Volume 32, Issue 2 , Pages 124-128, August 2006
The Fate of Target Visceral Vessels After Fenestrated Endovascular Aortic Repair—General Considerations and Mid-term Results
Article Outline
Abstract
Objective
To carry out a retrospective analysis of the short and mid-term target vessels (TV) patency following fenestrated endovascular aortic repair (f-EVAR) of abdominal aneurysm (AAA).
Patients and methods
Seventeen f-EVAR patients were analysed. The Zenith (Cook) fenestrated graft was used in all cases. Bare renal stents were used where good apposition existed between the stent graft and the aortic wall, and covered stents were chosen when this apposition appeared deficient.
Results
A total of 35 TV were treated: twenty with small fenestration and 15 with a scallop. Procedural technical success was achieved in 16 out of 17 patients. All TV were perfused at the completion angiography. Access to TV through small fenestrations was achieved in 18 out of 20 vessels. After a mean follow-up of 20.5 months no type I endoleaks were detected. No late complications were observed in any of the stented TV. One patient with perioperative bilateral renal artery occlusion remains on haemodialysis. One non-target renal artery, opposite a scallop was unintentionally covered. One kidney, initially perfused via a un-stented scallop fenestration, was atrophied 14 months post surgery. One patient died from heart failure.
Conclusions
f-EVAR is a valid and safe treatment option. Our series and the world literature demonstrates a >90% TV preservation rate. Long-term intensive surveillance is required.
Keywords: Fenestration, EVAR, AAA: target vessels, Renal artery, SMA, Endovascular
1. Introduction
Fenestrated endovascular aortic repair (f-EVAR) of abdominal aortic aneurysm (AAA) is still in its infancy. Short-necked infrarenal and juxta-renal AAA in high-risk patients are currently considered the principal indications for f-EVAR.1, 2 The f-EVAR enables the advancement of the sealing stent to a more proximal segment of the aorta in order to optimise wall contact. Over 800 AAAs have been treated with f-EVAR throughout the world. Early results are encouraging. The incidence of type I endoleak (EL) and of AAA related death is low, and preservation of over 90% of target vessels is reported.3, 4, 5, 6, 7
Fenestrations may be either large or small or a scallop. Fenestrations are designed to align at deployment with the orifice of the target vessel. Thus, stent graft planning depends upon critical appreciation of the aortic neck anatomy.3, 4, 8, 9 Stenting in f-EVAR will maintain this alignment of the fenestration to the target vessel. When the apposition of the fenestration against the aortic wall at the orifice of the target vessel is close, a bare stent is appropriate. If there is no apposition or a potential gap is likely to be present, a covered stent is required to avoid a leak at this site (Fig. 1).
Fig. 1.
Apposition of the stent graft against the aortic wall. (A) Case for a bare renal stent. (B) Case for a covered renal stent.
Fenestrated-EVAR aims to preserve and maintain target vessels patency and sealing. However, complications may occur during and after the procedure, which may compromise perfusion. These include immediate coverage and occlusion of the target vessel secondary to errors in planning or mal-alignment during deployment. Late complications include graft migration, rotation; and in situ stenosis and thrombosis, secondary to intimal hyperplasia.
We have analysed the short and mid-term target vessel patency in a single centre experience with 17 patients treated with f-EVAR.
2. Patients and Methods
Between February 2002 and February 2005, 17 patients with AAA greater than 50
mm in maximal diameter underwent f-EVAR. In all patients the anatomy of the AAA neck precluded the use of a standard EVAR.5 Eleven patients had a juxta-renal aneurysm with at least one visceral vessel originating from an aneurysmal segment.
Two patients of this group had proximal anastomotic false aneurysms following AAA repair. Seven patients had short infra-renal necks (<5mm).
2.1. Planning
Planning was based on a CT angiography and required 1mm slices from proximal coeliac down to the lowest renal artery and multi-planar reconstructions at all levels. Assessment of target vessel position, number, size, as well as luminal diameter, neck thrombus and angulation was necessary to calculate the position and size of the fenestration or scallop, as well as the choice of covered vs bare stents.
Aortography and selective catheterisation of the target vessel confirmed the ease of entry and clarified the anatomy. Access vessel calibre and tortuosity was assessed by both modalities.
2.2. Types of fenestration
Fenestrations were small (SF) 6×6mm2 or 6×8mm2, or large (LF) 8–12mm. Scallop fenestration (ScF) had a minimum width of 10mm and height range 6–12mm. The distance from the proximal fabric edge was at least 10mm for LF and 15mm for SF. All small, large, and scallop fenestrations were reinforced with a nitinol ring to ensure sealing when a covered stent was used (Fig. 2).
Fig. 2.
A close look at a small fenestration. (A) A non-reinforced fenestration. (B) Nitinol ring reinforced fenestration. (1) (thick arrow) Large fenestration. (2) (thin arrow) Small fenestration.
