Critical Limb Ischemia David L. Dawson, MD* Joseph L. Mills, Sr, MD Address * UC Davis Vascular Center, 4860 Y Street, ACC Building, Suite 3400, Sacramento, CA 95817, USA. E-mail:
[email protected] Current Treatment Options in Cardiovascular Medicine 2007, 9:159–170 Current Medicine Group LLC ISSN 1092-8464 Copyright © 2007 by Current Medicine Group LLC
Opinion statement Critical limb ischemia (CLI) is the most severe manifestation of peripheral artery disease (PAD). Without timely recognition, appropriate diagnosis, and revascularization, patients with CLI are at risk for amputation or potentially fatal complications. The past decade has seen substantial growth in endovascular CLI therapies and options now exist for treating long-segment lower-extremity arterial occlusive disease, but surgical bypass may yield more durable results. Patients who are younger, more active, and at low risk for surgery may have better outcomes with an operation. Surgical treatment is also indicated for failures of endovascular therapy, which may include early technical failures or later occlusion after placement of stents or other interventions.
Introduction Critical limb ischemia (CLI) results from severe occlusive disease that impairs distal limb perfusion to the point where oxygen delivery is no longer adequate to meet the metabolic needs of the tissue, even under resting conditions [1]. The limits of peripheral artery disease (PAD) compensatory mechanisms, such as distal vasodilatation and collateral formation, have been exceeded at this point. CLI manifests with ischemic rest pain (Rutherford PAD classification, category 4) or tissue loss. Tissue loss, in its mildest presentation, includes focal ischemic ulceration or nonhealing wounds (Rutherford category 5). Gangrene is the manifestation of particularly severe chronic ischemia (Rutherford category 6). Associated problems, such as chronic venous insufficiency or decreased cardiac output, can also exacerbate the hemodynamic consequences of arterial occlusive disease. The term “CLI” generally implies chronicity; the management of patients with CLI is different from that of patients with acute limb ischemia. Approaches to the management of acute limb ischemia are beyond the scope of this review. The diagnosis of hemodynamically significant PAD should be objectively confirmed, usually by measurement of ankle-brachial indexes, toe Doppler pressures, or transcutaneous partial pressure of oxygen measurements. Ankle-brachial pressure indexes should be routinely measured, but toe pressures should also be
recorded if the patient is a diabetic or if there are other indications that the ankle pressure is artifactually elevated by medial calcinosis. The diagnosis of CLI is generally confirmed if there is ischemic rest pain with an ankle systolic pressure less than 40 mm Hg (or toe systolic pressure < 30 mm Hg); or if there is ulceration or gangrene and the ankle systolic pressure is less than 60 mm Hg (or flat metatarsal pulse volume recordings, or toe pressure < 40 mm Hg) [2].
