- Definition
Peripheral artery disease is a blockage in the vessel that limits perfusion in distal tissues and thus normal functioning. This "arterial insufficiency" is often caused by atherosclerosis - thickening and hardening of the arteries.
Diagnosis is made if patient has the appropriate symptoms (below) and the ankle-brachial index (ABI: ankle sBP ÷ arm sBP) is 0.9 or less.
- Pathophysiology
Arterial walls can be damaged by different factors. Smoking introduces harmful chemicals that cause injury, and cholesterol buildup in blood makes it easy to stick to the walls. Damage to the wall and extra cholesterol aggregation create an uneven and rough surface that other material can further bind to. Eventually the accumulation of lipid and fibrous material forms the plaque. This narrows the vessel, and makes the wall thick and rigid as well.
Risks:
- Older Age, male gender
- Cigarette smoking
- Hypertension, diabetes, hyperlipidemia
- Family history of atherosclerosis
- Symptoms & Signs
Symptoms will appear if blood supply does not match the level of activity.
- Claudication: Pain from muscles caused by exercise, relieved with rest, not necessarily requiring change in position.
- Pain may be felt in buttock/hip/thigh/calf/foot
- Ischemic rest pain
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SEVERE restriction in blood supply can cause pain despite rest. Typically localied in forefeet and toes. WORSE when lying down, because the pressure gradient (gravity) that helps supply the feet would disappear.
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Interestingly, walking could partially relieve this pain, due to better use of gravity. Note that this will not resolve the root problem.
- Nonhealing injury - because the blood cannot reach the tissue to supply the platelet and clotting factors.
- Skin discoloration and GANGRENE: toe turns blue due to severe occlusion of vessels, then black as tissue dies. Goal is to prevent this!
- Atypically cold extremities
- Treatment
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- Minimizing Risk Factors: smoking cessation, antiplatelet therapy, lowering blood cholesterol, controlling blood pressure and sugars. Diet and exercise optimization.
- Revascularization if the above do not improve symptoms.
- Monitor with: physical exam (pulses, observation), ABI blood pressure measurements
- Classification
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TASC classification: based on anatomic location of the obstruction.
- Type A: short, focal; excellent results with endovascular therapy.
- Aortoiliac: external iliac artery stenosis (narrowing) of 3cm or less
- Femoropopliteal: SINGLE stenosis of 10cm maximum OR occlusion (total block) of 5cm maximum.
- Type B: preferred endovascular therapy, with good results.
- Aortoiliac:
- 3cm or less stenosis of infrarenal aorta
- common iliac artery occlusion
- external iliac artery stenosis 3-10cm in length
- unilateral external iliac artery occlusion
- Femoropopliteal:
- many lesions 5cm or less
- sigle popliteal stenosis
- calcified occlusion 5cm or less
- Type C: may have better prognosis with open revascularization.
- Aortoiliac:
- BILATERAL common iliac artery occlusions
- bilateral external iliac artery stenosis 3-10cm OR unilateral external iliac artery stenosis reaching the common femoral artery
- Femoropopliteal: MANY stenoses / occlusion of which the TOTAL LENGTH is >15cm OR recurrent stenoses / occlusion that need treatment.
- Type D: definitely poorer results with endovascular therapy.
- Aortoiliac: Aorta and both iliac arteries affected; Multiple stenoses of common/iliac arteries and common femoral artery. Bilateral occlusion of external iliac arteries.
- Femoropopliteal: Total occlusion of >20cm involving common or superficial femoral artery.
WIfI classification: based on perfusion, wounds, infection. Includes diabetic factors.
- Wound
- 0: Isolated pain at rest
- 1: shallow ulcers at lower leg/feet. Exposed bone only at distal phalanx if present.
- 2: Deeper ulcer on leg/feet with exposed bone/join/tendon.
- 3: Extensive deep ulcer @ forefoot/midfoot, full-thickness heel ulcer.
- Ischemia
- 0: ABI >0.8, ankle sBP >100mmHg, toe pressure/trancutaneous oxygen >60.
- 1: ABI 0.6-0.79, AsBP 70-100, TP/PO2 40-59
- 2: ABI 0.4-0.59, AsBP 50-70, TP/PO2 30-39
- 3: ABI < 0.39, sBP < 50, TP/PO2 < 30
- Infection
- 0: no signs of infection
- 1: two or more of:
- local swelling
- redness 0.5-2cm around ulcer
- local tenderness
- local warmth
- pus
- 2: same as 1 EXCEPT: redness >2cm, and affects deeper structures (abscess/osteomyelitis/septic arthritis)
- 3: same as 2 PLUS: SIRS criteria is met.
- Revascularization
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One option of performing revascularization is the percutaneous transluminal angioplasty (PTA):
- Incision is made below the inguinal line (where the leg folds near pelvis), and a guidewire with balloon is inserted into the vessel. There is the noncomplicant balloon, (which can handle a large pressure and expands to certain volume), and a compliant balloon (which can expand up to 800% of its nonstretched volume). For angioplasty we use the noncompliant balloon.
- The guidewire goes through the site of occlusion, until the segment with the deflated balloon lies in its lumen.
- The balloon is then expanded, widening the occlusion/stenosis.
- Stents are then placed, to maintain the dilation of vessel; either having expanded with the balloon, placed to expand by itself and fit the 'mold', or drug-eluting (paclitaxel or sirolimus-releasing, to chemically prevent the vessels from closing again (block cell division at vessel wall).
- Best Imaging Modality
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- X-ray Fluoroscopy
During the angioplasty procedure, it is important to view in real time where the guidewire is going and where the balloon is placed. X-ray fluoroscopy allows this by obtaining real-time images; wires can be seen moving through this type of imaging.
- Pros: very quick, readily available, cheap
- Cons: high radiation. All professionals must wear a lead vest and a thyroid collar to protect themselves.
- CT or MR Angiography
Allows evaluation of thrombus content and extent, as well as the wall quality.
References
- Dosluoglu HH. Endovascular techniques for lower extremity revascularization. UpToDate. 2021. (Accessed on Aug 2022).
- Davies MG, Dosluoglu HH. Approach to revascularization for claudication due to peripheral artery disease. UpToDate. 2021. (Accessed on Aug 2022)
- Berger JS, Davies MG. Overview of lower extremity peripheral artery disease. UpToDate. 2021. (Accessed on July 2022)
- Hardman RL, Jazaeri O, Yi J, Smith M, Gupta R. Overview of Classification Systems in Peripheral Artery Disease. Semin Intervent Radiol. 2014. 31(4):378-388.
- Cherian MP, Mehta P, Kalyanpur TM, Gupta P. Review: Interventional radiology in peripheral vascular disease. Indian J Radiol Imaging. 2008. 18(2):150-155.