FIGURE 8-27 Calcified thrombosed aneurysm. AP (A) and lateral (B) radiographs demonstrate peripheral calcification in the aneurysm (arrow).C) MR angiogram demonstrates complete occlusion (arrow) at the level of the aneurysm with extensive collaterals.

Radioisotope Imaging

Today, radionuclide studies are less frequently used to study flow and healing potential in ischemia of the foot and ankle [83,195]. In the past, technetium-99m, indium-111, xenon-133, and thallium-201 have all been evaluated as noninvasive imaging techniques [132,159,167]. Lawrance et al. [132] found that three-phase technetium scans were useful in assessing local perfusion and predicting healing of ischemic ulcers. All ulcers studied healed when activity was increased in the region of the ulcer compared with normal tissue background or the normal extremity. Healing was uncommon when uptake was not increased in the ulcerated areas.

Thallium-201 has been used for similar purposes [167,208]. Ohta [167] compared patterns of thallium-201 uptake (a marker of perfusion and tissue viability) in healing and nonhealing ulcers in 36 patients. The pattern of isotope uptake was correlated with hyperemia and inflammation in the ulcer bed. Both early (5 to 15 minutes) and delayed (3 hours) images were obtained after 2 mCi of thallium-201 was given intravenously. Four patterns of uptake were described (Table 8-8). All patients with no increase in uptake on either early or delayed studies eventually required amputation [167]. Siegel et al. [208] found thallium-201 comparable to Doppler techniques in predicting healing of cutaneous ulcerations.

Platelets labeled with indium-111 have also been employed in studies of patients with soft tissue ischemia. Comerford et al. [40] studied 20 patients using this technique. They noted reduced sensitivity from false-negative studies but found indium-111–labeled platelets useful in predicting healing. In addition, by combining indium-111 with technetium-99m three-phase studies, the results were more accurate. Intradermal xenon-133 injections have also been used to assess cutaneous flow [132]. This technique is more difficult to evaluate and causes more patient discomfort. Thallium-201 studies are accurate but are much more expensive than conventional three-phase technetium studies [132,144].

Radionuclide studies can be useful, but spatial resolution is limited, especially in the lower leg [83]. Therefore, other techniques, such as ultrasound, CT, or MR angiography or convention angiography are more often used at most centers.

Ultrasound

Ultrasonographic techniques provide a simple, noninvasive method of assessing peripheral flow in patients with peripheral arterial disease [6,18,20,41,63,83,124,128,129,179]. Today, color flow duplex sonography and power Doppler techniques provide improved sensitivity and specificity for evaluation of peripheral arteries. Doppler ultrasound is particularly useful in patients with ischemic disease, diminished peripheral pulses, and reduced peripheral systolic pressures (less than 70 mm Hg) [41]. Advantages of ultrasound include its low cost, versatility (can be used at the bedside), ease of use, and ability to differentiate occlusive from nonocclusive vascular disease [18,20,63,83,179]. The normal Doppler arterial wave form in the peripheral arteries is triphasic [20,179]. During systole, a fast forward pattern is followed by brief period of flow reversal during early diastole followed by the third phase of forward flow in late diastole (Fig. 8-28) [20]. The second phase (flow reversal) is absent in the presence of significant arterial stenosis. Distal to occlusions, the pulse is monophasic [128]. The reversal portion of the pattern may also be absent in diabetic patients. In the presence of neuropathy, the flow may be increased up to five times [16,41,128]. This flow abnormality is most likely related to peripheral autonomic neuropathy with dilatation of the vascular bed [41,129].

Stenosis can be evaluated using changes in the wave form and peak systolic velocity. Stenoses less than 20% may result in changes in the wave form, but peak systolic velocities do not change significantly. Stenoses between 20% and 49% demonstrate a 30% to 100% increase in peak velocity. More significant stenosis (greater than 50%) demonstrate greater than 100% increase in peak velocity compared to the normal prestenotic segment with loss of the flow reversal phase (Fig. 8-29) [20]. In the presence of long narrowed segments (greater than 5 cm), the peak velocity may decrease [179]. There is no Doppler signal with complete occlusion [179].

