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IBDs offer an endovascular solution to aortoiliac aneurysmal disease, allowing preservation of blood flow to the IIAs and preventing complications such as erectile dysfunction
Mohamed Khalifa MBBS BSc MRCS FRCR
Mohamad Hamady MD FRCR EBIR
Imperial College, London
Active treatment of abdominal aortic aneurysms (AAA) can be achieved by either open surgical repair or endovascular aortic repair (EVAR). When compared to open surgical repair, EVAR has significantly lower perioperative mortality. EVAR is also associated with significantly better aneurysm-related survival, shorter hospital stay and fewer complications.1
Since its introduction in 1991, EVAR continues to play an essential and growing role in the management of AAA. Throughout the years, interventional radiologists and vascular surgeons have worked closely with industry to develop techniques and devices to adapt to the challenges facing endovascular treatment of aneurysms, such as proximal or distal extension of aneurysmal disease, hostile anatomy, insufficient landing zones and other factors which can compromise use and deployment of stent grafts.
In response hybrid procedures, fenestration, scalloping and branching of endovascular devices have facilitated the use of endovascular techniques in a more diverse group of patients to enable better outcomes with fewer complications and risks to the patients.
The presence of hostile iliac anatomy is one such challenge and is the topic of discussion in this article, in particular, exploring the use of internal iliac branch-graft devices (IBDs) in aortoiliac aneurysmal disease.
Aortoiliac aneurysms are not uncommon, with unilateral common iliac aneurysm present in 43% and bilateral common iliac artery aneurysms present in 11% of patients with intact AAA.2 Distal aneurysmal extension therefore necessitates distal extension of the endo graft beyond the aneurysmal segment to ensure a healthy landing zone and therefore a good seal.
A number of approaches have been advocated for the management of such conditions. Open surgical repair is particularly challenging due to the deep pelvic location of these lesions and is associated with significant risk of complications and mortality, particularly when compared to an endovascular approach, which is widely accepted as the first-line treatment modality for this.3,4
Traditionally, the endovascular approach involved extending the endo graft beyond the aneurysmal segment and ostium of the internal iliac arteries (IIAs), landing in the external iliac artery. The IIAs were embolised of the internal iliac arteries to prevent retrograde flow of blood into the aneurysmal sac (type 2 endoleak). This was associated with a wide range of complications and a number of non-IIA sacrifice approaches were considered.
The IIAs are important sources of blood flow to pelvic organs, buttock skin and musculature. In significant atherosclerotic disease they are an important collateral source of flow to the colon, lower extremities, spinal cord and even small bowel. The extent of symptoms following sacrificing the IIA varies greatly from being quite mild to very severe. Complications include debilitating buttock claudication, erectile dysfunction, bowel and spinal ischaemia, lumbosacral plexus ischaemic injury and sloughing of the scrotum. The more severe complications are more likely to be associated with bilateral iliac artery occlusion.5
Although there is no consensus in the literature as to the group of patients at greatest risk, it is felt that young active patients, patients with unilateral iliac occlusion and those with severe atherosclerosis are more likely to suffer complications from IIA occlusion.
A number of approaches for preserving IIA flow have been described, which would be of great benefit to those patients who are deemed of higher risk category. These include surgical, hybrid and endovascular approaches.
Surgical and hybrid approaches are invasive techniques and are associated with significant morbidity and mortality as well as increased hospital stay. Often such patients are also poor surgical candidates. These approaches include IIA bypass and IIA transposition down onto the external iliac artery beyond the distal limb of the endo graft6,7 (Figure 1).
Hybrid approaches involve external-to-internal iliac stent-grafts with femoro-femoral crossover8 (Figure 2).
A number of endovascular techniques have also been employed to preserve the internal iliac artery. The Bell-Bottom, Sandwich and Chimney techniques are endovascular techniques which preserve pelvic circulation.
The Bell-Bottom technique9 uses a flared short aortic extension cuff that anchors the device in the distal common iliac artery (CIA) attachment zone to achieve a complete seal (Figure 3).
The diagram A shows devices used in the Bell-Bottom procedure: (a), main bifurcated device; (b), contralateral limb; and (c), aortic extension cuff. Diagram B shows Bell-Bottom procedures, unilateral or bilateral, as alternative to IIA occlusion and device extension.
