Stenting for Use in the Treatment of Aortoiliac Occlusive Disease

VASCULAR DISEASE MANAGEMENT 2012;9(2):E20–E26

Abstract

Aortoiliac stenting is the treatment of choice for aortoiliac occlusive disease. After reviewing treatment techniques, research shows that outcomes are similar for balloon expandable and self-expanding stents. Covered stents are now being studied but no published benefit exists over uncovered stenting. Secondary patency of aortoiliac intervention rivals open surgery through 3 years.

The era of endovascular imaging began in 1964 when Charles Dotter first described percutaneous angiography. In 1974, Andreas Gruentzig described the first percutaneous angioplasty. Within the next decade, endovascular treatment of iliac occlusive disease began to gain momentum as patients and radiologists fueled interest. Simultaneously in the 1980s, surgery was considered the gold standard therapy for aortoiliac occlusive disease (AIOD). The well documented long-term outcomes of aortofemoral bypass (AFB) were thought to have solidified the use of surgical therapy as the sole definitive therapy for this disease.¹ Angioplasty of the arterial tree was viewed with skepticism, as evidenced by the lack of publications in this area by surgeons. The first article describing results of iliac angioplasty in the Journal of Vascular Surgery was not published until 1986 and was done by an interventional radiologist.² Twenty-five years later, surgeons embrace the endovascular treatment of AIOD and are actively documenting outcomes. The endovascular treatment of the aortoiliac segment is now the standard of care for Trans-Atlantic Inter-Society Consensus II (TASC II) class A and B lesions.³ Increasing experience and success has led some investigators to extend endovascular treatment to TASC C and D lesions. Aortobifemoral bypass (ABF) is still common for TASC D lesions, but in some practices, it has become a rarely performed operation, relegated to the uncommon patient after failed endovascular therapy.

Evaluation of Disease

Patients with aortoiliac occlusive disease will commonly complain of hip, buttock, or thigh muscle group heaviness, achiness or pain with ambulation or exercise. Leriche syndrome describes the triad of hip or buttock claudication, impotence, and diminished femoral pulses, a hallmark of the patient with aortoiliac occlusive disease. Atheroembolism from unstable plaque can occlude the distal circulation leading to blue toe syndrome. Some patients will present with concomitant distal occlusive disease and will have calf or foot claudication, rest pain, tissue loss, or gangrene depending on the severity of the blockages.

Identification of AOID will be identified in most patients with simple physical exam and pulse palpation. Diminished femoral pulses are noted in many, but some with significant disease may still have femoral pulses at rest. Bruits or thrills over the aortoiliac and femoral vessels are common. Noninvasive imaging should start with segmental limb pressures with plethysmography. High thigh pressures should normally be higher than brachial pressure. In the setting of AIOD the high thigh pressure will be lower and pulse volume recordings will show diminished waveforms. Some patients may have normal ankle pressures that drop only after exercise. Duplex ultrasonography is commonly used to show the level and degree of disease in the iliac and femoral vessels. Limitation of this technology can be poor visualization of the vessels in obese patients and patients with gas-filled intestine. The study quality relies on the skill of the technician obtaining the study.

Computed tomographic angiography (CTA) has recently emerged as a popular noninvasive imaging modality that can show the amount of calcification, areas of stenosis, and occlusions as well as the current collateral circulation. Identification of the amount of occlusive disease in the femoral vessels is critical to improving the success of iliac intervention, as open surgical treatment of femoral vessels improves outcomes. The 2 biggest limitations of CTA are the risk of radiation and intravenous contrast related problems such as allergic response and contrast-induced nephropathy. Diabetic patients have a higher risk of contrast related nephropathy. In patients with impaired creatinine clearance, precontrast hydration with intravenous isotonic solutions can minimize this risk.

