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Flow-diverting for the treatment of arterial

George S. Sfyroeras, MD, Ilias Dalainas, MD, Triantafyllos G. Giannakopoulos, MD, Konstantinos Antonopoulos, MD, John D. Kakisis, MD, and Christos D. Liapis, MD, Athens, Greece

Background: Anatomic factors may limit the application of grafts for the treatment of arterial aneurysms. Flow- diverting stents (FDSs) are specially designed to reduce flow velocity in the sac and promote while maintaining flow in the main and branch vessels. FDSs include the Pipeline Device (ev3, Plymouth, Minn), the SILK Arterial Reconstruction Device (Balt Extrusion, Montmorency, France), and the Cardiatis Multilayer Stent (Cardiatis, Isnes, Belgium). The first two have been mainly used for the treatment of intracranial aneurysms. The aim of this study was to review the current role of FDSs in the treatment of extracranial arterial aneurysms. Methods: A systematic electronic health database search was conducted using PubMed, Ovid, Medline, and the Cochrane Database on all accessible published articles through March 2012. An additional search for abstracts presented in international congresses for vascular was also performed. Full-text articles and abstracts were analyzed separately due to the heterogeneity of the data. Results: Results of the use of FDSs in arterial aneurysms were reported in 12 full-text articles including 35 patients (26 ,(5 ؍ renal (n ,(6 ؍ splenic (n ,(12 ؍ men, age 65.4) with 38 aneurysms. The aneurysms were located in the hepatic (n and (1 ؍ and popliteal (n ,(1 ؍ gastroduodenal (n ,(2 ؍ subclavian (n ,(3 ؍ superior mesenteric (n ,(4 ؍ celiac (n The 30-day mortality was 5.7% (2 of .(2 ؍ and infrarenal (n (1 ؍ suprarenal (n ,(1 ؍ in the descending thoracic (n 35 patients). Three stent thromboses occurred (8.3%), none of them with clinical consequences. Thirty patients with 33 aneurysms and patent FDSs were monitored for an average of 9.2 months. Thrombosis occurred in 90.6%, and volume reduction was observed in 81% of the aneurysms. No branch vessel occlusion occurred. Twelve abstracts were identified, including 133 patients (mean age, 64.7 years). They included 62 peripheral, 28 visceral, and 43 abdominal and thoracoabdominal aneurysms. The Cardiatis Multilayer Stent was used in all cases. Thrombosis was achieved in all but two peripheral and visceral aneurysms. Volume reduction was observed in 82.7%, and no branch vessel occlusion occurred. In aortic aneurysms, better results regarding aneurysm thrombosis, reduction of the volume, and patency of collateral branches were reported at 12 months rather than at 6 months postoperatively. No aneurysm rupture has yet been described. Conclusions: Initial clinical experience with the use of FDSs in the treatment of visceral and peripheral aneurysms yielded satisfactory results in technical success, aneurysm thrombosis and shrinkage, and in patency of branch vessels. The results in aortic aneurysms are still under investigation. No aneurysm rupture has yet been described. There is a significant incidence of FDS thrombosis. Volume reduction of the aneurysm is a clearer evidence of the clinical success after treatment with FDSs than aneurysm thrombosis. (J Vasc Surg 2012;56:839-46.)

Complex peripheral aneurysm anatomy, with major eurysms regardless of their location and could be deployed branches in the immediate vicinity or arising from the covering collateral vessels that are not occluded. aneurysm, may impede endovascular management with The principle of the FDS represents a true revolution in conventional stent grafts. Treatment options in such cases the management of arterial aneurysms. An FDS is placed in are limited to fenestrated or branched stent grafts, hybrid the parent artery with the target to reduce blood flow in the procedures, or open surgery with reimplantation of major aneurysm sac to the point of stagnation, promoting gradual branches. Flow-diverting stents (FDSs) are specially de- thrombosis and neointimal remodeling, while maintaining signed to reduce the flow velocity vortex within the aneu- outflow in the side branches and perforators. To under- rysm and improve laminar flow in the main artery and stand the mechanism by which an FDS can cause aneurysm surrounding branches. Theoretically, FDSs could treat an- thrombosis, the within the sac must be studied. For an aneurysm without collaterals, blood flow- ing into the sac generates vortices. As these flow perturba- From the Department of , Athens University , Attikon University . tions progress, they become stronger until they reach the Author conflict of interest: none. aneurysm outlet. These continuous movements induce Correspondence: George S. Sfyroeras, Vascular Surgery Department, At- stress in the arterial wall. tikon University Hospital, 1 Rimini St, Haidari, 12461 Athens, Greece (e-mail: [email protected]). When an FDS is placed in the aneurysm, stent geometry The editors and reviewers of this article have no relevant financial relation- reduces the flow velocity within the aneurysm vortex while ships to disclose per the JVS policy that requires reviewers to decline improving laminar flow in the main artery.1 Computation review of any manuscript for which they may have a conflict of interest. hemodynamics suggests that a stent with an overall porosity 0741-5214/$36.00 Copyright © 2012 by the Society for Vascular Surgery. of 50% to 70% (30%-50% metallic coverage) will signifi- http://dx.doi.org/10.1016/j.jvs.2012.04.020 cantly reduce the inflow rate into an aneurysm.2 Optimal 839 JOURNAL OF VASCULAR SURGERY 840 Sfyroeras et al September 2012