CURRENT GUIDELINES FOR PAD CARE In 2000, the TransAtlantic Inter-Society Consensus (TASC) provided recommendations for standardized, evidence-based management approaches for PAD [2]. TASC guidelines attempted to define which patients with PAD might be better treated with endovascular versus surgical revascularization, categorizing patients by the pattern and extent of their arterial occlusive disease (Table 1). However, some elements of the TASC guidelines have already become dated, as the outcomes of endovascular therapies have improved, especially in more complex disease categories, such as the treatment of occlusions and long-segment atherosclerosis. Improvements in endovascular therapeutics have prompted the TASC participants to develop an updated document, a process currently unpublished as of late 2006. It is now recognized that complex TASC C and D iliac occlusive disease patterns can be treated success-
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Table 1. Morphology and preferred treatment of arterial lesions TASC classification Iliac A
B
C
D
Femoropopliteal
Preferred treatment approach (circa 2006)
Single stenosis < 3 cm of the CIA Single stenosis ≤ 3 cm in length, Endovascular or EIA (unilateral/bilateral) not at the origin of the SFA or the distal popliteal artery Single stenosis 3–10 cm in length, Single stenoses or occlusions Individualize approach based not extending into the CFA 3–5 cm long, not involving the on local capabilities and distal popliteal artery experience. Current practice now favors endovascular therapy for TASC B lesions. Endovascular therapy of TASC C lesions should be considered in selected, high-risk patients, particularly if surgical options are poor, medical comorbidity is high, or expected longevity is short Total of two stenosis < 5 cm long Heavily calcified stenoses ≤ 3 cm in the CIA and/or EIA and not in length extending into the CFA Unilateral CIA occlusion Multiple lesions, each ≤ 3 cm (stenoses or occlusions) Single or multiple lesions in the absence of continuous tibial runoff to improve inflow for distal surgical bypass Bilateral 5–10-cm-long stenosis Single stenosis or occlusion longer of the CIA and/or EIA, not than 5 cm extending into the CFA Unilateral EIA occlusion not Multiple stenoses or occlusions, extending into the CFA each 3–5 cm, with or without Unilateral EIA stenosis extending heavy calcification into the CFA Bilateral CIA occlusion Diffuse, multiple unilateral Complete CFA or SFA occlusions or Surgical bypass recommended stenoses involving the CIA, EIA, complete popliteal and proximal by TASC, but endovascular and CFA (usually > 10 cm) trifurcation occlusions approaches have become Unilateral occlusion involving both common for many patterns of the CIA and EIA disease previously treated only Bilateral EIA occlusions with operation Diffuse disease involving the aorta and both iliac arteries Iliac stenoses in a patient with an AAA or other lesion requiring aortic or iliac surgery
Italicized comments reflect current practice, which favors endovascular therapy more than the original TASC guidelines. AAA—abdominal aortic aneurysm; CFA—common femoral artery; CIA—common iliac artery; EIA—external iliac artery; SFA—superficial femoral artery; TASC—TransAtlantic Inter-Society Consensus. (Adapted from Dormandy and Rutherford [2].)
fully with endovascular techniques [3,4]. Further, more CLI cases with infrainguinal occlusive disease may be amenable to endovascular therapy than previously thought. The BASIL (Bypass Versus Angioplasty in Severe Ischaemia of the Leg) study, a multicenter, randomized, controlled trial, found similar survival
and limb salvage rates in patients with CLI with infrainguinal occlusive disease using either percutaneous transluminal angioplasty (PTA) or surgical revascularization in patients deemed suitable for either therapy [5]. At 6 months, there was no difference in amputation rates between angioplasty versus surgery first. There
Critical Limb Ischemia Dawson and Mills was also no difference in health-related quality-of-life outcomes, but costs were higher for the surgery group over the first year (hospital costs, length of hospital stay, and length of stay in skilled nursing units). The American College of Cardiology (ACC) and the American Heart Association (AHA) jointly published guidelines on PAD in 2005 [6••]. This document was produ ced in collaboration with major vascular medicine, vascular surgery, and interventional radiology societies. The ACC/AHA guidelines broadly address PAD management, but specific recommendations were included for the estimated 1% to 2% of patients with PAD who have CLI.
