Techniques for hypogastric artery embolization

Techniques for Hypogastric Artery Embolization Jacob Cynamon, MD, Priya Prabhaker, MD, and Todd Twersky, BA

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tent-grafts have become an alternative to standard surgical repair in the management of aortoiliac aneurysms. 1-1r Two grafts are currently FDA-approved, and others are in clinical trials. If an endoleak, the leakage of blood into a treated aneurysm, occurs, the procedure is considered a failure. t-3 Endoleaks may occur as a result of an incomplete seal around the proximal or distal attachment of a stent-graft (type I) or due to retrograde flow from collateral arterial branches (type II). Midgraft tears or modular disconnections are called type III endoleaks, and type IV endoleaks are due to graft porosity. Endotension is continued growth of the aneurysm after repair without a demonstrable endoleak. When a stent-graft crosses the origin of one of the hypogastric arteries, crosspelvic collaterals may allow retrograde flow through the hypogastric artery (HA) and into the treated aneurysm, resuiting in a type II endoleak. To prevent this, coils can be placed in the HA before placing the endovascular graft across its origin. Stent-grafts will cross the origin of the HA in the following circumstances: (1) abdominal aortic aneurysms (AAA) with short c o m m o n iliac arteries (CIA), making stent anchorage in one of the CIA difficult; (2) CIA aneurysms extending near the CIA bifurcation; and (3) an AAA with an aorto-unifemoral stent-graft, a cross-femoral bypass, and a contralateral CIA occlusion device, such as the type placed frequently at our institution (The Montefiore Endovascular Graft System [MEGS]). 6 HA coil embolization can decrease the incidence of these endoleaks. It will prevent retrograde flow via the HA into the aneurysm. The HA branches can still continue to be perfused via cross-pelvic collaterals. 7,8 Unfortunately, many patients treated in this manner will develop buttock claudication. This occurred in 41% of all patients in a study conducted at our institution, s The location at which the HA is coil-embolized is important in reducing the incidence of buttock claudication. A more proximal embolization may have a lower incidence of buttock claudication. In our study, 10% of patients with proximal HA coil embolizations developed buttock claudication versus 55% of those with distal embolizations. 8 Coils, as opposed to other embolic agents, permit proximal placement while also preventing backflow, but still preserve distal vessel patency, thus minimizing possible resultant ischemia. Proximal occlusion of the HA at its ori-

From the Montefiore Medical Center, Department of Radiology, Bronx, NY. Address reprint requests to Jacob Cynamon, MD, Montefiore Medical Center, Department of Radiology, 111 E. 210th Street, Bronx, NY 104672490. Copyright 2001, Elsevier Science (USA). All rights reserved. 1089-2516/01/0404-0007535.00/0 doi:l 0.1053/tvir.2001.31260

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gin, before its anterior-posterior bifurcation, sufficiently impedes retrograde filling of the aneurysm and the development of endoleaks. In addition, proximal occlusion still allows collaterals to contribute to the anterior and posterior divisions of the HA and permits continued communication between the anterior and posterior divisions. The vessels distal to the embolization site continue to fill via collaterals

Fig 1. (A) Appropriately positioned coils in the proximal HA allowing communication between its branches. (B) Coils extending into the branches of the HA are likely to isolate these branches, decreasing potential collateral flow, thereby leading to a higher incidence of buttock claudication.

Techniques in Vascular and Interventional Radiology, Vol 4, No 4 (December), 2001: pp 236-242

Fig 2. (A) A right CIA aneurysm. The origin of the HA is best seen on the RPO projection. (B) The size of the HA is measured using digital morphometry. (C) The RAO view best demonstrates the branches of the HA and the true length of the HA. (D) Note that the appropriately sized coils are placed in the proximal HA. The coils do not migrate because they are slightly larger than the vessel and the HA is tapering down as it gets closer to its branches. (E) Final arteriogram demonstrates the position of the coils. The RPO view shows that there is more room in the more proximal HA. However, it can be difficult to place the coils in the most proximal portion of the artery, especially when an ipsilateral approach is being used.

