Specific Guidelines for the diagnosis and treatment of PAD in a diabetic patient with a foot ulcer 2011

From the International Working Group on the Diabetic Foot.

Introduction

These guidelines are based upon two companion IWGDF papers: "A Systematic Review of the Effectiveness of Revascularisation of the Ulcerated Foot in Patients with Diabetes and Peripheral Arterial Disease" and "Diagnosis and treatment of peripheral arterial disease in diabetic patients with a foot ulcer. A progress report".

Screening and diagnosis

Peripheral arterial disease (PAD) is an important predictor of outcome of ulceration of the foot in patients with diabetes. The clinician examining a patient with diabetes and an ulcer of the foot should therefore always evaluate the vascular status of the lower extremity, specifically looking for signs of ischaemia, as up to 50% of these patients have PAD. Before a major amputation is undertaken a revascularization should always be considered and discussed preferably in a multidisciplinary diabetic foot team.

In all patients with diabetes and a foot ulcer the presence of PAD must be excluded. The following clinical examination must be performed in all patients:

  • A history to identify symptoms of PAD.
  • Palpation of pulses in the lower limb (including posterior tibial and dorsalis pedis arteries).

The following screening test are nessecary to exclude PAD:

  • Hand-held Doppler evaluation of the flow signals from both foot arteries (dorsalis pedis and posterior tibial).
  • Measurement of the ankle brachial index (ABI).
  • If there is diagnostic uncertainty, measurement of the toe-brachial index has additional diagnostic value.

PAD is likely when:

  • The patient has claudication or rest pain.
  • Both foot pulses are absent to palpation.
  • Absent or monophasic Doppler signals are obtained from one or both foot arteries.
  • The ABI is < 0.9.
  • A toe-brachial index <0.7 strongly suggests PAD in a foot acclimatised in a warm surrounding.

The diagnostic utility of each of these items has limitations in diabetes.

  • In patients without symptoms of ischaemia, with palpable foot pulses or with perfusion measurements suggesting only mild PAD, experts advise to evaluate the effect of maximal 6 weeks optimal wound care.
  • If the wound healing response is poor, perfusion should be reassessed. Duplex ultrasound or angiography of the arteries of the lower limb should be strongly considered.

Assessing severity

Once the diagnosis of PAD is established, the severity of the perfusion deficit should be assessed:

  • An ABI <0.6 indicates significant ischaemia with respect to wound healing potential.
  • An ABI > 0.6 has less predictive value and in these patients toe-pressure and/ or tcpO2 (transcutaneous pressure of oxygen) should be measured.
  • Prediction of wound healing based on perfusion testing, regardless of method, follows a sigmoid curve. Ulceration of the foot in diabetes will often heal if the toe pressure is >55 mmHg and the tcpO2 >50 mmHg. Healing is usually severely impaired when toe-pressure is <30 mmHg and tcpO2 <30 mmHg.

Treatment

If PAD of sufficient severity to impair wound healing is identified, revascularisation (endovascular or bypass) must be considered in all patients. Exceptions to this general rule may include: severely frail patients or patients with a short life expectancy (<6-12 months); patients with pre-existing severe functional impairment unlikely to be significantly worsened by an amputation; and patients who have such a large volume of tissue necrosis that the foot is functionally unsalvageable. Most studies report limb salvage rates after revascularisation procedures between approximately 80-85% and ulcer healing in > 60% at 12 months.

  • The entire lower extremity arterial circulation should be evaluated, with detailed visualisation of below-knee and pedal arteries.
  • One of the following techniques can be used: colour Doppler ultrasound, multi-detector-row computed tomography angiography (MD-CTA), contrast enhanced magnetic resonance angiography (CE-MRA) or intra-arterial digital subtraction angiography (DSA).
  • The aim of revascularisation is to restore direct pulsatile flow to at least one of the foot arteries, preferably the artery which supplies the anatomical region of the wound.
  • There are no randomised clinical trials comparing open with endovascular revascularisation techniques in patients with diabetes, a foot ulcer and PAD. Broadly speaking major outcomes of both techniques appear similar. The results of both open and endovascular procedures will greatly depend upon the morphological distribution of PAD as well as the local availability and expertise in a given centre. The definitive choice for either treatment should be based on a multi-disciplinary discussion that includes the different vascular specialists involved.
  • The peri-operative mortality of these procedures is in most case series < 5% and major systemic complications are observed in about 10% of the patients.
  • Mortality and amputation rates in patients with end stage renal disease are worse. However, even in these patients favourable results can be obtained, the majority of studies report 1-year limb salvage rates of approximately 70%.
  • "Time is tissue" in infected ischaemic diabetic foot ulcers. Patients with signs of PAD and a foot infection are at particularly high risk for major limb amputation and should be treated as a medical urgency, preferably within 24 hours.
  • The treatment of PAD should be part of a comprehensive care plan which should also include treatment of infection, frequent debridement, biomechanical off-loading, blood glucose control and treatment of co-morbidities.
  • Cardiovascular morbidity and mortality are markedly increased in patients with diabetes, a foot ulcer and PAD; these patients have an overall mortality at 5 years of 50%. All patients should receive aggressive cardiovascular risk management that should include support for cessation of smoking, treatment of hypertension and prescription of a statin as well as low-dose aspirin or clopidogel.