GENERAL MANAGEMENT CONSIDERATIONS All patients with PAD may achieve long-term benefit from smoking cessation, exercise, modification of atherosclerosis risk factors (low-fat diet, lipid lowering, control of diabetes and hypertension, and so forth), and antiplatelet therapy [2,6••,7,8,9•,10–12]. However, such general PAD therapies are directed at reducing the risk of future cardiovascular morbidity and mortality and do not specifically address CLI. Patients with CLI have immediate problems. The initial management of patients with CLI includes control of pain and infection, if present, as well as optimization of cardiac and respiratory function, in anticipation of the need for revascularization. Prompt referral of patients with CLI to a vascular specialist will improve the chances of successful treatment. Pain in an ischemic limb may be severe or recalcitrant. Pain control should not delay treatment of the arterial occlusive disease. Neuropathic pain, due to either ischemia or diabetes, may persist even after revascularization. Treatment strategies may include use of gabapentin, antidepressants, narcotics, behavioral therapy, or other pain management techniques. Intravenous antibiotics are indicated for acute therapy in patients presenting with soft tissue infections, such as cellulitis associated with ischemic ulcers or focal gangrene. Infection may be indicated by swelling, redness, and tenderness at the site of an ulcer, or there may be systemic signs and symptoms, such as fever or leukocytosis. Infections are often polymicrobial, particularly in patients with diabetes mellitus [13–16]. There is no need for antibiotic therapy for neuropathic, clinically uninfected ulcers. In selecting empiric antibiotic therapy, consideration should be given to local antibiotic susceptibility data, especially the prevalence of methicillin-resistant Staphylococcus aureus or other resistant organisms. Whenever possible, antibiotic use should be guided by local sensitivity patterns and information from cultures. Cultures of surface swabs have little clinical use. Deep cultures or cultures of débrided tissue are more likely to lead to identification of the true pathogens.
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Severe infections require parenteral therapy, at least initially. Highly bioavailable oral antibiotics may be considered in mild and moderate infections. It is appropriate to continue antibiotic therapy until there is evidence that the infection has resolved, but not necessarily until the wound has healed. In the absence of clinical improvement, empiric coverage should be broadened or augmented. The administration of antibiotic therapy should not delay more definitive treatment. Given the success of distal revascularization and aggressive multidisciplinary approaches to limb preservation, primary amputation is rarely indicated. Occasionally, patients with CLI will have other serious conditions limiting mobility, functional capacity, or life expectancy. Severe arterial occlusive disease, in combination with extensive tissue loss, may not allow preservation of the ankle joint. Primary amputation should be considered in such cases. Such decisions, although difficult, avoid excessive hospitalization, multiple surgical procedures, pain, or even mortality, allowing earlier placement into appropriate rehabilitation settings and more rapid return to a functional state. For fit patients who are good rehabilitation candidates, below-knee amputation and ambulation with a prosthesis may provide a more functional outcome than extensive foot amputations involving the mid- or hindfoot. Older and debilitated patients, however, may have trouble with a prosthesis for a below-knee amputation and such patients seldom ambulate with a prosthesis for an above-knee amputation. For patients with limited ambulation requirements, preservation of a weightbearing foot helps patients to accomplish activities of daily living with minimal assistance.
SPECIAL CONSIDERATION: DIABETES MELLITUS Diabetes is a particularly important risk factor for the development of atherosclerosis. Clinical manifestations of atherosclerosis are five to 10 times more common in diabetic patients than in nondiabetic patients [17]. Atherosclerosis in diabetic patients is more diffuse and more severe and manifests itself at an earlier age than atherosclerosis in nondiabetic patients [18]. For these reasons, CLI is a particular concern with diabetic vascular disease. However, the significance of diabetic microangiopathy in lower-extremity disease is controversial. The diabetic foot is at increased risk for complications of CLI due to the frequent coexistence of diabetic neuropathy, which can impair sensory, motor, and autonomic nerve function [19,20]. Protective sensation is decreased. Distal motor nerve defects and limited joint mobility may lead to foot deformities, resulting in pressure points that can become a focus for pressure ulceration. Autonomic neuropathy can result in decreased sweating, dry fissured skin, and arteriovenous shunting. However, diabetic patients with neuropathy
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can develop infection or ulceration even without significant ischemia. Therefore, confirmation of the diagnosis of hemodynamically severe arterial occlusive disease is an essential step in developing a management plan. Guidelines for antimicrobial therapy for foot infections in patients with diabetes were developed and published in 2004 by the Infectious Diseases Society of America [14]. Aerobic gram-positive cocci (eg, S. aureus) are the predominant pathogens in diabetic foot infections. Chronic wounds or patients who have recently received antibiotic therapy may also be infected with gram-negative rods. Those with ischemia or gangrene may have obligate anaerobic organisms. Advanced ischemia and gross infection may pose an immediate threat to survival. Diabetic patients who have neuropathy may present this way, often not recognizing the severity of their problem. Patients may also be the victims of delayed referral. Immediate surgical treatment is needed. Grossly infected and necrotic tissues need débridement for local control of infection. Deep soft tissue infections, such as a plantar space abscess, require drainage. Major amputation is needed if there is gas gangrene or severe sepsis, but in most cases the initial operation for drainage and débridement can be limited to the foot, with preservation of as much viable tissue as possible. Open digit, ray, or partial foot amputations may be revised later, after the ischemia has been corrected [2,21].