Studies comparing color-assisted duplex sonography with angiography demonstrate excellent results in the aortoiliac, femoral, and popliteal arteries. Results reported for sonography in the infrapopliteal vessels are more controversial [63,179,215]. Large series demonstrate that comparing sonography to angiography for occlusion and lesions with greater than 50% stenosis the sensitivities and specificities for the aortoiliac region were 86% and 97%, 80% and 96% respectively for the femoral and popliteal arteries, and 83% and 84% respectively for the arteries distal to the popliteal artery [122]. Postoperative evaluation of grafts (Fig. 8-30) and prior angioplasty can also be effectively evaluated with ultrasound [20].

Ankle pressure measurements can be obtained when Doppler is used with blood pressure cuffs [6,128,151,190]. This allows for detection of low systolic pressures, useful information in predicting healing and in determining whether conservative therapy may be helpful [128,151]. Healing occurs in 92% of nondiabetic patients if ankle pressures are greater than 55 mm of mercury. Seventy-six percent of diabetic ulcers heal at this pressure level. Amputation is likely required when ankle pressures fall below this level [151]. Toe pressures are more useful in predicting healing in more distal ischemic disease. Doppler is accurate in most situations, but falsely elevated pressures can be seen in diabetic patients or in patients with other diseases that cause extensive vascular calcification [128,188,193]. Improved accuracy has been reported using Doppler techniques. Karanfilian et al. [111] compared laser Doppler velocimetry with conventional Doppler ankle pressures and transcutaneous oxygen measurements to determine which was most accurate in predicting healing of ischemic ulcers. Transcutaneous PO₂ measurements were most accurate with a sensitivity of 100%, specificity of 88%, and accuracy of 95%. Laser Doppler studies were somewhat less reliable, but compared with Doppler ankle pressure the sensitivities were 79% and 75%, specificities were 96% and 26%, and accuracies were 87% and 52%, respectively [111].

Angiography

Color flow duplex combined with Doppler studies are useful and noninvasive, but, to date, angiography (conventional or digital) remains the gold standard for mapping vascular abnormalities (see Chapter 2) [73,196]. Angiography provides accurate information regarding the extent and sites of stenosis, pressure measurements or occlusion, the extent of involvement and collateral circulation, the anatomy of the vessel proximal and distal to the involved segment, prognostic information, and, when indicated, the appropriate level for amputation (see Figs. 8-21, 8-23, 8-24, and 8-31) [49,78,89,119,182,215].

Angiographic techniques also define vascular changes associated with specific disorders such as fibromuscular dysplasia and Buerger disease (see Figs. 8-23 and 8-24) [31,33,97,110,119].

Evaluation of the aorta, iliacs, and major vessels of the lower extremities can be easily accomplished using aortograms with run-off studies of the lower extremities or selective catheterization. However, smaller peripheral vessels in the feet and the pedal arch can be more difficult to identify, especially in the presence of small vessel disease [36,215]. The pedal arch, for example, is a low-resistance vascular bed with slow flow that can make angiographic filming difficult. Longer filming sequences or vasoactive drugs can be used to define these vessels to better advantage [11,169,199,216].

In recent years, the need for diagnostic angiography has been greatly reduced due to the improvements in CT and MR angiography [36,62,73,92,125,131,182]. In our department, digital subtraction angiography is most often performed when additional intervention may be required (thrombolysis, angioplasty, or stent placement).

Magnetic Resonance Angiography

Vascular imaging using MR techniques began using special pulse sequences with 2D time-of-flight or phase-contrast techniques [22]. These techniques were commonly degraded by artifacts (Fig. 8-32) including spin-saturation, turbulence, and step-ladder artifacts from reformatted thin-section images [22,88].

In recent years, multiple new approaches have resulted in improved evaluation of the smaller arteries in the foot and ankle [36,125,131,181,221]. Most approaches used today are performed with intravenous gadolinium, though intra-arterial gadolinium has also been studied [88,181,230]. Today, most MR imaging approaches use 3D bolus contrast injections (Fig. 8-33)[85,121]. Time of the contrast arrival to the area of interest is critical for optimal image quality [221]. Multiple methods have been described in the literature. Some are vendor related and others may be more universally used. Timing can be guessed (roughly 30 seconds from the antecubital fossa to the abdominal aorta) or more optimally, with a test dose to measure the peak contrast time. This is especially important for the small vessels of the foot and ankle [36]. Some MR systems can automatically track contrast arrival and initiate the imaging [221]. When this is not available, a test dose can be given. Several approaches have been described. Chomel et al. [36] imaged the malleolar region at 1-second intervals for 70 seconds following a small bolus test injection. The study was performed at the optimal contrast enhancement at that level. Tatli et al. [221] described a test injection consisting of 2 mL of contrast followed by 20 mL normal saline bolus using the same injection rate as planned for the examination. Images in the area of interest were performed every 2 seconds and analysis was performed to detect the time of peak enhancement.

