Introduction
Endovascular treatment of complex (TASC C and D) lesions of the aortoiliac arteries has been increasingly adopted since the early 2000s, especially after the introduction of stent grafts. Although the primary patency rates are reported to be 60%–86% at 5 years, which is lower than with direct revascularization, secondary patency rates are comparable ranging from 80% to 98%. In the most recent meta-analysis, the 5-year patency rates were reported to be 91% in patients with claudication and 87% in patients with critical limb ischemia. Mortality and morbidity were 3.3% and 8.3%, which is the main reason for adopting minimally invasive alternatives. There are no modern studies comparing direct revascularization with endovascular revascularization in patients with complex aortoiliac occlusive disease in large numbers; however, a few small series have explored this issue. Overall, they have shown that endovascular treatment has inferior primary patency with similar secondary patency rates and lower morbidity and mortality.
In contrast to outcomes in the femoropopliteal segment, patency of TASC C and D lesions in the iliac segment has been reported to be comparable with that of TASC A and B lesions. In a series of 433 patients who had systematic iliac stenting between 1997 and 2009, with a median follow-up of 72 months, primary patency rates at 5 and 10 years were 83% and 71%, respectively, in the TASC II C/D group and 88% and 83% in the TASC II A/B group ( P =0.17). However, the risk of complications (vessel rupture, dissections, loss of branch vessels, early and late occlusions, distal embolization) increased with the complexity of the revascularization. The complication rate was higher in the C/D group (9% versus 3%, P =0.014), with significantly longer procedure times in the above referenced study.
The most important aspect of aortoiliac revascularization is to anticipate and to avoid complications via careful preoperative planning. In addition to obtaining a detailed history and physical examination, any patient with suspected aortoiliac occlusive disease should undergo preoperative imaging, ideally with a computed tomography angiogram. The amount of calcium and clot content within the vessels, the anatomy of the critical vessels, and the anticipated re-entry level are all crucial to planning treatment of these lesions. However, despite appropriate planning, complications will occur and, in that event, timely and appropriate management can minimize adverse outcomes.
Patient Preparation
Management of aortoiliac disease often requires a combination of both open and endovascular techniques. While many complex lesions can be addressed percutaneously, a significant proportion of patients (up to 20%) have bulky common femoral artery disease and will require concomitant femoral endarterectomy. Open access may also be preferred in the setting of acute or subacute occlusion, as it facilitates protection from distal embolization. In addition, antegrade iliac crossing may result in a common femoral dissection, which is typically managed via open repair. If open femoral intervention is either likely or anticipated, the procedure should be performed in a setting appropriate for a hybrid repair.
Crossing aortoiliac lesions can be performed in either a retrograde or antegrade fashion and it is not unusual to need a combination of both approaches. Therefore, the possibility of both brachial and femoral access should be anticipated, and the patient should be prepared accordingly at the beginning of the procedure. Upper extremity access typically requires a sheath at least 90 cm in length. However, longer sheaths and crossing catheters up to 125 cm should be available for taller patients or in the event that a radial approach is preferred. When crossing via a contralateral femoral approach, a deflectable sheath may be necessary to increase support, especially when dealing with a short common iliac stump.
In the rare event that an aortoiliac lesion cannot be crossed, there should be a clear plan for open intervention. If revascularization is urgent, the patient should be prepared for possible femoral–femoral or axillary–femoral bypass at the beginning of the procedure.
Crossing and Treating Aorto-Iliac Lesions
There are four main issues to address when planning an endovascular intervention for aortoiliac lesions: (1) antegrade versus retrograde crossing; (2) femoral versus brachial access; (3) re-entry method; (4) stent selection. Of these, the crossing direction is the most important as it will, in many respects, dictate each of the subsequent choices. However, every decision is ultimately predicated on the desire to minimize the risks of vessel perforation, embolization, and occlusion associated with a difficult re-entry.
Crossing Direction and Access Site
Though crossing an aortoiliac lesion can be performed in either a retrograde or an antegrade fashion, our preferred initial approach to most lesions is antegrade. This strategy prevents proximal extension of the re-entry site, which can weaken the aortic wall and lead to either perforation or development of an obstructive flap. In addition, an antegrade approach provides more flexibility in the event that percutaneous re-entry is unsuccessful. Wire retrieval through a femoral cut-down is relatively straightforward and well-tolerated in most patients. For patients with external iliac artery occlusions and a patent internal iliac artery, crossing in an antegrade fashion also minimizes the chance that a dissection will compromise the internal iliac branch.
