The long-term graft patency after aortobifemoral bypass is excellent, and the procedure remains the gold standard for aortoiliac occlusive disease. Despite this favorable outcome, a small subset of patients will ultimately present with symptomatic occlusive disease resulting from graft occlusion of either one or both of the limbs with rates ranging from 5% to 10% at 5 years to approximately 30% at 10 years. The clinical presentation spans the spectrum from mild claudication to acute limb ischemia, although the symptoms are almost always worse than those that precipitated the original bypass and usually merit remedial intervention. The diagnosis can usually be made based upon the presenting history and physical examination and can be confirmed by noninvasive testing as necessary. Arteriography is rarely necessary as a diagnostic tool, but it is frequently used to plan the operative procedure. Although not routine, a CT scan can be helpful to rule out the presence of a graft infection or to confirm the diagnosis of a pseudoaneurysm. Indeed, both diagnoses should be considered during the diagnostic workup, given the excellent long-term patency rates associated with the aortobifemoral bypass.

The mechanisms responsible for graft thrombosis after all bypass procedures, including aortobifemoral bypass, are discussed extensively elsewhere in the text (see Chapter 57) and will be only briefly reviewed. They vary based upon the duration of the postoperative period, with the intervals arbitrarily defined as early (1 to 30 days), intermediate (30 days to 2 years), and late (>2 years).

Early graft thromboses after aortobifemoral bypass are almost exclusively related to either technical problems or errors injudgment. These may include anastomotic stenoses, intimal flaps, twisting and/or kinking of the graft limbs, unrecognized arterial inflow problems, and poor arterial runoff, among others. The less common causes of early graft thrombosis include systemic hypoperfusion from cardiac issues, graft thrombogenicity, and hypercoagulable states. Notably, these potential mechanisms can contribute to graft thrombosis during any of the time periods. Early graft thrombosis requires urgent/emergent re-operation with the procedure dictated by the underlying cause; this topic is not the focus of this chapter.

Graft thrombosis in the intermediate and late time frames is usually due to progression of the occlusive disease at either the anastomosis or arterial runoff vessels, with intimal hyperplasia accounting for the intermediate-term failures and progression of the underlying arterial occlusive disease in the later time period. Notably, the progression of the infrainguinal arterial occlusive disease is associated with the usual risk factors, including smoking, and emphasizes the importance of risk factor modification. Additional causes of late graft failure after aortobifemoral bypass include thrombosis of a femoral aneurysm/pseudoaneurysm, infection, embolus from a cardiac source, and progression of the occlusive disease in the infrarenal aorta. In the latter situation, patients usually present with occlusion of both graft limbs in contradistinction to anastomotic or outflow problems that cause single limb occlusions. Graft thrombosis from progression of the aortic occlusive disease usually occurs because the proximal anastomosis of the aortobifemoral bypass was sited too low on the infrarenal aorta and, thereby, further emphasizes the importance of originating the graft immediately below the renal arteries.

The indications for revascularization in patients with a failed inflow procedure, including a failed aortobifemoral bypass, are identical to those for the initial procedure and include lifestyle/economically limiting claudication and limb-threatening ischemia. The decision to offer patients a remedial procedure is oftentimes a difficult clinical decision and should be based upon the severity of symptoms, the likelihood of success/long-term outcome, and the perceived operative risk. As noted above, patients are oftentimes worse off in terms of their lower-extremity symptoms after a failed inflow procedure, but repeat operation is not mandatory. Furthermore, the threshold for intervention should be somewhat higher than the original one, given the inherent technical difficulties of a redo procedure, particularly in the subset of patients with claudication alone.

There are multiple treatment options for patients with failed inflow procedures. The extra-anatomic or nondirect bypass procedures (axillofemoral, femorofemoral) can be converted to the more durable, direct aortobifemoral bypass procedure in the appropriate clinical scenario. When a single
limb of an aortobifemoral bypass graft fails, it is usually possible to restore patency by thrombectomizing the limb and correcting the underlying cause of the failure that is usually an outflow obstruction, as noted above. This usually requires revising the femoral anastomosis and extending the toe of the graft farther down the profunda femoral to a segment relatively free of occlusive disease. This can require a fairly extensive dissection necessitating ligation of the crossing branches of the profunda femoral veins. Occasionally, it is necessary to perform an infrainguinal bypass in concert with the groin reconstruction if the profunda femoral outflow is inadequate. Although both mechanical and chemical means are reasonable options for the thrombectomy, the mechanical approach is preferred because of its ease, effectiveness, and frequent need to revise the femoral anastomosis. It is usually possible to remove the thrombus with a balloon thromboembolectomy catheter, although the more chronic, tenacious clots may require the Fogarty Adherent Clot Catheter (Edwards Lifesciences) or the Fogarty Graft Thrombectomy Catheter (Edwards Lifesciences). In the unusual case in which the limb of the aortobifemoral graft cannot be opened, it is possible to restore inflow with a crossover femorofemoral graft from the contralateral limb or from the ipsilateral axillary artery with an axillofemoral graft.

