Classification of acute and chronic lower extremity ischemia

INTRODUCTION — When selecting treatment options for lower extremity revascularization, the risks of a given intervention relative to the patient's medical condition must be weighed against the urgency and severity of the threat to limb, the expected improvement in the patient's clinical condition (eg, pain relief, ulcer healing, maintenance of ambulatory and functional status) and the durability of the intervention in the context of the patient's life expectancy [1]. Grading the symptoms of ischemia and the anatomic lesions responsible for these symptoms provides objective measures by which to follow patients clinically, and, importantly, provides consistency when comparing medical and interventional treatment strategies in clinical studies. For patients who suffer from symptoms related to peripheral artery disease (PAD), impairment and disability may need to be quantified for insurance purposes, or in order to qualify for a disability program.

Classification schemes that are useful in guiding management of acute and chronic lower extremity ischemia are reviewed here. The clinical diagnosis and treatment of peripheral artery disease presenting with claudication or chronic limb-threatening ischemia are discussed elsewhere. (See "Clinical features and diagnosis of lower extremity peripheral artery disease" and "Management of claudication due to peripheral artery disease" and "Management of chronic limb-threatening ischemia" and "Endovascular techniques for lower extremity revascularization" and "Lower extremity surgical bypass techniques".)

LOWER EXTREMITY ANATOMY — Knowledge of lower extremity arterial anatomy is important for understanding both acute and chronic lower extremity ischemia.

The lower extremity is perfused by the common femoral artery (figure 1). The common femoral artery branches into the superficial and deep femoral arteries a short distance inferior to the inguinal ligament. The superficial femoral artery runs anteriorly down the thigh between the adductor and quadriceps muscles within the anterior compartment (figure 2). In the distal third of the thigh, the superficial femoral artery is in close proximity to the femur. The superficial femoral artery passes through the adductor canal to become the popliteal artery (picture 1), which most commonly divides at the level of the tibial tuberosity into the anterior tibial artery and tibioperoneal trunk, which further divides into the posterior tibial and peroneal arteries (figure 3A-B). The anterior tibial artery accompanies the deep peroneal (fibular) nerve along the posterior margin of the tibia (figure 4). The peroneal artery passes adjacent to the medial margin of the fibula throughout its course distally. The posterior tibial artery is accompanied by the tibial nerve within the deep posterior compartment.

The collateral circulation in the lower extremity is derived from the deep femoral artery (profunda femoris) (figure 2). Collaterals are poorly developed in younger patients, who thus tend to develop severe acute ischemia with disruption of arterial continuity at the femoral or popliteal levels.

ANATOMIC LESION CLASSIFICATIONS

GLASS classification — The Global Limb Anatomic Staging System (GLASS) is an anatomic scheme proposed in the 2019 global vascular guidelines on the management of chronic limb-threatening ischemia (CLTI) [2]. The GLASS classification stratifies anatomic severity and provides a framework for evidence-based lower extremity revascularization of CLTI. More specifically, GLASS involves grading the level of disease in the femoropopliteal and infrapopliteal segments of the preferred target arterial path for revascularization (table 1), and these are combined to provide an anatomic stage (I to III) of overall complexity that is intended to estimate limb-based patency of lower extremity interventions for CLTI.

TASC classification — Arterial lesions can be classified by Trans-Atlantic Inter-Society Consensus (TASC II) as Type A, B, C, or D according to anatomic distribution, number and nature of lesions (stenosis, occlusion), and according to the overall success rates of treating the lesion using endovascular or surgical means [1]. In general, short segments of disease are more likely to be successfully and durably treated with an endovascular intervention compared with longer, occluded and heavily calcified segments; such considerations form the basis of the classification. However, most patients with peripheral artery disease have more than one lesion, at more than one level, so this classification scheme is limited in focusing on diseased segments rather than the entire limb. Scoring systems that take into account multifocal disease have been used predominantly in research studies [3,4]. (See 'Bollinger scoring method' below.)

The original TASC I classification included classifications for aortoiliac, femoropopliteal, and tibial vessel runoff. Tibial disease was omitted from TASC II. A new tibial classification system has been proposed by selected former TASC steering committee members; this proposed system considers tibial stenosis length, lesion number, presence of occlusion, density of calcification, and nonvisualization of collaterals [5,6]. However, this tibial classification system is not widely used and has not yet been validated.