PLANNING FOR REVASCULARIZATION The likelihood of successful revascularization and its functional benefit should be considered and balanced against the risks, costs, and procedural morbidity [22–25]. Contrast arteriography, including selective injections and
multiple projections, is the standard method for anatomic assessment. Ultrasound duplex scanning may complement, and in selected cases replace, arteriography [14,26–28]. In addition, the flow velocity information from the pulsed Doppler waveforms provides information about the hemodynamic significance of identified lesions. Duplex scanning may be sufficient for planning surgical approaches for revascularization [27,29,30], but intraoperative arteriography is generally needed to confirm the selection of a distal revascularization target.
EVALUATION OF CORONARY ARTERY DISEASE Routine cardiac evaluation in stable patients with CLI is not indicated or beneficial. Cardiac diagnostic testing strategies in patients with CLI should not be directed at selecting patients for coronary revascularization prior to limb revascularization. Coronary interventions have not been shown to reduce perioperative morbidity or mortality and will often result in an unacceptable delay in limb revascularization, possibly resulting in limb loss [2]. Patients with PAD, including those with CLI, can undergo vascular surgery with low mortality and morbidity, even if they have significant concomitant coronary artery disease, if they have aggressive medical management with  blockers, statins, and aspirin. Results are not improved by coronary artery revascularization prior to vascular surgery [31••]. In highly selected patients preprocedural cardiac risk assessment may provide useful information, potentially altering treatment plans [6••]. If preoperative cardiac risk assessment identifies the patient as having a particularly high risk of postoperative cardiac complications, less physiologically stressful (eg, endovascular therapy or extraanatomic bypass) treatment modalities may be selected.
Treatment Revascularization strategies for CLI • Clinical presentations of CLI vary considerably. Invasive treatment for CLI requires individualized therapeutic plans unique to every patient. Nonetheless, defined strategies and priorities guide treatment choices. • Interventions—whether surgical revascularization, catheter-based endoluminal therapy, or a combination of techniques—must be goal directed. The magnitude of intervention required for revascularization will vary depending on the severity of limb ischemia and the clinical circumstances. Although atherosclerotic occlusive disease in CLI often involves multiple arterial segments, single-level revascularization may provide sufficient improvement in distal tissue perfusion to overcome ischemic rest pain or heal minimal ulceration [32]. However, limited interventions will likely fail in the presence of active infection or extensive tissue necrosis. Patients suffering from more extensive ulceration and gangrene (with or without active infection) need to undergo procedures that will re-establish pulsatile flow at near systemic pressures [2].
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• Treatment of inflow-limiting arterial occlusive disease (aortoiliac segment) should be performed prior to (or concomitantly with) infrainguinal revascularization. Failure to treat proximal lesions (recognized or not) may compromise the patency of any distal procedures, resulting in compromise of graft longevity, symptom control, or limb salvage.
