Popliteal Artery Entrapment Syndrome (PAES): Provocative Duplex Tests
The Essence of the Problem
PAES (popliteal artery entrapment syndrome) is an extravascular compression of the popliteal artery by abnormally positioned or hypertrophied musculo-tendinous structures in the popliteal fossa (often the medial head of the gastrocnemius muscle). The typical patient is a young male athlete aged 20–40 years with pain/burning in the calf during exercise, which subsides after 1–2 minutes of rest; approximately one-third have bilateral involvement.
The classic 'at rest' protocol misses this syndrome: in a young active patient with exercise-induced leg pain and normal resting ABI, one should consider non-atherosclerotic arteriopathy (PAES/CAD/endofibrosis). Untreated anatomical entrapment over time leads to wall damage, post-stenotic aneurysm, thrombosis, and risk of embolism — hence early diagnosis is important.
Provocative Duplex Protocol
| Step | Action |
|---|---|
| 1 | Spectrum of the popliteal artery in a neutral position (baseline recording) |
| 2 | Active plantarflexion and dorsiflexion, preferably with resistance from the examiner's hand |
| 3 | Repeat the test several times, as compression may be transient |
| 4 | Comparison with the healthy side (if unilateral involvement) |
| 5 | Assessment of post-exercise spectrum in distal arteries (dorsalis pedis, PTA): attenuation/lengthening of acceleration time after exercise indirectly confirms transient obstruction above |
| 6 | Duplex in a standing on tiptoes position (simulation of isometric load on the gastrocnemius muscle) |
Exercise ABI
Measurement before and after physical exercise (running/fast walking until symptoms appear, plantarflexion with resistance). A drop in ABI of more than 20% is highly sensitive, especially for the functional type.
Tactics in the Absence of CTA/MRA
Ultrasound with functional tests takes precedence. The combination of exercise ABI and provocative duplex provides sufficient grounds to suspect PAES and refer the patient to a vascular surgeon even without tomography. However, final typing will still require CTA/MRA. Duplex criteria — WFUMB 2024 [specific threshold values to be clarified].
Frequently asked questions
What movements are used for provocation in duplex?
Active plantarflexion and dorsiflexion, preferably with resistance from the examiner's hand, as well as standing on tiptoes (isometric load on the gastrocnemius muscle). Tests are repeated several times as compression may be transient.
What drop in exercise ABI is significant?
A drop in ABI of more than 20% after exercise is highly sensitive, especially for the functional type of PAES.
Can PAES be diagnosed by ultrasound alone?
The combination of exercise ABI and provocative duplex allows suspicion of PAES and referral to a vascular surgeon even without tomography, but final typing requires CTA/MRA.
Why does a static examination at rest miss PAES?
PAES mimics PAD but has a different nature — extravascular compression that manifests only during exercise; at rest, the picture remains normal, so the key to diagnosis is dynamic testing and exercise testing.
How to account for unilateral involvement?
Comparison with the healthy side is performed. Post-exercise attenuation of the spectrum or lengthening of acceleration time in distal arteries (dorsalis pedis, PTA) indirectly confirms transient obstruction above.