Type A lesions — Type A lesions are relatively short and focal, and generally have excellent results with endovascular therapy.

●Aortoiliac – Unilateral or bilateral stenosis of the common iliac artery; unilateral or bilateral single short (≤3 cm) stenosis of the external iliac artery

●Femoropopliteal – Single stenosis ≤10 cm in length; single occlusion ≤5 cm in length

Type B lesions — Type B lesions have good results using endovascular methods, which are preferred, unless open revascularization is required for another lesion in the same anatomic area.

●Aortoiliac – Short (≤3 cm) stenosis of the infrarenal aorta; unilateral common iliac artery occlusion; single or multiple stenoses totaling 3 to 10 cm in length of the external iliac artery not extending into the common femoral artery; unilateral external iliac artery occlusion not involving the origins of the internal iliac artery or common femoral artery

●Femoropopliteal – Multiple lesions (stenoses or occlusions), each ≤5 cm; stenosis or occlusion ≤15 cm not involving the infra-geniculate popliteal artery; single or multiple lesions in the absence of continuous tibial vessels to improve inflow for a distal bypass; heavily calcified occlusion ≤5 cm in length; single popliteal stenosis

Type C lesions — Type C lesions may have better long-term results with open revascularization such that endovascular techniques should be used if the patient is at high risk for open surgical repair.

●Aortoiliac – Bilateral common iliac artery occlusions; bilateral external iliac artery stenosis 3 to 10 cm not extending into the common femoral artery; unilateral external iliac artery stenosis extending into the common femoral artery; unilateral external iliac artery occlusion of the origins of the internal iliac and/or common femoral artery; heavily calcified unilateral external iliac artery occlusion with or without involvement of the origins of the internal iliac and/or common femoral artery

●Femoropopliteal – Multiple stenoses or occlusion totaling >15 cm with or without heavy calcification; recurrent stenoses or occlusion that need treatment after two endovascular interventions

Type D lesions — Type D lesions have poorer results with endovascular treatment, and thus, surgery is the primary treatment for low-to-moderate risk patients. However, reasonable results can be obtained for type D iliac lesions with a hybrid approach that combines open femoral endarterectomy with patch closure and retrograde iliac stenting in this setting.

●Aortoiliac – Infrarenal aortoiliac occlusion; diffuse disease of the aorta and both iliac arteries requiring treatment; diffuse multiple stenoses of the unilateral common and iliac artery, and common femoral artery; unilateral occlusions of the common iliac and external iliac arteries; bilateral occlusions of external iliac arteries; iliac stenoses in patients with abdominal aortic aneurysm (that require treatment and are not amenable to endograft placement) or other lesions requiring open aortic or iliac surgery.

●Femoropopliteal – Chronic total occlusion of the common femoral artery or superficial femoral artery (>20 cm, involving the popliteal artery); chronic total occlusion of the popliteal artery and proximal trifurcation vessels.

Bollinger scoring method — For the Bollinger method, 13 infrainguinal arterial segments are assessed, and each of these segments is scored according to the severity and extent of disease [4,7]. Four lesion severities are characterized. To calculate the additive scores, the individual scores for each of the lesion severities are summed in accordance with the following rules: in the presence of occlusions, stenoses and plaques are not considered; when both severities of stenoses are present (ie, ≥50 percent and ≤50 percent), plaques are not scored; for each type of occlusive lesion, only one length category is indicated. The scoring system is somewhat complex and given in figure 2 of the associated reference [7].

Arterial segments:

●Profunda femoris artery

●Proximal (upper half) superficial femoral artery

●Distal (lower half) superficial femoral artery

●Above-knee popliteal artery

●Below-knee popliteal artery

●Tibioperoneal trunk

●Proximal (upper-half calf) posterior tibial artery

●Distal (lower-half calf) posterior tibial artery

●Proximal (upper-half) anterior tibial artery

●Distal (lower-half) anterior tibial artery

●Proximal (upper-half) peroneal artery

●Distal (lower-half) peroneal artery

●Plantar arch

Lesion severity described as:

●Occlusion of the lumen

●Stenoses that are more than one-half the luminal diameter (ie, >50 percent)

●Stenoses narrowing the lumen by more than 25 percent, but maximally 50 percent

●Plaques producing stenosis of the artery by no more than 25 percent

Lesion extent described as:

●Single lesion

●Multiple lesions affecting less than one-half of the segment

●Multiple lesions affecting more than one-half of the segment

Graziani morphologic classification — The Graziani morphologic classification refers to a system for defining arterial lesions in patients with diabetes with progressively increasing extent of arterial involvement [8,9].