A redo, direct aortoiliac revascularization is indicated in a small subset of patients with a failed aortobifemoral bypass procedure. This group of patients includes those with progressive inflow disease above the proximal anastomoses and those with repeated limb failures. It also includes patients who had previously undergone an aortobiiliac bypass for either aneurysmal (common iliac artery) or occlusive disease (external iliac artery) who have developed progression of their occlusive disease distal to the iliac anastomoses. The treatment options include a redo aortobifemoral bypass with prosthetic graft, a redo aortobifemoral bypass with autogenous superficial femoral/ popliteal vein (NAIS or neo-aortoiliac system), or a thoracobifemoral bypass. A redo aortobifemoral bypass is a daunting procedure regardless of the conduit, and harvesting the lower-extremity deep veins for the NAIS procedure adds significantly to its complexity and the overall length of the operation. However, the long-term patency rates after the NAIS procedure are excellent and should be considered among the treatment options, particularly among younger patients (<55 years of age).

The thoracobifemoral bypass has a tremendous amount of appeal as an alternative to a redo aortobifemoral bypass and is likely the procedure of choice for redo, direct aortoiliac revascularizations. The use of the descending thoracic aorta as an alternative inflow source for patients with aortoiliac occlusive disease was first described in 1961. After the initial reports, the less invasive axillobifemoral bypass was reported, and the axillary artery quickly became the popular alternative inflow source to the infrarenal aorta, thereby diminishing interest in the use of the thoracic aorta. During more recent years, however, the overall experience with the thoracobifemoral bypass has increased, and the indications, surgical technique, and long-term results have been defined. The major advantages of the procedure include the fact that it is relatively straightforward from a technical standpoint (in comparison to a redo aortobifemoral bypass); it avoids a redo infrarenal aortic procedure; it avoids entering the peritoneal cavity; it allows the limbs of the graft to be tunneled deep in the lateral retroperitoneal space, thereby reducing the incidence of an aortoenteric fistula; it uses an inflow source that is relatively free of occlusive disease; and it is associated with excellent long-term results in terms of patency. The potential disadvantages include the finite but small risk of paraplegia associated with the disruption of the spinal cord blood supply and the limited remedial options in the untoward event that the graft becomes infected. In addition to patients with a failed aortobifemoral bypass, the procedure is indicated in patients with a “hostile abdomen” that precludes an intraperitoneal procedure (e.g., radiation therapy, intestinal stoma, multiple previous abdominal operations), those with severe occlusive disease involving the visceral/infrarenal aorta, and those with a remote history of an infected infrarenal aortic graft with multiple failures of their extra-anatomic axillofemoral bypasses. The contraindications to thoracobifemoral bypass include involvement of the descending thoracic aorta with either aneurysmal or occlusive disease, severe obstructive lung disease, or prior left thoracotomy.

The pre-operative evaluation prior to any redo or direct aortoiliac revascularization including the thoracobifemoral bypass is similar to that associated with any major vascular surgical procedure. This includes the appropriate assessment and risk stratification of the various organ systems and optimization of all comorbidities. The noninvasive imaging should include a vein survey of the upper- and lower-extremity veins to determine their suitability as a conduit for an infrainguinal bypass. Although not essential, an aortogram and bilateral lower-extremity arteriograms are helpful to assess the severity of the occlusive disease and to plan the operative procedure. Notably, it may be difficult to image the infra-inguinal vessels in patients with a failed aortobifemoral bypass due to the inability to deliver contrast. An aortic arch injection may be helpful because the inferior mammary artery often forms an important collateral to the lower extremities. Patients undergoing evaluation for a thoracobifemoral bypass should also have pulmonary function tests with a room air blood gas to confirm that they are suitable candidates for a thoracotomy and a CAT scan of the descending thoracic aorta to confirm that it is a suitable inflow source free of aneurysmal and/or occlusive disease. Lastly, it is helpful to review the initial operative dictation to determine exactly what was done.