flow modulation through the layers is reached with a 65% its length has been extruded. No retrieval is possible mean porosity. Secondary to this porosity level, when an thereafter.4 aneurysm is bridged, the stent laminates the blood flow by The Cardiatis Multilayer Stent. The Cardiatis Mul- pressure drop. Using particle image velocimetry, Augs- tilayer Stent is a tubular, self-expanding stent consisting of burger et al3 demonstrated that velocity in the sac decreases multilayer braided wires made of a cobalt alloy. It is avail- by an average of 88%. Arterial branching is characterized by able in diameters from 6 to 16 mm for peripheral vessels a change in flow direction, which induces disturbances at and is delivered through a 6F to 12F sheath. Diameters for the inlet and results in turbulence. With a traditional stent aortic aneurysms range from 20 to 45 mm, and delivery is in place, the vortex persists; however, a multilayer FDS through an 18F to 20F sheath. The radiopaque delivery laminates the flow and eliminates the vortex.1 system consists of a guiding catheter. For peripheral use, the The FDSs currently available include the Pipeline Em- delivery system can accommodate a 0.018-inch guidewire, bolization Device (PED; ev3, Plymouth, Minn), the SILK and the stent can be removed or repositioned when Ͻ80% Arterial Reconstruction Device (Balt Extrusion, Montmor- of its length has been extruded. No retrieval is possible ency, France), and the Cardiatis Multilayer Stent (Cardiatis, thereafter. Access for the stent is preferentially from the Isnes, Belgium). , and it is advanced endoluminally under The PED. The PED is a self-expanding, microcath- angiographic visualization to the desired lesion site. When eter-delivered device. It is a mesh tube of woven wire, made the deployment site is reached, the top of the delivery of 25% platinum and 75% cobalt-nickel alloy, designed to system is placed a few centimeters above the target lesion provide 30% to 35% metal coverage of the inner surface of site. This is done so that the position of the stent can still be the target vessel, with a pore size of 0.02 to 0.05 mm2 at a adjusted while it is partially opened. To begin stent deploy- nominal diameter.4 The area of coverage provided by the ment, the metallic pusher is slowly pushed with the sheath PED is approximately three times more than other com- fixed under radioscopy, and the multilayer stent begins to monly used intracranial stents. Sizes for vessel diameters be released. If necessary, the positioning can be adjusted by retrieving the metallic pusher and the sheath together. The from 2.5 to 5 mm are available. The PED has been used for deployment is then continued by pulling the sheath gently the management of large, giant, wide-necked, and fusiform and progressively toward the fixed position of the metallic intracranial aneurysms by reconstructing the parent artery pusher. After full stent deployment, the pusher is pulled and restoring its natural course, with or without the use of back in its initial position so that the atraumatic tip comes in adjunctive embolic devices. The PED is attached to a front of the outer sheath. Finally, the delivery system is pusher wire, which has a platinum coil tip that extends 15 removed under radioscopy. mm beyond the distal edge of the device. The PED is The PED and SFD were originally developed for the delivered with a 3F (0.027-inch internal-diameter micro- endovascular treatment of intracranial aneurysms. By 2010, catheter) that requires a 6F guide catheter support. Once these two FDSs had been used to treat Ͼ2500 intracranial positioned across the aneurysm, the delivery wire is held while aneurysms, including wide-necked, fusiform, large, and the distal one-third to one-half of the PED is carefully un- giant unruptured intracranial aneurysms. Treatment of sheathed. Once the unsheathed segment begins to expand, these lesions is associated with a 5% to 10% permanent the distal end is released by clockwise rotation of the delivery major morbidity and mortality.4 The Cardiatis Multilayer wire. The proximal segment of the PED can then be de- Stent is mainly designed for peripheral, visceral, and aortic ployed, mainly through the application of forward pressure on aneurysms and has been approved for peripheral aneurysm 4 the delivery wire, supplemented by unsheathing. management in European countries since May 2009. The The SILK flow diverter. Another flow-modifying aim of this study is to review literature for the current role of device, the SILK flow diverter (SFD), is a flexible, self- FDSs in the treatment of extracranial arterial aneurysms. expanding device consisting of a braided mesh cylinder with flared ends, composed of 48 nickel-titanium (nitinol) METHODS ϳ ␮ alloy and platinum microfilaments of 35 m, designed to A systematic electronic health database search was con- provide 35% to 55% metal coverage of the internal diameter ducted using PubMed, Ovid, Medline, and the Cochrane 2 of the target vessel, with a pore size of 110 to 250 ␮m . Database for all accessible articles published through March Sizes for vessel diameters range from 3.5 to 4.25 mm. The 2012. The keywords were multilayer or flow diverting or insertion technique involves deploying the distal tip of a flow diversion or flow diverter and stent,ormultilayer flow delivery microcatheter to the aneurysm and then pushing modulator,orPipeline embolization device,orSILK flow the SFD to the tip of the delivery wire to which it is diverter,orCardiatis Multilayer Stent. The initial database attached. The system is then aligned with the aneurysm, search revealed 120 publications; of these, 36 were experi- and the SFD is deployed by unsheathing it from the con- mental or irrelevant, and 66 reported the results of FDS use straint of the microcatheter. This involves a combination of in intracranial aneurysms. One article was a commentary. pushing the delivery wire and retrieving the microcatheter Of the remaining 17 publications, one was a review article5 to allow the SFD to expand and to compensate for any and four were from the same author or institution and resulting foreshortening. The SFD can be retrieved into the reported the same material.6-9 Two were included in the microcatheter and removed or repositioned when Ͻ80% of analysis.7,9 Of 14 articles that we considered, 12 reported JOURNAL OF VASCULAR SURGERY Volume 56, Number 3 Sfyroeras et al 841

