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FIGURE 7-1 Arteries of the lower extremity.

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The profunda (deep) femoral artery supplies blood to the thigh. The origin of this vessel may be involved with atherosclerosis, but the remaining distal vessel is usually spared. A heavily diseased distal profunda is typical in diabetic patients.

The popliteal artery frequently harbors atherosclerosis. Other causes of occlusive disease in this artery include entrapment by the gastrocnemius muscle (popliteal entrapment) and cysts in the adventitia of the artery (cystic adventitial disease). These latter two conditions, which are more rare, may be found in younger patients.

long the pain has been present, and whether its onset was acute or gradual. Differential diagnosis includes arthritic pain and diabetic peripheral neuropathy.

Gangrene: location of the tissue loss, history of local trauma, evidence of infection (fevers, purulent drainage, local pain), and how long it has been present. Differential diagnosis of nonhealing foot ulcers in diabetic patients includes neuropathic ulceration and underlying osteomyelitis.

Risk factors for atherosclerosis: detailed questioning regarding history of diabetes mellitus, hypertension, tobacco abuse, hypercholesterolemia, and family history of atherosclerosis.

Cardiopulmonary assessment: thorough history and review of systems concerning the patient's cardiac and pulmonary history, including history of myocardial infarction, congestive heart failure, arrhythmia, chronic obstructive pulmonary disease, and exercise tolerance. Results of recent cardiac stress testing, catheterization procedures, and pulmonary function tests, if available, should be reviewed.

Neurological assessment: History of cerebrovascular accident, transient ischemic attack, or amaurosis fugax (see VII A 3) should be obtained as well as the results of recent carotid duplex imaging tests, if available.

Renal assessment: History of chronic renal insufficiency and prior blood urea nitrogen/creatinine levels should be reviewed, especially for patients who may need arteriographic assessment.

Physical examination. A thorough physical examination should be performed for general evaluation as well as for specific vascular diagnosis.

General evaluation. All patients with peripheral vascular disease should be assessed for neurological, cardiac, and pulmonary disease. Complete neurological assessment includes auscultation of carotid bruits as well as cranial nerve, sensory, and motor examinations. Diabetic patients should undergo two-point discrimination or light touch testing of the feet to rule out peripheral neuropathy. Cardiopulmonary examination should rule out evidence of active congestive heart failure, cardiac valvular disease, or evidence of chronic obstructive pulmonary disease.

Specific vascular evaluation. The pulse examination, performed by an experienced clinician, is the most important part of the physical examination for diagnosing peripheral vascular disease. The presence of normal, diminished, or absent pulses should be noted at the femoral, popliteal, and pedal (dorsalis pedis and posterior tibial) levels. Auscultation of abdominal, pelvic, and femoral bruits indicates turbulent blood flow, and hence atherosclerotic stenoses, at the aortoiliac and femoral arterial segments. Additional note should be made of enlarged abdominal aortic pulsations as well as popliteal pulsations, suggesting aneurysmal disease at these levels. Lower extremity skin changes should be carefully documented, including:

Ischemic ulcerations. These usually are punctate and located distally in the foot.

Elevation pallor/dependent rubor , noted in the foot. These indicate severe chronic peripheral vascular disease.

Trophic changes, noted in the skin. These include a shiny appearance to the skin, loss of hair, and diminished nail growth.

Noninvasive vascular laboratory testing. When history and physical examination suggest the presence of vascular disease, noninvasive testing is performed to confirm the diagnosis and to establish current patient baselines.

Segmental arterial blood pressures are obtained at each arterial segment within the lower

extremity, namely the thigh, calf, ankle, and toes. Systolic pressures obtained at each of these levels correspond to the pressure within underlying arterial segments, namely the aortoiliac, femoral - popliteal, tibial, and digital segments, respectively. The brachial pressure is obtained as a reference.

In the supine position, each of the lower extremity pressures should be greater than or equal to the brachial pressure. A pressure drop >20 mm Hg between segments indicates arterial obstruction within the underlying segment.

