Lower extremity surgical bypass techniques

INTRODUCTION — Lower extremity surgical bypass involves suturing a vascular conduit, preferably autogenous vein, from a site proximal to the level of an arterial obstruction to a distal site of uninvolved artery. Preoperative vascular imaging identifies the location of obstruction and proposed distal target, along with the preferred conduit. Prior to revascularization, a thorough preoperative medical risk assessment is necessary to identify comorbidities, which are common, and to optimize the patient before surgery. However, for patients who require emergency revascularization, vascular imaging may need to be performed intraoperatively, and preoperative medical risk assessment may be limited.

The most common indication for lower extremity surgical bypass is peripheral artery disease (PAD) due to atherosclerosis. PAD is increasingly common as the population ages, with epidemiological studies estimating that 15 percent of individuals over the age of 70 are affected [1]. PAD is part of a systemic atherosclerotic disease process that has a predilection for certain vascular beds, including the lower extremity, coronary, and cerebral vasculature. PAD often coexists with coronary and carotid artery disease. The overall prognosis is poor with mortality rates of 25 to 30 percent at five years with most deaths attributable to acute coronary syndromes and stroke.

The mainstay of treatment of PAD is medical therapy consisting of antiplatelet agents and statins to reduce the risk of future cardiovascular events, smoking cessation, and an exercise program of daily walking. For patients who present with claudication, progression to limb-threatening ischemia occurs in only 10 to 15 percent of patients, and the need for lower extremity amputation is uncommon. Progression to chronic limb-threatening ischemia (CLTI) often mandates intervention.

The traditional treatment of infrainguinal PAD was primarily an open surgical one, supplemented by endovascular therapy, but the approach has shifted to predominantly endovascular first approach with open surgery reserved for long-segment disease, or for failures of an endovascular-first approach. Both approaches to treatment are important and necessary as part of an aggressive limb salvage program. A decision to proceed with endovascular or surgical intervention for any indication requires thoughtful consideration of the patient's clinical presentation, functional capacity and medical comorbidities, and anatomic pattern of disease. Guidelines recommend using a classification system for CLTI based on wound extent, ischemia, and presence of foot infection to better identify those patients who would benefit from revascularization and improve outcomes [2]. The Society for Vascular Surgery Threatened Limb Classification System (Wound, Ischemia, foot Infection [WIfI] stage (figure 1)) is used for this purpose.

The indications, preoperative evaluation, conduit options, and techniques for lower extremity surgical bypass are reviewed. The overall approach to treating patients with symptomatic PAD, including claudication and chronic limb threatening ischemia is reviewed separately.

The principles of lower extremity bypass grafting are similar regardless of indication. Additional information for other conditions that may require open surgical bypass techniques can be found in separate topic reviews. (See "Femoral artery aneurysm" and "Surgical and endovascular repair of popliteal artery aneurysm" and "Embolism to the lower extremities" and "Surgical management of severe lower extremity injury" and "Surgical resection of primary soft tissue sarcoma of the extremities".)

INDICATIONS

Peripheral artery disease (PAD) — Lower extremity surgical bypass is commonly used to treat PAD related to atherosclerotic occlusion, which has predictable anatomic patterns and often involves points of arterial bifurcation (eg, femoral bifurcation) and fixation (eg, adductor hiatus).

Most patients with PAD are asymptomatic and are at low risk for limb loss; intervention is not warranted in asymptomatic patients. Symptomatic patients commonly present with claudication, although a significant subset can present with chronic limb-threatening ischemia (CLTI).

●For patients with claudication, revascularization should be pursued only for those patients who will derive a functional benefit (ie, increase in walking distance). It should also be noted that revascularization for disabling claudication is limited to those patients presenting with more proximal anatomical patterns of disease (ie, iliofemoral or femoropopliteal). Claudication is not usually considered a reasonable indication to perform a distal (eg, femorotibial) bypass, and distal bypass to a tibial artery for the treatment of claudication is rarely indicated. A distal bypass to the infrapopliteal vessels should be performed only in situations of CLTI in which femoropopliteal bypass is not feasible or will not provide direct flow into patent runoff vessels.

●For patients who present with CLTI (rest pain, varying degrees of tissue loss), progression to amputation is likely in the absence of some form of revascularization. CLTI is therefore considered a strong indication for intervention (endovascular revascularization, surgical bypass). However, CLTI is not an absolute indication for intervention and some patients who present with lower Wound, Ischemia, foot Infection (WIfI) stages (figure 1) can be managed without revascularization. Since patients with CLTI commonly have multilevel arterial occlusive disease that involves both the femoropopliteal and tibioperoneal segments, lower extremity surgical revascularization usually comprises bypass from the common femoral artery to the tibial arteries. But many patients, particularly those with diabetes, who have disease predominantly below the knee, may be effectively treated with a shorter bypass originating from the superficial femoral artery or popliteal artery.

When deciding between endovascular or surgical treatment for PAD, available guidelines suggest that the magnitude of tissue loss and the anatomic location and extent of disease are the most important determinants of treatment outcome and that patients with less extensive atherosclerotic disease and lower WIfI limb threat stages should initially be treated using an endovascular approach, while those with more severe tissue loss and disease extent should be treated by surgical bypass [2-4]. However, an increasing number of patients are treated using an endovascular-first approach [5]. This has been justified by continued improvements in endovascular treatment outcomes likely related to advances in endovascular technique and instrumentation, as well as better and more widespread adherence to best medical therapy to treat atherosclerosis.

