The GORE® VIABAHN® Endoprosthesis (W. L. Gore & Associates, Flagstaff, AZ) was approved by the FDA for the superficial femoral and popliteal artery application in June 2005. This device, previously known as Hemobahn, has been in use in Europe since 1996. The results of the international trial study group reported by Lammer et al1 showed a 1-year patency rate of 91% for iliac and 79% for the superficial femoral arteries (SFAs). The 1-year patency of the multicenter randomized postmarket approval study, conducted in the United States, was superior to percutaneous transluminal angioplasty but much lower at 65%.2 The published articles both in Europe and the United States have shown a wide range of results, from 49% at 6 months by Deutschman et al3 and 58% at 1 year by Bray et al4 to several reports of patency rates between 78% to 82%.5-7

Although study endpoints and patient populations were diverse, this variability in clinical study outcomes in several independent studies is in need of scrutiny. Several technical considerations to optimize outcomes for the GORE® VIABAHN® Device in the SFA have been identified over the years, including avoiding oversizing, treating all of the disease, and prescribing appropriate antiplatelet therapies (please see the Top 10 Technical Considerations in Using the GORE® VIABAHN® Device sidebar on page 4.) One of the significant controversies that remains is the treatment of collateral arteries. In reviewing 18 articles published from 2000 to 2010, 10 authors have no concern and made no comment as to treatment of the collateral arteries. Four authors recommended not covering the collateral arteries distal to the occlusion at any cost and suggested treatment with baremetal stents and cryoplasty.3,8-10 The others believe that it is more important to cover the entire diseased area even if the collateral arteries have to be sacrificed. 11-13

BIOLOGY OF COLLATERAL VESSELS

The body provides a natural system of preexisting collateral arteries. These vessels can dramatically increase their lumen size to provide enhanced perfusion to ischemic regions. This process is termed arteriogenesis.14 During this process, the collateral artery's diameter can increase up to 20-fold and restore circulation up to 30% in coronary arteries and 50% in peripheral arteries.15 Also, during arterial occlusion, there is a steep gradient causing shear force, which in turn stimulates the vascular endothelial growth factor that can cause collateral growth (Figure 1). This should not be mistaken for angiogenesis, which is the sprouting of capillaries that results in a capillary network. These capillary tubes lack vascular smooth muscle cells and are not surrounded by mural cells; therefore, they are fragile and prone to rupture.

THE COMPETITIVE FLOW CONCEPT

Although they can help to improve limb function in patients with peripheral artery disease, collateral arteries have a negative impact on parallel vessels, functioning as a competitive flow. The competitive flow occurs through the collateral arteries to perfuse the tissue distal to a graft or an artery compromised by a critical stenosis. Therefore, this competitive flow may lead to thrombosis when the flow velocity of the collateral arteries exceeds the velocity of the artery or graft. The hypothesis is that a lack of competitive flow prolongs the patency of an intraluminal stent graft in the SFA. This fact is well known in the coronary circulation in extraluminal coronary bypass grafts16 but has not been explored in the peripheral arteries.

STUDY DESIGN

To evaluate this hypothesis, we arranged a comparative study of 60 patients with long diffuse SFA disease treated with covered stents in two groups reflecting our shift in treatment strategy from early in our use of stent grafts. In group 1, the patients (treated early in our use of stent grafts) with distal collateral arteries reconstituting the distal run-off were not covered. In group 2, patients included those who were treated more recently in which the distal collaterals were covered. The study was limited to patients who primarily had long-segment SFA disease, mostly from the origin down to the adductor canal. The lower two-thirds of the popliteal arteries were spared even if they had mild stenosis of < 50%. The proximal device was extended to the origin of the SFA unless the proximal portion of the SFA was free of disease.

DEMOGRAPHICS AND MEDICAL HISTORY

Despite the differing time period of treatment between the groups, there was no significant change in demographics. There were more men in group 2 (25 in group 2 vs 12 in group 1). Also, there were 18 claudications and 12 incidents of critical limb ischemia (CLI) in group 1 whereas there were 24 and six in group 2, respectively.

Of the patients in group 1, 33% were diabetics—in group 2, 46%. Furthermore, 50% of patients had coronary artery disease in group 1 versus 77% in group 2; 73% of the patients were smokers at the time of treatment in group 1 whereas only 54% were smokers at the time of treatment in group 2. The patients were 38 to 88 years of age, with a median age of 68 years in group 1; however, they were 51 to 91 years of age in group 2, with a median of 71. Total occlusion was seen in 73% of group 1 and 63% in group 2. Calcification was seen in 46% of group 1 and 63% in group 2.

There were de novo lesions in 50% of group 1 and 40% of group 2. The length of occlusions ranged from 7 to 40 cm, and the median for group 1 was 21 cm and 24 cm in group 2. Patent distal arteries ranged from zero to three, with a median of two in both groups (Tables 1 and 2).

