Fractured superior mesenteric artery stents after fenestrated ...

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Stent fracture after fenestrated endovascular aneurysm repair is a recognized complication. ... computer tomography (CT) and duplex ultrasound (DUS) assess-.
Fractured superior mesenteric artery stents after fenestrated endovascular aneurysm repair Rana Canavati, MBBS, MRCS,a Thien V. How, PhD,b John A. Brennan, MD, FRCS,a Srinivasa Rao Vallabhaneni, MD, FRCS,a Robert K. Fisher, MD, FRCS,a and Richard G. McWilliams, EBIR, FRCR,a Liverpool, United Kingdom Stent fracture after fenestrated endovascular aneurysm repair is a recognized complication. In this report, we record the occurrence of superior mesenteric artery stent fractures in our series and describe the management of embolized stent fragments during secondary intervention. ( J Vasc Surg 2013;57:511-4.)

Although fenestrated endovascular repair of juxtarenal aneurysms is well established, there is no ideal stent recognized for the target vessels. Both uncovered and covered stents are used. We have favored the Palmaz Genesis (Cordis, Roden, The Netherlands) for the superior mesenteric artery (SMA) when using an uncovered stent. This is a closed-cell stainless steel stent. We have recently observed fractures in two Palmaz Genesis stents in SMA fenestrations after fenestrated endovascular aneurysm repair (f-EVAR). Secondary interventions were performed and in both cases the aortic portion of the stent embolized.

This made catheterization of the SMA easier, and it was relined with an 8 mm/38 mm Advanta V12 covered stent. Fluoroscopy showed the embolized stent fragment in the right limb of the stent graft (Fig 1, c). A catheter was used to engage the fragment, and a guidewire was introduced (Fig 1, d). A sheath passed freely through the fragment, indicating that the wire had not passed through the interstices. A 12 mm balloon was used to inflate the fragment, and the final image showed this apposed to the wall of the right iliac limb (Fig 1, e). The patient was discharged after 1 day, and DUS confirmed that the graft limbs were patent with normal groin waveforms.

CASE 1

CASE 2

An 82-year-old man with an 8.6 cm juxtarenal abdominal aortic aneurysm was treated using a fenestrated stent graft with fenestrations for the SMA and left renal artery. The right kidney was atrophic. The SMA stent was a Palmaz Genesis (9 mm/29 mm) and the left renal a 7 mm/22 mm Advanta V12 (Atrium, Hudson, NH). Baseline imaging showed well aligned stents, no fractures, and no endoleak. Surveillance at 1 year showed a complete transverse fracture of the SMA stent on abdominal radiographs (Fig 1, a). There was no evidence of migration, and there was normal flow in the SMA at computer tomography (CT) and duplex ultrasound (DUS) assessment. Although the patient was asymptomatic, secondary intervention was planned to protect the SMA from shuttering should future caudal or rotational migration occur. A femoral approach was used, and during the initial attempt to catheterize the stent, the aortic fragment embolized (Fig 1, b). From the Regional Vascular Unit, Department of Interventional Radiology, Royal Liverpool University Hospitala; and the Department of Clinical Engineering, University of Liverpool.b Author conflict of interest: Dr Vallabhaneni has received research grant and conference travel expenses from Cook Medical. Reprint requests: Rana Canavati, Regional Vascular Unit, Link 8C, Royal Liverpool University Hospital, Prescot St, Liverpool, L7 8XP (e-mail: [email protected]). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214/$36.00 Copyright © 2013 by the Society for Vascular Surgery. http://dx.doi.org/10.1016/j.jvs.2012.08.043

A 69-year-old man with a 6.2-cm juxtarenal abdominal aneurysm was treated with a fenestrated graft comprising three fenestrations. The SMA was stented with a Palmaz Genesis (10 mm/29 mm) and both renal arteries with Advanta V12 (7 mm/22 mm). Baseline CT at 1 month showed misalignment of the SMA fenestration with clockwise rotation with reference to the SMA ostium, resulting in a 45 degree angle in the SMA stent. One-year DUS demonstrated increased peak systolic velocities in the SMA. There was no stent graft migration. At 2 years, DUS highlighted turbulence in the SMA with an abnormal flow waveform. CT angiography confirmed fracture of the SMA stent, with the separated aortic fragment lying at the level of the right renal artery. Secondary intervention was planned to prevent occlusion of the SMA. A femoral approach was used, and fluoroscopy showed the aortic fragment at the level of the right renal artery (Fig 2, a). A catheter was guided along the posterior aspect of the endograft, avoiding the intravascular fragment. The SMA stent was catheterized, and a 6 mm/12 mm Jostent (Jomed; Abbott Vascular Instruments, Rangendingen, Germany) deployed to reline the SMA. As the sheath was removed from the SMA, it caught the intravascular fragment which embolized to the bifurcation of the endograft (Fig 2, b). A 12 mm/60 mm Wallstent (Boston Scientific, Paris, France) was deployed at the bifurcation, via the right limb, and postdilated to 12 mm. This caged the intravascular fragment, which was crushed securely against the wall as seen on postprocedure CT (Fig 2, c). The patient was discharged after 1 day, and 5-week DUS revealed normal flow in the SMA.

