|HOW I DO IT
|Year : 2014 | Volume
| Issue : 1 | Page : 16-19
How I Do it: Fenestrated Endovascular Aneurysm Repair?
Regional Vascular Unit, Royal Liverpool University Hospital, Liverpool, L7 8XP, United Kingdom
|Date of Web Publication||9-Oct-2014|
S R Vallabhaneni
Regional Vascular Unit, Royal Liverpool University Hospital, Liverpool, L7 8XP
Source of Support: None, Conflict of Interest: None
A proportion of abdominal aortic aneurysms is anatomically unsuitable for endovascular repair using standard stent-grafts, due to the absence of an adequate infrarenal neck. Fenestrated endovascular repair has been developed for use in such patients and has become well-established over the last decade. This article aims to provide an overview of the principles and technique of implanting a fenestrated endovascular aneurysm repair.
Keywords: Endovascular aneurysm repair, fenestrated endovascular aneurysm repair, Juxta-renal aneurysms, para-renal aneurysms, techniques
|How to cite this article:|
Vallabhaneni S R. How I Do it: Fenestrated Endovascular Aneurysm Repair?. Indian J Vasc Endovasc Surg 2014;1:16-9
| Introduction|| |
Endovascular aneurysm repair (EVAR) relies upon availability of disease-free segments of arterial tree above and below the aneurysm to provide seal zones. Standard stent-grafts require a minimum of 10-15 mm of such infrarenal neck for a durable EVAR, although a greater extent of neck is desirable. A proportion of aortic aneurysms do not have an adequate neck,  for whom fenestrated endovascular aneurysm repair (fEVAR) has been developed. Commercially available fenestrated stent-grafts have been in use for more than a decade with extensive literature reporting their results. ,,
A thorough understanding of the principles of durable aneurysm exclusion, engineering aspects of the stent-graft system and an ability to carry out extensive and often difficult endoluminal manipulation are all essential for successful fEVAR. The aim of this article was to provide an overview of COOK® Zenith® Fenestrated stent-graft system (Cook Medical, Bloomington, IN, USA) for juxtarenal and pararenal aneurysms, the most extensively used and evaluated system to date. This article is not meant to be a comprehensive technical or practical manual. Users are expected to be familiar with the manufacturer's instructions for use and follow them. Despite some similarities, branched EVAR for thoracoabdominal aneurysms is different and should be considered separately.
| Patient Selection|| |
In the early years of introduction, patients considered to be at a high risk for open surgery and with anatomy ideally suited were selected for fEVAR. Due to favorable perioperative mortality risk compared to open surgery and increasing confidence in the technique as it stood the test of time, fEVAR is being used increasingly as the choice of treatment in all anatomically suitable patients, irrespective of their fitness.
| Principle of Fenestrated Endovascular Aneurysm Repair|| |
The concept is to utilize the para-renal or visceral segment of aorta for proximal seal zone, while preserving the visceral perfusion via precisely located windows (fenestra [Latin] = window) within the stent-graft fabric. It is usual practice to deploy stents across the fenestrations bridging aortic lumen into the proximal visceral vessels (now called "target vessels") to maintain the orientation of the fenestration permanently and prevent the stent-graft fabric from encroaching on to the target vessel ostium.
Cook® Zenith® fEVAR device (Cook Medical, Bloomington, IN) is of a modular design with the following components in the most common configuration: (a) A proximal main body which is tubular and bears the fenestrations. This has one or two sealing stents and a proximal bare stent with barbs for improved fixation. The diameter of the sealing stents is sized to provide a modest oversize relative to the seal zone, with the lower end coming to 24 mm. Each fenestration is surrounded by four radio-opaque markers and a scallop fenestration by three or four markers. (b) Distal bifurcated main body, is once again of 24 mm in diameter and is deployed with the proximal main body with a minimum of three stent overlap and recreates the bifurcation of the aortic lumen. The ipislateral limb of this component is usually sized to provide the iliac seal and form the lower end of the device on this side. (c) Contralateral limb - is placed into the gate within the distal bifurcation, akin to a standard EVAR. The components are available in a range of diameters and lengths to suit individual anatomy. The components, particularly the proximal main body, has a number of specific features to facilitate the procedure and they are described under the section "Implantation" for ease of demonstrating their relevance.
| Stent-graft Planning|| |
Planning the stent-graft well is the key to success at all stages, starting from implantation, all the way into long-term follow-up. Planning should take into account a number of factors including anatomical factors such as access segments, proximal and distal landing zones, precise anatomic locations of aortic side branches that require preserving, and reducing the modularity of the device. Engineering constraints apply regarding location of fenestrations/side branches, maximum length of fenestration-bearing main bodies and the minimum overlap required between components. Stent-graft configuration of branches should be planned with ease of target vessel cannulation and tracking of target vessel stents in mind. It is necessary to strike a balance between covering extensive segments of aortic anatomy to ensure aneurysm exclusion versus preserving spinal cord blood supply as much as possible. Preservation of internal iliac arteries is recognized to be important in reducing the risk of paraplegia.
