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Axillofemoral Bypass

INTRODUCTION Although atherosclerosis is a diffuse process, distinct patterns of arterial occlusive disease can be identified. One such pattern is disease within the aortoiliac segment. Classic symptoms of aortoiliac occlusive disease include thigh and/or buttock claudication as well as impotence in male patients. This constellation of symptoms is known as Leriche syndrome. Aortoiliac occlusive disease can be seen in isolation, or in combination with infrainguinal occlusive disease. In patients with multilevel disease, the clinical presentation is more severe. The diagnosis of aortoiliac occlusive disease can be made on the basis of history and physical exam. Patients often have an extensive smoking history. Physical exam will reveal diminished or absent femoral pulses. The diagnosis can be confirmed with a number of diagnostic tests. Pulse-volume recordings, a plethysmographic evaluation of lowerextremity arterial circulation, will show decreased waveforms in all segments. This is in distinct contrast to infrainguinal occlusive disease, which will have normal thigh tracings and diminished waveforms in the calf and ankle segments. Arterial duplex mapping can be used to estimate the degree of stenosis or occlusion within the aortoiliac segment, as well as identify any infrainguinal disease. Traditional angiography provides detailed anatomic information of the abdomen, pelvis, and lower-extremity arterial tree. In addition, it can identify patterns of collateral flow around obstructions. If warranted, intervention can be performed at the time of the diagnostic procedure. In the setting of aortoiliac occlusive disease, femoral artery access may be difficult or impossible, and the use of alternative access sites, such as the brachial artery, may be required. Computed tomographic (CT) angiography is another useful imaging modality for defining aortoiliac anatomy and planning intervention. CT angiography has the added advantage of delineating the extent of calcification within the aortoiliac segment, which assists in operative planning. A potential limitation of CT angiography is its ability to evaluate the extent of disease in the tibial vessels in the case of concomitant infrainguinal disease. Magnetic resonance angiography can also be useful in the evaluation of aortoiliac and lower-extremity disease; however, it, too, may be limited in the evaluation of distal circulation and does not provide information on the extent of calcification. Axillofemoral bypass was first introduced in the early 1960s as an alternative to direct aortoiliac reconstruction with an aortoiliac or aortofemoral bypass. Axillofemoral bypass is considered an extraanatomic bypass as it does not course along the normal anatomic path of the vessels being bypassed (Figure 1). The grafts are tunneled subcutaneously, avoiding a midline laparotomy and aortic crossclamping, which significantly reduces the operative stresses, making this a favorable choice for reconstruction in patients at high risk (Figure 2). INDICATIONS Axillofemoral bypass is typically performed in patients with chronic arterial insufficiency and symptoms of critical limb ischemia, such as disabling claudication, rest pain, ischemic ulceration, or gangrene.

BOX 1:╇ Indications for axillofemoral bypass Anatomic Heavy aortic calcification Hostile abdomen Previous surgery Extensive scarring Pelvic irradiation Peritoneal dialysis Comorbid Conditions Severe cardiopulmonary disease Severe renal or hepatic disease Otherwise unfit for major surgery Infectious Infected intraabdominal graft Other intraabdominal infection Mycotic aneurysm Aortoenteric fistula Temporary Need for temporary visceral and renal perfusion during major aortic reconstruction