Magnetic resonance angiography (MRA) can also be used to image the aortoiliac segment. A limitation of MRA is that it is really a flow study, and low flow situations and previously stented vessels can cause signal drop out, falsely appearing as occlusions.⁴

Treatment Technique

Ipsilateral, contralateral, and brachial access routes can all be used successfully to access aortic and iliac lesions. In the setting of chronic total occlusions (CTO), several techniques can be used to cross the lesion. Spinning a hydrophilic guide wire with catheter or balloon support is the most commonly used method. Use of braided catheters and dedicated crossing catheters (Quick-Cross, Spectranetics) has diminished the need for using angioplasty balloons for support. When attempting to cross an iliac occlusion from an ipsilateral retrograde femoral approach the greatest difficulty comes in re-entry back into the true lumen (Figure 1). Often due to dense calcification at the aortic bifurcation, the catheter and wire will want to pass subintimally up the aorta and will not re-enter the true lumen. In this situation, contralateral retrograde femoral access can be helpful to start a new plane to direct a wire cranially across the occlusion. Once the wire is able to get through the proximal cap and within the subintimal channel, many times the wires will enter the same subintimal plane created from below and allow capture with a snare. This technique of snaring the wire will ensure true lumen to true lumen access above and below the occlusion. In the setting of a flush iliac occlusion with the aortic bifurcation, contralateral access is often unsuccessful in crossing the occlusion due to lack of pushability in the direction of the vessel. In these situations, brachial access is usually successful. By placing a long 5 Fr or 6 Fr sheath to the level of the aortic bifurcation, coupled with an angled catheter and stiff hydrophilic wire most CTOs are easily crossed.

Several options exist when re-entry into the true lumen after crossing a CTO has not occurred. In the patient with concomitant femoral occlusive disease, open distal external iliac and common femoral endarterectomy will allow communication to the true lumen with open retrieval of the wire through the endarterectomized vessel, or snaring of the wire after completion of the vessel patch and accessing through the patch with a sheath. The other method of gaining access back into the true lumen is by use of a re-entry device such as the Outback LTD (Cordis Corporation) or Pioneer catheter (Medtronic Medical).⁵ The Outback device uses angiography in 2 dimensions at orthogonal views to ensure correct aiming towards the flow channel. The technique has been described as locate, tune, and deploy. Once the needle is advanced into the true lumen flow channel, the 0.14” wire can be advanced allowing further treatment of the lesion. The Pioneer device uses Volcano intravascular ultrasound (Volcano Corporation) to locate the true lumen flow channel. The depth of penetration of the needle can be set to allow directed passage into the true lumen allowing a second 0.14″ wire to cross.

Treatment with angioplasty is acceptable, however multiple views may be necessary to ensure flow-limiting dissection does not exist. Pressure measurement across the area of treatment with a vasodilator challenge can unmask residual disease, which may not be apparent on angiography. Intravascular ultrasound has also been used to ensure adequate luminal expansion after interventional therapy. Despite many successful cases with angioplasty, the use of stents has become the most common treatment due to excellent long-term results. Although no outcome difference exists between self-expanding and balloon expandable stents, several engineering differences exist. Self-expanding stents most commonly used today are made out of nitinol and do not foreshorten with placement. They have chronic outward force and are typically oversized 1 mm larger than the reference vessel they are intended to treat. Nitinol self-expanding stents are flexible, making them ideal for external iliac disease.

In the setting of severe calcific disease, nitinol stents may not generate sufficient chronic outward force to achieve expansion of a diseased segment. In this setting, balloon expandable stents have a unique advantage. I prefer to use balloon expandable stents for common iliac disease due to accuracy of placement and the fact that most common iliac ostial disease has a component of calcified aortic plaque. Currently most balloon expandable stents are made from stainless steel and have greater hoop strength to keep a calcified lesion expanded after dilation. More recently work has been done with cobalt chromium and platinum to decrease the strut thickness to lower profile while maintaining visibility. Depending on the cell design, a balloon expandable stent will foreshorten to varying degrees with dilation above the designed diameter for use. The cell design limits the maximum size you can dilate a stent. Most commercially available premounted stents in the U.S. cannot be expanded above 12 mm in diameter.