PROCEDURE

All patients had arterial duplex sonography and resting ankle-brachial indexes assessed before treatment and complete diagnostic angiography at the time of treatment. A contralateral transfemoral approach was used in all patients. The total occlusions were recanalized with a Quick-Cross catheter (Spectranetics Corporation, Colorado Springs, CO) or a similar catheter with a Glidewire device (Terumo Interventional Systems, Inc., Somerset, NJ). An Outback re-entry device (Cordis Corporation, Bridgewater, NJ) was used in cases with extraluminal passage of the wire. Approximately 53% of the patients in group 1 and 57% in group 2 underwent excisional atherectomy for debulking prior to balloon dilatation. All patients underwent balloon dilatation with a 5- or 6-mm balloon catheter matching the reference vessel size. Further, 60% of the patients had a 5-mm SFA that was consequently dilated with a 5-mm balloon catheter and stented with a 5-mm GORE® VIABAHN® Device.

A total of 52 stents were used in group 1 and 63 in group 2. Ninety percent of the patients had GORE® VIABAHN® Devices extended up to the origin of the SFA. The segment to be treated was predetermined and was not deviated from. No atherectomy or percutaneous transluminal angioplasty was performed outside of the predetermined segment. The GORE® VIABAHN® Device was extended 1 cm below the predetermined segment to ensure that no treated segment was left uncovered. Mild stenosis of the popliteal artery (< 50%) was not treated (Table 3). In CLI cases, angioplasty and/or stenting of the infrapopliteal arteries was performed after implantation of the GORE® VIABAHN® Device. During the procedures, heparin was used to maintain an activated clotting time of 250 seconds, and postoperatively, all patients were treated with 80 to 350 mg of aspirin daily along with 75 mg of clopidogrel.

Any patient who was on warfarin for other reasons prior to the procedure was kept on this medication in addition to aspirin and clopidogrel. Patients were followed at our office at 6 weeks and 6 months postprocedure, then at 6-month intervals. Patients with CLI were seen every 3 months until their ulcers were healed. At each visit, complete arterial duplex sonography and assessment of resting ankle-brachial indexes were performed before physical examination. All of the patients in both groups have completed a 2-year follow-up evaluation. None of the patients were lost to follow-up or died.

RESULTS

The primary success rate was 100% in both groups for diffuse stenoses, as well as total occlusions. No significant complications were encountered, including no incidence of acute limb ischemia. There were three small hematomas and ecchymosis at the puncture sites in each group. No distal embolization was seen, but there were tiny visible pieces of atheroma captured by distal protection devices in the majority of the atherectomy cases. Distal protection devices were used in every single case that employed atherectomy. There were four graft thromboses in group 1 and two in group 2 within the first 6 months, with a patency rate of 86% in group 1 and 93% in group 2. At 12, 18, and 24 months, the patency rate was 66%, 60%, and 57% in group 1, respectively, versus 86%, 83%, and 80% in group 2, respectively.

Although at 6 months there was no significant statistical difference between group 1 and 2, as time elapsed, the difference between the patency rates of the two groups widened (Table 4). All thrombosed endoluminal grafts were successfully rescued by thrombolysis using an EkoSonic endovascular system (Ekos Corporation, Bothell, WA) and tissue plasminogen activator. The underlying cause of thrombosis was generally related to distal edge stenosis, which was often treated using a short GORE® VIABAHN® Device. Proximal edge stenosis was rarely seen, likely due to our liberal treatment of the proximal SFA.

Based on these very promising results, the following are our recommendations for improving the patency rate of endoluminal grafting (Figures 2 through 7):

  • Debulk the diseased SFA segment.
  • Avoid percutaneous transluminal angioplasty of the popliteal artery.
  • Cover the immediate collateral arteries to eliminate competitive flow.
  • Do not leave any treated segment uncovered.
  • Extend the GORE® VIABAHN® Device to the origin of the SFA if any disease is present.
  • Do not oversize the grafts.

In addition to these techniques, the latest device configuration with the heparin bioactive surface may have contributed to the excellent patency results in group 2. Also, coverage of collateral vessels may correlate strongly with more liberal treatment of diseased arterial segments. Further study is warranted to quantify the relative effects of those factors. Nevertheless, it appears that the latest GORE® VIABAHN® Device and the current treatment algorithm employed at our institution, including coverage of distal collateral vessels, can lead to excellent patency results.

CONCLUSION

The GORE® VIABAHN® Device is suitable for percutaneous endoluminal implantation in long-segment diffuse stenoses and total occlusion of the SFA and has been shown to be as effective as surgical femoropopliteal above-the-knee synthetic grafts.10 In properly selected cases and with improved techniques, a patency rate of 80% out to 5 years is well within reach.

Amir Motarjeme, MD, is Medical Director of Midwest Vascular Institute in Downers Grove, Illinois. He has disclosed that he is a paid speaker and consultant for Gore & Associates. Dr. Motarjeme may be reached at midwestvascular@aol.com.

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