the use of FDSs in arterial aneurysms (Table I),1,7,9-18 one Two of the 35 patients died, for a perioperative mor- in thoracoabdominal ,19 and one in carotid blow- tality of 5.7%. One patient died of pulmonary 24 out syndrome.20 The full texts of these articles were re- hours after the procedure and another died of myocardial trieved and reviewed. Data on patient age, location of the infarction on day 4. Postoperative antiplatelet is aneurysms, number and size of the stents, antiplatelet ther- described in Table I. There were three 30-day stent occlu- apy, follow-up time, branch vessel occlusion, aneurysm sions in the 33 surviving patients (36 aneurysms; incidence thrombosis and diameter decrease, and stent occlusion of stent thrombosis, 8.3%) involving three Cardiatis Multi- during follow-up were collected and summarized (Table I). layer Stents deployed in SMA, splenic, and hepatic artery In a second step, we searched for oral presentations and aneurysms.7,10 The SMA stent thrombosed because of abstracts presented in international congresses. Oral pre- poor runoff, the splenic artery stent thrombosis was attrib- sentations of the following congresses were searched: Soci- uted to the patient’s poor compliance with dual-antiplatelet ety for Vascular Surgery Annual Meeting: 2011 (previous therapy,10 and the reason for the hepatic artery stent occlu- congresses were not available online); European Society for sion is unknown.7 In all cases, there were no clinical se- Vascular Surgery Annual Meeting: years 2009, 2010, and quelae for the patients. Thirty patients with 33 aneurysms 2011; the VEITH Symposium: years 2009, 2010, and and patent FDSs were monitored for an average of 9.2 2011; Transcatheter Cardiovascular Therapeutics: years months. Follow-up was performed with computed tomog- 2009, 2010, and 2011; International Congress: 2011 (pre- raphy (CT) in all cases. The stents do not vious congresses were not available online); and Cardiovas- affect imaging interpretation. During follow-up, all branch cular and Interventional Radiological Society of Europe: vessels originating from or near the aneurysm and covered years 2009, 2010, and 2011. All available abstracts were by the FDS remained patent. There was no FDS thrombo- collected and reviewed. Abstracts written by identical au- sis after 30 days. Aneurysm thrombosis occurred in 29 of 32 thors or institutions were studied in detail and excluded if (90.6%). Nonthrombosed aneurysms were located in the necessary to prevent duplication. We identified 17 ab- SMA, renal artery, and suprarenal aorta. Shrinkage was stracts.21-37 Three reported the results of the Italian Reg- observed in 26 of 32 aneurysms (81%) during follow-up. istry of Cardiatis Procedures supported by the Italian Soci- Three reports covered the use of FDSs to treat aortic ety of Vascular and Interventional ,21-23 and the aneurysms. These include a 16-year-old girl with a tuber- most recent was included in the analysis.23 Five abstracts culous thoracoabdominal aneurysm,17 a 48-year-old HIV- came from the French group by Henry et al.25-28 The most positive patient with suprarenal and infrarenal aortic aneu- recent abstract reporting the results of the multilayer stent rysms, without an established infectious cause,14 and an on peripheral aneurysms27 and reporting on thoracoab- 81-year-old man with multiple comorbidities.16 The Car- dominal and abdominal aortic aneurysms were consid- diatis Multilayer Stent was used in all patients. Patients were ered.28 Nine more abstracts by different groups were in- monitored for 12 to 18 months, and all covered branch cluded in the analysis (Table II).29-37 vessels remained patent. Aneurysm thrombosis was ob- A separate analysis for full-text articles and abstracts was served in three of four aneurysms and diameter reduction in conducted due to the heterogeneity of the data. all four aneurysms. The Cardiatis Multilayer Stent was also used to treat an aortic type B dissection with aneurysmal RESULTS dilatation in a 69-year-old man.19 This patient had been Full-text articles. Fourteen full-text articles were operated on 4 years earlier for a type A dissection with left identified and are included in this systematic review. Twelve kidney malperfusion. During follow-up, he presented with reported the results of the use of FDSs in the endovascular aneurysmal dilatation of the descending thoracic aorta. repair of 38 arterial aneurysms (Table I) in 35 patients (26 Three re-entry vessels were feeding the false lumen. The men, nine women) who were a mean age of 65.4 years proximal was in the left subclavian artery and the distal at (range, 16-81 years). Of these 38 aneurysms, 31 were the origin of the visceral arteries. The aorta was covered located in the visceral vessels, including the hepatic (n ϭ from the left subclavian artery to the abdominal aorta under 12), renal (n ϭ 5), splenic (n ϭ 6), celiac (n ϭ 4), superior the renal arteries. Follow-up CT imaging at 3 months mesenteric (SMA; n ϭ 3), and gastroduodenal (n ϭ 1) demonstrated false-lumen thrombosis with aortic diameter arteries. One aneurysm was located in the popliteal artery. reduction.19 The aneurysms in three patients were located in the tho- Finally, a 61-year-old woman with history of nasopha- racic or the abdominal aorta. Four aneurysms, located in ryngeal carcinoma and carotid blowout syndrome under- the subclavian arteries bilaterally and the suprarenal and went endovascular treatment using a PED; however, this infrarenal aorta, were treated in a 48-year-old HIV-positive treatment was not successful. Rebleeding occurred 2 days patient. later and a second PED was inserted. She died of a massive Most patients were at high risk for open repair, and cerebral infarction 2 months later, probably related to operations were performed under local . Techni- complicated in-stent thrombosis. cal success was achieved in all cases. The Cardiatis Multi- Published abstracts. Twelve abstracts presented at layer Stent was used in all but two patients. The SFD was international congresses were included in the analysis (Ta- used in an SMA aneurysm12 and the PED in a splenic artery ble II). An FDS was used to treat 133 patients (mean age, aneurysm.15 64.7 years). JOURNAL OF VASCULAR SURGERY 842 Sfyroeras et al September 2012