Imaging parameters vary with MR vendor. However, ultra-short TEs and TRs and high performance gradients are essential for high quality MR angiography [36,62,221]. Most studies are currently performed on optimized 1.5T units, but with time the needed technology changes on 3T units could offer improved signal-to-noise ratios [62]. Three-dimensional imaging can be performed with short TE/TR spoiled gradient echo sequences. Oblique coronal image planes are most useful for the leg or thigh as the largest field of view with the shortest scan time can be accomplished. The sagittal plane is more optimal for the foot [62]. The approach varies with the anatomic region. For evaluation of the entire lower extremity moving table approach which images at each station. Hybrid techniques incorporate both a single station bolus 3D angiogram and a second injection with two stations to evaluate the pelvis and thighs [221].

Regardless of the approach, 3D contrast-enhanced MR angiography techniques compare favorably to conventional angiography [36,62,131,181,182,221]. Sensitivities of 92% to 97% and specificities of 89% to 98% have been reported [92,152]. In addition, MR angiography has fewer adverse effects, especially in older or diabetic patients, compared to conventional angiography [126]. The American College of Radiology (ACR) appropriateness criteria rank MR angiography and conventional angiography equally (8) with CT angiography slightly lower (6) for patients with claudication [195]. The appropriateness criteria for posttreatment imaging consider MR angiography a useful screening procedure when additional intervention is not a consideration [83].

Computed Tomography Angiography

Multidetector CT (MDCT) angiography along with MR angiography has replaced conventional diagnostic angiography in many practices unless angiographic intervention may be required. The ACR appropriateness criteria ranks CT angiography (6) just below MR angiography (8) for peripheral vascular disease [83,195]. MR angiography may not be appropriate in patients with metallic implants or electrical devices. In addition, MR angiography cannot effectively evaluate vessel wall thickness or calcification [170]. CT angiography is an alternative in patients when MR imaging is contraindicated or assessment of mural disease is required [85,130,147]. Advantages of CT angiography compared to conventional angiography include that it is minimally invasive (intravenous contrast), acquires 3D data, can visualize calcified plaque and there is dramatically shorter examination time [5,73,148,192,198,234]. Reported scan times vary from 31.5 to 70 seconds [5,198].

CT angiography is an effective technique for evaluation of peripheral vascular disease, aneurysms, and traumatic disruption (Fig. 8-34) [5,73,148,234]. Hemodynamically significant stenoses (≥50%) are detected with sensitivities ranging from 93% to 99% and specificities of 95% to 99% with CT angiography [5,170]. Mural calcifications can be assessed with conventional axial CT images. However, using CT angiography, the presence of extensive calcifications decreases the accuracy [170]. Extensive vascular calcification reduces accuracy related to the beam hardening artifacts (Fig. 8-35) [170]. In this setting, MR angiography is the preferred technique.

Similar to MR angiography, the timing of contrast and imaging in the region of interest is critical 32. Today, most scanners are equipped with bolus tracking software that optimizes vascular detail. Contrast volume may vary with the region of interest, but for the lower extremity 100 mL of nonionic contrast is injected and followed with a 70 mL normal saline flush. Protocols vary with equipment, but in most cases 120 kV and 140 mAs are used with rotation time of 0.5 seconds and table feed of 40 mm/sec. Reconstructions vary, but are typically 2 mm at 1.2 mm intervals [5,170,198].

Treatment

Treatment of soft tissue ischemic disorders depends on whether the process is primary or related to a systemic disease. Treatment also differs significantly between occlusive and vasospastic diseases.

Vasospastic Diseases

Patients with vasospastic conditions (see Table 8-5) are usually treated conservatively. For example, patients with Raynaud’s phenomenon should be instructed to protect their hands and feet properly in cold weather and to avoid smoking and vasoconstricting substances [65]. Patients with acrocyanosis and livedo reticularis should also be protected from cold exposure. Sympathetic blocking medications may be required in some patients [65]. Some physicians prefer to utilize calcium channel blockers such as nifedipine. Other medications include angiotensin II inhibitors and nitrites [180]. Most patients (90% of patients with Raynaud’s) respond and improve with these conservative measures [107,180].