Due to the limitation of diameter, I use self-expanding large diameter stents for aortic disease. Nitinol self-expanding stents can be very accurately placed but are limited at 14 mm in maximum diameter. However this size is generally adequate to treat occlusive disease to get an adequate hemodynamic result. Only when severe calcific disease is present I will use unmounted giant balloon expandable stents. I reserve the use of covered stents for rupture of the treated vessel. Depending on location, I use balloon expandable covered stents for aortic and common iliac locations and self-expanding covered stents for external iliac locations. Others perform parallel or kissing stents, which in effect raises the bifurcation. The large disadvantage of this approach is that the ability to cross from one femoral artery to the contralateral side is eliminated. This can make treatment of infrainguinal disease more difficult in future encounters. A hybrid technique of crossing the struts of a self-expanding stent placed from the aorta to one iliac artery by a balloon expandable stent from the contralateral side has been described as an alternative to the classic kissing stent technique.⁶ Aortic lumen dead space around the kissing stent has also been suggested as a risk factor for late failure for kissing stents.⁷ No study examines the long-term difference in outcome for the approach of recreating or raising the aortic bifurcation with kissing stents.

For flush aortic occlusions, the use of thrombolysis from a brachial approach can allow dissolution of chronic thrombus and allow successful endovascular treatment (Figures 2A and 2B). Typically, a catheter is used to cross into one iliac artery to the open vessel distally. Subintimal passage of the wire should be avoided. Thrombolysis is then initiated. After establishing flow into the aorta and one iliac artery, the catheter can be repositioned to the opposite iliac artery. After dissolution of the clot, endovascular treatment with stenting of residual disease is performed (Figures 3A and 3B).

Treatment Outcomes

The treatment of aortoiliac occlusive disease began with angioplasty. Some studies have found efficacy in up to 70% of cases although patients with longer lesions such as TASC type C and D lesions and patients with chronic renal failure tended to do worse and have been considered indications for primary stenting.⁸ 

Suboptimal expansion due to elastic recoil and or severe calcific disease remained a significant limitation angioplasty. The introduction of the Palmaz balloon expandable stent (Cordis) significantly altered the interventional landscape providing an option to achieve success when angioplasty alone did not have optimal results and led to approval of the P308 stent for iliac use in 1991.^9,10 Improved outcomes as compared to balloon angioplasty were confirmed by several other authors.1^1-15

The first premounted balloon expandable stent in the U.S. for iliac use was the AVE Bridge stent (Medtronic). In the Medtronic AVE Flexible Iliac Bridge Stent study, authors found primary patency was 94.1% at 30 days and was 82.7% at 6 months.¹⁶ Subsequent development by other companies has increased the number of balloon expandable stents approved for iliac use. In the MELODIE trial, Stockx reported the 2-year safety and effectiveness of the Express LD stent for atherosclerotic iliac artery disease.¹⁷ The authors reported 6-month angiographic outcomes of 151 patients compared to an objective performance criterion (OPC) based on published results with the Palmaz stent. The 6-month mean percent luminal diameter loss was 16.2% (upper 95% confidence boundary of 19.1%) and non-inferior to the 20% OPC (P=0.006). Primary patency was 92.1% at 6 months and 87.8% at 2 years.

Despite improved results in single-center series the randomized Dutch Iliac Stent Trial failed to show improved outcomes of primary stenting over selective stenting. In cases where the residual mean pressure gradient was greater than 10 mmHg across the treated site, 279 patients with iliac artery disease were randomly assigned to undergo primary stent placement or percutaneous transluminal angioplasty with selective stent placement. Patients who underwent PTA and selective stent placement had better improvement of symptoms (HR, 0.8; 95% CIs: 0.6, 1.0) than did patients treated with primary stent placement, whereas ABI (HR, 0.9; 95% CIs: 0.7, 1.3), iliac patency (HR, 1.3; 95% CIs: 0.8, 2.1), and score for quality of life for 9 survey dimensions did not support a difference between treatment groups.¹⁸