As a result, lower extremity surgical bypass is less commonly used and some surgeons have relegated the role of surgical bypass to the treatment of endovascular failures, suggesting that an endovascular-first approach has limited downsides and that this approach does not adversely affect the outcomes of surgical bypass. On the other hand, others have reported that endovascular failure can adversely affect limb salvage. The Bypass versus Angioplasty in Severe Ischaemia of the Leg (BASIL) trial was the first trial comparing open surgery with endovascular revascularization, and while it established clinical equipoise, the patient population was highly selected. The BEST CLI trial and BASIL 2 trials aimed to better define the preferred treatment option for CLTI, which remains controversial [6]. (See "Management of chronic limb-threatening ischemia".)

Other conditions — Lower extremity surgical bypass may also be needed to treat other disease entities such as femoral or popliteal artery aneurysms, arterial thromboembolism or dissection, popliteal artery entrapment syndromes, various forms of inflammatory arteritis, soft tissue sarcomas with vascular encasement, and arterial injury, which may be due to blunt or penetrating trauma. Surgical bypass for these indications is usually tailored to the anatomic disease pattern as determined by arteriography but uses the same basic principles that are discussed below. In general, these tend to be shorter segmental bypass grafts.

Lower extremity peripheral artery aneurysms (femoral, popliteal) are usually treated based on a threshold diameter or presence of mural thrombus in asymptomatic patients, or for symptoms of acute or chronic limb ischemia (algorithm 1 and algorithm 2). (See "Femoral artery aneurysm" and "Popliteal artery aneurysm" and "Surgical and endovascular repair of popliteal artery aneurysm".)

Arterial thromboemboli, dissection, and trauma all present with acute limb ischemia, while entrapment syndromes, vasculitis, and tumors will present with more chronic symptoms. The indications for surgical management for these diseases are reviewed separately. (See "Embolism to the lower extremities" and "Nonatheromatous popliteal artery diseases causing claudication or limb-threatening ischemia" and "Surgical management of severe lower extremity injury" and "Surgical resection of primary soft tissue sarcoma of the extremities".)

CONTRAINDICATIONS — Contraindications to lower extremity revascularization are few. In general, most patients benefit from an aggressive approach to limb salvage, leading to endovascular or surgical revascularization. However, any patient who is nonambulatory or has a limited functional capacity, has a prohibitive medical risk (eg, unstable coronary heart disease) or a limited life expectancy, has unreconstructable arterial anatomy, or presents with advanced gangrene with a nonsalvageable extremity is best managed with a "wound hospice approach" or primary amputation for advanced Wound, Ischemia, foot Infection stage chronic limb-threatening ischemia. (See "Lower extremity amputation".)

PREOPERATIVE EVALUATION — The preoperative evaluation includes a thorough vascular evaluation to identify appropriate targets for bypass grafting and to determine the availability of vein conduits, as well as medical risk assessment. However, for patients who require emergency revascularization, vascular imaging may need to be performed intraoperatively, and preoperative medical risk assessment may be limited.

Medical risk assessment — Under elective circumstances, medical risk assessment is particularly important for patients with peripheral artery disease (PAD), given the high likelihood of cardiac disease and other comorbidities (eg, diabetes, chronic kidney disease) [7]. As a result, preoperative risk stratification should be performed in all patients. Consultation with appropriate clinical specialties, particularly cardiology, is advised. Medical optimization improves the patient's overall condition and suitability for surgical intervention and includes evaluation and treatment of atherosclerotic risk factors (eg, hypercholesterolemia, hypertension, hyperglycemia). Risk factor modification may reduce the incidence of perioperative myocardial infarction and limb loss. (See "Evaluation of cardiac risk prior to noncardiac surgery" and "Management of cardiac risk for noncardiac surgery".)

Smoking cessation is strongly recommended prior to any revascularization procedure; bypass graft patency is decreased among those who continue to smoke [8,9]. (See "Evaluation of perioperative pulmonary risk" and "Strategies to reduce postoperative pulmonary complications in adults".)

Vascular evaluation — The main goals of the vascular evaluation are to quantify and document the severity of vascular disease, identify potential autogenous vein conduits, and identify appropriate proximal and distal targets for the surgical anastomoses.

Noninvasive studies in the vascular laboratory are an essential component in this assessment. Segmental arterial pressures along with an ankle-brachial index (ABI) and pulse volume recordings should be obtained in all patients presenting with PAD. (See "Noninvasive diagnosis of upper and lower extremity arterial disease".)

These studies help establish the extent, severity, and location of the patient's occlusive disease and also serve as a baseline with which postoperative studies can be compared. Arterial duplex ultrasonography is another important tool for preoperative assessment.

Vein mapping — Vein mapping is performed to determine the patency, diameter, and length of the great saphenous vein available for use as an autogenous conduit [10-12].

The ipsilateral great saphenous vein is generally the preferred conduit for lower extremity revascularization. Ideally the vein conduit should measure greater than 3 mm in diameter [10-14], although smaller veins may be appropriate.

On occasion, it may be necessary to use the contralateral great saphenous vein, the small saphenous vein, or even arm veins (eg, cephalic, basilic) [15], or to use multiple segments of vein to prepare a sufficiently long conduit. Vein mapping of these alternative sites should be done preoperatively if an adequate length of the ipsilateral great saphenous vein is unavailable.

Marking the skin overlying the great saphenous vein with indelible ink will help with the location of the skin incisions necessary for harvesting this conduit and is done after vein mapping is completed.

Arteriography — For all patients undergoing lower extremity revascularization, we obtain digital subtraction angiography (image 1) to aid in selecting the best approach to revascularization (open versus endovascular) and for planning the procedure. A good quality arteriogram can typically be accomplished with less than 100 mL of nonionic contrast media and, in our view, can be safely performed in the presence of chronic kidney disease with appropriate preventive measures. (See "Prevention of contrast-associated acute kidney injury related to angiography".)

