Aortic Bifemoral (Aortobifemoral) Bypass

Aortic bifemoral (aortobifemoral) bypass is a surgical procedure that is performed in patients with atherosclerotic disease of the infrarenal aorta and iliac vessels (see the images below). ^[1] Most patients who undergo this procedure have symptoms of claudication, impotence, and poorly healing ulcers. Examination usually reveals absent or very weak femoral pulses.

Endovascular revascularization has become a first-line treatment for aortoiliac occlusive disease. ^[2] However, aortic bypass grafting remains one of the best techniques for exposing and repairing aortic or iliac vessel disease. Although unilateral reconstruction of the iliac vessels used to be common, aortobifemoral bypass is currently preferred. The contralateral disease usually progresses, and a bilateral femoral bypass eliminates future revision of a unilateral bypass. ^{[3, 4, 5]}

The aortic bifemoral bypass is considered to be the most durable of all bypasses for the peripheral system. It is an ideal procedure for patients with aortoiliac disease, aortic aneurysms extending into the iliac arteries, or aortic atherosclerosis. ^[6]

Indications for aortic bifemoral bypass include the following:

• Atherosclerosis of the abdominal aorta or iliac arteries
• Presence of severe claudication symptoms
• Impotence
• Nonhealing ulcers in the extremities
• Aortic aneurysms involving the iliac arteries for which aortoiliac bypass cannot be safely performed
• Acute abdominal aortic occlusion
• Critical limb-threatening ischemia (CLTI)

The procedure can be combined with renal artery or superior mesenteric artery (SMA) revascularization if symptomatic stenoses are present in these visceral vessels. ^{[3, 4, 5]}

In some patients with severe aortoiliac occlusive disease (AIOD), aortoiliac stenting with bifurcation reconstruction (AISBR) may be an alternative to aortobifemoral bypass. ^[7]

Because aortic bifemoral bypass requires general anesthesia and is an extensive procedure, it is contraindicated in patients who are very old, frail, and unfit for surgery. Moreover, patients with symptomatic heart disease, recent stroke, or myocardial infarction (MI) need an extensive preoperative workup.

Those who have a very hostile abdomen (eg, from a previous colostomy), retroperitoneal fibrosis, or horseshoe kidney should be carefully worked up; surgery can be very demanding in these settings and is often associated with extensive blood loss. ^{[3, 4, 5]}  Patients with end-stage renal disease (ESRD) who are on dialysis constitute a high-risk group. ^[8]

Accurate assessment of the aorta and the iliac vessels is critical. Other options for treating aortoiliac disease may be considered. Appropriate patient preparation will minimize complications.

Best practices

A number of radiologic tests can help assess the aorta and iliac vessels. Conventional angiography, the previous standard, is being supplanted by computed tomography (CT) angiography (CTA) and magnetic resonance angiography (MRA).

The benefits of CTA include a peripheral needle-injection site and superb three-dimensional (3D) reconstruction images. The biggest disadvantage of CTA is that visualization of stenosis in the small vessels in the legs is not always possible. MRA is fast becoming a favored technique for visualizing large blood vessels; however, it tends to amplify the degree of stenosis. ^{[3, 4, 5]}

One benefit of contrast angiography is the ability to define the dynamics of collateral vessels and determine how they contribute to the reconstitution of the femoral, popliteal, and even visceral vessels. (See the image below.)

Procedural planning

In aortic surgery, as in most branches of surgery, minimally invasive ^[9]  and laparoscopic techniques have been introduced with the aims of improving outcome, decreasing postoperative pain, and shortening the hospital stay. In the past two decades, many experimental and clinical studies have attempted laparoscopic aortic bifemoral bypass. However, this technique is still challenging, and there is a need for better instruments. Current instruments do not allow very fine anastomoses to be made in difficult areas of the body (eg, the groin and pelvis).

The technique of laparoscopic aortobifemoral bypass surgery for aortoiliac disease has improved. A randomized trial revealed that the laparoscopic approach was safe and resulted in significantly lower postoperative morbidity, reduced stay in the hospital, and faster recovery. However, the number of patients was small and the follow-up period short. ^[10]  

Work by Segers et al suggested that the EndoVascular REtroperitoneoScopic Technique (EVREST), a clampless and sutureless aortic anastomotic technique used during retroperitoneal laparoscopic aortobifemoral bypass in extensive aortoiliac occlusive lesions, appears to be both feasible and safe in this setting. ^{[11, 12]}

Despite the plethora of reports on laparoscopic vascular procedures, the results are not yet considered to have matched those obtained with open techniques. ^[13]  Moreover, complications of laparoscopic procedures continue to occur, and there is still a need for long-term data. ^{[14, 15, 16]}  To make matters worse, the reporting of complications during laparoscopic procedures is not mandatory, and most complications are underreported.