2.3. Stent graft
The Zenith (WA Cook Australia Pty. Ltd, Brisbane, Australia) fenestrated graft was used in all cases. The device description and implantation technique has been described elsewhere.2, 3, 4, 6
2.4. Renal stents
Bare renal stents (Balloon expandable: Jostent renal, Jomed AG Beringen, Switzerland; or genesis, cordis endovascular—LJ Roden, The Netherlands) were used where good apposition existed between the stent graft and the aortic wall (Fig. 1(A)). Covered renal stents (Jostent-stent graft, Jomed Gmbh; Rangendinger, Germany) were chosen when apposition between the stent graft and the aorta appeared deficient (Fig. 1(B)). The nitinol ring reinforced fenestration permits a covered stent to seal at this point as well as within the target vessel. All renal stents were positioned so that at least 25% was left protruding into the stent graft. This protruding portion of the renal stent was subsequently flared with a larger angioplasty balloon (10–12mm).
2.5. Follow-up
All patients were followed-up according to the Cook Zenith protocol thereafter. Cases, in which the completion angiogram raised doubts with regard to type I endoleak underwent CTA prior to discharge. Renal function was assessed regularly.
3. Results
A total of 35 target vessels were treated in 17 patients: twenty with small fenestration and 15 with scallops. No large fenestrations were used in this series (Table 1). Nineteen fenestrations had nitinol ring reinforcement. Mean follow-up was 20.5 months (range 4–40).
Table 1. Distribution of vessels incorporated into the fenestrated device and type of fenestration
| Scallop fenestration | Small fenestration | Large fenestration | |
|---|---|---|---|
| SMA* | 7 | 1 | 0 |
| Renal artery | |||
| Main | 8 | 18 | 0 |
| Accessory | 0 | 1 | 0 |
| Total | 15 | 20 | 0 |
*SMA, superior mesenteric artery. |
3.1. Procedural technical success
Procedural technical success was achieved in 16 out of 17 patients. All the target vessels were perfused at the completion angiography. There were no conversions to open surgery.
3.2. Small fenestrations
Access to target vessels was achieved in 18 out of 20 vessels. Of the 20 SF 17 were stented: six with bare stents, and 11 with covered stents. One small diameter accessory renal artery was intentionally not stented.
In one patient with severely angulated neck, access was not achieved to one renal artery and to the superior mesenteric artery. These six target vessels were initially perfused via a proximal endoleak. Subsequent attempts to correct the situation controlled the endoleak but could not preserve flow to the renal arteries.
3.3. Scallop fenestrations
Fifteen target vessels were treated with ScF. Access to target vessels was achieved in all eight renal artery ScF during deployment. No attempt was made to gain access to the SMA. One renal artery ScF was stented with a bare stent. One non-target renal artery, opposite a scalloped artery was unintentionally covered and could not be salvaged.
3.4. Follow-up morbidity and mortality
No type I endoleaks were detected. No late complications were observed in any of the target vessels that had been stented (17 out of 18 stents). No specific adverse effects can be related to the use of covered or bare stents.
One kidney, initially perfused via a un-stented scallop fenestration, was confirmed to have atrophied 14 months post surgery. Renal artery occlusion was demonstrated. One patient with the perioperative bilateral renal artery occlusion remains on haemodialysis. Overall, four kidneys atrophied associated with stenting. In only one case the renal artery was stented. One kidney was lost intra-operatively (the case of non-target renal artery, opposite a scalloped fenestration); two kidneys (same patient) peri-operatively (the patient with severe angulated neck and an endoleak); and one kidney during follow-up. Only one patient ended up on permanent haemodialysis. One patient in the series died 7 months post procedure. The cause of death was not graft related.
4. Discussion
The principal goal of fenestrated endovascular aortic grafts is to extend the applicability of EVAR in medium to high-risk patient with an unsuitable proximal sealing zone.
f-EVAR achieves this goal by moving the sealing zone proximally. Consequently, f-EVAR must accommodate at least one of the four visceral vessels.
Compromised perfusion remains a potential hazard. Accurate positioning of the stent-graft at the time of the procedure and prevention of post procedural migration of the stent-graft along the aortic wall is crucial to minimise this. This particularly applies to small fenestrations when the tolerance to movement is low and partial covering of the orifice may not be detected on initial imaging.
Anderson et al. showed that without the use of trans-graft stenting, five renal arteries were either occluded or poorly perfused by the endo-graft.4 However, mandatory need for stenting raises other issues of concern. This relates to the potentially traumatic effect of the stent on the target artery. In f-EVAR the stents are functioning as ‘bridging side-arms’ between the relatively rigid stent graft and the normal target vessel. Repetitive stent movement may provoke intimal hyperplasia and accelerated atherosclerosis leading to stenosis or thrombosis.