While computed tomographic or magnetic resonance angiography may be very useful for planning aortoiliac interventions, their utility for femoropopliteal and tibial interventions is limited by a lower resolution, particularly in the more distal vessels. (See "Advanced vascular imaging for lower extremity peripheral artery disease".)

A complete lower extremity arteriogram should include an aortogram with iliac runoff as well as unilateral lower extremity arteriography to the level of the foot. Bilateral lower extremity arteriograms to the level of the foot are rarely indicated and are usually avoided to limit the contrast load and radiation exposure. It is important to identify both the inflow and outflow during this study and to develop a treatment plan prior to surgery. Deviating from the planned approach during surgery is usually ill-advised.

To perform arteriography, we most commonly use a 4 French sheath placed retrograde using a Seldinger technique in the ipsilateral groin. Through this sheath a diagnostic catheter is positioned at the level of the first lumbar vertebrae, and a total of 30 mL of contrast is injected at 15 mL per second at a pressure of 800 psi (pounds per square inch) to opacify the abdominal aorta and iliac arteries. The diagnostic catheter is removed and the lower extremity arteriogram is performed by injecting contrast through the side arm of the sheath with a total of 36 mL of contrast at 6 mL per second at a pressure of 600 psi. On occasion, additional runs in oblique position or delayed runs with a different timing sequence are needed to optimize view of the outflow. Alternatively, a diagnostic catheter can be positioned in the distal superficial femoral artery, if patent, through either an antegrade or contralateral femoral approach, to better image the outflow vessels.

Target selection — For the purpose of this discussion, we consider the inflow vessel to be the artery that provides flow to the proximal anastomosis of the bypass graft, and the outflow vessel as the recipient artery for the distal anastomosis at the level of the distal anastomosis. An infrainguinal bypass is one that originates at or below the inguinal ligament. An infrapopliteal bypass is one that inserts below the knee; it can originate above or below the inguinal ligament.

Traditionally, the common femoral artery has been used as the principal inflow source in the absence of significant aortoiliac artery occlusive disease. However, other inflow sources (eg, superficial femoral or popliteal arteries) have also proven reliable and are often preferred, as they shorten the length of the conduit. As an example, if the available length of adequate vein conduit is limited, it is acceptable to move the inflow source distally from the femoral to the popliteal artery. Alternatively, additional segments of autogenous vein can be harvested and spliced together to obtain a conduit of sufficient length. (See 'Alternative vein grafts' below.)

●A femoropopliteal bypass is chosen when the above- or below knee popliteal artery is patent and there is at least a single tibial artery that is patent and minimally diseased to the level of the foot.

●A femorotibial bypass is chosen in the presence of a significantly diseased or occluded popliteal artery, or if the proximal tibial vessels demonstrate significant stenosis or occlusion. Bypass to a robust tibial target is still warranted even in the presence of significant inframalleolar occlusive disease, as limb salvage rates are sufficiently high to warrant this aggressive but indirect revascularization approach.

For infrapopliteal bypass, revascularization is performed following the angiosome concept, if possible [16-22]. Angiosomes are defined as the tissue fed by a specific artery (eg, anterior tibial, posterior tibial, or peroneal). However, angiosome-guided revascularization is often not possible, and the most important factor in choosing an outflow vessel for the distal anastomosis is the overall quality of the vessel. We do not favor any one tibial vessel over the other but instead select the outflow principally on the basis of its angiographic appearance, preferring to use the most robust vessel with direct flow to the foot, even if this does not correspond with the angiosome where an ulcer or gangrenous tissue is located. In a retrospective review of 118 infrainguinal vein grafts, there were no flow-related or outcome differences for distal bypass grafts to the peroneal, anterior tibial, posterior tibial, or popliteal arteries [23].

VASCULAR CONDUITS

Options — Conduits used for vascular bypass are predominantly either autogenous (great saphenous vein, alternative veins) or prosthetic (expanded polytetrafluoroethylene [ePTFE], polyester). In general, autogenous conduits are preferred to prosthetic conduits, but their use may be limited by the availability of suitable veins of appropriate diameter, length, and quality. (See 'Vein mapping' above.)

Other grafts, such as human umbilical vein grafts [24-26], cryopreserved vein grafts, and arterial grafts, are rarely used for lower extremity bypass. A small number of reports have used radial artery conduit for short tibial bypasses [27,28].

Vein grafts

Great saphenous vein — The great saphenous vein is the most commonly used and best-performing autogenous conduit for lower extremity arterial reconstruction. (See 'Conduit selection' below.)

The great saphenous vein is typically used in one of three configurations:

●Reversed

●In situ

●Nonreversed, translocated

Each configuration has distinct advantages and drawbacks. While our preference is to use reverse saphenous vein rather than situ vein, this choice is largely a matter of surgeon preference combined with patient-specific anatomy. There is little evidence that the configuration alone is predictive of long-term performance; graft patency and limb salvage rates are similar [14,29,30].

For patients who do not have suitable great saphenous vein, which occurs in up to 40 percent of patients, alternative sources of vein will be needed. The ipsilateral saphenous vein may have been harvested for coronary or other bypass, ablated for reflux symptoms, been the site of superficial thrombophlebitis, or be excessively varicose. (See 'Alternative vein grafts' below.)

Reversed — Due to the presence of valves that are normally oriented to prevent the reflux of venous blood distally, vein grafts must either be reversed or the valves disrupted to allow arterial flow. Reversed vein grafts provide predictable reliability in most patients. They avoid the potential for vein injury associated with the use of a valvulotome or graft failure as a result of patent side branches. They are also more versatile since they can be left in a subcutaneous plane or tunneled anatomically. Also, when the length of vein is limited, a reverse configuration allows the surgeon to more easily splice several segments of autogenous vein together to lengthen the conduit. Because of these reasons, reverse vein grafts are commonly used.

