Femoropopliteal Bypass

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CHAPTER 26 Femoropopliteal Bypass

Clayton J. Brinster, Edward Y. Woo

Case Study

A 64-year-old mail carrier with a history of smoking and mild hypertension controlled with diet and exercise presents with increasing pain in his left calf muscles during ambulation. The pain has increased in frequency and intensity over the past year, forcing him to limit the distance he walks and compromising his ability to perform his job. Physical examination reveals a palpable left femoral pulse but absent left popliteal, posterior tibial, and dorsalis pedis pulses.

BACKGROUND

Peripheral arterial disease (PAD) is a common but underdiagnosed and undertreated disorder that affects 8 to 10 million Americans and an estimated 20% of the general population older than 55 years of age. The prevalence of PAD increases with age and in the presence of cardiovascular risk factors, such as diabetes, hypertension, smoking history, dyslipidemia, and hyperhomocysteinemia.

Intermittent claudication (IC) is defined as reproducible lower extremity pain on exertion that is caused by inadequate blood flow and is reliably relieved by rest. Classic IC occurs in only 30% of patients with symptomatic PAD, and many older patients with PAD instead complain of lower extremity fatigue, difficulty with ambulation, or other leg discomfort atypical of claudication. A thorough history and physical examination, as well as noninvasive vascular laboratory studies, will usually differentiate IC from other common diagnoses, such as arthritis, nerve root compression, and venous congestion.

Intermittent claudication is reproducible lower extremity pain on exertion that is caused by inadequate blood flow and is reliably relieved by rest.

Lower extremity PAD is typically classified as aortoiliac, femoropopliteal, or tibial in distribution. Symptoms frequently correspond to the level of occlusive disease and are localized to muscle groups one joint level below the region of occlusion; calf muscle claudication is most commonly due to superficial femoral artery occlusion, and hip, thigh, or buttock claudication is most commonly due to proximal aortoiliac disease. Multilevel disease can produce symptoms at any level. Importantly, calf claudication is the most common presenting symptom in patients with femoropopliteal disease and in those with occlusive aortoiliac disease because of the distal extent of this muscle group.

Intermittent claudication most commonly affects the calf muscles and most commonly results from atherosclerotic disease of the superficial femoral artery.

Patients with PAD often have concomitant comorbidities. Nearly one third of patients with IC die within 5 years of diagnosis of myocardial infarction, cerebrovascular disease, or other cardiovascular events, a rate more than three times that in age-matched control subjects. Based on the presence of risk factors, the global nature of atherosclerotic disease, and the high risk of systemic ischemic events, patients with PAD should be treated with aggressive lifestyle modification, appropriate pharmacotherapy, and when necessary, appropriate intervention.

Interventions for lower extremity PAD range from percutaneous procedures, such as angioplasty, stenting, or atherectomy, to operative bypass. Operative bypass is usually reserved for circumstances in which percutaneous procedures are unsuccessful or cannot be performed because of anatomic factors. Infrainguinal bypass refers to any major arterial reconstruction that originates below the inguinal ligament and uses a graft (i.e., autogenous vein, cadaveric vein, or prosthetic conduit such as polytetrafluoroethylene [PTFE]). Proximal inflow sites include the common, superficial, and deep femoral arteries, and target sites include the popliteal (above or below the knee), tibial, peroneal, and pedal arteries. This chapter focuses on femoropopliteal bypass for the treatment of PAD and IC.

INDICATIONS FOR FEMOROPOPLITEAL BYPASS

I. Disabling or refractory claudication is the most common indication for surgical revascularization of the lower extremity. Patients with claudication symptoms that significantly limit their lifestyle or compromise their ability to work or perform activities of daily living are candidates for lower extremity bypass. Claudication is deemed refractory when lifestyle modification (e.g., smoking cessation, exercise therapy, cholesterol reduction, blood pressure control, blood sugar control) and pharmacologic therapy (e.g., anticoagulation, antiplatelet therapy, arterial vasodilation) do not reduce symptoms or halt the progression of atherosclerotic disease. The primary reason to intervene in the patient with claudication is to improve lifestyle; the likelihood of a severe decline in cardiovascular status (<20%) or progression to major limb amputation (<5%) over a 5-year period is low, especially with lifestyle modification and appropriate medical therapy.

