Sponsored by Gore & Associates
Technical Considerations for Achieving Success With the GORE® VIABAHN® Endoprosthesis
Thought leaders in the field weigh in on the key aspects of this device at the GORE® VIABAHN® Endoprosthesis Forum.
The following is a summary of a panel discussion that was held on October 9–11, 2011, at the GORE® VIABAHN® Endoprosthesis Forum in Scottsdale, Arizona. Participants included Frank R. Arko, MD; Jean Bismuth, MD; Lawrence Hofmann, MD; John R. Laird, MD; Amir Motarjeme, MD; Constantino S. Peña, MD; Richard R. Saxon, MD; Darren B. Schneider, MD; Michael B. Silva, MD; Peter A. Soukas, MD; and Barry S. Weinstock, MD.
The GORE® VIABAHN® Endoprosthesis With Heparin Bioactive Surface (W. L. Gore & Associates, Flagstaff, AZ), which consists of a nitinol frame lined with expanded polytetrafluoroethylene (ePTFE), received US Food and Drug Administration (FDA) approval for use in treating occlusive superficial femoral artery (SFA) disease in 2005. It remains one of the only FDA-approved stent grafts for this endovascular application. The newest generation of the GORE® VIABAHN® Device has a lower- profile delivery system (6 F for 5- and 6-mm devices and 7 F for 7- and 8-mm devices, delivered over a 0.018- or 0.014-inch guidewire), a scalloped (contoured) edge at the proximal end, and a heparin-bonded surface.
In several randomized studies and large, multicenter series, the GORE® VIABAHN® Device has provided good patency and limb salvage results in patients with SFA disease of various degrees of severity, including TransAtlantic Inter-Society Consensus (TASC II) C and D lesions. Moreover, any restenosis that does occur is generally located at the edges of the device (“edge stenosis”) rather than within it. In-stent restenosis of a GORE® VIABAHN® Device has rarely been reported, which is probably because the ePTFE lining provides a barrier from tissue ingrowth into the lumen. Other reported advantages of the stent graft include a high degree of flexibility, a very low rate of stent fracture, and efficacy in the treatment of long-segment disease.
The GORE® VIABAHN® Endoprosthesis Forum was convened to bring together 11 highly experienced practitioners of peripheral artery disease treatment, including use of the GORE® VIABAHN® Device, for 3 days of presentations, discussion, and brief, anonymous surveys pertaining to the physicians' current practices and opinions. The goal of the forum was to identify the specific technical aspects of device implantation that optimize patient outcomes. Of the many issues discussed, three were identified as being the most important: avoiding device oversizing, covering the entire diseased vessel segment, and prescribing adequate postprocedure antiplatelet therapy. Techniques for achieving thrombolysis in a GORE® VIABAHN® Device were also presented. Please see the Top 10 Technical Considerations in Using the GORE® VIABAHN® Device sidebar for a summary of the views of the participants who participated in the forum.
The GORE® VIABAHN® Device is indicated for use in patients in whom the reference SFA diameter ranges from 4 to 7.5 mm. The device is available in various length, width, and delivery-profile configurations, including diameters of 5, 6, 7, and 8 mm and profiles of 6, 7, and 8 F. The recommended device diameters are 5 mm for vessels with a diameter of 4 to 4.7, 6 mm for 4.8- to 5.5-mm vessels, 7 mm for 5.6- to 6.5-mm vessels, and 8 mm for 6.6- to 7.5-mm vessels.
Both clinical experience and the findings of formal studies, including the recently completed VIPER trial,1 show that following these sizing recommendations (ie, using a GORE® VIABAHN® Device with a diameter that is sized appropriately for the patient's SFA) can lead to optimal long-term patency of the stent graft. There should never be more than a 20% difference between the luminal diameter of the vessel at the ends of the device and that of the stent graft. A difference of no more than 10% may provide the best results.
The primary mode for failure of stent grafts is focal edge stenosis,2 although the mechanism of this failure in cases of oversizing is not known. One possibility is that placement of the stent graft and subsequent balloon dilation may cause injury to the arterial wall that induces intimal hyperplasia adjacent to the prosthesis. Another possibility is the mismatched sizing of the stent graft. The mismatched diameters may also result in a turbulent flow pattern at the edge of the graft, which may trigger either thrombus accumulation or intimal hyperplasia. Finally, it is possible that if the stent graft is not able to fully expand and appose the vessel wall, thrombus may collect in the resulting gaps and folds in the ePTFE graft material.
However, oversizing a GORE® VIABAHN® Device is not uncommon, especially among new users of the device. Some clinicians may oversize because they believe that smaller-diameter SFA stent grafts are more likely to occlude, as was indicated by the results of a clinical series reported by Saxon et al in 2007.3 Others may not use an accurate method for estimating the diameter of the SFA, perhaps because their institution lacks the necessary imaging equipment or expertise. Finally, there may be an overriding perception that most SFAs have a diameter of 5 to 6 mm, which may not be the case in patients with heavily diseased vessels.