Occasionally it may be performed in the setting of acute occlusion or aortic dissection resulting in acute lower limb ischemia. The timing of intervention depends on the indication for the operation as well as the overall health status of the patient. The primary indication for axillofemoral bypass is a patient with severe aortoiliac disease, who is unable to undergo aortofemoral bypass. Aortofemoral bypass may be deemed unfavorable on the basis of anatomic considerations such as a heavily calcified aorta; a hostile abdomen or the need for peritoneal dialysis; medical comorbidities such as severe cardiopulmonary, renal, or hepatic disease; or the presence of intraabdominal infection (Box 1). Another indication is the temporary placement of axillofemoral bypass in order to maintain visceral and renal artery perfusion during complex thoracoabdominal aortic reconstruction. The development and advancement of endovascular therapies has altered, and will continue to alter, the treatment of aortoiliac disease. In the early 1990s, reports demonstrating the efficacy and relative durability of angioplasty and stenting of focal stenoses (Trans- Atlantic Inter-Society Consensus [TASC] A and B lesions) led many patients to undergo endovascular treatment as their primary mode of therapy, reducing the number of aortofemoral reconstructions performed. Since the mid-1990s, advancements for crossing total occlusions (TASC C and D lesions), including the development of subintimal angioplasty, have made the treatment of an even greater number of patients with endovascular methods possible. As a result, many of the patients who ultimately require surgical repair are older, have more significant comorbidities, and are thus not candidates for direct aortic reconstruction, therefore requiring axillofemoral bypass. A small subset of patients presenting with aortoiliac occlusive disease will also have associated abdominal aortic aneurysms, and axillofemoral bypass is not the preferred treatment for this group. These patients require aortofemoral bypass to address the aneurysmal component of the disease process, unless the aneurysms are particularly small or the patient is believed to be a prohibitive surgical risk. For those patients in whom the abdominal aorta is unsuitable for inflow, an alternative is to use the supraceliac or distal thoracic aorta for inflow, gaining access through a transperitoneal incision with medial visceral rotation, a retroperitoneal incision, or a thoracotomy. When the common femoral artery is occluded, an alternative outflow artery must be selected, such as the profunda femoral artery, superficial femoral artery, or popliteal artery. In patients with combined aortoiliac and infrainguinal occlusive disease requiring intervention, decisions regarding the extent of reconstruction are based on the patient’s clinical status. In patients with claudication, rest pain, or minor tissue lesions, it is preferable to first address the proximal aortoiliac segment. Restoration of inflow to the femoral level alone should be sufficient to relieve symptoms and the infrainguinal component treated subsequently only if needed. In cases of severe limb-threatening ischemia, concomitant axillofemoral and infrainguinal reconstruction may be required. PREOPERATIVE EVALUATION Patients should undergo a thorough preoperative evaluation. Many patients are selected for axillofemoral bypass on the basis of their comorbid conditions and therefore should be medically optimized to the greatest degree possible prior to surgery. The choice of donor axillary artery depends on a number of factors. The axillary arteries may be evaluated by a number of invasive and noninvasive methods. Most simply, blood pressure measurements are taken in both arms and compared. If there is a significant gradient between the two sides (>20–30╯mm╯Hg), the arm with the higher pressure is chosen as the inflow artery. The presence of such a gradient in the upper extremities may itself prompt further evaluation. Upper-extremity pulse-volume recordings and Doppler waveforms are useful in guiding therapy. Direct duplex of the subclavian arteries can be used to identify proximal stenoses. In addition, the inflow arteries may be evaluated with CT angiography or magnetic resonance angiography. Finally, digital subtraction angiography provides detailed anatomic information on the upper-extremity circulation. Full evaluation should include views of the aortic arch and great vessels. Although an invasive procedure, digital subtraction angiography provides the opportunity to address any lesion with angioplasty and stenting prior to the bypass procedure. In cases with no notable disease on either side, the right axillary artery is typically selected for inflow because of the somewhat higher propensity for the left subclavian artery to develop a stenosis. This choice is made despite the fact that most patients are right-handed. Some authors advocate choosing the axillary artery ipsilateral to the lower extremity with the more severe symptoms. Grafts should not be based off an upper extremity with significant distal ischemia or where dialysis access is present. Additional anatomic considerations include the presence of thoracic outlet syndrome, breast cancer, or the presence of an ostomy, abdominal hernia, or previous surgery, which may complicate graft positioning. Finally, in patients undergoing axillofemoral bypass for reasons such as intraabdominal sepsis, who in the future may be candidates for aortic reconstruction via left retroperitoneal approach, the right axillary artery should be used to avoid interference with the retroperitoneal approach by a left-sided graft. TECHNIQUES Although this procedure can be performed under local anesthesia with sedation, general anesthesia is preferred because of the large volume of local anesthetic required to cover the extensive area, including all incisions and the subcutaneous tunnels. The room should be kept warm to prevent hypothermia, given the large body surface area that is exposed. The patient is positioned supine on a fluoroscopy-compatible table with the donor arm abducted to 90 degrees. A rolled towel