What does a monophasic waveform in the distal left peroneal artery on duplex ultrasound indicate and what are the recommended next steps in management?

Monophasic Waveform in the Distal Left Peroneal Artery: Clinical Significance and Management

A monophasic waveform in the distal left peroneal artery indicates hemodynamically significant arterial stenosis or occlusion proximal to or at this level and requires immediate cross-sectional vascular imaging (CTA or MRA) to localize the lesion and determine whether revascularization is indicated. 1

What This Finding Means

• Monophasic waveforms are post-stenotic flow patterns that signal upstream arterial disease severe enough to dampen the normal triphasic arterial flow, indicating at least 50-70% stenosis or complete occlusion proximal to the measurement site 2

• This finding represents hemodynamically significant peripheral arterial disease (PAD) affecting the infrageniculate circulation, which carries substantial risk for limb-threatening ischemia 1

• The presence of monophasic flow in the peroneal artery suggests multilevel disease is likely, as isolated tibial vessel disease rarely produces such marked flow abnormalities 3

Immediate Clinical Assessment Required

Determine whether critical limb-threatening ischemia (CLTI) is present by assessing for:

• Rest pain (especially nocturnal pain relieved by dependency) 1
• Non-healing wounds or ulceration 1
• Gangrene or tissue loss 1
• Functional status and claudication distance 2

Measure ankle-brachial index (ABI) bilaterally, recognizing that heavily calcified vessels (especially in diabetic patients) may yield falsely elevated or non-compressible readings that underestimate disease severity 1

• A change in ABI of ≥0.15 from baseline is clinically significant 2
• Normal resting ABI does not exclude significant disease in multilevel PAD 1

Definitive Imaging Strategy

Order computed tomography angiography (CTA) of bilateral lower extremities with runoff as the definitive imaging modality 1

• CTA provides precise anatomic localization of stenosis/occlusion from the aorta through the pedal vessels in a single study 1
• This imaging directly determines technical feasibility of endovascular versus open surgical revascularization 1
• CTA is essential for planning tibial-level interventions, as duplex ultrasound alone cannot reliably provide the anatomic detail required for distal bypass target selection 2, 1

Magnetic resonance angiography (MRA) is an acceptable alternative, particularly in patients with renal insufficiency where non-contrast techniques can be employed, offering 90-100% sensitivity and specificity for detecting ≥50% stenosis 1

Critical Limitation of Duplex Ultrasound Alone

• While duplex identified your monophasic waveform, it is insufficient for comprehensive treatment planning in infrageniculate disease 1
• Duplex has only moderate agreement (κ = 0.4-0.6) with angiography in the tibio-peroneal trunk and peroneal artery, compared to good-to-excellent agreement in more proximal vessels 3
• Dense arterial calcification and multiple sequential lesions significantly reduce duplex accuracy in tibial vessels 1

Cardiovascular Risk Modification (Mandatory for All PAD Patients)

Initiate aggressive secondary prevention immediately, as lower extremity arterial disease reflects systemic atherosclerosis with elevated cardiovascular mortality risk 1:

• High-intensity statin therapy regardless of baseline lipid levels 1
• Antiplatelet therapy with aspirin or clopidogrel for cardiovascular event prevention 1
• Blood pressure optimization and strict enforcement of smoking cessation 1

Indications for Revascularization

Revascularization is a Class I indication if CLTI is present (rest pain, tissue loss, or gangrene) 1

Revascularization should be considered for lifestyle-limiting claudication that fails to improve after supervised exercise therapy and optimal medical management 1

Revascularization Approach

• CTA/MRA findings determine whether endovascular or open surgical approach is technically feasible 1
• Endovascular therapy is generally preferred when anatomy is suitable due to lower peri-operative morbidity 1
• Surgical tibial bypass requires high-quality pre-operative imaging to identify suitable target vessels 1

Post-Revascularization Surveillance (If Intervention Performed)

• Combined duplex ultrasound and ABI monitoring at 4-6 weeks, 6 months, 12 months, then yearly can detect restenosis early 2
• A drop in ABI >0.15 from post-procedure baseline suggests graft failure and warrants repeat imaging 2
• Surveillance is most reliable for infrainguinal autogenous vein bypass grafts (Class IIa recommendation) but of uncertain benefit for prosthetic grafts (Class IIb) 2

Critical Pitfalls to Avoid

• Do not rely on resting ABI alone in multilevel disease, as it may underestimate severity 1
• Do not attempt tibial-level revascularization planning based solely on duplex ultrasound, as anatomic detail is insufficient and agreement with angiography is only moderate in the peroneal artery 1, 3
• Do not delay cross-sectional imaging if any signs of CLTI are present, as tissue loss progression can be rapid 1
• Recognize that monophasic flow in a single tibial vessel suggests multilevel disease requiring comprehensive evaluation of the entire arterial tree from aorta to foot 3