Relative roles of surgery and endovascular intervention • Primarily, patient comorbid medical conditions, perceived longevity, desired long-term patency, and anatomic distribution of disease influence choice of a particular method of inflow revascularization. Aortoiliac revascularization can be achieved either surgically or using endoluminal, catheter-based techniques with good results. If similar results can be anticipated with either open surgery or a minimally invasive catheter-based therapy, the latter is preferable. However, results of endovascular therapy may not be as durable as surgical revascularization for distal disease, extensive lesions, or long occlusions. The TASC guidelines outlined extensive anatomic parameters and associated treatment recommendations [2], although contemporary management strategies more commonly favor endovascular therapy, if this is an option [3]. The use of open femoral artery reconstruction (eg, common femoral endarterectomy) extends the applicability of endovascular techniques for aortoiliac revascularization. • Endovascular interventions also have applications in infrainguinal vessels. Patients with focal disease and restorable runoff generally benefit, although patients with diffuse disease and compromised runoff (common with CLI) may be less likely to have successful and durable endovascular revascularization. • Long occlusions may be crossed using specialized guidewires and support catheters; dilation with a long balloon catheter can then create a channel through the previously occluded segment. Angioplasty is often in a subintimal plane by intent, but despite this “nonanatomic” approach, subintimal angioplasty yields moderately good initial and short-term results [33–37]. Many are reporting primary success rates of approximately 90% in the infrainguinal vessels, as well as 1-year limb salvage rates as high as 85% to 90%, and 5-year primary-assisted patency rates of 64%, while not “burning bridges,” (ie, preserving options for subsequent open surgical procedure, if required) [37]. • Stents are not recommended as primary therapy in the femoropopliteal and distal arterial segments [2,6••]; balloon-expandable stents perform poorly in the superficial femoral artery and are no longer commonly used. Randomized trials of femoral artery PTA and selective stenting versus PTA and routine balloon-expandable stenting have shown no benefit of routine stenting. Intimal hyperplasia within the stent interstices, stent strut fractures leading to vessel occlusion, and other shortcomings limit the long-term effectiveness of stents, especially in high mobile arteries such as the superficial femoral artery [38]. Three-year primary patency rates of approximately 50% have been reported for PTA and first-generation stents. Early results with newer, self-expanding nitinol stents appear promising, although longterm data are lacking [39]. One- and 2-year primary patency rates of 76% to 97% and 60% to 84%, respectively, have been reported with nitinol stents [40•]. However, stent use remains appropriate when there is an unacceptable result from PTA (eg, failure to establish patent lumen, residual > 50% stenosis, flow-limiting dissection). Preliminary clinical results with drugeluting stents [41] or bioabsorbable metallic stents [42] have suggested use of these devices in below-knee applications.
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Vascular Disease • Excimer laser–assisted angioplasty for CLI has also been shown to have good technical success and limb salvage rates in patients unfit for traditional surgical revascularization. In the LACI (Laser Angioplasty for Critical Limb Ischemia) trial, a multicenter study with 145 patients with 155 critically ischemic limbs (occlusions were present in 92% of limbs), procedural success (< 50% residual stenosis in all treated lesions) was achieved in 86% of limbs [43]. Stents were implanted in 45% of limbs. At 6 months, limb salvage was 92% in surviving patients or 93% of limbs. • Restenosis is a major shortcoming of PTA. One strategy to reduce restenosis is to perform PTA with a balloon cooled to -10ºC (cryoplasty). Preliminary experience indicates generally favorable results. After cryoplasty was performed to treat less than or equal to 10-cm stenoses or occlusions in the femoropopliteal arteries, clinical success was 83% at 9 months. After 3 years, clinical patency was maintained at 75%, but this study treated patients with claudication, not CLI, and patency of the arterial segment was not objectively verified [44]. • Options for endovascular PAD therapy are listed in Table 2. Although many new solutions to technical challenges have become available to the interventional specialist, the lack of level 1 data is the biggest challenge to an evidence-based treatment approach. Most of the available data are derived from nonrandomized registry trials or retrospective case series with short and intermediate follow-up and ill-defined patient subgroups. Almost no well-designed comparative studies have been performed, so the personal preference of the treating vascular specialist plays a major role in choosing a strategy for CLI intervention.