In order to choose components from off-the-shelf inventory or to order a custom-made device, in addition to the usual measurements of the aortoiliac anatomy such as aortic and iliac diameters at the seal zones, lengths of aortic, and common iliac segments, precise detail is also required of the location of the target vessel ostia. This is described in terms of longitudinal separation in mm length and clock face location in 15 min intervals. Good quality arterial-phase computed tomography (CT) with a slice thickness of 2.5 mm or thinner is essential for this purpose along with the hardware and skills necessary for image analysis. Attention to detail is essential for good planning. Accessory renal arteries are frequently seen and it is not usually possible to preserve perfusion of small arteries.
| Perioperative Management|| |
Prevention of contrast induced nephropathy is a high priority. In all but patients at low risk, prehydration is undertaken with approximately 100 ml per hour of normal saline for 12 h before the start of the procedure. A bolus of heparin is administered at the beginning and topped-up at intervals, guided by activated-clotting-time monitoring with a target of 290 ± 20 s. Prophylactic antibiotics are used. Paraplegia is a recognized complication and cerebrospinal fluid drainage is considered in high risk patients. We aim to extubate the patient at the end of the procedure, unless a serious metabolic abnormality has developed during the procedure which is better corrected with an intubated patient. Patient is allowed oral intake as soon as possible. All patients are recruited into a structured surveillance program for the rest of their life.
On the morning of the procedure, it is essential to verify that all of stent-graft components, ancillary implantables and consumables are available for the procedure. A review of the anatomy on a three-dimensional workstation before the start of the procedure is also important.
| Access|| |
The procedure starts with transfemoral access, either percutaneously or via surgical exposure, depending upon individual preference and state of the common femoral artery. A 5F pigtail catheter is placed just above the level of the visceral arteries. A stiff guidewire, usually Lunderquist, is placed into the ascending aorta (the nose-cone of a fEVAR device reaches more proximally compared to that of a standard device and the stiff part of the guidewire should be placed with this in mind). The next step is to check the orientation of the proximal main body under fluoroscopy, so that the left and the right renal fenestration markers correspond to their target vessels and anterior and posterior aspects of the device are not confused. The disparity in the level of renal ostia that naturally exist in most of the patients and the marking system of the device assists in this. The device in its constrained state shows a "ü" (right-handed tick) mark, anteriorly placed vertical row of three markers and posteriorly placed horizontal row of three markers. Their movement under fluoroscopy relative to each other aid to confirm correct orientation of the device.
| Introduction of the Proximal Main Body|| |
The proximal main body is then introduced over the Lunderquist wire, ensuring correct orientation, so that the fenestration markers are approximately at the level of the target vessels. Preoperative image analysis on a three-dimensional workstation helps identify bone landmarks of this level. Alternatively, a short angiographic sequence could be acquired. Fluoroscopy in lateral projection with or without angiography will further confirm accuracy of anteroposterior orientation [Figure 1]. Returning to AP projection, after ensuring that the fenestrations markers are orientated both longitudinally (check the relationship of renal ostia with corresponding fenestration markers) and circumferentially (the anterior and posterior markers should overlap forming a perfect "+" and the "ü" mark is profiled), one should commence unsheathing the proximal main body [Figure 2]. When this is completed, the device top bare stent is still within the top-cap and the device is only partially unconstrained due to the presence of "diameter reducing ties" [Figure 3].