Table I. Full-text articles reporting on the results of flow-diverting stents in extracranial aneurysms

Pts (n) Age Aneurysms Author (No.) (years) (No.) Location Stent Stents/size (n/mm)

Henry1 1 78 1 RA CMSa 1/6 ϫ 30

Ruffino10 19 60 19 5 SA, 5 HA, 3 CA, 2 SMA, 3 CMS NR RA, 1 GDA

Meyer11 1 74 1 RA CMS 1/6 ϫ 30 Shlomovitz12 1 64 1 SMA SILKb 1/5.5 ϫ 25 Carrafiello13 1 60 1 CA CMS 2/8 ϫ 60, 7 ϫ 60 Ferrero7 4 64.7 4 HA, 4 CMS 4/NR Euringer14 1 47 4 L SCA, R SCA, suprarenal aorta, CMS 2/12 ϫ 50, 12 ϫ 40, infrarenal aorta 1/12 ϫ 60, 1/25 ϫ 80 Abraham15 1 56 1 SA Pipelinec 1/5 ϫ 20 Balderi9 3 NR 3 HA CMS 3/8 ϫ 60, 7 ϫ 80, 10 ϫ 40 Natrella16 1 81 1 Abdominal aorta (juxtarenal) CMS 1/28 ϫ 100 Benjelloun17 1 16 1 DTA and suprarenal aorta CMS 3/16 ϫ 40, 16 ϫ 80, 16 ϫ 80 Pulli18 1 NR 1 PA CMS NR

ASA, Acetylsalicylic acid; CA, celiac artery; DTA, descending thoracic aorta; FU, follow-up; GDA, gastroduodenal artery; HA, hepatic artery; L, left; ; PA, popliteal aneurysm; R, right; RA, renal artery; SA, splenic artery; SCA, subclavian artery; SMA, superior mesenteric artery. aCardiatis Multilayer Stent, Cardiatis, Isnes, Belgium. bSILK Arterial Reconstruction Device, Balt Extrusion, Montmorency, France. cPipeline Embolization Device, ev3, Plymouth, Minn.