If the ipsilateral common iliac artery is patent, then we typically start with a contralateral femoral approach. The internal iliac artery is selectively cannulated and the initial wire is exchanged for a support wire (Storq, Cordis, Cardinal Health, Dublin, OH; Bentson, Boston Scientific, Marlborough, MA). A sheath is then placed from the contralateral femoral artery into the distal common iliac artery (CIA) and the occlusion is crossed with a Glidewire-Glidecatheter combination (Glidewire, Glidecath, Terumo, Somerset, NJ). If additional support is desired, then a 0.014′′ or 0.018′′ wire can be left in the internal iliac artery for support while a crossing catheter is delivered to the distal CIA in buddy-wire fashion.
While an internal iliac artery occlusion or the presence of a short common iliac stump can make antegrade crossing from the contralateral femoral artery more challenging, it is still our initial approach in most patients. In this situation we begin by probing the common iliac artery with a catheter (our preference is either the Omni flush or the IM catheter) and a stiff straight Glidewire. If the occlusion cannot be entered or the common iliac artery does not provide adequate purchase, a deflectable sheath can be used to support the wire-catheter combination. However, ultimately a brachial approach with a 90-cm sheath (typically 5 French) may be necessary. A brachial approach offers better support for the crossing wire and is our first choice in the setting of a flush iliac occlusion or extensive aortic involvement.
Although we typically prefer antegrade crossing of iliac lesions, there are situations in which retrograde crossing is preferable. In patients with a CIA occlusion and a large, patent internal iliac artery, retrograde crossing via an ipsilateral femoral access should be the preferred initial approach, as it minimizes the chance that the internal iliac artery will be occluded by extension of the dissection plane ( Fig. 32.1 ). Furthermore, an ipsilateral common femoral artery (CFA) access will ultimately be needed when placing a CIA stent; therefore, in cases that do not require stent extension above the aortic bifurcation, this approach allows the entire procedure to be completed via a single puncture. We also consider a retrograde approach when dealing with an isolated external iliac occlusion in combination with an occluded or diminutive internal iliac artery. In this case, there is little risk to the pelvic circulation and a retrograde approach can both simplify the procedure and increase support for the crossing wire/catheter.
Re-Entry Technique and Stent Selection
In severely calcified and chronic lesions, crossing is most likely to be subintimal and the distal re-entry must be carefully managed to limit the extent of the dissection plane and prevent occlusion of critical branch vessels. If the wire does not re-enter the true lumen at or above the CFA when crossing an iliac lesion in an antegrade fashion, the most expedient and safest solution is usually to perform a femoral cut-down, retrieve the wire manually, and then repair the distal aspect of the dissection surgically. A sheath can then be advanced over the wire in a retrograde fashion, while maintaining the wire externalized from the initial femoral or brachial access for support, and the iliac lesion treated via stenting. Our preference for the external iliac artery location is a self-expanding covered stent, because the course of the wire while crossing an occlusion is unpredictable. The guidewire path may be subadventitial and, in our observation, ballooning up the very thin arterial wall may result in external iliac artery rupture, which sometimes occurs in a delayed fashion.
When an iliac lesion is crossed retrograde, the main concern is continuation of the dissection into the aorta such that the re-entry point ends up proximal to the aortic bifurcation. Even in cases in which the crossing seemed easy, it is possible to have a higher re-entry point than suggested by the angiogram and a low threshold should be maintained for using intravascular ultrasound (IVUS) to confirm the course of the crossing wire. We use IVUS routinely when planning to place an iliac stent precisely at or just below the aortic bifurcation. If the re-entry site is above the aortic bifurcation, it may be necessary to raise the bifurcation with kissing stents ( Fig. 32.2 ). Alternatively, a re-entry device (Pioneer or Outback) can be used to re-enter the aorta distally in a more controlled fashion. This is our first choice when our goal is to land an iliac stent precisely at the bifurcation and also in those cases is which the distal aortic wall is known to be very diseased, such that it will resist luminal re-entry. We generally prefer the ultrasound-guided re-entry device (Pioneer) because it allows for direct visualization of the re-entry target and, consequently, reduces the number of attempts to achieve successful re-entry; however, Outback can be used equally effectively ( Fig. 32.3 ). In patients with heavy calcification of the iliac arteries, Outback is preferred because of the superior deliverability of the device to the target. The Pioneer is less sturdy to advance, even after balloon dilatation of the tract.
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