Self-Expanding Stents

In addition to balloon expandable stents used in the iliac arteries, self-expanding stents have achieved similar outcomes and approval for use. The Wallstent (Boston Scientific) was the first self-expanding stent to achieve approval for iliac use in the U.S., occurring in 1996. Martin reported the 2-year results of the FDA phase II, multicenter trial of the Wallstent in the iliac and femoral arteries.19 Stents were placed in the iliac system in 140 patients with a 6-month angiographic patency of 93%. Primary clinical patency was 81% at 1 year and 71% at 2 years. The secondary clinical patency was 91% at 1 year and 86% at 2 years. One of the first self-expanding nitinol stents to be used was the Strecker stent (Boston Scientific). A report on 64 iliac arteries treated with this stent showed a primary patency rate of 84% at 1 year and 69% at 2 years, and a secondary patency rate of 90% at 1 year and 81% at 2 years.20 The Smart Stent (Cordis) was the first nitinol stent to achieve iliac artery approval. In the Cordis Randomized Iliac Stent Project-US (CRISP-US) trial, investigators evaluated the SMART stent vs Wallstent for iliac artery disease after suboptimal percutaneous transluminal angioplasty (PTA). The 9-month composite end point rate was equivalent for the SMART stent and Wallstent (6.9% vs 5.9%), with low rates of restenosis (3.5% vs 2.7%), death (2.0% vs 0.0%), and revascularization (2.0% vs 4.0%) in the 2 groups. Primary patency at 12 months was 94.7% with the SMART stent and 91.1% with the Wallstent.²¹

The Zilver stent (Cook Medical) was the most recent nitinol stent to gain iliac approval. Jaff reported the 2-year outcomes of safety and effectiveness in the iliac artery with patency and ABI measurements showing improvement at 2 years as compared with preprocedure measurements. Kaplan-Meier estimate of overall patency at 2 years was 90% (n=117).²²

Iliac Stenting Outcomes

Single-center studies on iliac stenting have also shown good results with interventional therapy. Most of these series do not describe what types of stents were used. In 1998 Sullivan reported on 288 patients who underwent PTA and primary stenting of the common iliac (354, 69.4%) and external iliac (156, 30.6%) arteries and found cumulative patency rates of 84%, 76%, and 57% on the basis of TBI, ABI, and clinical limb status at 24 months.²³ In 2004 Murphy reported on 365 patients treated between 1992 and March 2001.²⁴ Eight years after stent placement, primary patency was 74%; primary assisted patency, 81%; and secondary patency, 84%. Variables associated with better patency included stenosis (rather than occlusion), shorter lesion length, older age, and limb-threatening ischemia.

Increased confidence in outcomes treating short occlusions and long stenoses with stents led physicians to treat more difficult lesions with interventional therapy. Ko et al reported on 151 consecutive patients with long (>5 cm) iliac artery lesions who underwent angioplasty with primary stent implantation from October 2004 through July 2008 with a subintimal vs intraluminal technique. The technical success rate of SA was lower than that of IA (93.0% vs 99.0%; P=.048). There was no difference in primary patency rates for either technique. Patency for SA and IA was 96.8% and 98.0% at 1 year, and 93.9% and 90.6% at 2 years, respectively (log rank P=.656).²⁵ Leville and colleagues reported on outcomes with angioplasty and stenting based on 89 patients with aortoiliac TASC-I B, C, and D lesions.²⁶ A technical success rate of 91% was noted. The authors stressed the importance of concomitant treatment of femoral occlusive disease, as evidenced by performing femoral endarterectomy in 24% of patients. The mean ankle-brachial index increased from 0.45 to 0.83. Three-year primary patency, secondary patency, and limb salvage rates were 76%, 90%, and 97%, respectively. Multiple access sites (including brachial artery) were used in the majority of patients to achieve lesion recanalization. Diabetes and critical limb ischemia (CLI) were associated with decreased patency but TASC classification did not significantly alter patency rates.

A more recent study over a 12-year period ending in 2009 evaluated endovascular treatments with primary stent placement for 533 lesions in 413 consecutive patients with iliac artery occlusive disease.²⁷ The authors treated TASC-II type A lesions in 134 patients (32%), type B in 154 patients (37%), type C in 64 patients (16%), and type D in 61 patients (15%) with a median follow-up of 72 months. Technical success rates were 99% regardless of TASC category. Cumulative primary patency rates at 1, 3, 5, and 10 years were 90%, 88%, 83%, and 71% in TASC-II C/D and 95%, 91%, 88%, and 83% in TASC-II A/B, respectively. In multivariate analysis, lesion length was an independent risk factor for in-stent restenosis (HR, 1.12, P=.03; 95% CI, 1.01-1.24).

