Endograft Assessment for EVAR Follow-up

Commentary

Submitted on Wed, 06/02/2010 - 10:39
Authors

Daniel G. Clair, MD


In this issue of Vascular Disease Management, the article “Aneurysm Rupture Following Limb Dissection of a Zenith Stent-Graft” by Houbballah et al points out several important issues regarding placement and long-term follow-up of patients with endovascular grafts used to treat aneurysmal disease. First, it is important to thoroughly understand the “anatomy” of the endovascular graft that you are using. In particular, as it relates to the Cook Zenith graft, it is important to understand the relationships between the overlapping zones of the limb placed in the proximal portion of the body. In the standard bifurcated graft limb, the proximal limb stent of a Cook Zenith graft is 22 mm in length. The overlap zone of the contralateral limb into which this limb is normally inserted is 22 mm as well. Overlapping at least one stent in this region provides a better than 2 cm overlap region for adequate seal during long-term use of the graft. On the ipsilateral side, the stent lengths at the distal aspect of this graft are 14 mm. In order to assure adequate length overlap, it is important to understand that the proximal aspect of the ipsilateral limb, which is 22 mm in length, needs to be placed fully within the ipsilateral stent in order to assure at least 2 cm of overlap of the stent graft proximally and the limb distally. Overlapping simply a single stent of the distal aspect of the ipsilateral limb will allow less than 1.5 cm of overlap and in many situations, this will prove inadequate to maintain long-term success of this junction region. The aortouniiliac device has a distal stent, which is 17 mm in total length. This stent length is different from the ipsilateral limb distal stents and also different from the 22 mm length of the contralateral limb-overlapping zone. The instructions for use with the device recommend a single stent overlap. Because of mismatching lengths between the limbs, it is unclear whether this single stent is meant to relate to the proximal body’s distal stent or the proximal stent on the limb, which is inserted. In this situation, it is likely that more is better and that placement of the graft to include, at the very least, the full 22 mm stent length of the proximal aspect of the inserted limb is necessary for adequate limb overlap and long-term junction seal. For those surgeons and interventionalists placing endografts, it is imperative that a full understanding of the differences between the stent lengths and the overlap zones in differing devices is well understood to assure that long-term success of these devices can be maintained. Second, and probably more important, is the issue of long-term follow-up and assessment of graft status and function in the era of computed tomographic (CT) scan follow-up alone. It is clear from this publication, as well as several other authors’ publications, that follow-up of these endografts with CT scanning alone that does not include three-dimensional (3-D) reconstructions to assess the status of the device and the stents in particular is inadequate to assure success of these grafts. Most 3-D reconstruction systems allow adequate manipulation of the images to provide detailed imaging of the stent and the stent framework of which these endografts are constructed. It is important for individuals following these patients to continue to maintain vigilance regarding the status of the graft and stents as well as the position of each piece of the stent in relationship to other portions of the stent graft itself. If this cannot be adequately assessed with either CT scanning or 3-D reconstructions, then the performance of X-ray imaging to assess these issues is imperative. While the outcome for this patient was successful, had this occurred in a situation where access to care was limited or had the patient not responded quickly enough to receive emergent attention to this problem, the outcome could have been quite different. Congratulations to the authors on pointing out the importance of these issues and long-term follow-up of these patients and for reminding us all that assessment of aneurysm size alone is inadequate as a method of long-term follow-up for patients with aneurysmal disease treated with endografts.

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From the Department of Vascular Surgery, Cleveland Clinic Foundation, Cleveland, Ohio. Disclosure: Dr. Clair discloses the following: board member of Boston Scientific and Medtronic; paid consultant for Cordis, Endologix and Sanofi-Aventis; honoraria from W.L. Gore & Associates. Address for correspondence: Cleveland Clinic Foundation, Vascular Surgery, 9500 Euclid Avenue, Cleveland, OH 44195. E-mail: claird@ccf.org