●Class 1 – Isolated, one vessel tibial or peroneal artery obstruction

●Class 2a – Isolated femoral/popliteal artery or two below-knee arteries obstructed but with patency of one of the two tibial arteries

●Class 2b – Isolated femoral/popliteal artery or two below-knee tibial arteries obstructed but with patency of the peroneal artery

●Class 3 – Isolated, one artery occluded and multiple stenoses of tibial/peroneal and/or femoral/popliteal arteries

●Class 4 – Two arteries occluded and multiple stenoses of tibial/peroneal and/or femoral/popliteal vessels

●Class 5 – Occlusion of all tibial and peroneal arteries (below-knee cross-sectional occlusion)

●Class 6 – Three arteries occluded and multiple stenoses of tibial/peroneal and/or femoral/popliteal arteries

●Class 7 – Multiple femoropopliteal obstructions with no visible below-the-knee arterial segments

SYMPTOM CLASSIFICATION

Chronic extremity ischemia — Patients with chronic lower extremity ischemia present with symptoms of peripheral artery disease that can include rest pain, which is pain across the base of the metatarsal heads and forefoot at rest and with recumbency relieved by dependency, or with tissue loss, which can be ulceration, dry gangrene, or wet gangrene. The Rutherford and Fontaine symptom classification systems were the most widely used classification systems for decades [10,11]. The walking impairment that defines mild, moderate, and severe claudication is specified by performance on five-minute treadmill test at 2 mph on a 12 percent incline in the Rutherford classification, and as part of the Fontaine classification is specified as 650 feet (200 meters).

Rutherford

●Stage 0 – Asymptomatic

●Stage 1 – Mild claudication

●Stage 2 – Moderate claudication

●Stage 3 – Severe claudication

●Stage 4 – Rest pain

●Stage 5 – Minor tissue loss with ischemic nonhealing ulcer or focal gangrene with diffuse pedal ischemia

●Stage 6 – Major tissue loss – Extending above transmetatarsal level, functional foot no longer salvageable

Fontaine

●Stage 1 – No symptoms

●Stage 2 – Intermittent claudication subdivided into:

●Stage 2a – Without pain on resting, but with claudication at a distance of greater than 650 feet (200 meters)

●Stage 2b – Without pain on resting, but with a claudication distance of less than 650 feet (200 meters)

●Stage 3 – Nocturnal and/or resting pain

●Stage 4 – Necrosis (death of tissue) and/or gangrene in the limb

WIfI (Wound, Ischemia, foot Infection) — The Society for Vascular Surgery (SVS) Lower Extremity Threatened Limb Classification System, Wound, Ischemia, foot Infection (WIfI), is an updated system for classifying the severity of limb threat that is intended to more accurately reflect important clinical considerations that impact management and amputation risk, and also to permit more meaningful analysis of outcomes for various forms of therapy [12]. The global vascular guidelines for the management of chronic limb-threatening ischemia (CLTI) recommend staging the limb using WIfI [2]. The WIfI threatened limb classification has been validated in multiple studies and provides a pragmatic means to assess the likelihood of wound healing and amputation risk in patients with a spectrum of CLTI [13-19]. The WIfI classification, with a calculator, is presented briefly below; the complete classification is available as an open access document from the SVS on the Journal of Vascular Surgery website [20], and as an Interactive Practice Guideline (iPG) app [21].

The Rutherford and Fontaine classifications, which are decades old, were designed to classify chronic limb ischemia among patients with pure ischemia due to peripheral artery disease (PAD). However, due to marked demographic shifts, particularly a dramatic rise in diabetes prevalence, these classifications are less useful for appropriately classifying patients with diabetes, neuropathy, or an index wound with or without infection, across a broader spectrum of PAD severity. In such patients, limb perfusion is only one determinant of outcome. Wound extent and infection also significantly impact the threat to a limb. The classification can be visualized as three intersecting rings of risk (figure 5) [17,22]. WIfI also helps identify which of these risks is "dominant" at a given point in time throughout the patient's life.