II. Limb Salvage in the Presence of Critical Limb Ischemia: Critical ischemia is defined as ischemic rest pain or tissue loss (e.g., ulceration or gangrene). A significant number of patients with critical ischemia eventually require vascular bypass or major limb amputation during the course of treatment.

III. Other Indications: Less common indications for lower extremity bypass include trauma (e.g., popliteal artery injury from posterior knee dislocation), popliteal entrapment syndrome, and femoropopliteal arterial aneurysmal disease.

URGENT SURGICAL EVALUATION IS INDICATED IN PATIENTS WHO HAVE PAIN AT REST, GANGRENE, ISCHEMIC ULCERATION, OR AN ACUTE CHANGE IN PULSE EXAM.

Surgery should be performed only if: (1) the risk–benefit ratio is acceptable, (2) the patient’s lower extremity vascular anatomy suggests that a favorable and durable result is plausible, and (3) symptomatic relief or limb salvage is expected.

PREOPERATIVE EVALUATION

The clinical diagnosis of lower extremity ischemia should be confirmed with a thorough physical examination and a noninvasive arterial evaluation. Radiographic imaging of the arterial anatomy should be obtained when an intervention is planned.

I. Physical examination of the patient with exercise-induced leg pain should aim to confirm the diagnosis of IC and determine the level of occlusive disease. Palpation of the aortic, bilateral femoral, popliteal, posterior tibial, and dorsalis pedis pulses is essential. Patients with aortoiliac disease will have dampened or absent femoral pulses. Occlusive disease of the superficial femoral artery presents with normal femoral pulses and absent or reduced popliteal and pedal pulses. Palpable femoral and popliteal pulses in the setting of absent pedal pulses suggest infrapopliteal disease.

II. Noninvasive Diagnostic Evaluation

A. The ankle–brachial index (ABI) is the primary noninvasive study used in the diagnosis of PAD. If occlusive disease is suspected, based on presentation, but the resting ABI is normal, the ratio should be recalculated after a period of exercise. Any decrease in ABI with exercise is considered abnormal. The ABI may be falsely elevated and unreliable in patients with extensive arterial calcification as a result of noncompressibility of lower extremity vessels (Fig. 26-1).

B. Segmental limb pressures are obtained with a blood pressure cuff and Doppler probe, comparing brachial artery pressures and pressures at various arterial levels in the bilateral lower extremities. ABI and segmental limb pressure recordings are commonly used in conjunction with pulse volume recordings (PVR) of arterial waveforms to further delineate the anatomy of the occlusive disease. A normal PVR resembles an arterial waveform, with a sharp systolic spike and a diastolic downstroke. A change in contour, typically observed as a dampened waveform, indicates proximal occlusive disease. The extent of this change correlates with the severity of disease.

C. Arterial duplex ultrasonography can confirm the diagnosis of PAD, identify the level of disease, and differentiate between stenotic and occlusive lesions. Lower extremity examination begins at the common femoral artery and proceeds distally. Arterial stenosis is localized with color Doppler imaging and assessed by measuring Doppler velocities at several arterial levels.

D. Vein mapping with duplex ultrasonography is useful preoperatively in the selection of appropriate bypass conduits. In the absence of a suitable greater saphenous vein (GSV), the cephalic, basilic, and lesser saphenous veins can be evaluated for potential use in a spliced vein graft (discussed later).

III. Radiographic Evaluation

A. Computed tomography angiography (CTA) provides rapid, high-resolution images of the aortoiliac and lower extremity arteries. The utility of CTA, however, is limited by the need for intravenous iodinated contrast, which precludes the evaluation of patients with renal disease.