The ankle brachial index (ABI) is the ankle pressure compared with that of the brachial artery (i.e., ABI = ankle systolic pressure divided by the highest brachial systolic pressure). In general, a patient's ABI correlates with his or her functional status.

1.00 represents a normal ABI.

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0.5–0.99 is consistent with a history of claudication.

0.2–0.49 is consistent with a history of ischemic rest pain.

< 0.20 represents impending tissue loss.

Exercise testing can be used to increase the sensitivity of ankle pressure testing. After exercise, the ankle pressure (or ABI) should remain normal or increase. In a patient who has claudication but is found to have a normal ABI at rest, a decrease of ABI >0.20 after exercise indicates that symptoms may be due to peripheral vascular disease.

Sources of error in segmental pressure testing include:

Abnormal cuff width. The ideal cuff width is 1.2 times the limb diameter.

Noncompressible arteries. Vessels that are calcified will not compress normally using the standard blood pressure cuff and will yield falsely elevated pressures. The tibial vessels of diabetic patients commonly are noncompressible.

Segmental waveform analysis. Similar to pressure measurements, two types of waveforms can be obtained from each arterial segment, namely Doppler waveforms and pulse -volume recordings.

Doppler waveforms are obtained by recording the Doppler signal over each of the lower extremity arteries. A normal waveform, indicating normal blood flow up to that segment, is polyphasic. As blood flow diminishes to a segment, it becomes monophasic.

Pulse -volume recordings measure the volume change in a limb under an inflated cuff with each cardiac cycle. A normal waveform has a sharp upstroke, with a dicrotic notch in diastole. As blood flow diminishes to a segment, the notch disappears, and the upstroke diminishes.

The morphology of these waveforms is generally not influenced by compressibility of the vessels. Waveform analysis, therefore, serves as a complementary test to segmental pressure testing.

Arteriography. Invasive testing, as mentioned previously, is reserved for patients who are intended to undergo some form of arterial revascularization (see Treatment, II D). Because of the invasive nature of the test, it is generally not used solely to make the diagnosis of peripheral vascular disease.

Technique. During conventional arteriography of the lower extremity, contrast media is injected into the abdominal aorta by utilizing catheters placed through a femoral artery puncture. As the media flows distally within the arterial tree, images are recorded either fluoroscopically (digital subtraction arteriography) or on conventional film (cut film arteriography).

Complications. Arteriography generally can be performed with a low rate of complications.

Contrast media complications

Dye -induced nephrotoxicity may cause acute tubular necrosis following an arteriogram. Risk factors include diabetes mellitus, dehydration, advanced age, elevated creatinine level, and total dye load. It generally presents 1–2 days after the examination and may produce a high-output renal failure. Prevention with periprocedure hydration and limiting the dye load (using CO2 as a contrast agent and digital subtraction techniques) are

helpful. Treatment is supportive.

Dye allergy may result in cutaneous flushing and itching, but if serious, it can cause cardiovascular collapse. Risk factors include prior history of dye allergy and shellfish sensitivity. Preprocedural steroid and antihistamine administration, as well as using low - ionic contrast media, are helpful in avoiding this complication.

Arterial complications

Arterial thrombosis may result from pericatheter thrombus formation or direct trauma to the diseased arterial wall (i.e., dissection).

Atheroembolization during an arteriogram refers to the disruption of an arterial plaque by a catheter, with subsequent discharge of debris distally. This may result in ischemic “blue” toes after the examination. Treatment is supportive.

Puncture site complications

Hematoma , if large, may result in adjacent nerve compression and damage or in necrosis of the overlying skin. The brachial plexus is at particular risk if hematoma forms within the axillary sheath following an axillary artery approach for arteriography. Treatment under these conditions is prompt surgical decompression.

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Pseudoaneurysm may also result if hemostasis is not properly achieved. False aneurysms larger than 2 cm are at risk for rupture. Ultrasound -guided compression of the neck of the pseudoaneurysm is used to produce thrombosis within the false cavity; those arteries not successfully treated by this method are repaired surgically.

Magnetic resonance angiography (MRA) is rapidly becoming a more accurate and common method of assessing the arterial circulation. Its main advantage over conventional arteriography is that MRA avoids the invasive complications noted previously. Successful MRA requires radiologists with specific training in this area as well as special hardware designed for angiographic imaging.

