Historical Background
Extraanatomic procedures were developed as alternatives to direct aortofemoral bypass for patients deemed to be at high risk for direct aortic surgery or for those presenting with a “hostile” abdomen, an infection of the native aortoiliac arterial system, or prior prosthetic replacement of the aortoiliac system. The first extraanatomic procedure to be described for treatment of aortoiliac occlusive disease was the femoral-femoral bypass, which was first reported by Freeman in 1952. In 1962 Vetto provided the first comprehensive description of a significant number of cases with an analysis of clinical outcomes. Axillofemoral bypass was first reported by Blaisdell and Louw in 1963, and by 1968 growing experience supported this option as a safe alternative to direct aortic reconstruction. The feasability of thoracofemoral bypass was first reported in 1961, but it was not until the 1980s and 1990s that retrospective reviews reported long-term outcomes for patients treated with this approach. Balloon thromboembolectomy was introduced by Fogarty and colleagues in 1963, with reports of its utility for treatment of aortoiliac embolism appearing soon thereafter.
Preoperative Preparation
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Prophylactic antibiotics. Extraanatomic bypass is nearly always performed with prosthetic material, either expanded polytetrafluoroethylene (ePTFE) or polyester. Infection of these grafts is associated with a high risk of loss of life or limb. Thus preexisting infection should be treated to the extent possible before placing the grafts, and antibiotics administered to reduce the risk of secondary graft infection.
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Risk assessment. Cardiac, pulmonary, and renal function should be assessed and optimized.
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Emergent or urgent intervention. Arterial embolectomy is implicitly an urgent or emergent procedure in most cases, so preoperative care is usually limited to volume resuscitation, transfusion, and other measures to optimize organ function. Mortality related to arterial embolectomy remains high, due to advanced age and associated comorbidities, particularly cardiac disease.
Pitfalls and Danger Points
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Injury to the axillary and subclavian arteries, veins, and brachial plexus. The axillosubclavian artery is characteristically less robust than the femoral artery, and injury from dissection, clamp placement, or sutures tearing through the artery is more likely. Injury could conceivably require transection of the clavicle, sternotomy, or thoracotomy to facilitate repair. The axillary artery and vein and brachial plexus may also be injured during tunneling of the axillofemoral graft.
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Disruption of the axillary artery anastomosis. The axillary artery anastomosis should be placed as medial (adjacent to the clavicle) as possible and to allow some redundancy in the axillary end of the axillofemoral graft. This will minimize the risk of “axillary pullout,” or disruption of the axillary anastomosis with arm abduction. The axillofemoral graft should also be placed in the midaxillary line to reduce the risk of kinking during torso flexion.
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Bladder or bowel injury. Bladder or bowel injury is possible when tunneling a femoral-femoral graft if the graft is placed in the retrofascial space or if the patient has a suprapubic hernia, particularly if there has been previous surgery in this area.
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Iatrogenic injury during embolectomy. Embolectomy leads to arterial perforation, rupture, and dissection. The catheter should not be “forced” when advancing it, (i.e., if the catheter meets with resistance, it should be withdrawn a significant distance and then readvanced and rotated somewhat to try to “give a different look” to the catheter tip). The surgeon must learn to get tactile information from both hands, (i.e., a sense of resistance when advancing the catheter and drag on the catheter when withdrawing with the balloon inflated), and a sense of the resistance to inflation using the syringe. Pulling back on an overinflated balloon can do irreparable damage in the short term and produces significant vasospasm, particularly in the infrapopliteal arteries.