A recent study from 2011 compared the results of iliac stenting for stenotic lesions vs occlusive lesions and found no difference in outcomes despite having a higher percentage of CLI in the occlusion group.²⁸ Over a 10-year period, the authors compared outcomes for 109 patients with occlusions vs 114 patients with stenosis. At 60 months, primary patency in occlusion group vs stenosis group was 82.4% vs 77.7% (P=.9), assisted primary patency was 90.6% vs 85.5% (P=.4), and estimated secondary patency was 93.1% vs 92.8% (P=.3).

Primary stent placement for localized distal aortic occlusive disease has also been examined. In a study by Simons et al, primary clinical patency was 68%, primary aortic hemodynamic patency was 83%, and secondary aortic hemodynamic patency was 100%, at 3 years.²⁹

Despite increasing documentation of good results in complex lesions, many surgeons still feel surgery with aortofemoral bypass is more appropriate. In order to address this criticism, Kashyap reported a retrospective study comparing the outcomes of aortoiliac stenting vs ABF bypass for severe AIOD.³⁰ The authors noted limb-based primary patency at 3 years was significantly higher for ABF than for stenting (93% vs 74%, P=.002). However, secondary patency rates (97% vs 95%), limb salvage (98% vs 98%), and long-term survival (80% vs 80%) were similar. Diabetes mellitus and the requirement of distal bypass were associated with decreased patency (P<.001). Other publications assessed the durability of endovascular aortoiliac interventions against surgery. In a large single institutional experience over 10 years, Burke et al found no difference in 30-day mortality (0.8% AFB vs 1.1% stenting).³¹ Aortobifemoral bypass was associated with increased surgical complications but had a larger difference between pre-procedure and post-procedure ABI than stenting (R, 0.39 and 0.18, P<0.001; L, 0.41 and 0.15, P<0.001). This difference was maintained when patients were stratified by TASC category. In a similar study, Timaran et al evaluated the influence of risk factors on outcome of iliac stenting and operative procedures used to treat TASC type B and type C lesions.³² Over the 5 years from 1996 to 2001, 188 endovascular and aortoiliac operations were performed on TASC type B and type C iliac lesions in patients with chronic limb ischemia. Surgical patients (n=52) had significantly higher primary patency rates compared with stented patients (n=136) at univariate analysis. Primary patency rates were 85% at 1 year, 72% at 3 years, and 64% at 5 years after iliac stenting, 89% at 1 year, 86% at 3 years, and 86% at 5 years after surgical reconstruction. Univariate and multivariate Cox regression analysis enabled identification of poor runoff as the only independent predictor of decreased primary patency in all patients. External iliac artery disease and female gender were also identified as independent predictors of decreased primary stent patency. These results show the improved primary patency of surgery although at a higher morbidity, but iliac stenting can obtain equivalent secondary patency in some hands.

Aortic Occlusions and Thrombolysis

The idea of using thrombolysis to treat infrarenal aortic and iliac occlusions is not new. Iyer et al in 1991 described using the brachial approach for recanalizing an abdominal aortic occlusion and using thrombolysis and balloon angioplasty of the aortoiliac bifurcation. Despite the technique being described over 20 years ago, it is still viewed with skepticism. Moise et al from the Cleveland Clinic reported on treatment of chronic infrarenal aortic occlusion in 2009.³³ Thirty-one patients underwent attempted recanalization of chronic aortic and iliac arteries with a 93% technical success rate and no mortality. Thrombolysis was used in 29%, with 3 significant complications, 1 iliac artery rupture treated with a covered stent and 2 occlusions requiring intervention. Postoperative ankle-brachial indexes increased significantly from preoperative values (P<0.0001). At 1 and 3 years, the primary and secondary patency rates were 85%/100% and 66%/90%, respectively. Sixteen percent of patients experienced renal dysfunction, which was felt to be most likely due to embolism during thrombolysis into the renal arteries. The criticism of this study was the high risk of renal dysfunction and the question of whether aortobifemoral bypass would have been more appropriate. The management of aortic occlusion at the Cleveland Clinic continues to use thrombolysis for flush aortic occlusions but we have found that angioplasty to create a flow channel at initiation of thrombolysis diminishes the occurrence of renal dysfunction due to embolism.

