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

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