An important drawback of the reversed vein graft configuration is a potentially significant change in diameter of the vein from the saphenofemoral junction distally. When reversed, this can create a size mismatch between the inflow artery (typically a 6 to 7 mm common femoral artery) and the smaller diameter of the distal saphenous vein (3 to 4 mm), as well as between the proximal saphenous vein (4 to 6 mm near saphenofemoral junction) and distal target (3 to 4 mm), particularly for a tibial target. Also, complete removal of the vein from its bed theoretically may result in a combination of ischemic and mechanical injury that may lead to earlier graft failure, though this has not been substantiated. Another drawback for subcutaneously positioned grafts is that wound dehiscence can result in exposure of the graft. Unfortunately, wound complications are common in all lower extremity bypass patients, even more so in the presence of renal failure or diabetes.

In situ — In situ saphenous vein bypass was introduced in the mid-1980s to respond to concerns that the trauma of vein harvest was detrimental to long-term bypass graft performance. With this technique, a sufficient length of the proximal and distal aspects of the great saphenous vein is mobilized to allow tension-free anastomoses to the inflow and outflow vessels. The remainder of the vein is left in place (ie, in situ) to preserve the native blood supply to the vessel wall. There is some evidence that the endothelium is better preserved by limiting mobilization of the vein. The vein valves that normally prevent the reflux of venous blood distally are disrupted using a valvulotome to allow antegrade arterial flow. Significant side branches must be obliterated to prevent arterial blood from stealing through the venous tributaries.

When exposing the vein for in situ bypass, some surgeons make a single longitudinal incision exposing the superficial surface of the vein in its entirety, while others expose only the proximal and distal anastomotic segments preferring to ligate the side branches through separate small stab incisions using ultrasound to identify their location. An endoscopic technique for obliteration of side branches has also been used. Others have described using endovascular embolization of side branches using coils or glue.

The in situ bypass is particularly well suited for distal bypass (ie, infrapopliteal) because it can limit the severity of surgical trauma associated with harvesting and avoids the issues related to size mismatch, which can be problematic with reversed vein grafts. A drawback when the entire vein is exposed is the potential that wound dehiscence or infection can result in exposure of the graft in the subcutaneous tissue. Failure to obliterate significant side branches and incompletely lysed valves can result in poor distal perfusion or graft failure.

Nonreversed, translocated — The nonreversed, translocated great saphenous vein graft shares some of the features of both reversed and in situ grafts. The nonreversed great saphenous vein graft, like the in situ graft, attaches the large end of the vein to the large inflow artery and the smaller end of the vein to the smaller artery. Valves are lysed using a valvulotome and venous side branches are divided. The great saphenous vein is removed entirely from its native bed and the graft is tunneled either subcutaneously (eg, laterally) or anatomically. Anatomic tunneling, which follows the course of the native arteries, places the vein graft in a deeper tissue plane, decreases the length of conduit needed for bypass grafting and protects the graft in the event of wound complications.

Alternative vein grafts — Other less commonly used autogenous alternatives include the small saphenous vein, upper extremity cephalic or basilic veins, and the superficial femoral vein. These veins can also be used in a reversed or nonreversed configuration depending on surgeon preference; however, given the thinner vein wall, particularly of upper extremity veins, these may be more prone to injury when using a valvulotome. As such, these are more commonly used as reversed grafts.

Occasionally, multiple venous segments can be spliced together to create a bypass conduit of an appropriate length for the specific clinical scenario [31,32]. Alternative and spliced vein grafts exhibit a higher frequency of reintervention, and durability is inferior to grafts constructed from a single segment great saphenous vein. (See 'Conduit selection' below.)

Prosthetic — The most commonly used prosthetic graft for lower extremity bypass is ePTFE. While Dacron grafts are preferred for aortic replacement, they are uncommonly used in the lower extremities; there remains some debate on whether they may perform better in the long term in the above knee position compared with ePTFE [24,33-38].

With ePTFE grafts, heparin bonding and the addition of external rings to provide resistance against external compression are adjuncts that may improve the patency of these grafts [39-43]. In general, ePTFE grafts have acceptable patency in above knee positions but compare unfavorably to autogenous vein below the knee. The use of a vein patch or cuff and distal arteriovenous fistula have also been used to improve patency with variable results [44-48]. (See 'Conduit selection' below.)

Prosthetic grafts do have several advantages. Most importantly, they decrease operative time and avoid the need for autogenous vein harvest, along with the associated potential wound complications. Prosthetic grafts can also provide a better size match to the inflow and outflow arteries and may facilitate performance of thrombolysis in the event of graft failure.

Composite grafts consist of a segment of prosthetic graft and autogenous vein spliced together. These grafts perform poorly and offer no patency advantage. When they are used, patency may be improved by avoiding an end-to-end prosthetic to vein anastomosis and also avoiding a direct anastomosis, rather using a vein cuff or patch in an end-to-side configuration.

Conduit selection — The preferential use of autogenous vein, specifically the great saphenous vein over other conduits (alternative vein, prosthetic graft), is based on randomized trials that consistently demonstrate their improved patency and limb salvage rates [2,24,49-54]. The benefits of autogenous vein are accentuated for more distal bypass outflow targets.

Femoropopliteal bypass — Based on randomized trials for lower extremity bypass to the above- or below knee popliteal artery [24,26,49,55-61], we suggest using the great saphenous vein from the ipsilateral lower extremity, whenever possible [24,49]. A prosthetic graft may be an acceptable option when autogenous veins are lacking, runoff is robust, when medical comorbidities warrant an expedient revascularization, or when life expectancy is limited.