Peripheral and visceral aneurysms. Sixty-two pe- classification. A mean of 2.54 stents were used per patient. ripheral aneurysms were managed; however, no informa- Overall clinical success, as defined in terms of aneurysm tion was provided on the location for 35. Of the 27 thrombosis, reduction of the lesion volume, as well as peripheral aneurysms with location information, there were collateral branches patency, was achieved in 40% of 22 21 iliac aneurysms (one ), four popliteal, patients at 6 months.37 Seven patients were treated in one femoral, and one subclavian. Morocco. Clinical success was achieved in 83% at 12 Multilayer stents were also used in 28 visceral aneu- months.37 These 29 patients underwent a total of four rysms, including the renal artery (n ϭ 6), the SMA (n ϭ 2), secondary interventions (13.7%), including intestinal resec- and the common hepatic artery (n ϭ 1). No information tion due to celiac necrosis resulting from implant throm- was given on the location of the other 19 visceral aneu- bosis at day 15, secondary surgical revision at 8 months for rysms. Technical success was achieved in all cases. Patients a femoral pseudoaneurysm, and a type 1 endoleak that was were monitored for 1 to 30 months, and no branch vessel corrected using an additional multilayer stent proximally to occlusion was reported. In all but two patients, aneurysm seal off the leak completely, followed by a secondary em- thrombosis was achieved at the last follow-up. bolization of the left subclavian.37 In 12 more cases, re- Volume reduction was observed in 24 of 29 aneurysms ported by Henry et al,28 no branch vessel occlusion was (82.7%). Diameter reduction was observed more frequently detected and aneurysm thrombosis was achieved in all with longer follow-up. Ruffino et al23 reported that 33 of cases. 47 of the aneurysms decreased in diameter at 6 months and 21 of 26 at 12 months.23 No stent thrombosis was re- DISCUSSION ported. Endovascular therapy of arterial aneurysms has signifi- Aortic aneurysms. The stents in 43 cases were de- cant advantages because of its minimally invasive nature. ployed in the aorta to treat 37 thoracoabdominal aneu- Stent grafting is now in the third decade of its life. The use rysms, five abdominal aortic aneurysms, and one penetrat- of stent grafts is mainly limited by anatomic factors. Ana- ing aortic ulcer with rupture. In the largest clinical series, tomic factors that preclude the use of stent grafts include presented by Vaislic et al,37 22 patients (18 men; mean age, the presence of important collateral branch vessels in the 72 years) were treated using the Cardiatis Multilayer Stent vicinity or arising from the aneurysm. To move a step at nine centers in France. All patients had American Society forward in the treatment of patients with challenging anat- of Anesthesiologists score Ն3, with a mean aneurysm di- omy, several endovascular techniques have been developed, ameter of 69.4 mm (range, 55.5-87 mm) and a mean including fenestrated and branched endografts, the chim- length of 257 mm (range, 174-343 mm). Ten aneurysms ney technique, and hybrid procedures. These techniques were class 2 and 12 were class 3 according to the Crawford are characterized by complexity, increased operation time, JOURNAL OF VASCULAR SURGERY Volume 56, Number 3 Sfyroeras et al 843

Table I. Continued.

30- day 30-day stent Branch vessel Aneurysm Aneurysm diameter Antiplatelets death occlusion FU (m) occlusion thrombosis decrease

ASA ϩ clopidogrel for 1 month 0 0/1 6 0/1 1/1 1/1 then ASA Dual for 1 month (ASA 100 1 2/18 6 (16 pt) 0/16 14/16 12/16 mg ϩ clopidogrel 75 mg or ticlopidine) then ASA ASA 100 mg ϩ clopidogrel 0 0/1 5 0/1 1/1 0/1 ASA 100 mg ϩ clopidogrel 0 0/1 12 0/1 1/1 1/1 Clopidogrel 0 0/1 12 0/1 1/1 1/1 NR 1 1/4 12.4 0/2 2/2 1/2 ASA 100 mg ϩ clopidogrel 0 0/3 18 0/4 3/4 4/4