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Fig 1. a, Lateral abdominal radiograph showing fractured superior mesenteric artery (SMA) stent with the aortic portion at the level of the fenestration (arrow). b, Fluoroscopic image showing a guidewire and balloon catheter in the SMA. The aortic fragment of the SMA stent is no longer visible and has embolized. c, Aortic portion of the Palmaz Genesis stent shown in the right limb of the bifurcated graft (circle). d, Aortic portion well aligned with the stent graft. e, Aortic portion of the Palmaz Genesis stent apposing the iliac segment securely after ballooning. SMA, Superior mesenteric artery.

DISCUSSION The literature on fenestrated grafts records a total of 25 stent fractures in a population of 888 patients.1-14 These were all renal stents: eight bare metal, three covered stents, and in 14 cases, the type was not reported. There are no reports of embolized fragments. Eleven target vessels were lost due to stent fracture or complications from secondary procedures to address them. In our institution, 165 visceral arteries were stented in 81 patients who underwent f-EVAR between February 2003 and December 2010. There were 82 covered stents (76 Advanta V12, six Jostent) and 72 bare metal stents, of which 51 were Palmaz Genesis. The details of the remaining 11 stents are not available. In this cohort of patients, 19 superior mesenteric arteries were stented, of which four were covered stents (three Advanta V12, one Jostent), and 14 bare metal stents of which 12 were closed-cell stents (Palmaz Genesis), and two open-cell stents. We have seen a

total of four stent fractures, all of which were Palmaz Genesis. Two were SMA stents and two renal stents. To our knowledge, these are the first SMA stent fractures recorded after f-EVAR. It is unsurprising that fractures occur in the target vessel stents used in f-EVAR. Such stents, which were not specifically designed for this environment, are subjected to forces due to respiratory movement of the viscera, longitudinal movement of the endograft, circumferential forces due to aortic diameter changes, and side branch motion during the cardiac cycle.15 If the fenestrated endograft is not perfectly positioned within the native anatomy either because of errors in the original plan or technical difficulties at deployment, then the stents will be subjected to additional forces as they are forced to realign to accommodate the geometrical mismatch. The geometrical design of stents has an influence on mechanical properties such as radial strength and flexi-

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Fig 2. a, Fractured superior mesenteric artery (SMA) stent with the aortic portion lying at the level of the right renal stent (circle). b, The aortic portion of the stent has embolized. c, Axial computed tomography (CT) image showing the crushed stent fragment (z) between the graft limb (y) and the Wallstent (x).

bility. Closed-cell stents consist of a regular cell structure where all strut elements forming each cell are linked to those of adjacent cells. This results in a structure with high radial strength that provides good resistance to compressive forces but limited flexibility. When used for f-EVAR, the high radial strength and rigidity help to resist caudal migration of the endograft across the target vessel ostium.16 However, high rigidity makes the stent more prone to fatigue fracture when it is subjected to repetitive stresses. In open-cell designs, the linkage to some adjacent cells is omitted, resulting in stents with greater lateral flexibility compared with closed-cell designs but at the expense of reduced radial strength. Open-cell stents conform better to the anatomy of aortic side branches, and the use of these stents has advantages at the distal landing zone. However, these stents may be prone to compression and elongation, eventually leading to fracture.17 The four stent fractures in our series were all in the closed-cell Palmaz Genesis stent. The published literature on stent fractures after f-EVAR does not allow a detailed analysis of the type of stent, with many reports either not commenting on fractures or not specifying the stent type