A systematic review and meta-analysis identified eight trials that involved 1132 patients with 608 saphenous vein and 663 prosthetic grafts used for above knee popliteal bypass [49]. The primary patency, primary assisted patency, and secondary patency rates at five years were significantly higher for vein grafts compared with prosthetic grafts (primary patency: odds ratio [OR] 1.73, 95% CI 1.17-2.55; primary assisted patency: OR 4.02, 95% CI 2.84-5.70; secondary patency: OR 1.83, 95% CI 1.20-2.80). Vein grafts also required significantly fewer reinterventions (OR 0.33, 95% CI 0.18-0.60). However, 30-day mortality, major amputation, and overall survival were similar between the groups.

The efficacy of prosthetic grafts to the above knee popliteal artery is approximately equivalent to autogenous vein for the first two years; thereafter, the patency curves tend to diverge with lower patency thereafter for prosthetic grafts [62,63]. In a review of femoropopliteal grafts published since 1990 (randomized and observational studies), overall primary patency rates with saphenous vein grafts were 86, 72, and 51 percent at 1, 5, and 10+ years, respectively, and secondary patency rates were 92, 83, and 63 percent [62,64]. For ePTFE, primary rates at 1, 5, and 10+ years were 77, 51, and 32 percent, respectively, and secondary patency rates were 79, 62, and 24 percent.

●For the above knee popliteal position:

•For saphenous vein at 1, 5, and 10+ years:

-Primary patency: 86, 75, and 44 percent

-Secondary patency: 89, 80, and 46 percent

•For ePTFE at 1, 5, and 10+ years:

-Primary patency: 80, 53, and 32 percent

-Secondary patency: 87, 70, and 24 percent

●For the below knee popliteal position:

•For saphenous vein at 1, 5, and 10+ years

-Primary patency: 86, 71, and 53 percent

-Secondary patency: 92, 83, and 71 percent

•For ePTFE at 1, 5, and 10+ years:

-Primary patency: 74, 44, and 29 percent

-Secondary patency: 49 and 46 percent (data not available at 10+ timepoint)

Infrapopliteal bypass — For lower extremity bypass to a tibial or pedal artery, we recommend using autogenous vein. If a long segment of good quality saphenous vein is not available, a short segment vein originating from a more distal target should be considered, whenever applicable [65]. While alternative autogenous vein (eg, small saphenous arm, spliced vein) performs better than prosthetic grafts to more distal targets, patency rates are inferior to a single segment of great saphenous vein.

From the review cited above [62]:

●For distal bypass (overall for all sources of inflow) using saphenous vein at 1, 5, and 10+ years:

•Primary patency: 82, 69, and 48 percent

•Secondary patency: 88, 79, and 60 percent

Reported primary patency rates for ePTFE grafts in the infrapopliteal position at three to five years are overall low [52,62,66,67]. Thus, based on the available data, most surgeons avoid prosthetic material for bypass to infrapopliteal arteries, if at all possible. However, for patients without adequate autologous vein and no endovascular option, an ePTFE graft may be an acceptable option, provided the tibial or pedal target is adequate.

From the review cited above [62]:

●For distal bypass (overall for all sources of inflow) using ePTFE at one and five years:

•Primary patency: 60 and 24 percent

•Secondary patency: 65 and 28 percent

ANESTHESIA AND PREPARATION — Either general or regional anesthesia is chosen. Patients are fully monitored and a Foley catheter should be placed. (See "Anesthesia for infrainguinal revascularization".)

Regional anesthesia is usually favored in the presence of a difficult airway or significant pulmonary disease. Of note, prolonged operations in patients who have aortic stenosis, scoliosis, or prior spine surgery, or those who tolerate sedation poorly may preclude the option of regional anesthesia. Special considerations need to be taken into account for patients who will continue perioperative antiplatelet therapy, which is common, and those requiring ongoing anticoagulation. (See "Neuraxial anesthesia/analgesia techniques in the patient receiving anticoagulant or antiplatelet medication".)

Antibiotics — Preoperative antibiotics (table 1) are administered to all patients undergoing lower extremity bypass one hour prior to skin incision and redosed for prolonged procedures or for those with significant blood loss. (See "Antimicrobial prophylaxis for prevention of surgical site infection in adults".)

For patients in whom the indication for lower extremity bypass is foot wounds accompanied by foot infection, intravenous antibiotics are re-dosed prior to surgery and continued for 7 to 14 days.

Antithrombotic therapy — For lower extremity surgical bypass procedures, preoperative antiplatelet therapy (eg, secondary prevention of cardiovascular disease, ie, coronary heart disease or peripheral artery disease) or anticoagulant medications initiated for acute limb ischemia are not discontinued. For elective surgery, depending on the indication for anticoagulation, a heparin bridge may be used (eg, cardiac valvular disease, recent venous thromboembolism). (See "Perioperative management of patients receiving anticoagulants", section on 'Deciding whether to interrupt anticoagulation' and "Perioperative management of patients receiving anticoagulants", section on 'Timing of anticoagulant interruption'.)

Positioning and skin preparation — For lower extremity bypass, the patient is positioned supine, and preoperative skin preparation, typically using chlorhexidine, should include the lower abdomen and the entire extremity, including the foot. The foot can be covered with a sterile towel that is secured with an adhesive bandage or a transparent plastic bag. Open wounds or areas of gangrene are excluded from the operative field. Hair removal (clipping), if necessary, is done immediately prior to surgery. (See "Overview of control measures for prevention of surgical site infection in adults", section on 'Skin antisepsis' and "Overview of control measures for prevention of surgical site infection in adults", section on 'Hair removal'.)