Intravascular ultrasound and quantitative angiography are commonly used to determine vessel size. Intravascular ultrasound can be used at the distal and proximal landing zones to visualize and measure the vessel cross-section. With quantitative angiography, the landing zone diameter can be estimated using a calibrated intravascular catheter or guidewire or with an external radiographic ruler as a size reference. In addition, in-vessel inflation of an angioplasty balloon to its nominal diameter represents a size reference that can provide a rough determination of vessel size. It is essential to keep in mind that the smaller the vessel, the greater the importance of accurate sizing and that the GORE® VIABAHN® Device should not be used in an SFA with a luminal diameter of < 4 mm.
Most of the published experience with the GORE® VIABAHN® Device so far has been with previous generations of the device, which did not have a heparin surface, contoured proximal end, or 6-F delivery profile. The recently completed VIPER study, in which the GORE® VIABAHN® Devices used did have a heparin surface, found that 1-year primary patency outcomes were significantly better when appropriate sizing at the landing zones was achieved, even in patients with extensive vessel disease.1,4 The VIPER study also showed that outcomes with 5-mm GORE® VIABAHN® Devices can be similar to those with 6-mm devices (possibly because of the new heparin surface), thereby permitting successful treatment of 4- to 4.7-mm-diameter vessels.
TREAT ALL DISEASE
Treating the full extent of disease in the SFA is also important in achieving optimal results with the GORE® VIABAHN® Device. Leaving significant uncovered atherosclerotic plaque adjacent to the device allows disease progression that may limit flow and lead to patient symptoms or device failure. However, there has been some speculation about whether it is harmful to cover collateral vessels with the stent graft.
When stent grafts were first introduced for use in the SFA, some clinicians assumed that collateral vessels may mitigate the risk of limb-threatening ischemia by providing flow if a stent graft occludes suddenly and that such vessels should therefore always be preserved. However, occlusion of GORE® VIABAHN® Devices has not been associated with a higher rate of acute limb ischemia than occlusion of bare-metal stents, which have fenestrations that, theoretically, would allow flow to continue through collateral vessels during occlusion. 4
In addition, investigators have noted re-recruitment of collateral vessels during progression of disease at the edge of a stent graft.5 Moreover, preservation of a distal collateral often results in not covering all of the disease adjacent to that collateral, thus allowing progression of disease and increasing the risk for loss of patency. Therefore, the best practice is to preserve collateral vessels whenever possible but to not refrain from covering them in cases in which all existing lesions would not otherwise be treated. Completely covering disease in the proximal SFA is especially important, and the GORE® VIABAHN® Device can be accurately placed flush with the origin of the SFA when the vessel has been properly prepared by predilation or debulking. The profunda femoris artery, which is essential to the lower limb circulation, should never be covered by a stent graft.
PRESCRIBE ADEQUATE POSTPROCEDURE ANTIPLATELET THERAPY
Patients who have undergone placement of a GORE® VIABAHN® Device (either heparin-bonded or non–heparin- bonded) should, if they can tolerate it, take aspirin for the rest of their lives. Concomitant administration of clopidogrel (Plavix, Bristol-Myers Squibb/Sanofi Pharmaceuticals Partnership, New York, NY) for at least 3 to 12 months is highly recommended, and a number of physicians who have reported excellent results with the GORE® VIABAHN® Device have used this approach. This is consistent with the CASPAR study, in which dual-antiplatelet therapy provided a distinct benefit in patients who underwent synthetic bypass graft implantation. 6 However, for at least 3 to 12 months, adverse effects (particularly bleeding), may limit the use of clopidogrel in some patients. In addition, patients with no or inadequate health insurance may not be able to take clopidogrel because they cannot afford to pay for it. Fortunately, this may change as the US patent for Plavix expired in 2012.
- Saxon RR. The VIPER trial. Endovasc Today. 2010;9:66-67.
- Interim 1-year VIBRANT results presented for Gore Viabahn in SFA treatment. Endovascular Today website. http://bmctoday.net/evtoday/2009/10/article.asp?f=eNews102909_05.htm. Published October 22, 2009. Accessed May 23, 2011.
- Saxon RR, Coffman JM, Gooding JM, Ponec DJ. Long-term patency and clinical outcome of the Viabahn stent-graft for femoropopliteal artery obstructions. J Vasc Interv Radiol. 2007;18:1341-1349.
- Saxon RR. VIPER 1-year results in long SFA lesions. Presented at: VIVA 2011: Vascular Interventional Advances (Late-Breaking Clinical Trials); October 18–21, 2011; Las Vegas, NV.
- Wixon CL. Debunking the myth of failed lower-extremity endoprostheses. Endovasc Today. 2007;(Feb suppl):13-16.
- Belch JJ, Dormandy J, CASPAR Writing Committee, et al. Results of the randomized, placebo-controlled clopidogrel and acetylsalicylic acid in bypass surgery for peripheral arterial disease (CASPAR) trial. J Vasc Surg. 2010;52:825-833.