B. Magnetic resonance angiography (MRA) also offers adequate imaging of the arterial anatomy. Intravenous gadolinium, however, is contraindicated in the setting of renal insufficiency because of the high risk of associated nephrogenic systemic fibrosis, a sclerosing disorder of the skin and visceral organs that can result in severe end-organ damage.

C. Invasive digital subtraction angiography remains the gold standard in the imaging of PAD. It is, however, an invasive procedure that also requires iodinated contrast.

Figure 26-1 The ankle–brachial index (ABI).

COMPONENTS OF THE PROCEDURE AND APPLIED ANATOMY

General Operative Principles of Lower Extremity Bypass

There are three basic requirements for successful lower extremity bypass: (1) adequate arterial inflow to the bypass graft; (2) a target vessel that is relatively disease-free and provides adequate run-off, or continuous blood flow, to the foot; and (3) an adequate conduit. The ideal conduit for most bypasses is the GSV. In the absence of an adequate GSV, alternative veins, cadaveric veins, or a prosthetic graft can be used.

In general, the proximal anastomosis is performed at the level of the common femoral artery. If the length of available saphenous vein is limited, the deep femoral or superficial femoral arteries may be used. If the deep femoral or superficial femoral arteries are stenosed, an endarterectomy may allow appropriate inflow. Bypass with reversed saphenous vein graft (SVG) is described in the next section. Alternatively, lower extremity bypass can be accomplished with any of the following conduits:

I. In situ SVG, with the saphenous vein left in its native location. Ligation of the tributaries and lysis of the valves are performed without disrupting the GSV vein bed.

II. Spliced vein, consisting of combinations of the cephalic, basilic, or lesser saphenous veins, or portions of the greater saphenous vein.

III. Cadaveric vein

IV. Prosthetic grafts; PTFE is most commonly used in infrainguinal bypasses.

Preoperative Considerations

I. Lower extremity bypass can be performed under regional anesthesia (e.g., spinal or epidural) or general anesthesia, depending on the patient’s comorbidities and whether arm veins are harvested.

II. A Foley catheter is inserted.

III. Prophylactic antibiotics are administered intravenously before incision.

IV. A radial arterial line is commonly placed to allow for continuous hemodynamic monitoring.

Patient Positioning and Preparation

I. The patient is placed in the supine position with the arms extended.

II. The sterile skin preparation and draping should include the entire groin, leg, and foot. A sterile, clear plastic bag is commonly placed over the foot.

III. During the procedure, the hip may need to be externally rotated and abducted, with the knee flexed and the thigh supported with a soft bolster or “bump.”

Exposure of the Common Femoral Artery

I. The groin is palpated, and the femoral pulse is located. To expose the common femoral artery, a vertical or oblique incision is made over the pulse. A self-retaining retractor is placed in the wound, and the common femoral artery is located, dissected free of surrounding tissue, and controlled with vessel loops (Fig. 26-2).

II. The superficial femoral and deep femoral arteries may also need to be exposed and controlled with vessel loops.

III. To prevent seroma formation and reduce the risk of postoperative infection, care is taken to identify and ligate or cauterize the lymphatic tissue surrounding the femoral arteries and saphenofemoral junction.

IV. The circumflex femoral vein is a large vessel that crosses the proximal deep femoral artery just distal to the common femoral artery bifurcation. If more distal exposure of the profunda is needed, this vein should be divided to allow adequate exposure of the deep femoral artery.

Figure 26-2 A, Exposure and control of the common, superficial, and deep femoral arteries. B, Exposure and control of the above the knee popliteal artery with conservation of the greater saphenous vein (inferior).

(From Khatri V, Asensio J: Operative Surgery Manual. Philadelphia, Saunders, 2003.)

Exposure of the Popliteal Artery

I. The distal target vessel for lower extremity bypass is determined by preoperative imaging or intraoperative arteriogram. This discussion focuses on the use of the popliteal artery, although the posterior tibial, peroneal, and pedal arteries are used as distal target vessels in appropriate circumstances.