If additional sources of vein for conduit are anticipated (eg, contralateral leg, arm), the appropriate sites should also be prepared.

TECHNIQUES

General conduct of the operation — Lower extremity surgical bypass is carried out in a stepwise fashion:

●Arterial exposure and control

●Vein exposure/harvest

●Systemic anticoagulation

●Proximal anastomosis

●Graft tunneling

●Distal anastomosis

●Completion imaging

The authors' preference is to construct the proximal anastomosis first, to tunnel the graft anatomically, and then to construct the distal anastomosis. Identifying strong pulsatile flow through the graft confirms that no twisting or kinking the graft has occurred throughout the tunnel. We also favor using the great saphenous vein as a conduit and adjusting for insufficient conduit length by creating a spliced graft, or by moving the graft origin more distally or the target artery more proximally, when possible. We may need to rely on endovascular treatment of a diseased superficial femoral artery to improve inflow for a more distal bypass (eg, popliteal-tibial bypass).

Arterial exposure and control — Vascular exposure is obtained at the proximal inflow and the distal outflow target vessels in a standard fashion, which involves isolating the vessels to control bleeding using either vessel loops or vascular clamps placed proximal and distal to the planned arteriotomy site, as well as controlling any important branches. Proximal inflow vessels that have significant calcification may require concomitant endarterectomy to avoid complications (eg, intimal flap, dissection).

If significant calcification is present in the distal target vessels, vascular control can also be achieved using a sterile pneumatic tourniquet placed proximally. The tourniquet can be applied above the knee to control the popliteal artery or below the knee to control any of the tibial vessels. The tourniquet is inflated only after constructing the proximal anastomosis and tunneling the conduit. Alternatively, a balloon occlusion technique can be used (eg, #3 Fogarty catheter attached to a three-way stopcock).

Vein harvest — Options for harvesting vein for lower extremity bypass include direct exposure of the entire extent of the vein or exposure of only portions of the vein leaving skipped segments, or using endoscopy [68-70]. The technique described below is for complete removal of the great saphenous vein from its bed for either a reversed graft or translocated graft. For in situ grafts, the vein may similarly be exposed along its entire length or only enough to perform the proximal and distal anastomoses. (See 'In situ' above.)

For harvesting the great saphenous vein, we prefer to use multiple skip incisions rather than a single longitudinal incision, or endoscopy. Typically, three incisions are made over the thigh each extended for 8 to 10 cm with two intervening skin bridges of approximately 3 to 5 cm. The proximal incision is used for exposure of the femoral vessels and to harvest the proximal great saphenous vein. The next incision is made by placing the index finger over the saphenous vein and dissecting bluntly in a distal direction. A skin incision is made using a #15 scalpel blade at the distal aspect of the surgeon's finger, leaving the intervening skin intact. The incision extended longitudinally and carried down through the subcutaneous tissue to identify and mobilize the vein. This process is repeated one more time, with the distal incision terminating just above the knee joint, leaving two skin bridges. Of note, the incisions should correspond with the skin markings made during preoperative vein mapping. If the distal anastomosis will be to the below knee popliteal artery, a fourth incision is made below the knee and a longer segment of saphenous vein is harvested. This incision is used to expose the below knee popliteal artery. (See 'Arterial exposure and control' above.)

After exposing the great saphenous vein, the vessel is dissected from its bed. An elastic vessel loop can be placed around the vein using gentle traction to facilitate the vein harvest. Using an army-navy retractor will aid exposure of the vein for dissection beneath each skin bridge. All vein tributaries are carefully identified and divided, with care taken to avoid incorporating the adventitia of the vein within the silk ligatures used to tie off the vein, which would narrow the conduit. Once a suitable length of vein has been harvested, the vein conduit is divided proximally and distally, and irrigated with heparinized saline. It is important to extend the hip and knee joints before cutting the vein graft to length; otherwise, the graft will be too short when the extremity is extended.

The vein is irrigated and temporarily stored in heparinized saline solution while the distal target vessel is exposed and controlled. Any leaks (typically unligated small tributaries) are repaired with 7-0 polypropylene sutures.

Vascular anastomoses and graft tunneling — Following vein harvest or exposure (in situ graft), the proximal anastomosis is constructed. If the graft will be tunneled (anatomically, non-anatomically), some surgeons prefer to tunnel the graft prior to the creation of the proximal anastomosis and therefore prior to systemic anticoagulation to reduce the risk of bleeding.

After exposure of the selected inflow vessel (femoral artery, popliteal artery) and prior to clamping, the patient is systemically anticoagulated. Anticoagulation is typically using unfractionated heparin, which is maintained throughout the period of vascular occlusion. A weight-adjusted bolus of unfractionated heparin is given. The activated clotting time (ACT) is used to monitor anticoagulation, and for prolonged procedures, heparin is redosed as needed to maintain an ACT >200.

A longitudinal arteriotomy is made over the common femoral artery with a #11 scalpel blade. Significant occlusive disease of the common or deep femoral arteries will sometimes warrant endarterectomy to improve inflow and limit complications (eg, intimal flap, dissection). The arteriotomy is extended for a distance of 1.5 to 2 times the diameter of the harvested vein. Permanent monofilament suture (eg, 5-0 or 6-0 double-armed polypropylene) is used to create the anastomosis, beginning at the heel of the anastomosis and carrying the suture in a continuous fashion from either side to meet on the external aspect of the toe of the anastomosis. Prior to completion of this anastomosis, all vessels are backflushed, and irrigated with saline.

Following completion of the proximal anastomosis, the vein graft is brought down to the distal target (tunneled, nontunneled). Before tunneling, marking the superficial surface of the vein with indelible ink may help avoid twisting or kinking the graft. Before the distal anastomosis is performed, pulsatile flow through the vein graft should be confirmed.