Femoral-Femoral Bypass
Incision and Exposure
Femoral-femoral bypass depends on the ability of one “donor” iliac artery to supply enough blood flow to perfuse both the donor and the “recipient” legs ( Fig. 29-1 ). Oblique, groin-crease incisions may be used, but longitudinal groin incisions centered over the femoral arteries and beginning approximately at the inguinal ligament provide the most flexibility and are preferred by most surgeons. Incision length depends on patient habitus. Anastomoses to the common femoral artery may extend onto the deep or superficial femoral artery and may occasionally be made directly to the deep or superficial femoral arteries. This decision is most often made after exposure, inspection, and palpation of the femoral arteries, but it is also predicted by complete preoperative imaging. The extent of dissection to control femoral arteries and the use of vascular clamps, silicone elastomer (Silastic) vessel loops, or occasionally balloon catheters are dictated by the site of anastomosis, surgeon preference, and whether there has been previous surgical exposure of the femoral arteries.
Tunneling of the Bypass Graft
Most femoral-femoral grafts are placed in the immediately prefascial subcutaneous position. The tunnel should begin in line with the planned arteriotomy to be used for anastomosis and should be made in a continuous arc, avoiding abrupt right-angle turns to reduce the risk of graft kinking and subsequent thrombosis. The tunnel can be made bluntly with index fingers from both sides, with fingers meeting in the midline. A large clamp, such as a curved DeBakey aortic clamp, or uterine packing forceps may be used to complete the tunnel, but the surgeon must be careful not to perforate the fascia or a hollow viscus in an unsuspected hernia. The same clamp may be used to pull the graft from one side to the other, taking care that the graft does not twist during passage. Some surgeons prefer larger-diameter grafts, but there is no evidence that grafts larger than 6 mm in diameter perform better hemodynamically or that patency is improved with larger-diameter grafts. A 6-mm-diameter, externally supported ePTFE graft is an acceptable choice, but there is also no evidence that external support or the use of ePTFE as opposed to polyester is associated with better outcomes.
Anastomosis
Systemic heparin or another suitable anticoagulant is administered, and in most cases a longitudinally oriented or slightly oblique arteriotomy is created in a convenient place for anastomosis. Making the anastomosis on a more distal portion of the femoral system, such as the deep or superficial femoral artery, may be dictated by local anatomy and may reduce the tendency of the graft to kink in the sagittal plane in patients with protuberant abdomens. As with most end-to-side anastomoses, arteriotomies are made about three times as long as the graft diameter. The graft ends are spatulated by placing a curved hemostat on the graft and then using a scalpel to cut the ePTFE graft along the inside of the hemostat curve. An end-to-side graft to artery anastomosis is then created using running 5-0 or 6-0 polypropylene or CV-5 or CV-6 polytetrafluoroethylene (PTFE) suture. The donor-side anastomosis is usually performed first, although either side may be completed first and the anastomoses may be performed simultaneously if there are two surgeons. For at least one anastomosis, preferably the recipient side, the suture is not tied to complete the anastomosis until the clamps and vessel loops have been briefly released to fill the graft with blood and to allow expulsion of air and thrombus or other debris.
Closure
A sterile, handheld continuous wave Doppler probe is used to interrogate outflow on both donor and recipient sides and to ensure that flow is qualitatively better on the recipient side, as evident by a higher Doppler frequency shift, with the graft open than with the graft clamped. Anticoagulant may then be reversed, the wounds may be closed with running subcutaneous absorbable suture, and the skin may be closed with staples in most cases.
Axillofemoral Bypass
Selection of a Donor Artery
The versatility of the axillofemoral bypass depends on the ability of one axillosubclavian artery to supply enough blood flow to adequately perfuse both the donor arm and one (axillounifemoral bypass) or more often both (axillobifemoral bypass) legs. Either axillary artery may be a donor artery, but the donor vessel is almost always the ipsilateral axillary artery in the case of axillounifemoral bypass ( Fig. 29-2 ). However, if there is any suggestion of a stenosis in the proposed donor side, as evident by a weak brachial or radial pulse, or presence of a lower blood pressure than in the contralateral arm, then preoperative angiography is warranted.