Bypass surgery for CLI • Revascularization of any distal artery, including pedal branches, can be performed with acceptable patency and limb salvage rates. Long-term infrainguinal graft patency is influenced by three major factors: inflow, outflow, and conduit. The proximal anastomosis for infrainguinal bypass must be constructed to an inflow artery that provides uncompromised flow to the graft. Donor vessels may include common femoral, superficial femoral, deep femoral, popliteal, or even tibial arteries. Late inflow failure as a consequence of progression of proximal disease in superficial femoral, deep femoral, or popliteal-based bypasses is a relatively infrequent occurrence [2,45–47]. Therefore, given adequate proximal blood flow, choice of inflow vessel should be made based upon length of available conduit. • The distal anastomosis of an infrainguinal bypass should be inserted into the least diseased, patent artery with the best continuous outflow, preferably in direct communication with the pedal circulation [2]. In threatened limbs with severe tibial or pedal occlusive disease that precludes surgical anastomosis or clamping, bypass to an isolated popliteal segment can be performed with reasonable long-term patency and limb salvage in patients with rest pain or limited tissue loss [48]. • Ipsilateral greater saphenous vein in a reversed, nonreversed, or in situ configuration remains the treatment of choice for infrapopliteal bypass. Bypasses to suprageniculate popliteal artery segments can be performed with prosthetic grafts. However, despite a lack of significant differences in early graft patency and limb salvage rates between autologous and prosthetic conduits in an above-knee configuration, long-term patency results favor vein.
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• If ipsilateral greater saphenous vein is not available, alternative autologous venous conduits should be used. Alternative sources include contralateral greater saphenous vein, lesser saphenous veins, cephalic or basilic arm veins from the upper extremities, or even lower-extremity deep veins (ie, the superficial femoral and popliteal veins). Such alternative sources of autologous veins will often necessitate vein-to-vein splicing to provide a conduit of adequate length for bypass. With careful surgical technique, autologous conduits constructed from multiple vein segments can achieve durable graft patency and limb salvage [49]. • If alternative autologous sources have been exhausted, or the available veins are of inadequate quality, infrapopliteal revascularization can be performed with a prosthetic or alternative conduit. Polytetrafluoroethylene (PTFE) or cryopreserved allografts are available options. Controversy remains as to the long-term performance of PTFE infrainguinal grafts and thromboembolic complications associated with prosthetic graft failure [50,51]. In addition, prosthetic bypasses should be avoided in patients with foot sepsis or active infection in order to avoid arterial graft infection. Unfortunately, these grafts have poor long-term patency when placed in crural or infracrural configurations. Adjunctive measures, such as a vein cuff or patch at the distal anastomosis, have been shown to improve patency of prosthetic grafts and should probably be used with infrapopliteal bypasses. Also, a recent study showed PTFE with heparin bonded to the surface may offer patency improvement [52]. This newer material was reported to yield primary and secondary 2-year patency rates of 73% and 86%, respectively. The 2-year limb salvage rate in patients with CLI was 90%. • Following successful revascularization, continued vigilance must be kept on controlling foot sepsis and débridement of devitalized tissues. Successful bypass does not preclude limb loss secondary to uncontrolled infection from undrained abscess. Serial débridements, wound irrigations, intravenous antibiotics, and amputation revisions are often required to achieve the goal of preserving a functional, weight-bearing foot. In extreme cases, the necessity for aggressive resection of necrotic tissue may leave large cavities in the foot, exposing tendon and bone. Adjuvant skin grafting or even free tissue transfer can be done to provide coverage [53]. • Antiplatelet agents appear to offer benefit in reducing the risk of postprocedural thrombosis or restenosis after peripheral interventions [54]. Daily aspirin doses exceeding 325 mg have no advantage and are more likely to cause gastrointestinal side effects. Little data about newer, more potent antiplatelet drugs such as clopidogrel are available, but clopidogrel use has become common after peripheral interventions.