The distal anastomosis is performed in a similar fashion using continuous monofilament suture (eg, 6-0 or 7-0 polypropylene) as previously described above for the proximal anastomosis. If the target vessel is markedly calcified, using a CC (ie, conventional cutting) needle can be quite helpful. The graft is flushed, and the vessels backflushed and irrigated before completing the anastomosis.

Completion imaging and wound closure — After completion of the bypass, we use either graft duplex ultrasound or handheld continuous wave Doppler to assess the adequacy of revascularization. Whether completion arteriography should be routinely performed after the bypass anastomoses have been completed is debated [71-73]. We favor a selective approach; however, proponents argue that intraoperative arteriography is relatively easy to accomplish and may help identify a problematic graft.

When a selective approach is used, intraoperative arteriography is indicated if there is any evidence of a stenosis on duplex ultrasound (ie, peak systolic velocity >300 cm/s), if a biphasic or triphasic signal cannot be found over the artery beyond the distal anastomosis, or if based on preoperative vascular imaging a pedal pulse is expected and none is found and there is no augmentation of flow with graft occlusion. Any defect identified on intraoperative angiography is immediately repaired.

The subcutaneous tissues are closed using running absorbable sutures (eg, 3-0 Vicryl) and staples are used to close the skin. A sterile dressing is placed and maintained in place for two days postoperatively.

POSTOPERATIVE CARE — Following revascularization, all patients who undergo lower extremity bypass are managed in a monitored setting for 24 to 48 hours. All invasive lines and the Foley catheter can typically be removed on the first postoperative day. Oral diets are advanced quickly and patients are encouraged to ambulate with assistance after 24 hours.

The graft is routinely evaluated each hour for six to eight hours, then every four to six hours for strong pulsations and evidence of good distal perfusion. Loss of a palpable pulse or Doppler signal, a cool pale extremity, or severe pain are signs of graft thrombosis and warrant immediate attention. A graft ultrasound is performed urgently and reintervention is considered depending on the initial indication for revascularization and other clinical factors.

Graft failure in the immediate or early postoperative period can occur due to technical complications or judgment error, or because of hypotension, either from an adverse cardiac event, bleeding, or sepsis, or from a hypercoagulable state.

For patients who have an indication for foot surgery (eg, debridement, amputation), surgery is not delayed beyond 48 hours.

Antithrombotic therapy — Multidisciplinary guidelines recommend long-term antiplatelet therapy with aspirin or clopidogrel for all patients with peripheral artery disease (PAD) [2,74,75]. Direct oral anticoagulants may also benefit patients with PAD [76,77].

We do not routinely prescribe anticoagulation or dual antiplatelet therapy to prevent graft failure. For patients at high risk for graft thrombosis (eg, spliced vein conduit, poor runoff) who are not at increased risk for bleeding, adjunctive treatment may be considered. Vitamin K antagonists (eg, warfarin) may provide more benefit for those with a vein bypass graft, while antiplatelet therapy may provide more benefit for patients with a prosthetic graft [78-80]. Bleeding complications are consistently increased in patients receiving anticoagulants [80-82].

The use of dual antiplatelet therapy is speculated to improve patency after lower extremity revascularization [83-87]. The Clopidogrel and Acetylsalicylic Acid in Bypass Surgery for Peripheral Arterial Disease (CASPAR) trial randomized 851 patients to receive clopidogrel (75 mg/day) plus aspirin (75 to 100 mg/day) versus placebo plus aspirin [83]. The overall incidence of graft occlusion, amputation, or death was similar between the treatment groups. In a prespecified subgroup analysis of patients with prosthetic grafts, clopidogrel plus aspirin significantly reduced the primary endpoint (graft occlusion/revascularization) compared with aspirin alone (hazard ratio [HR] 0.65; 95% CI 0.45-0.95). For patients with vein grafts there was also no significant difference. The incidence of severe bleeding (2.1 versus 1.2 percent) was similar between the groups, although significantly more episodes of bleeding overall were recorded in the clopidogrel group.

Lipid-lowering therapy — Lipid-lowering therapy with moderate- to high-dose statins is recommended for all patients with atherosclerotic cardiovascular disease irrespective of the baseline low-density lipoprotein cholesterol [2,74,75,88]. (See "Management of low density lipoprotein cholesterol (LDL-C) in the secondary prevention of cardiovascular disease".)

Statin therapy has also been associated with improved infrainguinal graft patency [88-90]. In a retrospective study of 931 patients (1019 affected limbs) who underwent first-time revascularization (endovascular or surgical) over a nine-year period (2005 to 2014) [91], discharge on the recommended intensity of statin therapy was associated with lower mortality (HR 0.73; 95% CI 0.60-0.99) and lower major adverse limb event rate (HR 0.71; 95% CI 0.51-0.97) over a median follow-up of 380 days.

Graft surveillance — Initial postoperative noninvasive vascular studies are obtained one to two days postoperatively (ie, ankle-brachial index [ABI] values, graft duplex study). Initial studies help assess the adequacy of revascularization and establish a baseline reference for future studies. Duplex ultrasonography is considered by many to be the best method for detecting problems with the bypass graft; however, whether routine duplex improves outcomes over careful clinical monitoring consisting of vascular examination and ABI with selective graft imaging remains debated [92-95].

For ongoing evaluation, given the ease in obtaining it, its noninvasive nature, and its generally low cost, we include duplex ultrasonography in our clinical surveillance. Our surveillance schedule is consistent with practice guidelines [2,54,96]. In addition to history and physical examination including wound assessment, we repeat noninvasive vascular studies every three months for two years and then every 6 to 12 months thereafter [97]. Arteriography is indicated if there is any evidence of graft stenosis, specifically a graft duplex with a peak systolic velocity of 300 cm/s and velocity ratio of greater than 3.5, or a greater than 0.15 reduction in ABI [98].