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Fig 3. (A) A right ClA aneurysm requiring a ClA-to-EIA stent graft. (B) Selective catheterization of the HA demonstrates a short vessel that enlarges closer to its bifurcation. Routine Gianturco coils are likely to embolize to the bifurcation or into its branches. (C) A nonfibred GDC coil was used to buttress additional coils and prevent migration of the fibred coils into the branches of the HA. In this case, the GDC was compressed by the coils placed above, and this patient did develop buttock claudication.

Fig 4.

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Fig 4. Continued. (A) Aorta and right CIA aneurysm to be treated with a stent-graft extending into the EIA. The RPO projection does not show the origin of the HA. It may be very difficult to catheterize the HA without identifying its origin, (B) In the RPO projection with caudio-cranial anguiation, the origin of the HA becomes visible; note the tortuosity and the potential difficulty in catheterizing this vessel. (C) Using a reversed-curve catheter, the HA was easily catheterized. The nondilated portion of the vessel measured approximately 5 mm. (D) A 6-mm microcoil was used through a microcatheter coaxially placed into the reversed-curve catheter. Note the relatively soft coil embolized to a branch of the HA. (E) To prevent this from recurring, a GDC coil was deployed into the HA via the coaxially placed microcatheter. (F) Microcoils were then injected and lodged within or above the GDC and formed a complex structure in the mid-HA. (G) Completion angiogram in the AP projection demonstrating the occlusive coils in the mid-HA projecting over the CIA aneurysm.

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Fig 5. (A) Small aortic iliac aneurysms. There is a large HA aneurysm. To isolate and occlude the HA, a stent-graft can be placed across the HA origin after first coil-occluding the distal portion of the HA aneurysm. Although it appears from the angiogram that the distal HA before its bifurcation may be normal, it is more likely filled with clot. Therefore, it is the branch vessels that should be embolized. (B) The branches of the HA were embolized, and a stent-graft was placed from the CIA to the EIA. (C) Contrast-enhanced computed tomography (CT) shows the HA aneurysm to be thrombosed.

and thus can help prevent ischemia-induced claudication (Fig 1).

Techniques for HA Embolization The traditional method of embolizing the HA involves first sizing the HA luminal diameter using digital angiographic morphometry. This is necessary to determine the appropriate size of the initial Gianturco (Cook, Bloomington, IN) coil to be deployed. A coil larger than the luminal diameter is selected to reduce the risk of its subsequent embolization into the hypogastric branches. Markedly oversized Gianturco coils are avoided to prevent displacement of the catheter from its selected location (Fig 2). This traditional method has proved useful in most patients with normal HA anatomy; severely tortuous iliacs may make it very difficult to deploy these coils. This is so because a reverse-curve catheter is often used to gain

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access to the HA in these cases, and pushing coils through this catheter can be problematic. Occasionally, to ensure more accurate proximal placement of embolization coils and maintain communication between the branches of the HA, nonfibered GDC coils (Boston Scientific/ Target, Watertown, MA) can be used in conjunction with Gianturco coils. GDC coils may be used in cases in which Gianturco coils are likely to embolize to the hypogastric bifurcation or beyond, which can occur in patients with difficult anatomy, such as a HA that does not taper as one moves distally toward its bifurcation (Fig 3). A nonfibered GDC coil will prevent microcoils and Gianturco coils from embolizing into the branches of the HA, while still allowing communication between the anterior and posterior divisions of the HA even if it is lodged at the hypogastric bifurcation. In addition, GDC coils can be useful in difficult ipsilateral HA catheterizations in which a reversedcurve catheter may be necessary to adequately seat the proximal

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Fig 6. |A) HA aneurysm to be treated by coiling the distal HA and a CIAto-EIA stent-graft. (B) Selective angiogram of the HA. (C) Coils were deployed in the distal HA, not in the branches. (D) Follow-up contrast CT demonstrates contrast in the HA aneurysm. (E) The coils are noted to be in the HA aneurysm, not in the branches. This HA eventually ruptured and was repaired by standard surgical technique.

