• Clinical science

Peripheral arterial disease

Abstract

Peripheral arterial disease (PAD) is characterized by narrowing and, in final stages, occlusion of the peripheral arteries due to atherosclerotic plaques. Smoking is the most important risk factor for developing PAD. PAD is often a silent disease, but patients may present with features of arterial insufficiency (intermittent claudication, reduced temperature and pulse rate in affected limb, skin discoloration, and trophic changes). On occasion, critical limb ischemia is the only presenting complaint. Segmental blood pressures and pulse volume recordings, particularly the ankle-brachial index (ABI), may support the diagnosis. Further imaging may confirm and assess the location and severity of arterial stenosis or occlusion. Treatment focuses on smoking cessation, graduated exercise, avoiding extremely cold temperatures, and modifying other cardiovascular risk factors. If conservative treatment fails, interventional and surgical management is recommended for low-risk patients with potential long-term success.

Epidemiology

  • Prevalence: 8.5 million in the US
    • Prevalence increases with age, starting from the age of 40
    • US incidence rates are highest among African Americans, followed by Hispanics, who are at a slightly higher risk than non-hispanic whites.
  • Peak incidence: 60–80 years of age
  • Sex: =

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

PAD usually coexists with coronary artery disease. Smoking is the most important risk factor for PAD!
References:[3]

Classification

Fontaine Classification of PAD

Stage I
  • Asymptomatic PAD
Stage II
Stage III
Stage IV

References:[4]

Clinical features

Characteristic features Description
Silent disease
  • Up to 20–50% of patients with PAD are asymptomatic!
Intermittent claudication (10–35% of patients)
Absent or diminished pulses
Trophic changes
Rest pain
  • Typically in distal metatarsals
  • Worse at night
  • Improved when hanging feet over bed or standing
Critical limb ischemia
  • The presence of any one of the following:
  • Indicative of limb-threatening arterial occlusion

A bruit, suggestive of arterial stenosis, may be heard in > 60–70% of cases with PAD!

References:[5][6][7][8]

Diagnostics

Ankle-brachial index (ABI)

  • ABI is the ratio of systolic ankle blood pressure (BP) to systolic brachial BP
    • Right ABI = higher right ankle BP/higher brachial BP
    • Left ABI = higher left ankle BP/higher brachial pressure
  • Normally, ankle BP and brachial BP are equal (ABI = 1), or ankle BP is only slightly higher because of gravity (ABI ≥ 0.9)
  • Differences in systolic BP indicate different pathologies:
    • > 1.3 = medial sclerosis with incompressible vascular wall (generally calcified vessels)
    • 1.0–1.30 = normal value
    • 0.91–0.99 = borderline
    • 0.40– 0.90 = mild to moderate PAD → claudification
    • < 0.40 = severe PAD → resting pain, gangrene (critical limb ischemia)
  • Exercise testing may be required if patients have a normal resting ABI [9]

Imaging

While vascular imaging is not necessarily required for diagnosis, it is useful to determine the site and severity of arterial stenosis or occlusion (especially preoperatively and postoperatively)

  • Color-coded duplex ultrasonography
  • Digital subtraction angiography (DSA): gold standard
  • CT angiography
  • MR angiography
  • Oscillography

Measurements in diabetic or older patients may be inaccurate because of Monckeberg's sclerosis!

References:[10][11][12]

Differential diagnoses

Differential diagnosis of claudication
Patient characteristics Clinical Features
Causes of arterial occlusion Vasculitides Takayasu's disease
  • Asian females
  • 15–45 years
Obliterating thromboangiitis
  • 20–40 years
(Lower-extremity) Fibromuscular dysplasia
  • Middle-aged women
Popliteal aneurysm
  • Similar risk factors as PAD
Arterial embolism
  • Sudden onset of symptoms
  • 6 Ps
Popliteal entrapment syndrome
Cystic adventitial disease
  • Generally affects men between 30–50 years
  • Foot pulses may be present during rest and absent following exercise
Mimics of arterial occlusion Deep vein thrombosis
  • Swelling
  • Warmth
  • Erythema
  • Progressive tenderness
  • Dull pain: worsened by walking, improved by resting
Spinal stenosis
  • Middle-aged to older patients
Diabetic neuropathy
  • Middle-aged to older patients
  • High BMI
  • Progressive symmetrical loss of or abnormal sensation in the distal lower extremities (glove and stocking sensation)
  • Normal ABI
  • Neuopathic diabetic foot: warm, dry skin, palpable foot pulses

References:[13]

The differential diagnoses listed here are not exhaustive.

Treatment

Conservative

  • Smoking cessation!
  • Supervised graded exercise therapy
  • Foot care (especially in diabetic patients)
  • Avoid cold temperatures

Medical therapy

Revascularization

  • Indications
    • Critical limb ischemia
    • Failure of conservative and pharmacologic treatment
    • Inability to perform normal work or activities because of claudication
    • No limitations to exercise by other disease (e.g., chronic heart failure) if claudication is improved
    • Anatomy of the lesion allows low-risk and long-term success of intervention
  • Minimally invasive interventional radiology: percutaneous transluminal angioplasty (PTA) with or without stenting
  • Surgical procedures

Amputation

  • Last resort in the event of gangrene

References:[10][12][14][15][7][6]

Complications

  • Arterial ulcer
    • Definition: skin defect due to impaired blood flow to the lower extremities
    • Etiology: most often seen in peripheral arterial disease
    • Clinical features
      • Punched-out ulcer with well-defined borders
      • Usually involves the foot, particularly pressure points (e.g., lateral malleolus, tips of the toes)
      • Often severe pain
    • Differential diagnosis: venous ulcer
  • Infection of ulcers; sepsis
  • Acute limb ischemia
  • Surgical complications: bleeding, infection of vascular prosthesis, relapse

References:[16][17]

We list the most important complications. The selection is not exhaustive.

Prognosis

A low ABI in PAD is also predictive of an increased risk of all-cause and cardiovascular mortality!References:[5]

Prevention