Clopidogrel 6 wks and ASA 0 0/1 20 0/1 1/1 1/1 NR 0 0 12 0 3/3 3/3

ASA 100 mg ϩ clopidogrel 0 0 12 0 1/1 1/1 ASA 100 mg ϩ clopidogrel for 0 0 18 0 1/1 1/1 1 month Dual-antiplatelet therapy 0 0 NR NR NR NR

radiation time, postoperative complications, and cost; tions include hybrid procedures and the chimney moreover, fenestrated and branched endografts are not technique. Hybrid procedures, which involve surgical by- available “off the shelf” and usually require several weeks to pass grafting of the major aortic branches and endovascular be ready. coverage of the , are associated with a Visceral artery aneurysms can be treated with surgical 30-day and in-hospital mortality incidence of 12.8%, 8.8% exclusion, bypass, or simple ligation. Endovascular options renal failure, 7.5% spinal cord , 4.5% irreversible include stent graft exclusion and coil embolization. The paraplegia, and 22.7% endoleak during follow-up.38 location of the aneurysm is an important factor for the The chimney technique involves deployment of stents choice of treatment. An endovascular approach is prefera- and stent grafts into the aortic visceral branches and deploy- ble for aneurysms involving the splanchnic arteries.10 If ment of an aortic endograft such that the proximal parts of stent grafting is attempted, the collateral branches must be the visceral stents are placed parallel to the main aortic covered. Aneurysms may be associated with elongation and endoprosthesis (between the aortic stent and the aortic increased tortuosity of the vessel, a characteristic often seen wall) and extend above (typical chimney technique) or in splenic artery aneurysms. Deployment of a covered stent beyond (reversed chimney technique) it to ensure perfu- may be technically unattainable in these aneurysms because sion. Endovascular procedures with the chimney tech- of the existing device limitations. niques are associated with 30-day mortality of 4.3%, 3.2% FDSs can represent a new alternative treatment option , 2.1% myocardial infarction, and 11.8% renal func- for aneurysms given their unique characteristics. Up to tion impairment.39 Because of the anatomic limitations of now, the largest published experience comes from use of the proximal aortic neck, long-term endograft durability FDSs in the visceral aneurysms. The results are very encour- and proximal fixation remain significant concerns and limit aging, with a significant incidence of aneurysm thrombosis widespread use of the method.39 Neither technique has and shrinkage during follow-up and without any branch offered a widely accepted solution in these difficult aortic vessel occlusion. Regarding peripheral aneurysms, FDS . have been mainly used for the treatment of iliac, popliteal, The deployment of multilayer stents may overcome the and subclavian aneurysms. In these anatomic areas, signif- anatomic limitations. Until now, multilayer stents have icant collateral branches have to be preserved, including the been used in 45 patients for the treatment of aortic aneu- internal iliac artery, the genicular arteries, and the vertebral rysms, including a patient with HIV and a teenaged girl arteries, respectively. with tuberculosis. Reported data suggest that 12-month Juxtarenal, suprarenal, and thoracoabdominal aneu- clinical success is achieved in a significant proportion of rysms represent challenging aortic pathologies. Open sur- patients. Earlier, 6-month data may not be equally satisfac- gery carries significant morbidity and mortality. Other op- tory; however, Vaislic et al,37 with the largest series from JOURNAL OF VASCULAR SURGERY 844 Sfyroeras et al September 2012

Table II. Published abstracts reporting on the results of flow-diverting stents in extracranial aneurysms

Author Congress Pts (No.) Age (years) Aneurysms (No.) Location

Ruffino18 TCT 2011 54 NR 54 35 peripheral, 19 visceral

Henry22 TCT 2011 32 61 Ϯ 8 32 20 iliac, 1 femoral, 41 popliteal, 6 renal, 1 mesenteric Henry23 TCT 2011 10 61.4 10 6 TAAs, 4 AAAs Santoro24 CIRSE 2010 1 47 1 Subclavian artery Hamada25 ESVS 2011 1 76 1 1 TAA (type II) Butarrelli26 CIRSE 2011 1 NR — Rupture of penetrating aortic ulcer Burdi27 CIRSE 2011 1 63 1 Common hepatic artery Mauri28 CIRSE 2011 1 NR 1 Iliac pseudoaneurysm Natrella29 CIRSE 2011 1 NR 1 Juxtarenal AAA Petrocelli30 CIRSE 2011 1 NR 1 SMA pseudoaneurysm Mauri31 CIRSE 2011 1 NR 1 TAA Vaislic32 VEITH 2011 22b 72 227 22 TAAs (10 type II, 12 type III) 7d NR 7 TAAs

AAA, Abdominal aortic aneurysm; CIRSE, Cardiovascular and Interventional Radiological Society of Europe; ESVS, European Society for Vascular Surgery; NR, not reported; TAA, thoracoabdominal aneurysm; TCT, Transcatheter Cardiovascular Therapeutics. aCardiatis Multilayer Stent, Cardiatis, Isnes, Belgium. bPatients treated in France. cOverall clinical success: aneurysm thrombosis, volume decrease, and all vessels patent. dPatients treated in Morocco.