WIfI grades each of three factors on a scale from 0 to 3: the wound, the severity of ischemia, and the presence and severity of foot infection. The 64 resulting potential combinations of grades were placed (by Delphi consensus) into one of four clinical stages (1 through 4) that correlate with the potential for wound healing and risk of major limb amputation at one year (table 2). Clinical stage 1 limbs rarely require revascularization and can usually be healed with simple wound care and offloading. By contrast, patients with clinical stage 4 limbs have very high amputation risk. Clinical stages 2 and 3 are intermediate in threat to the limb. It is important to remember that the stage of limb threat, not the individual grades of wound, ischemia, or infection, drive urgency and potential need for admission and revascularization.

●Wound:

•Grade 0 – Rest pain; no wound, no ulcer, no gangrene.

•Grade 1 – Small shallow ulcer(s) on distal leg or foot, any exposed bone is only limited to distal phalanx; no gangrene, or gangrene limited to distal toe (ie, minor tissue loss: limb salvage possible with no more than simple digital amputation [1 or 2 digits], or skin coverage).

•Grade 2 – Deeper ulcer on distal leg or foot with exposed bone, joint, or tendon, or shallow heel ulcer without involvement of the calcaneus; gangrenous changes confined to the digits (ie, major tissue loss: salvageable with ≥3 digital amputations or standard transmetatarsal amputation [TMA] plus skin coverage).

•Grade 3 – Extensive deep ulcer of the forefoot and/or midfoot, or full-thickness heel ulcer with or without involvement of the calcaneus (ie, extensive tissue loss: salvageable only with complex foot reconstruction or nontraditional TMA [eg, Chopart or Lisfranc amputation]).

●Ischemia (note that toe systolic pressures are preferred in patients with diabetes):

•Grade 0 – ABI ≥0.8, ankle systolic pressure >100 mmHg, toe pressure (TP)/transcutaneous oxygen (TcPO₂) ≥60.

•Grade 1 – ABI 0.6 to 0.79, ankle systolic pressure 70 to 100 mmHg, TP/TcPO₂ 40 to 59.

•Grade 2 – ABI 0.4 to 0.59, ankle systolic pressure 50 to 70 mmHg, TP/TcPO₂ 30 to 39.

•Grade 3 – ABI ≤0.39, ankle systolic pressure <50 mmHg, TP/TcPO₂ <30.

●Foot infection

•Grade 0 – No symptoms or signs of infection.

•Grade 1 – Infection is present and at least two of the following are present: local swelling or induration, erythema >0.5 to ≤2 cm around ulcer, local tenderness or pain, local warmth, or purulent discharge. Other causes of an inflammatory response of the skin have been excluded (eg, gout, fracture).

•Grade 2 – Local infection is present as defined for Grade 1 but extends >2 cm around ulcer or involves structures deeper than the skin and subcutaneous tissues (eg, abscess, osteomyelitis, septic arthritis, fasciitis). No clinical signs of systemic inflammatory response.

•Grade 3 – Local infection is present as defined for Grade 2, but clinical signs of systemic inflammatory response are present as manifested by two or more of the following: temperature >38°C or <36°C; heart rate >90 beats per minute, respiratory rate >20 breaths per minute or PaCO₂ <32 mmHg; white blood cell count >12,000 or <4000 (cu/mm) or >10 percent immature band forms present.

The system is not intended to dictate treatment but rather to more precisely stratify patients according to their initial disease burden in a manner that is analogous to Tumor-Nodes-Metastasis (TNM) staging for cancer. WIfI stages at presentation have correlated strongly with wound healing time and wound healing rate at one year [23-27]. The use of WIfI to stratify amputation risk has been reported from multiple centers across the United States and from France, Italy, Germany, Spain, and Japan [23,28,29]. In a systematic review and meta-analysis of WIfI staging for CLTI, estimated one-year major amputation rates (569 patients from four studies) for WIfI stages 1 to 4 were 0 percent, 8 percent (95% CI 3-21), 11 percent (95% CI 6-18), and 38 percent (95% CI 21-58), respectively. The likelihood of an amputation after one year was increased for patients with CLTI and higher WIfI stages, which is important prognostic information [13]. Two publications suggest that WIfI clinical stage 4 patients have a very low wound healing rate (44 percent) and high reintervention rate (46 percent) after endovascular therapy [24]. In one of these, a prospective cohort study, freedom from major limb amputation was superior for clinical stage 4 patients who underwent bypass compared to those who underwent endovascular therapy. If these results can be confirmed prospectively, WIfI may prove to be a useful tool to aid in the selection of endovascular therapy or open bypass in patients with CLTI [28].