In some patients, conservative measures are not successful. In this setting, more aggressive therapy may be indicated. Although the role of sympathectomy is unclear, this procedure may be useful in selected cases. Janoff et al. [107] noted a successful response to sympathectomy in 10 patients with refractory Raynaud’s phenomenon and painful lower extremity vasospasm.

Vascular Occlusive Diseases: Arterial

Treatment of vascular stenosis and occlusion depends on the cause, the location (proximal or large vessel vs. distal small or microvascular disease), and the patient’s medical status. Therapy generally falls into three categories: conservative, percutaneous intervention, or surgery [8,13,17,19,38,51,84,105,115,161,164,194,207,217,218].

Conservative therapy is used when possible, especially in patients with small vessel disease, such as, in diabetic patients, or in patients with peripheral ulcers and minor infections. These patients should have ulcer debridement, be given appropriate footwear to reduce pressure on ulcerated areas, and be given appropriate antiseptic or antibiotic therapy [17,165,173,188]. In the absence of significant vascular disease, larger soft tissue ulcerations can be treated with skin grafts, local flaps, or vascularized muscle flaps [17].

Two therapeutic percutaneous techniques have been commonly employed over the years. Percutaneous transluminal angioplasty (PTA) and thrombolysis, either mechanical or chemical, have both proven useful and provide options to bypass surgery [8,51]. More recently, additional procedures include angioplasty with stent placement, cutting-balloon angioplasty, cryoplasty, and laser atherectomy [8]. Treatment decisions are related to patient status and disease location. Decision making is based on location and extent of disease. Typically, these decisions are based on whether the disease involves the aortoiliac, femoropopliteal, or infrapopliteal vessels [8].

Endovascular therapy is most effective for iliac disease (Fig. 8-36). Current percutaneous angioplasty techniques are successful in 88% of patients with a 5-year posttreatment patency of 66%. Success rates are even higher with combined stent placement (39% reduction in long-term failures) [8]. Endotherapy for iliac disease is less successful for long lesions (≥5 cm), when iliac aneurysms are present and in the presence of severe bilateral aortoiliac disease [8,19,164].

Stenosis is more common in the iliac artery while more extensive long segment disease is more prevalent in the femoropopliteal segments. These segments have higher resistance, reduced flow rates, and are more prone to spasm [8]. The failure rate of endovascular procedures is higher [8,51].

Whereas imaging of the proximal leg vasculature is straightforward, meticulously performed angiography of the tibial arteries and, particularly, the arteries of the foot and ankle is essential in delineating appropriate target sites for distal intervention [8,17,125]. This may require selective antegrade catheterization, delayed image acquisition, use of intra-arterial vasodilators, and digital subtraction angiography with magnification [8,109,116]. In addition, the identification of adequate arterial outflow distal to the site of intervention is a major determinant of success for both distal surgical bypass and endoluminal procedures [8,15,30,49]. This is particularly true for the inframalleolar interventions in which pedal outflow is mandatory for success [12].

Though not commonly performed in our practice, development of microcatheters with mounted balloons less than 4 mm in diameter has permitted angioplasty not only of the tibial and peroneal arteries proper, but also of the pedal branches of these vessels (Fig. 8-37). Because of the diffuse nature of atherosclerotic disease of the lower extremities, patient selection based on the anatomy depicted on preliminary arteriography is the critical step in ensuring a successful outcome for tibial and peroneal angioplasty. Most patients with critical lower leg ischemia do not have a disease distribution appropriate for percutaneous management and are better served with operative intervention [8,17]. Anatomic features predicting a successful outcome to infrapopliteal percutaneous angioplasty include the presence of fewer than four to five stenoses or an occlusion less than 6 cm long in a single tibial or peroneal artery. In addition, there should not be significant proximal vessel disease [227].

Using careful technique in patients with relatively focal infrapopliteal disease and potentially restorable run-off below the site of angioplasty, endoluminal therapy should result in a technical success rate of greater than 90% [98,199,223]. A limb salvage rate of approximately 80% should be expected [15,223]. Successful limb salvage is optimized if straight-line flow to the foot is established, the patients are nondiabetic, and gangrene is absent at the time of the procedure [15,199,223].