is placed between the scapulae to facilitate exposure of the medial-most portion of the axillary artery. This also facilitates exposure of the lateral body wall for creation of the subcutaneous tunnel. The chest, abdomen, pelvis, and upper thighs are prepared and covered with impervious, sterile, plastic dressing. This permits wide exposure in the event that a thoracotomy or celiotomy is required. The donor arm is prepared, and an impervious stocking is placed to the level of the mid upper arm. This allows the operator to move the arm during the procedure to ensure that undue tension has not been placed on the axillary anastomosis. A transverse, infraclavicular incision is made approximately one fingerbreadth below the lateral third of the clavicle, and the dissection is carried down through the clavipectoral fascia. The pectoralis major muscle fibers are split in the horizontal plane, exposing the deep fascia with the investing fat of the axillary artery, vein, and brachial plexus below. The pectoralis minor may be retracted laterally to enhance exposure of the first portion of the axillary artery; however, in most cases, it is preferable to divide the pectoralis minor. This both improves exposure and reduces the risk of graft kinking. The axillary vein is first identified, then isolated and retracted caudally. Frequently this requires ligation of venous tributaries. The axillary artery is then exposed and encircled with silicon vessel loops. Branches of the axillary artery are either controlled with silicone vessel loops under gentle tension or with removable microclips. Division of these arteries is rarely required. Because of the proximity to the brachial plexus, it is best to avoid excessive use of electrocautery in the vicinity of the vessels (Figure 3). The femoral arteries are exposed through longitudinal groin incisions. This approach allows flexibility in the placement of the femoral anastomoses and facilitates the performance of any adjunctive procedures, which may be required, such as femoral endarterectomy. Oblique incisions may be used but can limit the ability to perform adjunctive procedures in the femoral vessels. If such incisions are used, the location of the femoral bifurcation should be identified preoperatively. The anastomoses are generally placed in the distal common femoral artery over the takeoff of the profunda femoris artery. In cases with a concomitant superficial femoral artery occlusion, the anastomosis can still be placed onto the common femoral artery, provided there is no stenosis of the profunda femoris artery. If there is an orificial stenosis, the distal anastomosis can be used to perform a profundaplasty, with the heel of the anastomosis over the common femoral artery and the toe onto the profunda femoral artery. Direct anastomosis to the profunda femoris may also be performed. If the common, superficial, and deep femoral arteries are all occluded, direct reconstruction to the popliteal artery may be required. Once the vessels are exposed, a long, standard tunneling device is used to create a tunnel between the axilla and the groin. The graft must initially take a lateral course under the pectoralis major and away from the axillary anastomosis before heading caudally in the subcutaneous tissue along the midaxillary line. It then courses anteromedially over the iliac crest and inguinal ligament to the groin. The use of a counter incision below the inferior aspect of the pectoralis major on the chest wall facilitates tunneling along the abdominal wall, thereby avoiding inadvertent injury to the abdominal contents. In the cases when a bifemoral bypass is being performed, a suprapubic tunnel for the crossover bypass is made in the subcutaneous space over the inguinal ligaments with either a tunneling device or large aortic clamp. An externally supported polytetrafluoroethylene (PTFE) or Dacron graft is used for conduit. An 8-mm graft is preferred, but a 6-mm graft may be used in patients with small arteries without compromising patency. The graft is passed through the tunnels, and the patient is systemically heparinized. The graft is then cut to the appropriate length. It is essential that the graft not be made too short to avoid undue tension on the anastomoses, as well as not too long to prevent redundancy and possible kinking of the graft. We prefer to leave external ring supports to within 1╯cm of the anastomosis as a further protection against kinking. The axillary anastomosis is fashioned so that the graft takes an acute angle relative to the artery as it travels laterally to the abdominal sidewall (Figure 4). This is essential to reduce tension on the anastomosis and avoid graft dehiscence. It is sewn with a 5-0 or 6-0 polypropylene suture. The axillary artery is generally soft and delicate, so it should be handled with care when dissecting or suturing to avoid tearing of the vessel. The anastomosis can be constructed either in standard fashion from heel and toe toward the center of the arteriotomy, or the suture can be initiated at the midpoint of the posterior aspect of the anastomosis and run toward the heel and toe. In either case, it is essential to ensure that the posterior suture line is secure and without gaps because this area is difficult if not impossible to repair after the suture line is completed. The femoral anastomosis is sewn in standard fashion, beginning with the heel and proximal half of the anastomosis, then completing the distal anastomosis with the toe suture. Confirmation of the patient’s pulse status in both upper and lower extremities should be performed prior to reversal of heparin and closure. The incisions are closed in layers using absorbable polypropylene sutures. We prefer to use a subcuticular closure for all skin incisions, as staples and exposed sutures can catch clothing, requiring dressings until removed. GRAFT CONFIGURATIONS Multiple possible graft configurations can be used when constructing the axillofemoral bypass, depending on the surgeon’s preference and the patient’s anatomy (Figure 5). There are now preformed grafts available with the femorofemoral graft fastened to the long axillary graft. Using such