Intentional Internal Iliac Artery Occlusion in Endovascular Repair of Abdominal Aortic Aneurysms

EDITORIAL NOTE — The authors have succeeded in providing a complete and yet concise summary of all the important issues concerning occlusion/exclusion of hypogastric arteries (HA) in the context of endovascular repair of aorto-iliac aneurysms. It is hard to find anything to disagree with, attesting to their vast experience and complete understanding of the subject matter. Our own experience now exceeds 100 cases of unilateral or bilateral coil embolization, using a staged approach in virtually every instance. We have not had any serious or catastrophic ischemic complications, and only 1 instance of sexual dysfunction, following unilateral HA occlusion with documented patency of the contralateral vessel. The incidence of buttock claudication has been 35%; of these 70% have experienced resolution or improvement of the symptom over time. Techniques of HA revascularization with transposition or bypass are a valuable addition to our armamentarium; I have successfully performed this 5 times, and failed on the sixth attempt because of the finding of a heavily calcified HA. The procedure is technically sound, but it can be extraordinarily difficult to perform in the face of significant obesity. I suspect the “controversy” and the discussions will continue on the merits of HA preservation versus occlusion.1,2 In my view, coil embolization should still be viewed as the most useful technique when endograft attachment within the common iliac artery proves impossible or inappropriate, necessitating extension into the external iliac artery. The concept of “tributary technology” is appealing, but I doubt very much stent-grafts with HA branches will become commonplace in the foreseeable future”. REFERENCES 1. Criado FJ. Commentary: Iliac bifurcation relocation: More complex and controversial. J Endovasc Surg 1999;6:348–349. 2. Criado FJ. Commentary: The hypogastric artery in aortoiliac stent-grafting: Is preservation of patency always better than intentional occlusion? J Endovasc Ther 2002;9:493–494. -Frank J. Criado, MD Union Memorial Hospital/MedStar Health Baltimore, Maryland Since its introduction by Parodi in 1991, endovascular stent graft (EVSG) repair of abdominal aortic aneurysms (AAA) has evolved significantly.1 The internal iliac arteries frequently present a challenge to the interventionalist who attempts endovascular repair of abdominal and iliac artery aneurysms. In the normal anatomic situation, the paired arteries are important sources of blood flow to pelvic organs and buttock skin and musculature. When atherosclerotic disease of any number of vessels becomes significant, the hypogastric artery may become an important collateral source of flow to the colon, lower extremities, spinal cord and even small bowel.2 If the internal iliac artery is diseased, there can be significant collateral flow from above or below to compensate for occlusive disease on either side of the pelvis. As seen in Figure 1, the collateral network centered on the internal iliac arteries is complex and significant. In cases of open AAA repair, one or both of the internal iliac arteries may need to be sacrificed. The incidence of significant morbidity following hypogastric artery interruption during open aortoiliac surgery is low.3–5 The advent of endovascular aneurysm repair has renewed interest in the effects of internal iliac artery sacrifice. In the absence of the ability to reimplant the inferior mesenteric artery, the sacrifice of one or both hypogastric arteries may have more significant effects. Anatomy. The internal iliac arteries arise in the pelvis as one of two branches of the common iliac artery. The external iliac artery continues laterally and inferiorly to exit below the inguinal ligament and become the common femoral artery. The internal iliac artery descends into the pelvis, giving off branches to pelvic structures. Anastomotic communications between the internal and external iliac arteries exist via the circumflex iliac vessels. Occlusive disease of the common, internal or external iliac arteries can result in significant enlargement of these collateral pathways. In this way, the common femoral artery can provide flow to pelvic structures and the internal iliac artery can assist in supplying the lower extremity. In addition to these collateral paths, the hypogastric artery and the inferior mesenteric artery can provide each other with important assistance if one becomes diseased. The importance of these communications becomes more apparent when one considers that endograft repair of AAA requires exclusion of the internal mammary artery and may require exclusion of one or both hypogastric arteries. Results of internal iliac artery sacrifice. Based on the literature on open AAA repair, a number of potential complications can result from hypogastric artery occlusion. Buttock claudication occurs most commonly and can be disabling. Sexual dysfunction, colon ischemia, distal spinal cord infarction and gluteal necrosis may also occur. A review of open and endovascular aortic repair with hypogastric