The purpose of graft surveillance is to identify failing grafts and subsequently to treat these grafts prior to thrombosis [94,99-107]. Failure between 30 days and two years is most often the result of myointimal hyperplasia within the vein graft or at anastomotic sites. It is estimated that vein graft stenosis develops in 20 to 30 percent of infrainguinal vein bypasses during the first year [92-95]. Vein grafts that are carefully monitored and treated (eg, balloon angioplasty, surgical revision) do better in the long term compared with grafts that are revised following complete thrombosis. As an example, in one review, five-year assisted primary patency rates were 82 to 93 percent for bypass grafts treated for stenosis compared with secondary patency rates of 30 to 50 percent for vein grafts that had thrombosed [95]. It is important to note that for chronic limb-threatening ischemia, limb salvage rates are typically higher than graft patency rates. Wounds that heal do not necessarily recur if graft patency is ultimately lost.

There are no specific recommendations regarding surveillance and reintervention for prosthetic grafts. While graft surveillance improves long-term patency of vein grafts, the same benefit has not been shown for prosthetic grafts. Duplex ultrasound surveillance of prosthetic grafts does not reliably detect correctable lesions that precede failure. However, surveillance may serve as a predictor of graft thrombosis by the detection of midgraft velocities below 45 cm/s [108-112].

Late graft failure is usually due to the natural progression of atherosclerotic disease [95].

COMPLICATIONS — In addition to graft failure and the potential for limb loss, complications of lower extremity surgical bypass can include adverse cardiac events, such as myocardial infarction, arrythmias, or sudden cardiac death, acute renal failure, and wound complications (eg, hematoma formation, wound infection, wound dehiscence) [113-115]. (See "Overview of the evaluation and management of surgical site infection".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Occlusive carotid, aortic, renal, mesenteric, and peripheral atherosclerotic disease".)

SUMMARY AND RECOMMENDATIONS

●Lower extremity bypass – Lower extremity surgical bypass involves suturing a vascular conduit, preferably autogenous vein, from a site proximal to the level of an arterial obstruction to a distal site of uninvolved artery. The most common indication for lower extremity surgical bypass is peripheral artery disease (PAD) due to atherosclerosis. Lower extremity surgical bypass may also be needed to treat other diseases that result in arterial occlusion. (See 'Introduction' above and 'Indications' above.)

●Preoperative evaluation – Prior to lower extremity bypass, the patient with PAD should undergo a thorough vascular evaluation to identify appropriate targets for bypass grafting and determine the availability of vein conduit, as well as undergo medical risk assessment to optimize the patient's overall condition and suitability for surgical intervention. Medical risk assessment is particularly important given the high likelihood of cardiac disease and other comorbidities (eg, diabetes, chronic kidney disease). (See 'Preoperative evaluation' above.)

●Conduits and selection – When lower extremity bypass surgery is indicated for PAD, autogenous vein is the preferred bypass conduit. The ipsilateral or contralateral great saphenous vein should be used preferentially. If the great saphenous vein is not available, the small saphenous or arm vein (basilic vein, cephalic vein) can be used. If the length of available vein is limited, splicing together more than one vein segment or using prosthetic graft are alternatives. When prosthetic graft is used, our preference is heparin-bonded expanded polytetrafluoroethylene (ePTFE). (See 'Vascular conduits' above.)

●Antithrombotic therapy – For lower extremity surgical bypass procedures, preoperative antiplatelet or anticoagulant medications initiated for treatment of coronary heart disease, PAD, or acute limb ischemia are not discontinued. Antithrombotic (aspirin or clopidogrel) and lipid-lowering medications (ie, statins) are recommended for all patients with PAD to reduce the risk of future cardiovascular events and may also reduce the risk of future adverse limb events. For patients at high risk for graft thrombosis (eg, spliced vein conduit, poor runoff) who are not at increased risk for bleeding, adjunctive antiplatelet therapy or anticoagulation may be considered. Dual antiplatelet therapy (aspirin plus clopidogrel) may be more appropriate for high-risk patients with a prosthetic graft, whereas vitamin K antagonists may provide more benefit for those with a vein bypass graft. (See 'Medical risk assessment' above and 'Antithrombotic therapy' above.)

●Postoperative care – Following revascularization, the graft is routinely evaluated each hour for six to eight hours, then every four to six hours for strong pulsations and evidence of good distal perfusion. Loss of a palpable pulse or Doppler signal, a cool pale extremity, or severe pain are signs of graft thrombosis and warrant immediate attention. Following discharge, periodic clinical evaluations should evaluate wound healing progression, the presence of pulses, and measurement of the ankle-brachial index (ABI). Any changes or return of symptoms warrant further evaluation (eg, graft duplex). (See 'Postoperative care' above.)

●Graft surveillance – Vein graft stenosis of lower extremity bypass grafts is common during the first year and can lead to graft failure. Grafts that are monitored and treated when a significant stenosis is identified have better long-term patency rates compared with those that require thrombectomy and revision following a complete thrombosis. Thus, we use duplex imaging surveillance to periodically evaluate for graft stenosis. We examine grafts perioperatively and repeat noninvasive vascular studies every three months for two years and then every 6 to 12 months thereafter. Arteriography is indicated if there is any evidence of graft stenosis, specifically a graft duplex with a peak systolic velocity of 300 cm/s and velocity ratio of greater than 3.5, or a greater than 0.15 reduction in ABI. (See 'Graft surveillance' above and 'Complications' above.)