D

Treatment options for lower extremity occlusive disease are generally based on the patient's symptoms. Asymptomatic patients with arterial occlusions do not require surgery. The decision to perform a revascularization procedure on a symptomatic patient depends on the natural history of the present symptom. Claudication is not considered a limb -threatening condition; revascularization is considered only in patients with incapacitating symptoms. The presence of ischemic rest pain or tissue loss is considered a limb -threatening condition, and

revascularization needs to be considered strongly for limb salvage.

Medical treatment. In patients without limb threat (i.e., claudication), medical treatment is most appropriate.

Risk factor modification. The cessation of tobacco abuse represents the most important risk factor to control. Treatment of hyperlipidemia, hypertension, and diabetes mellitus is generally important for long-term prognosis.

Pentoxifylline is approved for the treatment of intermittent claudication. It reduces whole blood viscosity by decreasing plasma fibrinogen and platelet aggregation. After a 6–8 week course of treatment, approximately one half of patients will double their walking distance. If a positive effect is gained, the medication is continued indefinitely. One of the few adverse effects is gastrointestinal upset.

Exercise program. A walking program for patients with claudication, during which they attempt increasingly farther walking distances, has been successful in alleviating some symptoms. Improved collateral circulation and modification of muscle group usage are proposed but unproven mechanisms for this effect.

Percutaneous intervention. For patients who are intended to undergo revascularization, arteriography is performed. Those who are found to have focal stenoses or occlusions, generally in the iliac or femoral vessels, are considered candidates for percutaneous procedures at the time of the arteriogram.

Percutaneous transluminal angioplasty (PTA).

Technique. An inflatable balloon catheter is fluoroscopically guided over a wire through the stenotic area. The balloon is then inflated to 4–8 atm to fracture the plaque, restoring patency to the artery.

Results. Patency rates vary with the anatomic location and character of the stenosis. The larger, proximal arteries, such as the common iliac arteries, show more durable results than the distal femoral, popliteal, or tibial vessels. Lesions that are focal, short, and concentric also have better long-term results.

Stents may be used as an adjunct to percutaneous angioplasty. They are expandable metal mesh conduits inserted over a balloon catheter. The balloon is inflated within the lesion to expand the stent, is deflated, and then is withdrawn. Stents are indicated to prevent recoil of a lesion after angioplasty and to “tack down” an area of dissection. Currently, drug -eluting stents are used in the coronary circulation to impede the process of restenosis. Similarly, investigation is under way to evaluate this technology in larger circulatory beds where stents have been less durable, such as the SFA.

Complications

Atheroembolism. Clinically significant embolism of atherosclerotic debris follows this procedure in less than 3% of cases. Small vessel atheroembolism (e.g., “blue toe syndrome”) is treated conservatively. Large vessel embolism may be treated with thrombolytic therapy or operative intervention.

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Intimal hyperplasia. As with any form of arterial injury, lesions treated with angioplasty may produce an exuberant healing response, resulting in restenosis of the lesion. These lesions are generally responsible for failures within 2 years of the angioplasty. It is not proven that stents prevent this occurrence. Repeat angioplasty can be successful in treating this event.

Thrombosis. Acute thrombosis of the artery may occur secondary to in situ thrombus formation or dissection of the treated lesion. Treatment may involve thrombolytic therapy, stenting, or operative intervention.

Rupture. With careful measurements of the lumen of the artery to undergo angioplasty, this complication can be kept to a minimum.

Surgical interventions. For patients intended to undergo revascularization, arteriography is performed. If a percutaneous intervention is not suitable, surgical revascularization methods are used, provided the patient is a suitable medical risk for surgery.

Indications. The indications for surgery are the same as the indications for revascularization in general.

Incapacitating claudication. Because the natural history of claudication is generally benign, without limb loss, surgery to relieve this symptom is considered solely elective. If the symptoms interfere with a patient's desired lifestyle or ability to work, surgery may be offered. Ideally, the patient should be a good medical risk, having undergone a period of failed medical therapy (exercise program, risk factor modification).