Incision and Exposure
The operation is performed with the patient supine but with elevation of the flank ipsilateral to the donor artery using a soft roll or gel pad. In most cases the procedure is performed under general anesthesia. Wide prepping and draping are essential to allow exposure of the ipsilateral clavicle, lower neck, anterior chest and sternum, flank, abdomen, and both groins. The ipsilateral arm is abducted to 90 degrees and may be prepped into the field with the hand and lower arm placed in a stockinette. Groin incisions are made as described earlier. The first portion of the axillary artery, between the clavicle and the pectoralis minor muscle, is exposed using a transverse incision about 5 cm in length that is placed a few centimeters inferior to the midportion of the clavicle. The deep fascia is incised parallel to the incision, and the pectoralis major muscle fibers are split, exposing the fat containing the axillary artery and vein and their branches. The artery is dissected free of the surrounding tissues, and small branches are ligated as necessary from the clavicle medially to the medial edge of the pectoralis minor muscle. At least one large venous branch crossing the artery is almost always encountered, ligated, and divided to allow exposure of the artery. Division of the pectoralis minor insertion may improve exposure.
Tunneling the Bypass Graft
A subcutaneous tunnel is created between the axillary artery and the ipsilateral groin incision. The tunnel is brought posterior to the pectoralis minor muscle. These tunnels are most conveniently made with a tubular tunneler. Early descriptions included placement of an intermediate incision at the midpoint of the tunnel, but this is not necessary with a 65-cm-long Gore tunneler (W.L. Gore and Associates, Newark, Del.). The graft is passed through the tubular tunneler, taking care not to allow it to twist during passage. An externally supported 8-mm ePTFE graft can be used. The use of larger grafts may predispose the patient to thrombosis. There is no evidence that external support or a specific graft material is associated with superior results.
Axillary Anastomosis
The patient is systemically anticoagulated with heparin or another suitable anticoagulant, the axillary artery is controlled with clamps, and a 1.5- to 2-cm longitudinal arteriotomy is created in the axillary artery. Since the axillary artery is easily kinked when elevated into the wound following clamp placement, care should be taken not to puncture the back wall during the performance of the arteriotomy. Alternatively, the thoracoacromial branch can be divided near its take off from the axillary artery and used as an entry point for Potts scissors. The axillary end of the graft is spatulated using a hemostat, and an end-to-side graft to axillary artery anastomosis is created using running 5-0 or 6-0 polypropylene or CV-5 or CV-6 PTFE suture. In addition to medial placement of the axillary anastomosis, some redundancy of the graft in the axilla reduces the risk of axillary pullout because of excess traction upon abduction of the arm.
Femoral Anastomosis
If the graft is placed in the axillounifemoral configuration, then the distal anastomosis is made to the femoral arterial system. In the case of an axillobifemoral configuration, two common approaches have been described for the distal anastomoses. The preferred approach is to first place the femoral-femoral graft, create an oval graftotomy in the ipsilateral anastomotic “hood” of the femoral-femoral graft, and then anastomose the spatulated femoral end of the axillofemoral graft to the femoral-femoral graftotomy ( Fig. 29-2 , C ). An alternative approach is to first place an axillounifemoral graft, create an oval graftotomy on the femoral anastomotic hood of the axillounifemoral graft, and then perform the ipsilateral anastomosis of the femoral-femoral graft to this graftotomy ( Fig. 29-2 , D ). A number of other approaches have been described for revascularization of target femoral arteries. Grafts are also available with manufactured femoral-femoral “side arm” components. Prior to completing the distal anastomoses, the grafts are flushed to allow expulsion of air, thrombus, or other debris.
Closure
A sterile, handheld Doppler probe is used to interrogate outflow, ensuring augmented flow with the graft open than when clamped. It is important to assess flow in the donor arm distal to the axillary anastomosis by checking the radial pulse after completing all anastomoses. Poor flow in the donor-side hand implies a technical defect, thrombosis, or occult flow-limiting lesion, which must be addressed immediately to assure adequate flow in the donor arm. A running subcutaneous absorbable suture is used to close the subcutaneous tissue and the skin closed with staples or suture.
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