Complications associated with percutaneous angioplasty are infrequent, but primarily they include thrombosis and distal embolization. These complications may be readily managed percutaneously using thrombolysis or suction embolectomy. The possibility for procedural complications can be reduced by the periprocedural administration of antiplatelet agents, heparin, and vasodilators [8,9,51]. Fortunately, a failed percutaneous angioplasty or the occurrence of a procedural complication rarely precludes the performance of bypass graft surgery or alters previously planned surgery.

Thrombolysis.

The discovery of effective thrombolytic agents and the development of sophisticated catheter delivery systems have encouraged increased utilization of nonoperative techniques for treating peripheral vascular occlusive disease [8,39,54,75,79,80,95,99,113,127,171,222]. Thrombolytic therapy plays an important role not only as a primary treatment for these vascular occlusions, but also as an adjunct to percutaneous angioplasty when the patient has an underlying focal stenosis. The basis of thrombolysis lies in the ability of exogenously administered agents to dissolve unwanted clot. The action of these agents is targeted toward the lysis of clot fibrin. Fibrinolysis is mediated by the proteolytic enzyme plasmin, which is effective in breaking down fibrin into its inactive degradation products. Plasmin is derived from activation of an inactive proenzyme called plasminogen, which is normally circulating with plasma. Thrombolytic therapy has evolved over the years with new agents and techniques. Agents capable of activating plasminogen include streptokinase (SK), urokinase (UK), tissue plasminogen activator (t-PA), recombinant tissue plasmin activator (rt-PA), third-generation plasminogen activator reteplase and glycoproteins IIb and IIIa platelet receptor antagonist abciximab [56,152,155,198,200,207,225]. Recent reports with third-generation agents demonstrate complete clot resolution in up to 92% of patients [56]. The patients included in the study were treated for thombosis of native arteries (36%) and graft thrombosis (64%). Ten percent of occlusions were embolic and 90% thrombotic [56]. Patients can be followed with Doppler ultrasound to evaluate treatment. Thirty days following treatment, Drescher et al. [56] reported 92% success rate with consistent clinical improvement.

Long-term patency following thrombolysis of lower extremity occlusions can be more variable. The longevity of treated proximal occlusions tends to exceed that of more distal occlusions, and grafts exhibit a more durable response than native vessels [153]. Vein grafts typically remain patent longer than synthetic grafts [56]. Most important seems to be correction of the underlying lesion responsible for vessel thrombosis. Long-term patency for lysed vessels with a corrected lesion far exceeds patency of those in which the stenotic lesion remains uncorrected. In the case of grafts, older grafts appear to have greater long-term patency than newer grafts following thrombolysis [8,56].

Patient selection is critical in order to avoid hemorrhagic complications. The incidence of this complication is reported to range from 1% for hemorrhagic stroke to 5% for major hemorrhages. Minor hemorrhage occurs in up to 15% of patients [8,207]. Drescher et al. [56] reported major hematomas in 12% of patients that required transfusions and 8% with hematomas at the puncture site. Hematuria occurred in 4% of patients and 4% of patients developed thrombocytopenia due to decreased platelet count. An additional 8% of patients developed distal emboli following treatment of the thrombosis. Two percent of patients developed a stroke just over a month following treatment [56].

As noted above, distal embolization of the thrombus during lysis of a lower extremity clot is one of the most uniformly reported complications and occurs in 5% to 50% of cases [112,225]. Identification, in most cases, requires careful angiographic evaluation, especially of the ankle and foot vessels. This unavoidable complication fortunately responds well to continuation of thrombolytic infusion [112,225]. Although emboli may be asymptomatic, dramatic worsening of lower extremity ischemia during treatment should indicate that embolization has occurred. Fortunately, irreversible tissue necrosis and occlusion of distal run-off preventing subsequent surgical reconstruction occur only rarely [225].