II. Above the Knee:

A. A longitudinal incision is made along the medial aspect of the distal thigh, below the muscle belly of the vastus medialis.

B. Care is taken not to injure the GSV during this incision and exposure of the popiteal artery because this vein may be the planned bypass conduit.

C. The sartorius muscle is reflected posteriorly, and dissection is carried out along the posterior aspect of the femur.

The superficial femoral artery passes through Hunter’s canal and the adductor hiatus and then enters the popliteal space; it is then called the popliteal artery.

III. Below the Knee:

A. A longitudinal incision is made along the medial aspect of the proximal calf.

B. The GSV is identified and mobilized.

C. The medial head of the gastrocnemius muscle is reflected posteriorly, and the popliteal space is entered.

D. The popliteal artery courses inferiorly in association with the paired popliteal veins, and after adequate dissection and exposure, the artery is controlled with vessel loops.

Saphenous Vein Harvest

I. The saphenous vein is exposed by connecting the femoral and popliteal incisions or with multiple short “skip” incisions along the medial thigh. The vein is excised, and tributaries are ligated (Fig. 26-3).

II. After the vein is harvested, it is injected and distended with heparinized saline; leaks are identified and ligated (Fig. 26-4).

III. The vein is reversed (to permit flow past valves) such that the end originally in the groin can be anastomosed to the popliteal artery and the end originally in the lower thigh or calf can be anastomosed to the femoral artery.

IV. The vein is marked for orientation to avoid twisting.

V. The graft is then tunneled with a blunt instrument or a specifically designed tunneling device in a subcutaneous plane shallow enough to allow for postoperative graft surveillance (Fig. 26-5).

Figure 26-3 Saphenous vein graft harvest. A, The greater saphenous vein is harvested from the saphenofemoral junction proximally (top) and to the level of the bypass target distally (bottom). B, The surgeon isolates the vein and ligates venous side branches while the assistant irrigates and retracts.

(From Rutherford RB, Ouriel K: Reversed saphenous vein femoropopliteal bypass. In Ouriel K, Rutherford RB: Atlas of Vascular Surgery: Operative Procedures. Philadelphia, Saunders, 1998.)

Figure 26-4 Vein graft preparation.

(From Rutherford RB, Ouriel K: Reversed saphenous vein femoropopliteal bypass. In Ouriel K, Rutherford RB: Atlas of Vascular Surgery: Operative Procedures. Philadelphia, Saunders, 1998.)

Figure 26-5 Vein graft tunneling. The vein graft is tunneled to the distal (A) and proximal (B) target sites.

(From Rutherford RB, Ouriel K: Reversed saphenous vein femoropopliteal bypass. In Ouriel K, Rutherford RB: Atlas of Vascular Surgery: Operative Procedures. Philadelphia, Saunders, 1998.)

When the bypass is carried out to the popliteal artery below the knee, the graft is sometimes routed via the anatomic popliteal course to avoid angulation or kinking of the graft as it crosses the knee joint.

Construction of the Bypass

I. The patient is systemically heparinized, and the inflow artery is atraumatically clamped.

II. An arteriotomy is made on the anterior surface of the artery with a scalpel and extended with angled scissors.

III. The proximal anastomosis is performed with a running suture. Care is taken to approximate the intimae of the vessels (Fig. 26-6).

IV. After completion of the proximal anastomosis, blood flow is temporarily restored to confirm unimpeded flow through the conduit.

V. The distal anastomosis is carried out in similar fashion (Fig. 26-7).

VI. Before completion, adequate forward blood flow through the graft and back-bleeding from the target artery are confirmed.

VII. A completion arteriogram or color flow duplex ultrasound should be performed to document graft patency before the patient leaves the operating room.

VIII. After hemostasis is achieved, the wound is thoroughly irrigated to remove any debris. Scarpa’s fascia is reapproximated, subdermal sutures are placed, and the skin is stapled or closed with sutures.

Figure 26-6 Proximal anastomosis.