The WIfI system was also intended to be used for restaging after therapy, much as TNM is used when treating cancer. In other studies, wound, ischemia, and infection grades at one and six months correlated highly with amputation-free survival (AFS) and suggested that serial WIfI staging and restaging identifies a cohort at especially high risk of amputation who may merit timely reintervention [28,29]. WIfI stages have also been reported to correlate with costs of care [28,30]. WIfI also allows comparison of therapeutic alternatives among patients with threatened limbs who have a similar risk for amputation.

Acute extremity ischemia — Acute limb ischemia is defined as a sudden decrease in limb perfusion that causes a potential threat to limb viability in patients who present within two weeks of the acute event [1]. The SVS/ISCVS (Rutherford) classification stratifies limb ischemia based upon the presence and degree of sensorimotor deficits and Doppler findings [10,31-33]. There are numerous etiologies, including but not limited to cardiogenic or arteriogenic emboli, thrombosis of an existing aneurysm (eg, popliteal artery), occlusion of a previously placed bypass graft or stent, and thrombosis at the site of preexisting atherosclerotic disease (adductor canal SFA stenosis). (See "Clinical features and diagnosis of acute lower extremity ischemia", section on 'Etiologies'.)

Viable (I) — Viable limbs are under no immediate threat of tissue loss. There is no sensory loss or muscle weakness, and both arterial and venous Doppler signals are audible.

Marginally threatened (IIa) — Marginally threatened limbs are salvageable if treated promptly. There is minimal pain and minimal (toes only) or no sensory loss, and no muscle weakness; arterial Doppler signals are often inaudible, but venous Doppler signals are audible.

Immediately threatened (IIb) — Immediately threatened limbs are salvageable with immediate revascularization. Sensory loss involves more than the toes and may be associated with rest pain in the foot (not just confined to toes). There is mild-to-moderate muscle weakness, arterial Doppler signals are usually inaudible, and venous Doppler signals are audible.

Irreversible (III) — Irreversible ischemic (nonviable) limbs have a severe and permanent nerve deficit. Sensory loss is profound, muscle weakness is profound with paralysis and possible rigor, and arterial and venous Doppler signals are inaudible. These nonviable extremities require major amputation regardless of the therapy that is instituted. Revascularization may be required to permit healing of the amputation or to lower the level of amputation needed.

LOWER EXTREMITY IMPAIRMENT — Vascular disease impairs the individual's ability to function in society. The American Medical Association (AMA) lower extremity impairment grading scale defines increasing degrees of disability based upon clinical features [34-36]. The AMA scale includes symptoms and signs primarily related to peripheral artery disease but also includes chronic venous disease. The elements of this scale that pertain to peripheral artery disease are included below. We prefer to use validated scales for venous disability, which are presented separately. (See "Classification of lower extremity chronic venous disorders", section on 'Venous disability score'.)

Class 0 — (Whole person impairment [WPI]: 0 percent.) The patient does not have claudication or pain at rest or the patient experiences only transient edema, but one of the following physical examination findings is present:

●Loss of pulses

●Minimal loss of subcutaneous tissue

●Calcification of arteries detected on radiographic examination

●Asymptomatic stenosis of arteries not requiring surgery and not resulting in curtailment of activities

Class 1 — (WPI: 2 to 10 percent.) The patient has at least one of the following:

●Intermittent claudication is present on walking at least 100 yards at an average pace

●Evidence of tissue damage such as healed stump (single amputated digit) or a healed ulceration

Class 2 — (WPI: 11 to 23 percent.) The patient has at least one of the following:

●Intermittent claudication on walking as few as 25 yards and no more than 100 yards at average pace

●Evidence of tissue damage such as healed amputations (two or more digits in one extremity) with evidence of superficial ulceration

Class 3 — (WPI: 25 to 40 percent.) The patient has at least one of the following:

●The patient experiences intermittent claudication on walking less than 25 yards

●The patient experiences intermittent pain at rest

●Evidence of vascular damage such as amputation at or above an ankle of one extremity, or amputation of two or more digits of two extremities with persistent vascular disease with persistent widespread or deep ulceration involving one extremity

