical & Vascular Neurology 2020;5: highlight their clinical applications and outcomes. outcomes is explained by haemodynamic flow e000347. doi:10.1136/svn- modulation as endovascular stents directly 2020-000347 INTRODUCTION disrupt blood flow into the aneurysmal sac Received 9 February 2020 The arrival of the Guglielmi detachable coil from the parent artery and accelerate intra- 10 11 Accepted 28 February 2020 system has given rise to the field of neuroend- aneurysmal thrombosis. FD with braided Published Online First ovascular intervention. Multiple randomised mesh device is based on two principles:1) the 24 March 2020 controlled trials have demonstrated the placement of a high-mesh density device in the efficacy and safety of coil embolisation1 2; parent vessel alters blood flow away from the however, post- treatment aneurysm recana- aneurysm lumen, and 2)the device construct lisation remained a significant challenge at provides a scaffold on which endothelium can that time, with rates in some reports up to grow in a process termed 'neoendothelialisa- 50%.3 4 tion', thereby isolating the aneurysm from Since then, many technological advance- the parent circulation, allowing for gradual ments have been developed to address intra- aneurysmal thrombosis, and eventually the shortcomings of endovascular coiling, resulting in a curative outcome with complete radiographical occlusion of the aneurysm.12 including significant changes in coil prop- http://svn.bmj.com/ © Author(s) (or their 3 4 The advantage of FD techniques lies in the erties. Adjunctive devices such as intracra- employer(s)) 2020. Re- use ability to treat the weakened arterial wall. permitted under CC BY- NC. No nial stents and balloons were developed to Neoendothelialisation leads to more resil- commercial re- use. See rights augment coil embolisation. Balloon- assisted and permissions. Published by ient aneurysm occlusion, compared with coil embolisation reduces the risk of coil BMJ. the high rate of recurrence associated with 1 prolapse into the parent artery and can provide Department of Neurosurgery, coil embolisation. Additionally, the endolu- University of California Irvine immediate proximal control with balloon minal approach in deploying flow diverters on September 28, 2021 by guest. Protected copyright. School of Medicine, Orange, inflation in case of intraprocedural aneurysm (FD) does not require direct access to the California, USA rupture. Similarly, stent- assisted coiling allows 2 aneurysmal sac, thereby removing the risk of Oregon Health and Science for increased coil packing density, critical for University School of Medicine, intraprocedural aneurysm rupture inherent Portland, Oregon, USA the treatment of wide-necked, large and giant with coiling. 3 Neurosurgery, Johns Hopkins aneurysms, thereby significantly improving In 2007, the arrival of the Pipeline Embo- University, Baltimore, Maryland, 5–7 the obliteration rate. lization Device (PED; Medtronic Neurovas- USA Despite these technological developments, 4Johns Hopkins University cular, Irvine, California, USA) marked the School of Medicine, Baltimore, aneurysms with unfavourable parameters first clinical application of FD in treating Maryland, USA such as large diameters (>10 mm), wide necks, cerebral aneurysms.13 Many FDs have since 5 UCLA Neurosurgery, Ronald small dome- to- neck ratios (<2) and fusiform continued to expand the neuroendovascular Reagan UCLA Medical Center, morphologies remain significant dilemmas, Los Angeles, California, USA field, including Surpass (Stryker Neurovas- 6Carondelet Neurological with poor outcomes including aneurysm cular, Fremont, California, USA), Silk (Balt Institute, St. Joseph's Hospital, recurrence as well as treatment-related Extrusion, Montmorency, France), Flow- 8 9 Carondelet Health Network, morbidity and mortality. Flow modulation Redirection Endoluminal Device (FRED; Tucson, Arizona, United States techniques with braided mesh devices have MicroVention, Tustin, California, USA), been designed to tackle these challenges Correspondence to p64 Flow Modulation Device (Phenox, Dr Alexander L Coon; and ushered in a new era of endovascular Bochum, Germany), Derivo Embolization dralexandercoon@ gmail. com neurointervention. Device (Acandis, Pforzheim, Germany) and Campos JK, et al. Stroke & Vascular Neurology 2020;5:e000347. doi:10.1136/svn-2020-000347 1 Open access Stroke Vasc Neurol: first published as 10.1136/svn-2020-000347 on 25 March 2020. Downloaded from Tubridge (MicroPort Medial, Shanghai, China). In the vessel.22 The SCENT trial included the highest percentage USA, the Food and Drug Administration (FDA) approved of PCoA aneurysms compared with pre-existing FD clin- PED in 2011, Surpass in 2018, and FRED in 2019, all for ical trials with resulting comparative efficacy, as well as the treatment of large or giant, wide- neck intracranial morbidity and mortality rates.21 aneurysms along the internal carotid artery (ICA) (FDA. gov). Comparatively, most FDs are commercially avail- Silk able outside the USA. Table 1 summarises the technical The Silk and Silk+ are the first-generation and second- specifications for the more commonly used FDs to date. generation FDs from Balt (Balt Extrusion, Montmor- Table 2 summarises major studies for the different flow ency, France). Lubicz and colleagues reported their diverter devices. experience with Silk in treating 29 patients with 34 aneurysms. Angiographical follow-up demonstrated complete occlusion in 20 aneurysms (69%). Morbidity FD indications 23 On-label large and giant ICA aneurysms and mortality rates were 15% and 4%, respectively. Several other groups have demonstrated success with Pipeline Embolization Device (PED) Silk, reporting complete occlusion rates of 68% at 6 The efficacy, safety and cost- effectiveness of the initial PED months to 93.9% at 1 year. Morbidity and mortality rates experience was demonstrated in the literature primarily are comparable to other FDs at 4%–10% and 2%–3%, for on- label usage in large and giant ICA aneurysms. respectively.24 25 Initial experiences from Buenos Aires and Budapest Due to technical complications related to the lower case series showed complete angiographical occlusion radial force, the second-generation Silk+ was developed. rates of 90%–93% at 6 months’ follow- up.14 15 The Pipe- Lubicz et al conducted a retrospective study of 58 patients line Embolization Device for the Intracranial Treatment with 70 aneurysms and found a 73% complete occlusion of Aneurysm (PITA)trial and the Pipeline Embolization rate with no recanalisation or retreatment necessary. Device for Uncoilable or Failed Aneurysms (PUFS) trial Permanent neurological morbidity was 5.5% (all within followed and simarly showed acceptable occlusion rates the subgroup of patients treated with the first- generation (81.8%–93.3% at 6 months) with low complication rates Silk) with no procedure- related mortality.26 reported (5.6%–6.5%).13 16 The literature continues to grow as newer generations are released. The pipeline flex Flow-Redirection Endoluminal Device (FRED) with shield technology, with its new phosphorylcholine Safety and Efficacy Analysis of FRED Embolic Device in stent- surface modification aimed at minimising thrombo- Aneurysm Treatment(SAFE) is a single-arm, prospective, genicity, was used in two studies, and adequate occlusion multicentre, observational study conducted by Pierot et rates were achieved with similar morbidity and mortality 17 18 al. A total of 103 aneurysms were treated, and at 1 year to previous PED reports. of follow- up, complete occlusion was observed in 73.3% with no evidence of recurrence. Morbidity and mortality Surpass http://svn.bmj.com/ were 2.9% and 1.9%, respectively.27 Several additional Initial experience from The Netherlands showed a 94% case series demonstrate the effectiveness of FRED, each complete neck coverage and aneurysm occlusion with no showing excellent radiographical outcomes and low major periprocedural morbidity or mortality at 6 month morbidity and mortality.28 29 of follow- up.19 A prospective, multicenter study of 165 patients with 190 intracranial aneurysms treated with Derivo Surpass was conducted by Wakhloo et al. Follow-up angi- Brazilian Registry of Aneurysms Assigned to Intervention on September 28, 2021 by guest. Protected copyright. ography available in 158 (86.8%) intracranial aneurysms with the Derivo Embolization Device (BRAIDED) is a showed complete occlusion in 75% of cases. Permanent multicentre, prospective, single- arm trial with 183 aneu- neurological morbidity and mortality were 6.0% and rysms treated.