What is the management plan for a patient with a left digit/brachial index (ankle-brachial index, ABI) indicating severe peripheral artery disease (PAD)?

Management of Digit/Toe-Brachial Index <0.4

A digit/toe-brachial index (TBI) <0.4 indicates severe peripheral artery disease with critical limb-threatening ischemia requiring urgent vascular imaging and revascularization evaluation to prevent limb loss. 1

Immediate Diagnostic Steps

Obtain urgent anatomic imaging to plan revascularization strategy. 1 A TBI <0.4 falls well below the abnormal threshold of <0.70 and represents severe ischemia with high amputation risk. 1

Required Vascular Imaging

• Duplex ultrasound is the first-line imaging method to assess arterial anatomy and hemodynamic status 1
• CT angiography (CTA) or MR angiography (MRA) should be obtained when revascularization is being considered 1
• Catheter angiography including foot run-off vessels should be considered for below-the-knee lesions to guide intervention 1

Additional Perfusion Assessment

Obtain supplementary perfusion measurements to assess wound healing potential: 1, 2

• Transcutaneous oxygen pressure (TcPO₂): Values >30 mm Hg predict wound healing potential 1, 2
• Skin perfusion pressure (SPP): Values >40 mm Hg associated with increased wound healing likelihood 1, 2

Clinical Assessment for Chronic Limb-Threatening Ischemia (CLTI)

Evaluate for signs of CLTI, which is present when TBI is this severely reduced: 1

• Ischemic rest pain in the foot
• Non-healing wounds or ulcers
• Gangrene or tissue loss
• WIfI score assessment (Wound, Ischemia, foot Infection) to stratify amputation risk 1

Revascularization Decision

Revascularization is indicated whenever feasible for limb salvage in patients with CLTI. 1 The 2024 ACC/AHA guidelines emphasize that patients with this degree of ischemia require urgent evaluation for either endovascular or surgical revascularization. 1

Guideline-Directed Medical Therapy (GDMT)

Initiate aggressive medical management immediately: 1

Antiplatelet Therapy

• Single antiplatelet therapy is recommended for all patients with symptomatic PAD 1
• Consider dual therapy with low-dose rivaroxaban 2.5 mg twice daily plus aspirin 100 mg daily in patients without high bleeding risk 1

Lipid Management

• Target LDL-C <1.4 mmol/L (<55 mg/dL) or ≥50% reduction as patients with PAD are at very high cardiovascular risk 1

Glycemic Control

• Optimize glucose control in diabetic patients to improve foot outcomes 1

Preventive Foot Care

Implement intensive preventive foot care measures immediately: 1

• Patient education about daily foot inspection
• Proper footwear to prevent pressure injuries
• Early recognition and treatment of any tissue loss or infection
• Referral to multidisciplinary team including vascular specialist and diabetologist is mandatory 1

Critical Pitfalls to Avoid

Do not delay imaging or vascular surgery consultation. 1 A TBI <0.4 represents severe ischemia where tissue loss and amputation risk are imminent without revascularization. 1, 2

Do not rely on ABI alone in this patient. 2, 3 The fact that TBI was measured suggests either elevated/noncompressible ABI (>1.40) or clinical suspicion despite normal ABI—both scenarios where ABI underestimates disease severity. 1, 3

Ensure perfusion measurements are obtained in a warm room to prevent arterial vasoconstriction that could yield falsely low readings. 2

Structured Exercise Therapy

While structured exercise is beneficial for claudication, patients with CLTI and TBI <0.4 require revascularization first before exercise therapy can be safely implemented. 1 Exercise therapy alone is insufficient for limb salvage at this severity level.