Complications With Branched Endovascular Devices

Points of Attention in Branched EVAR

Branched endovascular aortic aneurysm repair (B-EVAR) was developed for the treatment of thoracoabdominal aortic aneurysms (TAAA). With increasing physician experience and device evolution we can at the moment treat almost all types of aneurysms extending from the aortic arch to the iliac bifurcation. In connective tissue disease, open reconstruction remains the first choice of treatment. There is a multitude of different configurations for branched devices, including downward- or upward-oriented branches, internal or external configurations, and a combination of branches and fenestrations. A typical branched-only device has four downward-facing branches intended for the celiac artery (CA), the superior mesenteric artery (SMA), and two renal arteries (RA). This common design has led to the development of the single currently available off-the-shelf branched device (T-branch, Cook Medical, Bloomington, IN, USA). Other companies (WL Gore & Associates, Newark, DE, USA; Jotec GmbH, Hechingen, Germany) are developing comparable systems that will enable physicians to treat patients even in an acute setting. Despite increasing standardization, applicability of off-the-shelf endografts is not universal, and a significant proportion of patients with TAAA will still require treatment with custom-made devices (CMD) to address specific anatomical characteristics. This underlines the need for meticulous planning of this complex endovascular procedure, which is the first step to avoid intraoperative complications. Nevertheless, a number of technical challenges can arise during B-EVAR, requiring experience with specific endovascular techniques and bail-out measures to achieve technical success.

Device Planning

Preoperative planning of B-EVAR requires good-quality imaging with thin cut (≤1 mm) spiral computerized tomography angiography (CTA) from the chest to the groin with the option of axial, coronal, and three-dimensional reconstructions. To this purpose, physicians have an increasing software arsenal for multiplanar reconstructions and center-line measurements enabling precise placement and orientation of side branches as well as selection of proximal and distal components in composite systems. If a tube graft is required proximally in the descending thoracic aorta, it should be designed to land 3 cm above the orifice of the CA. This facilitates catheterization of the target arteries, while ensuring sufficient overlap between components. In compromised proximal neck, additional fixation with endoanchors can be considered. Typical branch orientation includes clock positions of 01:00 for the CA, 12:00 for SMA, 09:00–11:00 for the right RA and 01:00–03:00 for the left RA. Usually, the endograft main body consists of 10–12 bare metal stents covered with graft material. Branches originate at the midportion of the endograft, and each single stent can accommodate up to two branches; this means that in cases of three or more vessels originating at the same level, one branch has to be positioned higher and the target vessel secured with a longer bridging stent. In situations when the aorta has an hourglass shape, with narrowing of the renomesenteric segment or narrow true lumen in postdissection TAAA, fenestrations or branches can be an option. Specific points of attention are supraaortic artery anatomy in association with proximal landing and intraoperative stroke risk, shaggy aorta, which is the main contraindication for B-EVAR, and access vessels that may restrict endovascular solutions or mandate use of low-profile devices.

• Landing zone: Maximal diameter is 40 mm. In hostile anatomy, adequate sealing length is mandatory with possible additional fixation with endoanchors.

• Access-vessels tortuosity, calcification, or stenosis: surgical exposure for conduit.

• Kinked anatomy (aorta, target vessels): Plan longer overlap and consider ways for accurate device deployment.

• Focally narrow aortic segment: Consider a combination of branches and fenestrations to accommodate individual anatomy.

• Shaggy aorta: Main contraindication for B-EVAR.

In order to exclude the aneurysm completely with endovascular methods, physicians need to extend the level of repair well above and below the aneurysm to a parallel segment of the aorta to achieve a safe and durable seal. A problem arising particularly in the case of B-EVAR is the risk of spinal cord ischemia (SCI) with increasing length of covered aorta. Preservation of the left subclavian artery and pelvic circulation should always be targeted. Proximally, this can be achieved with the use of carotid–subclavian or carotid–carotid–subclavian bypass and debranching or arch stent grafts with branch fenestrations and, in some cases, chimneys for supraaortic vessels. In cases of common iliac artery involvement, the distal sealing zone can be extended below the iliac bifurcation with iliac branched devices that preserve flow to the external and internal iliac arteries. Despite these measures, published studies have demonstrated that extensive TAAA repair is associated with considerable SCI rates. It is therefore advisable to try to reduce the length of covered descending aorta to the minimum required for an adequate seal. In the case of descending aortic diameters of 32–38 mm, where the branched component usually has to be extended proximally with deployment of a tapered tube-graft and additional aortic coverage of approximately 10 cm, we now have the option to use a double-barrel “2-in-1” CMD device (Cook Inc.). This consists of two coaxial stent grafts with a maximal outer diameter of 44 mm, allowing for adequate seal at the level of the branched component, without extension of the proximal landing zone. Aside from stent graft planning, prevention of SCI requires care with operative timing, pre-, intra-, and postoperative management.

An additional consideration during TAAA repair is the risk of bowel and liver ischemia, caused by embolic complications or malperfusion of main tributaries and important collaterals. Studies have reported an estimated risk of 2%–3% for bowel ischemia in aortic endovascular repair, with a respective mortality of 50%. Specific planning to avoid this in extensive TAAA repair can include additional branches or fenestrations in case of separate orifices of intestinal vessels, an additional branch to prominent (≥4 mm) inferior mesenteric arteries (IMA) when mesenteric circulation is compromised, and branches for the preservation of the internal iliac arteries.

• SCI Prevention: Preserve flow to LSA and IIA, do not unnecessarily extend aortic coverage.

• Bowel ischemia: Preserve all important tributaries.