In reviewing the combined series in Table 2, we observe that short and mid-term patency of 387 target vessels in 139 patients was 95% (n=368). These figures are expected to improve now that the stenting of small fenestration has become an integral part of the procedure.
Table 2. The fate of targeted visceral vessels in f-EVAR: comparison of the current published experience
| Author (year of publication) | FU period (months) | No. of patients | Target visceral vessels | Lost kidneys (patients on dialysis) | |||||
|---|---|---|---|---|---|---|---|---|---|
| Mean | Range | Total | Mean/patient | Occluded vessels | |||||
| Peri-operative (within 1 month) | Follow-up | ||||||||
| Occluded | Stenosed | ||||||||
| Verhoeven et al.3 (2004) | 9.4 | 1–18 | 18 | 46 | 2.6 | 1* | 1† | 1† | 1 (0) |
| Anderson et al.4 (2001) | na | 3–24 | 13 | 33 | 2.5 | 0 | 6 (5†+1) | na | |
| Stanley6 (2004) | 14 | na | 19 | 48 | 2.5 | 1 | 0 | na | |
| Greenberg et al.5 (2004) | 9.2 | 0–24 | 32 | 83 | 2.6 | 2 | 3 | 2 (1) | |
| Haddad, Greenberg et al.7 (2005)‡ inclusive of previous series5 | 6 | 1–24 | 72 | 142‡ | 2.0‡ | 1 | 5 | 10 | 5 (2) |
| Halak et al. (2005) | 20.5 | 4–40 | 17 | 35 | 2.0 | 3§ | 1 | 4 (1) | |
| Total | 139 | 387 | 6‡, § | 13 (6†) | 14 | 12 (4) | |||
*Accessory renal artery. |
†Non-stented renal artery. |
‡Renal artery fenestrations only. |
§Contra-lateral non-targeted renal artery. |
Our current policy is to stent ScF to the renal arteries and we emphasise, that stenting of a scalloped fenestration to the renal artery is also of value in securing patency of the fenestration against migration and/or rotation. Verhoeven et al. recommended that ScF should not be stented as sealing is not the issue.3 Our case of kidney loss 14 months post procedure might confirm that this potential problem does exist.
As stated above, we reserved the use of covered renal stents to cases where a potential residual gap between the stent-graft and the aortic wall was likely. No adverse effects on target vessels were found to be related to this practice but concerns persist. Long-term anti-platelet therapy is strongly recommended for this group. Covered stenting of the target vessels demands intensive long-term surveillance.
Perfusion of target vessels should be regularly assessed in the post f-EVAR patient. Duplex ultra-sound can detail the blood flow velocities as well as early signs of ischaemic nephropathy (i.e. cortex medulla ratio and the kidney length). Interval physiological renal tests might be of value (e.g. calculated glomerular filtration rate-cGFR, serum creatinine-Sr-Cr, and renal scintography).
We believe that fenestrated EVAR can be advocated as a safe procedure with respect to the patency of the target vessels in the hands of experienced operators. While there are potential risks, the absence of graft related mortality in this and other reported series is encouraging and strengthens ones ability to advocate f-EVAR as a valid option for treating high-risk patients. We have demonstrated a small incidence of target vessel complications. Meticulous attention to detail in planning and deployment should keep this to an absolute minimum. Although with experience, the spectrum of patients offered this technique may widen, complex neck anatomy may always remain a barrier.
In conclusion, f-EVAR is a valid and safe treatment option for high-risk patients. The world literature demonstrates a >95% target vessels preservation rate following f-EVAR. Stenting of small fenestration as an integral part of the procedure should improve these results further. f-EVAR mandates modification of pre and post EVAR work-up protocols with more specific investigation of the targeted vessels. The technique incorporated the use of covered stents in a proportion of patients. This requires long-term intensive surveillance. Target vessels stenting appears to be safe, therefore, stenting through scalloped fenestration to the renal arteries is recommended to prevent long-term complications.
References
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- Treatment of short-necked infrarenal aortic aneurysms with fenestrated stent-grafts: short term results. Eur J Vasc Endovasc Surg. 2004;27:477–483
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- . Fenestrated endoluminal grafting: early experience. Aust N Z J Surg. 2004;74:A145–A154
- Fenestrated endovascular grafting: the renal side of the story. J Vasc Surg. 2005;41(2):181–190
- Evaluation of patient selection guidelines for endoluminal AAA repair with the Zenith stent-graft: the Australasian experience. J Endovasc Ther. 2001;8(5):457–464
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PII: S1078-5884(06)00059-1
doi:10.1016/j.ejvs.2006.01.012
© 2006 Elsevier Ltd. All rights reserved.
Volume 32, Issue 2 , Pages 124-128, August 2006