At present, laparoscopic aortic bifemoral bypass is less widely performed than the equivalent open procedure. ^{[17, 18, 19, 20, 21]}  It is not the criterion standard. ^[22] Future improvements in instrumentation and ongoing development of surgeons' skills may someday make this procedure more routine. ^[23]

Besides open surgery, there are several options for treating disease in the aorta and iliac vessels, including the following:

• Angioplasty, with or without stenting
• Endovascular bypass
• Extra-anatomic bypass grafting

Angioplasty, with or without stenting, is an ideal option for isolated lesions in the iliac artery. Currently available stents have excellent patency rates for the iliac vessels. Long lesions in the iliac vessel can be treated with angioplasty, but the results are not durable in the long term. ^{[3, 4]}

The chief advantage of angioplasty is that it eliminates the morbidity associated with aortic bifemoral bypass. Except for bleeding at the groin site and pseudoaneurysm, complications are much less common with angioplasty. Recurrence of stenosis is a problem and may present as recurrence of symptoms.

A unilateral endovascular aortofemoral bypass is performed with available prosthetic material. The proximal end of the aorta is held with a Palmaz stent and sent into the ipsilateral outflow vessel. The procedure is then completed with an associated femorofemoral bypass. There remains a need for additional long-term follow-up data. ^{[3, 4]}

In a small study, patients with total occlusion of the aorta were successfully treated by using an endovascular approach, and midterm patency was favorable. The authors warned that patient selection for this procedure is crucial. The rates of procedural complications, such as embolization, pseudoaneurysm, and artery rupture, are high. ^[24]

Advances in endovascular techniques led to the development of various clampless and sutureless devices for the proximal aortic anastomosis. Here too, there remains a need for long-term data. ^[25] Similar sutureless devices were once recommended for the proximal anastomosis of the vein graft during coronary bypass surgery, but the results were abysmal owing to severe anastomosis at the site in just a few months. Until more long-term data are available, caution should be exercised in using such grafts.

Studies by Maldonado et al ^[26] and Van Haren et al ^[27]  reported good midterm results with the use of a unibody bifurcated endograft (Endologix; Irvine, CA) to treat complex aortoiliac occlusive disease.

In some cases, a patient may have significant aortoiliac disease but may not be a candidate for general anesthesia. For these patients, options such as extra-anatomic bypass grafts are available. Femorofemoral bypass and axillofemoral bypass are decent alternatives to aortic revascularization. Femorofemoral bypass is an excellent procedure if one iliac artery is normal. Axillofemoral bypass is suitable for high-risk patients in whom a transabdominal procedure cannot be performed.

In rare cases, the surgeon may also use the thoracic aorta as an inflow vessel and then tunnel the graft into the groin. Others have used the ascending aorta as an inflow vessel. Use of the thoracic aorta requires a concomitant lateral thoracotomy, whereas use of the ascending aorta requires a median sternotomy. These are rare procedures and are not performed at all community hospitals. Sometimes, aortic bifemoral bypass is combined with a median sternotomy and coronary artery bypass. ^{[28, 29]}

Complication prevention

To prevent complications, a careful workup is essential. In all patients, cardiac and respiratory status must be assessed before the aortic procedure; at least 10-20% of patients have significant coronary artery disease (CAD) that may have be addressed preoperatively. In particular, all high-risk patients must be cleared by the cardiologist before the procedure because most of these patients have CAD.

Even though there are reports of combined coronary artery bypass and aortofemoral bypass procedures being performed in the same setting, these are isolated reports and do not represent the standard of care. Complications with combined procedures are significant.

In the hands of experienced surgeons, the mortality for aortic bifemoral bypass is 2-5%. In hospitals where the surgery is not regularly performed, mortality is much higher. The most common causes of death after surgery are perioperative myocardial infarction (MI) and stroke. Other causes of death include renal and respiratory failure. At 5 years, mortality is 25-30%; at 10 years, mortality is 50%. ^{[3, 4]}

Meta-analysis of multiple studies reveals that the long-term patency of aortic bifemoral bypass grafts ranges from 91% at 5 years to 80% at 10 years. Patency rates are lower if the procedure is performed in patients with ischemic rest pain, ulcerated toes, or coexisting distal disease. Although women tend to have smaller blood vessels, there is no evidence that the results of the procedure are any worse in women than in men. ^{[3, 4, 5]}

A study by DeCarlo et al found that the Society for Vascular Surgery (SVS) femoral runoff score, which can be determined from preoperative axial imaging studies, is associated with long-term limb patency after aortofemoral bypass, with scores of 6 or higher portending worse limb outcomes and a greater incidence of operative complications. ^[30]

A retrospective review of laparoscopic aortobifemoral bypass surgery for aortoiliac occlusive diseases by Bath et al assessed 46 patients over a 10-year period at a single center. ^[31]  The approach was completely laparoscopic in eight patients and laparoscopic-assisted in 38. Median length of stay was 6 days (range, 2-30). Within 30 days, there were two MIs (4.3%), one transient ischemic attack (2.2%), and one death (2.2%). Twelve patients (26.1%) required reintervention during the study period. Primary, primary-assisted, and secondary patency rates at 60 months were 79.4%, 93.9%, and 94.9%, respectively. Overall mortality was 17% at a mean follow-up of 60 months (range, 1-116).