grafts reduces the total number of anastomoses from four to three, thereby reducing operative time. The order of anastomosis completion depends on the surgeon’s preference as well as the number of operators. It is advantageous to have two teams so that anastomoses can be performed simultaneously, reducing operative and total anesthesia time. RESULTS The overall 5-year patency for axillobifemoral grafts, once as low as 30% to 40%, is now as high 60% to 80% since the introduction of externally supported grafts. These external rings prevent compression of the graft when the patients lie on their sides. Although this effect has not been proven by direct comparison, the use of externally supported grafts has been widely adopted on the basis of these theoretical advantages. There does not appear to be any difference in externally supported Dacron versus PTFE. The actual patency rates achieved vary widely according to the indication for surgery, patient selection, and extent of disease. Patients undergoing axillobifemoral bypass for infected abdominal grafts originally placed for aneurysmal disease, without concomitant occlusive disease, can be expected to have better patency than patients for whom the grafts were placed for severe occlusive disease. Axillobifemoral bypass grafts have better 5-year patency than the axillounifemoral grafts, presumably because of the increased flow rate in the axillary limb. In the event of graft thrombosis, patency can frequently be reestablished with thrombectomy performed under local anesthesia. We prefer to perform these procedures under direct fluoroscopic guidance for several reasons. First, the chance of injury to the native vessel is reduced by preventing overdistention of the balloon-thrombectomy catheters. Second, it allows the surgeon to identify and possibly treat any underlying inflow or outflow lesions with an endovascular approach. Finally, should a revision be required, an angiogram defining the patient’s anatomy can be obtained. When comparing reports in the literature regarding axillofemoral bypass grafts, it is important to note that there is considerable variability in the techniques used and the outcome measures defined (e.g., primary versus secondary patency). In addition, it must be noted whether graft components are considered separately in patency calculations, as some authors may consider the axillofemoral and the femorofemoral components as distinct grafts. COMPLICATIONS Potential complications of this procedure include the standard risks of bleeding and wound infection common to all surgical procedures. The risk of graft infection is especially problematic because the majority of patients undergoing these procedures already have limited reconstructive options and significant medical comorbidities. Another potential complication is injury to intrathoracic or intraabdominal contents during tunneling of the graft. As noted earlier, care must be taken to avoid injury to other neurovascular structures, such as the axillary vein or brachial plexus. POSTOPERATIVE MANAGEMENT Patients are placed on an antiplatelet agent if not already on one preoperatively. Anticoagulation with warfarin is reserved for patients with a known hypercoagulable state, or in whom a secondary procedure was required to reestablish patency. As in all patients with peripheral artery disease, the use of a statin is recommended. Graft surveillance is performed every 3 months for the first year, every 6 months for the second year, and yearly thereafter. The need for a subsequent intervention or other abnormal findings on duplex may necessitate more frequent surveillance. CONCLUSIONS Axillofemoral bypass is an important and valuable option in the treatment of patients with aortoiliac occlusive disease. For many reasons, it is the preferred or only viable option for patients with significant anatomic or medical comorbidities, which preclude standard bypass options. Axillofemoral bypass can be performed with acceptable morbidity, mortality, and long-term results, even in patients at high risk. For these reasons, surgeons should be familiar with the indications and application of this technique. S u g g e s t e d R e a d i n g s Johnson WC, Lee KK: Comparative evaluation of externally supported Dacron and polytetrafluoroethylene prosthetic bypasses for femoralfemoral and axillofemoral arterial reconstructions, J Vasc Surg 30:1077– 1083, 1999. Landry GL, Moneta GI, Taylor LM Jr, et al: Axillofemoral bypass, J Vasc Surg 14:296–305, 2000. Musicant SE, Giswold ME, Olson CJ, et al: Postoperative duplex scan surveillance of axillofemoral bypass grafts, J Vasc Surg 37:54–61, 2003. Schneider JR, Golan JF: The role of extraanatomic bypass in the management of bilateral aortoiliac occlusive disease, Sem Vasc Surg 7:35–44, 1994. Seeger JM, Preetus HA, Wellborn MB, et al: Long-term outcome of treatment of aortic graft infection with staged extra-anatomic bypass grafting and aortic graft removal, J Vasc Surg 32:451–459, 2000.

Figure 1: Typical configuration of a right axillobifemoral bypass.

Figure 2: A three-dimensional reconstruction of a computed tomographic angiogram in a patient with a left axillobifemoral bypass.

Figure 3: Following division of the pectoralis major, the

approximate position of the axillary anastomosis at the distal portion of the first segment of the axillary artery is shown (arrow). The divided pectoralis minor is indicated by the dashed lines and overlies

the second portion of the axillary artery.

Figure 4: The course of the graft at the proximal anastomosis with the axillary artery.

Figure 5: Standard outflow configurations for axillobifemoral grafts.

A, C configuration: axillofemoral graft precedes femorofemoral graft (authors’ preference). B, Alternate C configuration: femorofemoral graft precedes axillofemoral graft. C, “Rutherford” configuration. D, Lazy S configuration. E, Ram’s horn configuration: stress is displaced from the anastomosis to the inferior curve of the graft, reducing the risk of disruption (preferred in obese patients). Can be used with either the C

or alternative C configuration.

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