Fig 7. (A) CIA-to-iliac vein fistula. (B) A CIA-to-EIA stent-graft should prevent direct inflow into the fistula. However, HA collaterals would allow retrograde flow through the HA into the CIA and through the fistula. Therefore, the HA was embolized before the stent-graft placement. (C) Three months after treatment, a small, residual fistula is noted. There is a lumbar artery-to-iliolumbar artery communication with retrograde flow in the HA into the CIA under the stent-graft and into the fistula. This occurred because the coils were not placed above the iliolumbar artery. When the lumbar arteries are not going to be occluded, such as when treating a solitary lilac aneurysm or fistula, it is even more important to lodge the coils in the proximal HA above the iliolumbar artery.

HA. Gianturco coils cannot always easily advance through a reverse-curve catheter. Instead, a nonfibered GDC coil can be placed to prevent distal embolization, followed by Tornado (Cook) or Vortex (Boston-Scientific/Medi-tech, Watertown, MA) microcoils placed through SP or Tracker catheters (Boston-Scientific/Medi-tech) l°,lr (Fig 4).

due to other intraoperative events such as hypotension and severing of important collaterals that stem from the distal external iliac, common femoral, and profunda femoral arteries. In conclusion, the HA has become a very important vessel in interventional radiology. More knowledge and research is needed to prevent unanticipated complications that may occur when embolizing the HA in patients with aortoiliac aneurysms.

Isolated HA Aneurysms When treating a HA aneurysm, one must occlude the distal and proximal end of the HA. If the anterior and posterior divisions arise from the body of the aneurysm, as they often do in a hypogastric aneurysm, proximal embolization would not be possible. Coil embolization of its branches and a common iliac artery to external iliac artery endoluminal graft would isolate or occlude the aneurysm (Figs 5 and 6) 7 -9 If there is enough space in the proximal HA, an occluder can be placed in this vessel instead of the common iliac-to-external iliac stent-graft.

Isolated CIA Aneurysms and Arteriovenous Fistulas Common iliac aneurysms or arteriovenous fistulas involving the CIA provide another challenge. The usual HA embolization may not prevent endoleaks into the aneurysm or flow through the fistula even after the proximal CIA-to-external iliac artery stent-graft is placed. This occurs because of a communication between the iliolumbar and lumbar arteries that allows flow into the CIA and through the fistula. 8 In these cases, coils should extend above the iliolumbar artery or be placed into the iliolumbar artery to prevent a persistent lumbar-to-iliolumbar collateral (Fig 6).

Bilateral HA Embolization So far, our discussion has focused on unilateral HA embolization. Bilateral HA embolization is usually avoided for fear of causing significant morbidity in the form of perineal necrosis, severe lower-extremity neurologic deficits, ischemic colitis, impotency, or buttock claudication. Bilateral occlusion is more likely required in aortic aneurysm cases that also affect the iliac arteries. This occurs in about 20% of aortic aneurysms, which often involve the distal CIA. Interruption of one or both HA may be necessary in these cases, along with aortoiliac or aortofemoral bypass to completely exclude the aneurysm. A study performed by vascular surgeons at our institution revealed that the incidence of severe morbidity might actually be quite low for bilateral HA interruption, n No patients in this study suffered perineal necrosis, ischemic colitis, or death. In addition, only a small percentage experienced impotency, neurologic deficits, or persistent buttock claudication after occlusion of the HA unilaterally or bilaterally. These results suggest that unilateral or bilateral HA occlusion is most probably not a dangerous procedure, and thus can be performed to completely exclude aneurysms that involve the iliac bifurcation or HA. It is proposed that the complications seen in other series are more likely

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