France, reported a 40% overall clinical success in 22 pa- extracranial aneurysms has been reported in the published tients, as defined in terms of aneurysm thrombosis, reduc- literature; however, this may be a result of publication bias. tion of the aneurysm volume, and collateral branches pa- More clinical studies and longer follow-up are needed to tency. The addition of patients with HIV and tuberculosis understand the evolution of the aneurysms after their ex- may be confusing for the interpretation of the results; clusion using FDSs. however, these are two of the three full-text reports avail- Another complication frequently encountered is FDS able for the use of multilayer stents in aortic aneurysms. We thrombosis, which occurred in 8.3% of the cases. Fortu- still do not have the definite answers on the results of nately, when stent thrombosis occurred in SMA, splenic, multilayer stents in thoracoabdominal, suprarenal, and pa- and hepatic arteries, there were no clinical consequences for rarenal aneurysms; however, they seem to need time to the patients. Visceral arteries usually have a well-developed achieve optimal results in aneurysm thrombosis and shrink- collateral network that sometimes prevents organ ischemia age. Therefore, their use in large aneurysms has to be done in cases of acute occlusion. Particularly for the SMA stent with caution and the patients kept under close surveillance. occlusion, the stent remained patent at the level of two The traditional definition of endoleak and aneurysm collateral vessels, one feeding retrogradely the hepatic ar- thrombosis may be not sufficient to describe clinical results tery, previously occluded at its takeoff from the celiac trunk, after the deployment of an FDS. Because the FDS is a flow and the other supporting the bowel vascular bed. The modulator and not a sealing stent graft, the goal is to patient did not experience any symptoms of hepatic infarc- reduce pressure into the aneurysmal sac and promote tion or bowel ischemia.10 The experience of the SFD stent thrombosis. However, the image of a thrombosed aneu- in intracranial aneurysms showed quite high delayed clinical rysm in a postoperative CT scan does not preclude sac and anatomic complication rates, with significant parent pressurization, and the risk of rupture may not have been artery stenoses in 33%.41 eliminated. Adequate antiplatelet therapy is important after deploy- Moreover, it is difficult to differentiate a type I en- ment of an FDS.11,41 Dual-antiplatelet therapy was not the doleak, as classically defined, after implantation of a stent standard treatment in all patients. Poor compliance of a graft with contrast leaking through the pores of an FDS. patient with dual-antiplatelet therapy was the reason of a Evidence of incomplete coverage of the proximal landing splenic artery stent thrombosis10 However, other factors, zone with distal deployment of the FDS is suggestive of a like poor runoff, also predispose to stent thrombosis.10 “true” type I endoleak. Clinical success is better described with reduction of aneurysm volume, which reflects aneu- CONCLUSIONS rysm depressurization and prevention from rupture. A lack Initial clinical experience with FDSs in the treatment of of reduction with an FDS should raise suspicion of contin- visceral and peripheral aneurysms yielded satisfactory re- ued pressurization of the aneurysm. Aneurysm rupture was sults in technical success, aneurysm thrombosis and shrink- reported after treatment of an using age, and branch vessel patency. In aortic aneurysms, better the PED.40 No aneurysm rupture after FDS placement in results are achieved 12 months after the procedure rather JOURNAL OF VASCULAR SURGERY Volume 56, Number 3 Sfyroeras et al 845

Table II. Continued.

Follow-up Branch vessel Aneurysm thrombosis Aneurysm diameter Stent Stent (months) occlusion (months) decrease (months) occlusion

CMSa 1-12 0/49 45/49 (1); 45/47 (6); 33/47 (6); 21/26 (12) 0 24/26 (12) NR 6-30 0/32 32/32 NR NR

CMS 6-18 0/10 10/10 NR NR CMS 3 0 1/1 NR 0 NR NR 0/1 1/1 1/1 0/1 CMS NR NR NR NR NR CMS 3 0/1 1/1 1/1 0/1 CMS 3 0/1 1/1 NR NR 9 0/1 1/1 1/1 0/1 CMS 6 NR NR NR NR CMS 9 0/1 1/1 1/1 0/1 CMS 6 40%c 40%c 40%c NR CMS 12 83%c 83%c 83%c NR