The Sandwich technique refers to the deployment of multiple paralleled stent grafts into main distal and side branches in overlapping with a single proximal stent graft. This often requires brachial access10 (Figure 4).
The Chimney technique employs a covered stent that provides a conduit that runs outside the aortic stent graft to an overstended side branch. This is parked in the aortic side branch without being released. The standard aortic stent graft is released. The covered stent, extending from within the side branch up to the proximal end of the aortic stent graft, is then expanded11 (Figure 5).
The endovascular techniques described above are novel and their effectiveness and durability are yet to be demonstrated. They have proven to be technically demanding, lack a standardised technique and reporting structure. Bell-Bottom techniques have also been associated with cuff migration and subsequent graft failure.
The solution: Internal Iliac Branch-Graft Devices
Internal Iliac Branch-Graft Devices (IBDs) offer an appealing endovascular solution in comparison to the techniques described above. This device is a novel iliac extension that has a side branch for cannulation and stent implantation of the IIA, thus preserving flow to it.
Studies have shown IBDs to be associated with high technical success rates with few complications. As with all endovascular procedures there is a contrast and radiation burden on the patient, but in spite of this, the results are promising.
Currently, Cook and Gore provide IBDs which are available for use in the market.
Cook provided the first endovascular graft specifically designed to preserve flow to the internal iliac artery in straight and helical systems (Figure 6). The data available on IBDs specifically examine these devices assessing their immediate and mid-term outcome.
A review article looking at nine series of IBDs used in a total of 196 patients demonstrated a success rate of 85–100% with no aneurysm-related mortality. This was shown to improve with time secondary to the learning curve associated with device deployment, and with the development of newer IBD devices. Occlusion of IIA occurred in 12% of patients, with half of those patients developing claudication. Endoleak rates were low, with one type 1 endoleak and two type 3 endoleaks reported, all of which were managed endovascularly with success.12
Although the results were promising, the design of the device meant that many patients would not be suitable for the procedure due to the selection criteria and morphological factors stipulated in the Manufacturer’s Instructions for use (IFU) (Table 1).
In fact, a study demonstrated that in 66 target IIAs, 62% of IIAs were non-compliant with the manufacturer’s IFU and 71% of IIAs were non-compliant with experienced operators’ criteria the most common adverse feature being an aneurysmal IIA.13
In addition, difficulty was also encountered in the aortic crossover, particularly where the aortic bifurcation angle was <40%, necessitating an axillary or brachial approach for IIA cannulation, thus exposing patients to a potential risk of stroke.14
Many of the problems encountered with the earlier IBDs have been addressed and overcome with the more recent GORE Excluder Iliac Branch Endoprosthesis, which came to market in November 2013. This dedicated device is composed of an iliac branch component and an internal iliac component, designed to be compatible with the GORE AAA endoprosthesis, thus providing a complete system for the treatment of aortoiliac disease (Figure 7).
One of the greatest benefits of this device is the ability to allow for greater patient inclusion, as it accommodates a wider anatomical variability (Table 1), and in particular a wider internal iliac artery treatment range (6.5–13.5mm).
The device’s low profile system which allows for better vessel access and trackability in tortuous vessels addresses the frequently encountered challenge of cannulating hostile IIAs. In addition, the ability to reposition the stent graft before final deployment allows for greater precision.
As this device is still relatively new, no published literature is available on its mid to long-term results. Institutes who have been using this device however, have been encouraged by its immediate to short term results.
The ilustration above is a pre and post IBD stent graft demonstrating a left iliac branch graft (Figure 8).
On the left is an angiogram demonstrating aortoiliac aneurysmal disease. On the right, post left IBDs deployment.
IBDs offer an exciting and effective treatment for endovascular treatment of aortoiliac disease whilst preserving the IIAs. Improved endo graft designs have overcome previously encountered anatomical hostilities, offering excellent success rates and encouraging mid-term patency results.
Although no data is available to identify patient groups most likely to benefit from this treatment, it is felt that young active patients, patients with unilateral iliac occlusion and patients with marked atherosclerotic disease may gain most benefit from IBD use.
Although IBD is a slightly more expensive procedure, especially when compared to IIA embolisation or open surgery, the potential improvement in quality of life and short hospital stay should make it a more attractive option. Moving forward, formal risk stratification data and cost effectiveness appraisal may be of use to evaluate the use of IIAs in the management of aortoiliac disease.