Kim et al reported a larger series of endovascular treatment of aortic occlusion in 49 patients over 14 years with or without the use of thrombolysis.34 They achieved a slightly lower technical success rate of 81.6%, with major complications occurring in 16.3%. In patients treated successfully, the primary patency rate was 88.4% at 1 year and 80.1% at 3 years. The major amputation rate was 0%. Seven patients (17.5%) required repeat intervention (n=5) or bypass surgery (n=2) during the follow-up period.

A recent meta-analysis identified 19 studies reporting on the endovascular treatment of extensive AIOD (TASC type C and D) in 1711 patients from January 2000 to June 2009.³⁵ The authors noted technical success was achieved in 86% to 100% of the patients, with clinical symptoms improving in 83% to 100%. Mortality was low in the 7 studies where it was documented, ranging from 1.2% to 6.7%. Impressive durability was noted with 4- or 5-year primary and secondary patency rates ranging from 60% to 86% and 80% to 98%, respectively. Another meta-analysis of 958 patients from 16 articles over a 10-year period ending in January 2010 with TASC C and D aortoiliac lesions found 5-year primary and secondary patency rates of 64% and 81%.³⁶

Covered Stents

Intimal hyperplasia has been the major etiology of failure within stents. The development of covered stents has fueled interest in studying the possibility of eliminating this problem. Bosiers and colleagues studied polytetrafluoroethylene (PTFE) covered balloon expandable stents in 65 patients with iliac artery stenoses and occlusions and found a primary limb patency of 91.1% at 1 year.³⁷ Sabri et al reviewed outcomes of balloon-expandable covered iliac kissing stents as compared with bare metal stents in the treatment of atherosclerotic disease at the aortic bifurcation. They found improved primary patency of 92% at both 1 and 2 years for covered vs 78% after 1 year and 62% after 2 years for uncovered stents.³⁸ Giles noted the off-label use of the Atrium ICast balloon-mounted polytetrafluoroethylene-covered stent for in-stent restenosis, aneurysmal disease, and vessel rupture to be successful.³⁹ For the 38 iliac artery stents used in their series, primary patency was 97% at 6 months and 84% at 12 months with an assisted primary patency of 100% at 12 months. Stents placed for recurrent in-stent restenosis (n=16; 10 were renal lesions) had a primary patency of 85%, assisted primary patency of 93%, and a 15% restenosis rate at 12 months.

The ultimate role for covered stents has yet to be answered. In the U.S., the Viabahn (W.L. Gore & Associates) has an approved iliac artery indication, but has not been independently studied in this area. Atrium has completed a clinical trial using the ICast stent in iliac artery occlusions in order to gain FDA approval of safety and efficacy, but has not reported the study outcomes.

Conclusion

Aortoiliac stenting has emerged as the treatment of choice for short occlusions and stenoses of the aorta and iliac arteries. No documented difference exists in outcomes between balloon expandable or self-expanding stents in treating iliac arteries. In experienced hands, treatment of long occlusions and severe multisegment disease achieves secondary patency equivalent to ABF bypass at 2 years with a lower morbidity and mortality. The long-term durability still favors ABF bypass, but if interventional therapy is performed without burning surgical bridges then interventional therapy will continue to grow in usage. For patients with aortic occlusions, the use of thrombolysis makes interventional therapy possible, albeit with higher risks of renal related problems. The creation of a flow channel during thrombolysis may diminish this risk. Recurrent in-stent stenosis due to intimal hyperplasia is an unsolved problem. The use of covered stents to improve primary patency and eliminate intimal hyperplasia is being researched, but the efficacy of this treatment remains unanswered.

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From the Vascular Surgery Desk, Cleveland Clinic, Cleveland, Ohio.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr. Lyden reports board membership for Medtronic Medical; consultancy for Cook, Medtronic, Terumo, Cordis, and Covidien; grants for the Cleveland Clinic from Cordis, Gore, Trivascular, Cook, Medtronic, and Medrad.
Manuscript submitted September 10, 2011, provisional acceptance given September 19, 2011, final version accepted November 29, 2011.
Address for correspondence: Sean P. Lyden, MD, Cleveland Clinic, Vascular Surgery Desk H32, 9500 Euclid Avenue, Cleveland, Ohio 44147, USA. Email: lydens@ccf.org