than at 6 months. No aneurysm rupture after treatment 7. Ferrero E, Ferri M, Viazzo A, Robaldo A, Carbonatto P, Pecchio A, et with an FDS has been described to date. There was a al. Visceral artery aneurysms, an experience on 32 cases in a single significant incidence of FDS thrombosis. Larger clinical center: treatment from surgery to multilayer stent. Ann Vasc Surg 2011;25:923-35. series with longer follow-up will enlighten in the near 8. Balderi A, Antonietti A, Pedrazzini F, Ferro L, Leotta L, Peano E, et al. future the role of FDSs in aortic, splanchnic, and peripheral Treatment of a hepatic artery aneurysm by endovascular exclusion using aneurysms. the multilayer Cardiatis stent. Cardiovasc Interv Radiol 2010;33: 1282-6. AUTHOR CONTRIBUTIONS 9. Balderi A, Antonietti A, Ferro L, Peano E, Pedrazzini F, Fonio P, et al. Conception and design: GS Endovascular treatment of visceral artery aneurysms and pseudoaneu- rysms: our experience. Radiol Med 2012;117:815-30. Analysis and interpretation: GS, ID, TG, KA 10. Ruffino M, Rabbia C, Italian Cardiatis Registry Investiagtors Group. Data collection: GS, TG, KA Endovascular treatment of visceral artery aneurysms with Cardiatis Writing the article: GS multilayer flow modulator: preliminary results at six-month follow-up. Critical revision of the article: GS, ID, JK, CL J Cardiovasc Surg (Torino) 2011;52:311-21. Final approval of the article: GS, ID, TG, KA, JK, CL 11. Meyer C, Verrel F, Weyer G, Wilhelm K. Endovascular management of Statistical analysis: GS complex renal artery aneurysms using the multilayer stent. Cardiovasc Interv Radiol 2011;34:637-41. Obtained funding: Not applicable 12. Shlomovitz E, Jaskolka JD, Tan KT. Use of a flow-diverting uncovered Overall responsibility: GS stent for the treatment of a superior mesenteric artery aneurysm. J Vasc Interv Radiol 2011;22:1052-5. REFERENCES 13. Carrafiello G, Rivolta N, Annoni M, Fontana F, Piffaretti G. Endovas- cular repair of a celiac trunk aneurysm with a new multilayer stent. J Vasc 1. Henry M, Polydorou A, Frid N, Gruffaz P, Cavet A, Henry I, et al B. Surg 2011;54:1148-50. Treatment of renal artery aneurysm with the multilayer stent. J Endo- 14. Euringer W, Südkamp M, Rylski B, Blanke P. Endovascular treatment vasc Ther 2008;15:231-6. of multiple HIV-related aneurysms using multilayer stents. Cardiovasc 2. Liou TM, Li YC. Effects of stent porosity on hemodynamics in a Intervent Radiol 2012;35:945-9. sidewall aneurysm model. J Biomech 2008;41:1174-83. 15. Abraham RJ, Illyas AJ, Marotta T, Casey P, Vair B, Berry R. Endovas- 3. Augsburger L, Farhat M, Asakura F, Ouared R Stergiopulos N, Rüfen- cular exclusion of a splenic artery aneurysm using a pipeline emboliza- acht D. Hemodynamical effects of CARDIATIS braided stents in tion device. J Vasc Interv Radiol 2012;23:131-5. sidewall aneurysms silicone models using PIV. Available at: http:// 16. Natrella M, Castagnola M, Navarretta F, Cristoferi M, Fanelli G, www.cardiatis.com/images/stories/info/etude%20luca%20in%20vitro. pdf. Meloni T, et al. Treatment of juxtarenal aortic aneurysm with the 4. Wong GK, Kwan MC, Ng RY, Yu SC, Poon WS. Flow diverters for multilayer stent. J Endovasc Ther 2012;19:121-4. treatment of intracranial aneurysms: current status and ongoing clinical 17. Benjelloun A, Henry M, Ghannam A, Vaislic C, Azzouzi A, Maa- trials. J Clin Neurosci 2011;18:737-40. zouzi W, et al. Endovascular treatment of a tuberculous thoracoab- 5. Chisci E, Setacci F, de Donato G, Cappelli A, Palasciano G, Setacci C. dominal aneurysm with the multilayer stent. J Endovasc Ther 2012; Renal aneurysms: surgical vs. endovascular treatment. J Cardiovasc Surg 19:115-20. (Torino) 2011;52:345-52. 18. Pulli R, Dorigo W, Fargion A, Pratesi G, Innocenti AA, Angiletta D, et 6. Ferrero E, Ferri M, Viazzo A, Nessi F. Endovascular treatment of al. Comparison of early and midterm results of open and endovascular hepatic artery aneurysm by multilayer stents: two cases and one-year treatment of popliteal artery aneurysms. Ann Vasc Surg 2012;26: follow-up. Interact Cardiovasc Thorac Surg 2011;13:545-7. 809-18. JOURNAL OF VASCULAR SURGERY 846 Sfyroeras et al September 2012

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