Class 4 — (WPI: 45 to 65 percent.) The patient has at least one of the following:

●The patient experiences severe and constant pain at rest

●There is evidence of tissue damage such as amputation at or above the ankles of both extremities, or amputation of all digits of two or more extremities, and evidence of persistent widespread or deep ulceration involving two or more extremities

●Whole person impairment (100 percent)

DISABILITY — Patients applying for disability with the Social Security Administration of the United States must meet the requirement for cardiovascular impairment [37]. To qualify, the patient must demonstrate the presence of a body system impairment severe enough to prevent gainful activity. The impairment is expected to last for a continuous period of at least 12 months.

For patients with intermittent claudication, one of the following must also be present:

●Resting ankle/brachial systolic blood pressure ratio of <0.5

●Decrease in systolic blood pressure at the ankle on exercise of 50 percent or more from pre-exercise level and requiring ≥10 minutes to return to pre-exercise level

●Resting toe systolic pressure of <30 mmHg

●Resting toe/brachial index <0.4

For patients with extremity amputation (any cause), one of the following is required [38]:

●Both hands

●One or both lower extremities at or above the tarsal region, with stump complications resulting in medical inability to use a prosthetic device to ambulate effectively

●One hand and one lower extremity at or above the tarsal region, with inability to ambulate effectively

●Hemipelvectomy or hip disarticulation

For patients with chronic venous disease, incompetence or obstruction of the deep venous system and one of the following must be present [37]:

●Extensive brawny edema involving at least two-thirds of the leg between the ankle and knee or the distal one-third of the lower extremity between the ankle and hip

●Superficial varicosities, stasis dermatitis, and either recurrent ulceration or persistent ulceration that has not healed following at least three months of prescribed treatment

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Occlusive carotid, aortic, renal, mesenteric, and peripheral atherosclerotic disease" and "Society guideline links: Acute extremity ischemia".)

SUMMARY AND RECOMMENDATIONS

●Treatment options for lower extremity revascularization must take into consideration the urgency, duration, and severity of ischemia and the risk of the intervention relative to the patient's medical condition versus the expected improvement in the patient's clinical condition (eg, decreased pain, ulcer healing) and the durability of the intervention in the context of the patient's life expectancy. Grading the symptoms of peripheral artery disease and the anatomic lesions responsible for these symptoms provides an objective measure by which to follow patients clinically and, importantly, provides consistency when comparing interventional strategies in clinical studies. (See 'Introduction' above.)

●The Rutherford and Fontaine symptom scales have traditionally been the most widely used classifications for chronic lower extremity ischemia. These have largely been replaced by an updated threatened limb classification system, put forth by the Society for Vascular Surgery (SVS) in 2014 to stratify the threat to limb caused by a spectrum of wounds, ischemia, and foot infection (WIfI), in part to reflect the global, epidemic rise in the prevalence of diabetes and diabetic foot ulcers. WIfI clinically predicts major limb amputation rates, wound healing, intensity of care, and costs of care.

A Rutherford scale for acute limb ischemia is a separate and distinct scale from those applied to chronic limb ischemia. (See 'Symptom classification' above.)

●Arterial lesions are classified anatomically by Trans-Atlantic Inter-Society Consensus (TASC II) as Type A, B, C, or D based upon the overall success rates of treating the lesion using endovascular or surgical means. Most patients with peripheral artery disease have more than one lesion, at more than one level, so the classification scheme is limited in focusing on singular patterns. TASC II Type A lesions represent simpler, focal lesions of the iliac, femoral, and popliteal arteries, while Type D lesions represent complex, long-segment lesions. Type B and Type C lesions are intermediate lesions. A classification system for the tibial vessels had been proposed but has not been validated. The Global Guidelines Committee has proposed a new classification system for chronic limb-threatening ischemia, the Global Limb Anatomic Staging System (ie, GLASS) for grading femoropopliteal and infrapopliteal disease. The GLASS classification remains to be validated. (See 'TASC classification' above and 'GLASS classification' above.)

●For patients who continue to suffer symptoms related to peripheral artery disease, impairment and disability may need to be quantified for insurance purposes or in order to qualify for disability. (See 'Lower extremity impairment' above and 'Disability' above.)