Surgical Intervention

The goal of any infrapopliteal arterial intervention, regardless of whether it is percutaneous angioplasty or surgery, is the permanent relief of ischemic symptoms. Surgical interventions for peripheral vascular disease primarily involve bypass graft techniques and endarterectomy [8,48,69,71,108,224,227,235]. Bypass grafts are most commonly employed in distal or diffuse occlusions while endarterectomy may be preferred for aortoiliac or proximal femoral disease [8]. Vascular stents have been successfully used in the aorta and iliac vessels. Autogenous vein grafts are more commonly used in the infrainguinal regions (Fig. 8-38). Vein grafts are reversed so the valves to not obstruct flow. Vein grafts demonstrate patency rates of 70% to 80% over 5 years which is more favorable than prosthetic grafts [4].

Atheroembolus to the lower extremity arterial system is a unique type of occlusive disease in which the source of the embolus, rather than the embolus itself, is of primary therapeutic concern [178]. Aortic aneurysms and occlusive aortoiliac disease are the most common sources of atheroemboli [114,117,125]. Plaques in these regions are prone to degeneration with showering of cholesterol, calcium, and thromboembolic debris to the distal circulation. The shaggy aorta, which is lined with irregular, ulcerated plaques, seems to be particularly strongly implicated in atheroembolication [114]. These emboli have a propensity to travel to the small arteries of the foot and ankle, where they may give rise to the classic blue toe syndrome [28]. If allowed to proceed unabated, atheroembolization can result in limb- threatening ischemia. There is no role for percutaneous, nonsurgical interventions in atheroembolic disease. Surgical correction consists of exclusion by bypass or removal of the source by endarterectomy [8,114].

Treatment of arterial insufficiency in the foot and ankle may be a complex undertaking, especially when atherosclerosis is involved. Because atherosclerosis tends to be a diffuse disease, there is the potential for multiple sequential sites of vascular stenosis proximal to the foot and ankle that need to be addressed to optimize therapeutic outcome (see Fig. 8-38) [227]. Treatment of traumatic lower extremity arterial lesions must be individualized, depending on the physical examination and mode of injury [70,73].

Postoperative evaluation of patients with prior endarterectomy or bypass grafts can be accomplished with ultrasound, MR and CT angiography, and conventional angiography. The latter is most useful if additional intervention may be indicated [8,192,221,232,233]. Detection of graft patency issues is important before thrombosis occurs. For the most part, noninvasive modalities such as the ABI and arterial duplex ultrasound are utilized. Ultrasound is more useful in most situations because it is can enable one not only to diagnose impending intervention failure, but also to identify the actual site responsible for the failure [20,212,213,226].

Ultrasound is capable of detecting those grafts with a high likelihood of failure. A peak systolic velocity measurement less than 40 or 45 cm/sec within the graft strongly suggests impending graft failure, but it is not specific as to cause [16,18,101]. By using color-flow Doppler sonography, the entire length of the bypass graft may be examined in real time, and sites of suspected stenosis may be identified and quantified using Doppler spectral analysis. The severity of stenoses is graded according to a peak systolic ratio. This is calculated by dividing the peak systolic velocity at the site of suspected stenosis by that measured in the normal graft 2 to 4 cm more proximally. Velocity ratios of 2 or greater correspond to a 50% diameter reduction, whereas ratios of 3 or greater indicate a 75% stenosis [20,135,178]. Peak systolic velocity ratios greater than 3 generally indicate impending bypass occlusion and warrant intervention [135,178].

Graft failure occurs for a variety of reasons, depending on the interval that has passed since the operation. Early failures are apparent within 1 month of surgery and are usually ascribed to technical errors. These include suture placement errors, graft kinking, clamp injuries, residual venous side branches, poorly lysed venous graft valves, and poor selection of the anastomotic sites. Intermediate failures occur during the first 1 to 2 years and are attributed to the formation of fibrointimal hyperplasia at the anastomotic sites or within the graft conduit, usually at a venous valve site. Late failures, beyond 2 years, are believed to be a result of the continued atherosclerotic disease process in the native vessels proximal and distal to the anastomosis. The purpose of graft surveillance is to detect intragraft or perianastomotic abnormalities before graft thrombosis can occur [16,135].

Failed or failing revascularization interventions can be managed in several ways. The method selected depends on the type of revascularization performed, the length of time since intervention, and the cause of the failure [21,55,74,153]. Surgical grafts to the lower leg are usually of autologous vein. Early graft failures (less than 30 days postoperatively) usually present with graft thrombosis that is due to a technical problem associated with graft placement. These patients typically return directly to the operating room for a directed graft revision and removal of thrombus. If the precipitating cause of failure is poor outflow, an additional or replacement graft may be required. Percutaneous angioplasty is not indicated in these patients [94].