when fractures were observed. In those reports where detail is provided, there are reports of fractures of Genesis, Atrium, and Jomed stents.5,13 Endovascular manipulation in the vicinity of a fractured stent risks embolization of the aortic fragment, as occurred in our cases. Retrieval of the stent fragment is possible; however, this may require the use of large sheaths and surgical closure of the puncture site.18 An alternative is the repositioning of the stent fragment in a stable location as described in both of our cases. REFERENCES 1. Semmens JB, Lawrence-Brown MM, Hartley DE, Allen YB, Green R, Nadkarni S. Outcomes of fenestrated endografts in the treatment of abdominal aortic aneurysm in western Australia (1997–2004). J Endovasc Ther 2006;13:320-9. 2. Muhs BE, Verhoeven EL, Zeebregts CJ, Tielliu IF, Prins TR, Verhagen HJ, et al. Mid-term results of endovascular aneurysm repair with branched and fenestrated endografts. J Vasc Surg 2006; 44:9-15. 3. Halak M, Goodman MA, Baker SR. The fate of target visceral vessels after fenestrated endovascular aortic repair– general considerations and mid-term results. Eur J Vasc Endovasc Surg 2006;32:124-8.

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4. O’Neill S, Greenberg RK, Haddad F, Resch T, Sereika J, Katz E. A prospective analysis of fenestrated endovascular grafting: intermediateterm outcomes. Eur J Vasc Endovasc Surg 2006;32:115-23. 5. Verhoeven EL, Vourliotakis G, Bos WT, Tielliu IF, Zeebregts CJ, Prins TR, et al. Fenestrated stent grafting for short-necked and juxtarenal abdominal aortic aneurysm: an 8-year single-centre experience. Eur J Vasc Endovasc Surg 2010;39:529-36. 6. Haddad F, Greenberg RK, Walker E, Nally J, O’Neill S, Kolin G, et al. Fenestrated endovascular grafting: the renal side of the story. J Vasc Surg 2005;41:181-90. 7. Amiot S, Haulon S, Becquemin JP, Magnan PE, Lermusiaux P, Goueffic Y, et al. Fenestrated endovascular grafting: the French multicentre experience. Eur J Vasc Endovasc Surg 2010;39:537-44. 8. Kristmundsson T, Sonesson B, Malina M, Björses K, Dias N, Resch T. Fenestrated endovascular repair for juxtarenal aortic pathology. J Vasc Surg 2009;49:568-74; discussion: 574-65. 9. Bicknell CD, Cheshire NJ, Riga CV, Bourke P, Wolfe JH, Gibbs RG, et al. Treatment of complex aneurysmal disease with fenestrated and branched stent grafts. Eur J Vasc Endovasc Surg 2009;37:175-81. 10. Ziegler P, Avgerinos ED, Umscheid T, Perdikides T, Stelter WJ. Fenestrated endografting for aortic aneurysm repair: a 7-year experience. J Endovasc Ther 2007;14:609-18. 11. Ziegler P, Perdikides TP, Avgerinos ED, Umscheid T, Stelter WJ. Fenestrated and branched grafts for para-anastomotic aortic aneurysm repair. J Endovasc Ther 2007;14:513-9.

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12. Troisi N, Donas KP, Austermann M, Tessarek J, Umscheid T, Torsello G. Secondary procedures after aortic aneurysm repair with fenestrated and branched endografts. J Endovasc Ther 2011;18:146-53. 13. Roselli EE, Greenberg RK, Pfaff K, Francis C, Svensson LG, Lytle BW. Endovascular treatment of thoracoabdominal aortic aneurysms. J Thorac Cardiovasc Surg 2007;133:1474-82. 14. Tambyraja AL, Fishwick NG, Bown MJ, Nasim A, McCarthy MJ, Sayers RD. Fenestrated aortic endografts for juxtarenal aortic aneurysm: medium term outcomes. Eur J Vasc Endovasc Surg 2011;42:54-8. 15. Oshin OA, How TV, Brennan JA, Fisher RK, McWilliams RG, Vallabhaneni SR. Magnitude of the forces acting on target vessel stents as a result of a mismatch between native aortic anatomy and fenestrated stent grafts. J Endovasc Ther 2011;18:569-75. 16. Scurr JR, How TV, McWilliams RG, Lane S, Gilling-Smith GL. Fenestrated stent graft repair: which stent should be used to secure target vessel fenestrations? J Endovasc Ther 2008;15:344-8. 17. Watanabe T, Tamura A, Miyamoto K, Kadota J. Fracture of a paclitaxoleluting stent implanted for in-stent restenosis at the site of sirolimuseluting stent fracture. Int J Cardiol 2010;140:e12-13. 18. Slonim SM, Dake MD, Razavi MK, Kee ST, Samuels SL, Rhee JS, et al. Management of misplaced or migrated endovascular stents. J Vasc Interv Radiol 1999;10:851-9.

Submitted May 29, 2012; accepted Aug 8, 2012.