|Figure 1: Lateral fluoroscopic projection with the delivery system introduced. A vertical row of three anterior markers (A), a horizontal row of posterior markers (P) and a 'Tick' mark aid anteroposterior orientation of the system. A cluster of markers also show the location of each fenestration and appear crowded when the device is still within the delivery system|
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|Figure 2: Magnified angiographic view in antero-posterior projection. The anterior and posterior markers form a 'cross' like appearance and together with the correctly oriented 'right-hand tick' mark (labelled), confirm accurate circumferential orientation of the stent-graft. The relationship between each renal artery and the upper and lower markers of the corresponding fenestration (shown with pairs of arrows) reassures accuracy of longitudinal positioning of the device|
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|Figure 3: The proximal main body has been unsheathed. At this stage the fixation bare-stent is still within the top cap and the device is still constrained by 'diameter reducing ties'. The renal arteries have been accessed via corresponding fenestrations and are shown with sheaths and target vessels stents in position|
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| Target Vessel Stents|| |
A separate puncture is made in the contralateral common femoral artery and via this access, the proximal main body is cannulated. A 20F sheath is then passed into the proximal main body taking care to avoid cephalad displacement of the proximal main body by the advancing dilator. Through this sheath, using catheters and guidewires, target vessels are cannulated. Once cannulated, suitable guidewires to deliver the target vessel stents, are introduced well into the target vessel. My preference is to use Amplatz Supertiff® with 1 cm floppy tip or Rosen® wire. Appropriately, sized sheaths are then tracked into the target vessel ostia - 7F Flexor® sheaths (Cook Medical, Bloomington, IN) are my favorite due to their soft dilator tips and hydrophilic coating. There is only space for two sheaths at a time within the large sheath and it is reasonable to work from simple moving average (SMA) downward. It is usual for the SMA and the renal arteries to be cannulated and expect the CA orientation to be satisfactory in most four fenestration designs of fEVAR. The sheaths are introduced into the target vessels, dilators removed and the target vessel stents are then tracked. Atrium Advanta® stents are preferred for target vessels.
Accessing target vessels and tracking stents can be the most challenging of the steps, with a potential to test one's technical abilities.
| Completion of the Deployment of the Proximal Main Body|| |
At this stage, as it is reassuring that all the fenestrations have been orientated with their corresponding target vessels, the diameter reducing ties can be removed. The next step is to remove the trigger wire, followed by advancement of the top-cap to release the bare fixation stent. The top-cap is then retrieved. Working from top to bottom, one by one, the target vessel stents are unsheathed, profiled, adjusted for position, deployed, and flared [Figure 4]. Check angiography should be performed for each vessel to verify a satisfactory state-free from rupture, dissection or embolization [Figure 5]. Any complication should be dealt with appropriately.
|Figure 4: All three target vessels have been deployed. Flaring of the right renal stent is shown here|
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|Figure 5: is essential to perform magnified and good quality selective angiography of each target vessel at the completion of target vessel stent insertion to rule out iatrogenic dissection or rupture|
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| Distal Main Body|| |
Distal main body is then introduced and its position verified so that there is adequate overlap between the proximal and distal main bodies. The contralateral limb gate is positioned above the aortic bifurcation and orientated correctly with the bottom end of the ipsilateral limb free from the internal iliac artery. This component is then deployed, followed by completion of the contralateral limb. Modular junctions are then molded with a (Cook Medical, Bloomington, India), ready for completion angiography [Figure 6].
|Figure. 6: Completion angiogram demonstrating patency of all target vessels and aneurysm exclusion|
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Access is then repaired and lower limbs examined for adequate perfusion, concluding the procedure.
| Conclusion|| |
Fenestrated endovascular repair using (Cook Medical, Bloomington, India) platform has been in use for more than a decade. It is increasingly being seen as the choice of treatment in patients of all levels of fitness, although, the advantage of lower perioperative mortality is most marked in patients considered to be at a high risk for conventional surgery. Fenestrated EVAR ranks as one of the most complexes of endoluminal procedures calling for an extensive repertoire of skills and inventory of consumables to achieve satisfactory results.
| References|| |
|1.||Elkouri S, Martelli E, Gloviczki P, McKusick MA, Panneton JM, Andrews JC, et al. Most patients with abdominal aortic aneurysm are not suitable for endovascular repair using currently approved bifurcated stent-grafts. Vasc Endovascular Surg 2004;38:401-12. |
|2.||Marzelle J, Presles E, Becquemin JP, WINDOWS trial participants. Results and Factors Affecting Early Outcome of Fenestrated and/or Branched Stent Grafts for Aortic Aneurysms: A Multicenter Prospective Study. Ann Surg 2014. doi:10.1097/SLA.0000000000000612 (ahead of print). |
|3.||Suominen V, Pimenoff G, Salenius J. Fenestrated and chimney endografts for juxtarenal aneurysms: Early and midterm results. Scand J Surg 2013;102:182-8. |
|4.||British Society for Endovascular Therapy and the Global Collaborators on Advanced Stent-Graft Techniques for Aneurysm Repair (GLOBALSTAR) Registry. Early results of fenestrated endovascular repair of juxtarenal aortic aneurysms in the United Kingdom. Circulation 2012;125:2707-15. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]