(From Rutherford RB, Ouriel K: Reversed saphenous vein femoropopliteal bypass. In Ouriel K, Rutherford RB: Atlas of Vascular Surgery: Operative Procedures. Philadelphia, Saunders, 1998.)

Figure 26-7 Distal anastomosis.

(From Rutherford RB, Ouriel K: Reversed saphenous vein femoropopliteal bypass. In Ouriel K, Rutherford RB: Atlas of Vascular Surgery: Operative Procedures. Philadelphia, Saunders, 1998.)

POSTOPERATIVE MANAGEMENT

I. Patients are maintained on antiplatelet therapy (aspirin, aspirin and clopidogrel, or systemic anticoagulation), unless contraindicated.

II. A pulse examination should be undertaken at regular intervals. This examination consists of palpation, with or without portable Doppler evaluation. The graft pulse and distal arterial pulses should be documented.

III. If the bypass was performed in the setting of acute severe ischemia, monitoring of lower leg compartment pressures is essential to exclude reperfusion-induced compartment syndrome.

IV. Postoperative vein graft surveillance is an essential component of postoperative follow-up. Patient evaluation and duplex ultrasonography of the graft are performed at 1, 6, 9, and 12 months postoperatively, and yearly thereafter. Recurrent symptoms or a change in findings on pulse examination, ABIs, or PVRs may reflect graft stenosis and require evaluation with CTA, MRA, or invasive angiography.

COMPLICATIONS

I. Cardiac complications are a major cause of morbidity and mortality in patients with PAD. Preoperative optimization of cardiac status, routine postoperative β-blockade, and judicious perioperative fluid management are critical to minimizing cardiac risk.

II. Patients with diabetes or chronic renal insufficiency are at increased risk for postoperative renal failure. Maintaining intravascular euvolemia and minimizing the use of nephrotoxic contrast agents and drugs are important preventive strategies.

III. Infection, wound dehiscence, and skin flap necrosis are common because of the length of the incision required and the long case duration. Gentle handling of tissues, avoidance of skin flap creation, use of prophylactic antibiotics, and meticulous wound closure reduce the risk of these events.

IV. Perioperative graft thrombosis occurs infrequently and should be treated promptly with surgical thrombectomy and correction of the underlying cause.

V. Early graft failure occurs within 1 month of the operation and usually reflects a technical problem. Immediate reoperation is generally indicated. Late graft failure, occurring within the first 1 to 2 years, is more likely to be caused by intimal hyperplasia of the graft itself, whereas graft failure after 2 years reflects progression of atherosclerotic disease. Reoperation may be necessary in these cases, but should be preceded by a thorough investigation of the anatomy and cause of the graft failure.

VI. Pulsatile hematoma or hemorrhage is usually caused by a dislodged ligature on the vein graft or an anastomotic disruption. This situation can be life-threatening and requires immediate reexploration. Inadequate intraoperative hemostasis may lead to a slowly accumulating hematoma. Large hematomas should be drained expeditiously to prevent superinfection, wound dehiscence, and graft failure secondary to compression.

VII. Disruption of lymphatic tissue in the groin during dissection of the femoral vessels can lead to seroma formation. The rate of seroma formation in the groin, leg, or popliteal wounds from lymphatic disruption can be decreased by obliterating dead space during wound closure.

SUGGESTED READINGS

Freischlag JA, Angle N. Reversed vein bypass [[eds]]. Baker RJ, Fischer JE, editors. Mastery of Surgery, 4th ed. Lippincott Williams & Wilkins, Philadelphia, 2001, 2160-2166.

Ouriel K, Rutherford RB. Reversed saphenous vein femoropopliteal bypass. In: Ouriel K, Rutherford RB, editors. Atlas of Vascular Surgery: Operative Procedures. Philadelphia: Saunders, 1998.

Rosenthal D. Femoropopliteal occlusive disease [[ed]]. Cameron JL, editor. Current Surgical Therapy, 8th ed. Mosby, Philadelphia, 2004, 777-781.

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