Surgical outcomes and follow-up • Arterial reconstructions bypassing different arterial segments of disease are associated with variable graft patency rates. Pooled data suggest that aortofemoral reconstructions are associated with 5-year graft patency rates that exceed 90% [2]. Femoropopliteal and tibial level revascularizations with autologous conduit are associated with graft patency rates of approximately 70% at 5 years [2]. • Infrainguinal autologous bypasses should undergo routine postoperative surveillance to identify developing graft-threatening lesions. Noninvasive and relatively inexpensive, color-flow duplex scanning can accurately detect the development of hemodynamically significant stenoses. Angiography should be considered when the clinical and vascular laboratory findings are abnormal or equivocal.
General use for stenosis or occlusion
Mechanism of action
Advantages
atm—atmosphere; PTA—percutaneous transluminal angioplasty; PTFE—polytetrafluoroethylene; SFA—superficial femoral artery.
Stenting
Atherectomy
Conventional
Angioplasty
Common applications
Disadvantages
Balloon compresses and Low cost, rapid, simple, May create flow-limiting dissecfractures plaque, creates low profile tion. Restenosis or early occludissection planes sion from recoil Cutting balloon Dilatation of calcific or Atherotomes on the surface Rapid and simple to use Larger crossing profile than confibrous stenoses of noncompliant balloon ventional PTA balloons. No long score plaque balloon sizes. More expensive Refrigerated balloon Atherosclerotic or restenotic Balloon cooled to -10°C with Thought to reduce dissection at Crossing profile. Inflation pressure (cryoplasty) lesions. Iliac, femoral, inflation using nitrous oxide treatment site. Cryotherapy may limited to 8 atm. More expensive popliteal, tibial inhibit restenosis Plaque excision De novo and restenotic Rotating carbide cutter shaves Minimal radial force, may be Time consuming. Increased radialesions in peripheral material from vessel wall. used at bifurcations. tion exposure and contrast use. arteries. Commonly used to Tissue captured in catheter, Debulks lesion Restenosis common. Larger treat femoropopliteal and removed from patient profile. Cost tibioperoneal segments Laser ablation Lesion debulking. Crossing 308-nm ultraviolet Excimer Facilitates angioplasty and Rarely used as "stand-alone" chronic occlusion. Effective laser (Coherent Inc., stenting. Some efficacy with therapy. Cost for atheromatous or Santa Clara, CA) ablates calcified lesions. Satisfactory thrombotic material tissue. No thermal injury outcomes with complex disease Orbital atherectomy Investigational for peripheral Eccentrically shaped wire coil Gradually ablates stenotic Investigational. Generates arterial applications and diamond-coated abrasive tissue. Debulks occlusion or microemboli, although these crown. Rotated at high speed, lesion. May reduce deeper are not thought to be clinically crown moves in orbital path vessel wall injury significant around vessel periphery Improves results from PTA, especially if there is dissection or residual stenosis. Femoropopliteal stenting is not preferred as a primary approach Balloon expandable Iliac artery stenoses Balloon expands metallic stent May be postdilated to larger Permanently deforms if bent or (stainless steel or or occlusions size. Radial force maintains compressed. Limited use in cobalt chromium) lumen infrainguinal locations Self-expanding Iliac, femoral, and Unconstrained, stent expands. Dynamic radial force. Flexible, Metal fatigue and strut fracture nitinol popliteal arteries Select stent diameter larger trackable. Low profile in mobile locations (eg, SFA). than target vessel Restenosis common within stent Covered stents Cover diffuse atherosclerosis. Self-expanding nitinol stents. Smooth luminal surface. PreLarger access sheath required. Treat recurrent stenosis after Bonded PTFE membrane. Func- vents ingrowth of hyperplastic Poorer results in arteries < 5 iliac stenting. Management tional similar to endoluminal intimal tissue. Can cover vessel mm. Intimal hyperplasia at ends. of perforation during placement of prosthetic graft. wall perforations Difficult to track through atherectomy or angioplasty Small balloon-expandable tortuous or narrow vessels coronary-covered stents occasionally used in tibial artery
Options
Technique
Table 2. Endovascular procedures
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Options
Common applications
Mechanism of action
Advantages
Disadvantages
atm—atmosphere; PTA—percutaneous transluminal angioplasty; PTFE—polytetrafluoroethylene; SFA—superficial femoral artery.
