What is the management approach for patients with an Ankle-Brachial Index (ABI) value below 0.9?

Management of Patients with ABI <0.9

An ABI below 0.9 confirms the diagnosis of peripheral arterial disease (PAD) and mandates immediate cardiovascular risk stratification and aggressive risk factor modification, as these patients face a 4-5 times increased risk of major adverse cardiovascular events and mortality regardless of symptoms. 1

Immediate Diagnostic Confirmation

• Confirm PAD diagnosis: An ABI <0.90 is the definitive threshold for diagnosing lower-extremity PAD 1
• Assess both legs separately: Use the lower ABI value between the two legs, as PAD may be unilateral or asymmetric, and using the higher value risks missing high-risk patients 1
• Verify measurement accuracy: If the ABI is borderline (close to 0.90), repeat the measurement, as the 95% confidence interval is ±0.10 1
• Check for bilateral arm pressure differences: If the first arm's systolic blood pressure exceeds the other by >10 mmHg, remeasure and discard the first reading 1

Cardiovascular Risk Stratification

Patients with ABI <0.90 are at very high cardiovascular risk and require the same aggressive management as those with established coronary artery disease. 1

• Recognize the mortality risk: These patients have significantly elevated risk of cardiovascular death, myocardial infarction, and stroke independent of symptoms or other risk factors 1
• Assess for masked PAD: Even "asymptomatic" patients may have reduced walking capacity from other conditions (heart failure, arthritis, deconditioning) or reduced pain sensitivity (diabetic neuropathy) that masks claudication symptoms 1
• Evaluate amputation risk in wound patients: Use the WIfI (Wound, Ischaemia, and foot Infection) classification system for any patient with chronic lower-limb wounds, as diabetes and infection compound amputation risk even without critical limb ischemia 1

Mandatory Medical Management

Lipid Management

• Target LDL-C <1.4 mmol/L (<55 mg/dL) or achieve at least 50% reduction from baseline with high-intensity statin therapy 1
• This aggressive target reflects the very high cardiovascular risk status of all PAD patients 1

Antiplatelet Therapy

• Initiate antiplatelet therapy in all symptomatic PAD patients 1
• Consider dual pathway inhibition: Low-dose rivaroxaban 2.5 mg twice daily plus aspirin 100 mg daily should be considered in patients without high bleeding risk (no history of intracranial hemorrhage, recent GI bleeding, liver failure, or eGFR <15 mL/min) 1

Blood Pressure Control

• Optimize hypertension management as part of comprehensive cardiovascular risk reduction 1

Diabetes Management (if applicable)

• Screen annually: Yearly ABI measurement is indicated for all diabetic patients 1
• Optimize glycemic control, particularly in patients with chronic limb-threatening ischemia, to improve foot outcomes 1

Symptom Assessment and Functional Evaluation

Determine whether the patient has intermittent claudication, atypical leg symptoms, or is truly asymptomatic (not just "masked" by other limitations). 1

• Use walking impairment questionnaires and objective tests like the 6-minute walk test or short physical performance battery 1
• Distinguish true asymptomatic PAD from masked PAD: Patients with reduced walking capacity from comorbidities or neuropathy may have unrecognized ischemic symptoms 1

Further Vascular Imaging

When to Image

• Duplex ultrasound is first-line for anatomic assessment and hemodynamic evaluation of lower extremity arteries 1
• CT angiography or MR angiography is indicated when revascularization is being considered 1
• Do NOT perform invasive or noninvasive angiography in truly asymptomatic PAD patients, as anatomic assessment without planned intervention is not appropriate 2

Special Considerations for Diabetic Patients

• If chronic limb-threatening ischemia is present with below-the-knee lesions, obtain angiography including foot run-off before revascularization 1

Additional Hemodynamic Testing

If ABI is close to 0.90 (borderline) and clinical suspicion remains high, or if symptoms are present with ABI 0.90-1.00:

• Post-exercise ABI testing: A decrease >20% or ankle pressure drop >30 mmHg after treadmill exercise confirms PAD 1
• This is particularly useful when resting ABI is normal but symptoms suggest PAD, as nearly one-third of symptomatic patients with normal resting ABI will have abnormal post-exercise values 3

Patient Education and Foot Care

• Mandatory foot care education for all PAD patients, especially those with diabetes 1
• Early recognition and referral: Educate patients to immediately report tissue loss or infection, with prompt referral to a multidisciplinary team for limb salvage 1

Common Pitfalls to Avoid

• Don't dismiss asymptomatic patients: ABI <0.90 predicts cardiovascular events even without leg symptoms 1
• Don't use only the higher ABI: This misses unilateral disease and underestimates cardiovascular risk 1
• Don't rely solely on ABI in diabetics with wounds: Nearly 25% of chronic limb-threatening ischemia patients have normal ABI; use toe pressures, TcPO2, or skin perfusion pressure for comprehensive assessment 4
• Don't forget the systemic nature: PAD is a marker of generalized atherosclerosis; screen for coronary and carotid disease 5, 6