Rest pain. Presentation with rest pain suggests severe arterial insufficiency. Surgical revascularization is considered for limb salvage and should be offered to all, except those with prohibitive medical comorbidities.

Tissue loss. Like rest pain, tissue loss is considered a limb -threatening condition. Surgical revascularization is offered, unless specific contraindications exist.

Contraindications. Surgical therapy is indicated for the previously noted symptoms, unless the following conditions exist.

Nonambulatory status

Nonreconstructible vessels. When arteriography does not reveal a patent distal vessel (popliteal, tibial, or dorsalis pedis) with adequate runoff to support a graft, surgical reconstruction should not be attempted.

Extensive tissue loss. If the foot is not considered salvageable because of either extensive gangrene precluding an appropriate foot amputation or extensive infection such as widespread osteomyelitis, amputation at the below -knee or above-knee level is indicated.

Prohibitive medical comorbidities. If coexisting medical conditions make an extensive revascularization procedure too risky, the patient may undergo amputation or medical therapy for the rest pain or tissue loss.

Operative procedures. Because the most common lesions of lower extremity occlusive disease involve long segment occlusions of the femoral -popliteal system, bypass of the occluded arteries is the most common procedure. For the rarer focal lesions in the femoral system, local endarterectomy accompanied by a patch angioplasty may be appropriate.

Inflow vessel. The most common site for proximal anastomosis in constructing a bypass is the common femoral artery. In the diabetic population, in which the occlusive disease may be isolated to the tibial vessels, the popliteal artery may be a suitable inflow vessel.

Outflow vessel. The most appropriate outflow vessel in constructing a bypass is the artery with the best unobstructed distal outflow. The above-knee and below -knee popliteal arteries, each of the three tibial vessels (posterior, anterior, and peroneal), and the dorsalis pedis artery all are used for distal anastomosis. The name of a specific bypass is derived by using the names of the inflow and outflow vessels (e.g., femoral -popliteal bypass).

Conduit. Many types of conduits have been used, depending on the availability of ipsilateral greater saphenous vein.

Greater saphenous vein (GSV). The ipsilateral greater saphenous vein is the conduit of choice in lower extremity revascularization procedures. It is generally excised and placed in a reversed position, without the need for lysing the valves. For femoral -tibial bypasses, reversal of the vein creates a size discrepancy at each anastomosis. In this situation, the GSV is left in situ , and the valves are lysed and the vein branches ligated.

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Other autogenous veins. In the absence of usable GSV, the lesser saphenous vein as well as arm veins may be used with acceptable results.

Prosthetic conduits. Polytetrafluoroethylene and Dacron bypass grafts have been used with near -equal success to the GSV in the above-knee position. Prosthetic grafts overall have poor patency rates when used in vessels below the knee. Adjuncts to prosthetic grafting to the tibial vessels designed to improve patency rates include the creation of an arteriovenous fistula as well as a venous cuff (Miller cuff) or patch (Taylor patch) at the distal anastomosis.

Results

Primary patency of a bypass refers to the length of time the graft remains patent without any type of intervention, either surgical or percutaneous. The primary patency rates of most GSV bypass grafts range between 65%–80% at 5 years. Limb salvage rates are even higher, generally being 90% at 5 years.

Assisted primary patency refers to a graft that has always remained patent but has required some sort of intervention, either surgical or percutaneous, to maintain adequate blood flow through it.

Secondary patency refers to a graft that has thrombosed and has had patency restored with either thrombolytic therapy or operative thrombectomy.

Amputation. Without revascularization, most patients with severe limb -threatening ischemia eventually suffer limb loss.

Indications. Patients with rest pain or tissue loss who are not candidates for revascularization are generally treated medically, unless one of the following conditions exists:

Intractable rest pain. If ischemic rest pain cannot be managed with a reasonable amount of pain medication, amputation is appropriate.

Sepsis. Patients with tissue loss, complicated by systemic sepsis, undergo amputation to remove the source of infection.

Level. In general, the more distal the amputation is, the more functional the patient's gait will be. The