Vein graft problems occurring in the intermediate postoperative period (1 to 2 years) are most common and are usually the result of an intrinsic graft lesion, such as fibrointimal hyperplasia at the anastomotic sites or at a venous valve. Stenotic lesions occur in 20% to 30% of grafts [21,164]. Various surgical interventions are available and include patch angioplasty, jump graft extension, and excision with either primary reanastomosis or interposition vein graft [8,18]. Excision of the abnormal vein segment with primary anastomosis or interposition grafting restores hemodynamics to a more natural state and may provide the more durable secondary patency [16].

If a failing graft is identified before thrombosis occurs, a surgical secondary patency rate of approximately 85% can be expected [16]. Unfortunately, once graft thrombosis has occurred, surgical secondary patency rates fall precipitously, with 1-year patency rates reported as low as 40% [16,74]. Replacement of the clotted vein graft (secondary revascularization) has been advocated by many, with 5-year patency rates of 55% to 65% being achieved when suitable autologous vein is available. Results using synthetic replacement grafts are not as satisfactory [16,74,164].

Grafts that fail in the late postoperative period (more than 2 years) may do so because of intrinsic graft lesions, although this is not common. Usually, late failure is due to the progression of atherosclerosis in the native arterial inflow to the graft, at the anastomotic sites, or in the arterial run-off distal to the graft. Arteriographically proven anastomotic narrowings usually benefit from surgical revision, whereas occlusive disease proximal or distal to the graft may require some sort of secondary grafting procedure or percutaneous angioplasty [16,74,164]. Percutaneous transluminal interventions (Fig. 8-39) may possess some role in the management of patients with jeopardized lower leg bypass grafts. Because early graft failures are usually technical in nature, there is really no indication for percutaneous therapy in that patient group. The role of percutaneous therapy for grafts failing in the intermediate postoperative period has been examined, with controversial results. Several investigators have had good immediate technical success and long-term patency of graft stenoses treated with percutaneous angioplasty [79,212]. Midgraft stenosis at valve sites, as opposed to anastomotic stenoses, appear to require higher balloon inflation pressure, longer dilatation times, and over dilatation to achieve success [212].

The majority opinion is that percutaneous angioplasty of bypass graft stenosis achieves a high initial technical success rate, but the results are not durable because fibrointimal hyperplasia, unlike atherosclerotic narrowing, exhibits a tendency for elastic rebound following dilatation [16,173,175,203–205]. Disparate results from these PTA studies may be a reflection of the composition of material causing the graft stenosis. With anastomotic stenoses resulting from progressive atherosclerosis, rather than fibrointimal hyperplasia, angioplasty results may be better than if the stenosis is composed entirely of hyperplastic tissue. Varying combinations of fibrointimal hyperplasia and atherosclerosis have been retrieved from these stenotic sites [52,55]. Percutaneous transluminal directional atherectomy devices have been used to remove the noncompressible material causing graft anastomotic stenoses. The experience is limited, but this technique has generated results superior to those for percutaneous angioplasty alone and approaching those reported for surgical revision [52,55]. Adjunctive percutaneous angioplasty following atherectomy is frequently necessary to achieve optimal results [52,55].

Perhaps the most important contribution percutaneous angioplasty can offer is in patients with grafts that have failed or are failing in the late postoperative period. Because late graft failures are frequently secondary to progressive narrowing of graft in-flow or run-off vessels, PTA (see Fig. 8-39) can be used to extend the life of lower extremity bypass grafts [16]. In addition, percutaneous endoluminal procedures may benefit patients who have no suitable veins available for graft revision or replacement. If percutaneous interventions are utilized in intermediate or late graft problems, postprocedure surveillance with ultrasound is critical for continued graft maintenance [18].

More aggressive surgical approaches are often required in patients where revascularization or endoluminal procedures fail. Diabetic patients are the best example [17]. Diabetic patients account for the majority of ischemic complications in the foot and ankle. From 55% to 75% of diabetics require vascular reconstruction [17]. Nonhealing skin wounds and ulcerations may require repair with vascularized muscle flaps [17,219]. More than 80% of major amputations occur in the diabetic population [17].

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