artery sacrifice demonstrated a significant incidence of buttock claudication and impotence, especially when both arteries were sacrificed.6 A number of series have been reported where one or both hypogastric arteries have been sacrificed to facilitate endovascular AAA repair (Figure 2). Wolpert and colleagues reported on 18 patients who had unilateral or bilateral (39%) hypogastric artery embolization in preparation for endovascular AAA repair.7 Half of these patients had persistent buttock claudication which improved but did not disappear over time. Most patients had erectile dysfunction preoperatively, but two worsened after the procedure. No cases of colon ischemia or gluteal necrosis occurred. Lee et al. reported on 157 consecutive patients undergoing AAA repair with an AneuRx device.8 Twenty-three patients (15%) had unilateral hypogastric artery occlusion while there were no bilateral occlusions. Thirty-nine percent of patients had buttock claudication and a worsening in their disability score. All but one had resolution of the buttock claudication but disability scores never returned to normal in any of the patients. In our series of 103 cases of unilateral or bilateral internal iliac artery sacrifice, twenty-one percent of patients had clinical evidence of pelvic ischemia.9 Five of these patients with minimal symptoms became symptom-free by one year. We noted that the presence of contralateral internal iliac artery stenosis and absence of circumflex iliac artery collaterals predicted the development of symptoms after internal iliac artery sacrifice (Figure 3). Other groups have reported smaller series with similar rates of pelvic ischemia symptoms.10,11 While the incidence of serious complications is low, there is a significant rate of claudication and sexual dysfunction persisting beyond several months. The risk of complications is higher with bilateral internal iliac artery occlusion and may be reduced by planned, sequential embolization of the internal iliac arteries prior to the scheduled aneurysm repair. An additional problem associated with internal iliac artery sacrifice involves occlusion of the stent-graft limb. In our experience, carrying a stent-graft limb into the external iliac artery and excluding the hypogastric artery seems to result in higher rates of occlusion of the ipsilateral limb of the device (data not shown). The reasons for this are not clear; however, it may reflect the length and smaller diameter of the limb as it extends into the external iliac artery. Strategies to preserve the internal iliac artery. Although the results published in the literature are remarkable in that they show low rates of serious complications following hypogastric artery sacrifice, we believe the overall rate of buttock claudication and sexual dysfunction after this approach justifies attempts to preserve one or both internal iliac arteries. In a case where aneurysmal involvement of both common iliac arteries precludes effective stent-graft sealing above the iliac artery bifurcation, we have sacrificed one internal iliac artery while transposing the other hypogastric artery further down the external iliac. This permits landing of the device into normal external iliac artery while preserving pelvic flow (Figure 4). We have performed this procedure in 11 cases with no evidence of pelvic ischemic symptoms in any patient. All grafts have remained patent at a mean follow-up of 10 months.12 Another method of avoiding hypogastric artery compromise requires the use of stent-grafts with large iliac limbs. Ectatic common iliac arteries up to 2 cm in diameter can be sealed with custom-made 22 mm limbs. Such devices need to be custom-made in order to assure that the common iliac artery is fully covered while the internal iliac artery orifice remains patent. By designing devices with specific lengths and diameters for each patient, one can precisely exclude the common iliac artery, achieve adequate seal and preserve the internal iliac artery (Figure 5). In the case of significant internal iliac aneurysm, coil embolization of the distal branches preoperatively followed by stent-graft coverage of the hypogastric orifice can effectively exclude these lesions. A number of devices with sidebranches are currently being developed to allow endografting of the common, internal and external iliac arteries. Summary. The internal iliac arteries and their collateral networks are remarkably versatile. This fact explains the relatively low incidence of serious complications following hypogastric artery sacrifice during endovascular AAA repair. Since overall complication rates are significant, we believe a strategy designed to preserve one or both internal iliac arteries should be pursued whenever possible. The ability to use larger devices in the common iliac arteries and to precisely deploy them at the iliac artery bifurcation allows ectatic iliac arteries to be treated without internal iliac sacrifice. The development of branch vessel technology will allow secure exclusion of aneurysms while assuring preservation of internal iliac artery flow.

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