Contraindications Relative to the status of the patient. Long segments of diffuse disease or occlusion may be better treated surgically. See Table 1 to endovascular therapy Complications 30-day mortality rates vary from 0% to 10%, depending on patients’ underlying condition Major complications: bleeding, pseudoaneurysm development, embolization, acute occlusion, renal failure, and contrast reactions. These may occur in approximately 1% to 6% of iliac and femoropopliteal angioplasties Higher complication rates: complex lesions, long procedure times, multiple catheter manipulations and exchanges, and stent use Late complications include recurrent stenosis or occlusion Cost/costCosts vary greatly, depending on number of endovascular devices used effectiveness Additional bypass, angioplasty, or thrombolysis increase costs Usefulness and cost-effectiveness of multiple stents yet to be established Endovascular therapy costs may be lower than surgery, but cost advantage may eventually be lost due to recurrence, higher follow-up costs, and complications
Technique
Table 2. Endovascular procedures (Continued)
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Vascular Disease • Limb salvage rates generally exceed graft patency rates (ie, during late follow-up it is possible to find a viable limb with an occluded graft or failed endovascular intervention). Typically, revascularization may have been necessary for wound healing because of the presence of ischemia and the increased metabolic demands associated with infection. However, blood flow levels to maintain viability are significantly less than those required to promote and allow healing. Therefore, late failure does not always return a limb to a critically ischemic state. • Each case must be individualized, but surgery as the initial approach to infrainguinal revascularization should be considered if the patient has a long life expectancy, there is low or moderate anticipated surgical risk, there is sufficient length of autologous saphenous vein for bypass, and there is an appropriate inflow vessel and a suitable target. Increasingly, endovascular therapies are favored if life expectancy is limited, the patient has a poor functional status, or surgical risks are high, due to either systemic conditions or local factors. An experienced vascular surgeon should be involved in such complex decision making.
Adjunctive therapies for CLI • In addition to the direct effects of impaired arterial inflow with CLI, low tissue perfusion pressure induces local microcirculatory responses. Targeting microcirculatory changes is a potential therapeutic option in patients for whom revascularization is impossible or unsuccessful. Drug treatment could also augment results when revascularization is incomplete. • Pentoxifylline and cilostazol are the two drugs with US Food and Drug Administration approval for the treatment of claudication, but they have not been appropriately studied for efficacy in the treatment of CLI. Because studies of these and other currently available vasoactive drugs have been equivocal or negative, they are not generally recommended for CLI [9•]. • Prostanoids have potentially useful effects on platelet activation, leukocyte activation, and endothelium function. Prostaglandin E1 and more stable prostacyclin analogues (ciprostene and iloprost) have been used in Europe for the treatment of ischemic rest pain and ulceration. Available data suggest benefit for CLI, relieving rest pain and improving healing of ulcers, but the magnitude of benefit is small [56,57].
References and Recommended Reading Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance 1. 2.
3.
Strandness DE Jr, Sumner D, eds: Hemodynamics for Surgeons. New York: Grune & Stratton; 1975:278–281. Dormandy JA, Rutherford RB: Management of peripheral arterial disease (PAD). TASC Working Group. TransAtlantic Inter-Society Consensus (TASC). J Vasc Surg 2000, 31(1 Pt 2):S1–S296. Leville CD, Kashyap VS, Clair DG, et al.: Endovascular management of iliac artery occlusions: extending treatment to TransAtlantic Inter-Society Consensus class C and D patients. J Vasc Surg 2006, 43:32–39.
4.
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