Indications
Blood pressure asymmetry between the arms, upper limb claudication, digital ischaemia or Raynaud's phenomenon, suspected thoracic outlet syndrome, planning of radial artery harvest (coronary bypass) or radial cannulation, assessment before device implantation (pacemaker, port), trauma, and follow-up after endovascular procedures.
Equipment and patient position
- Linear array transducer 7–12 MHz for the distal subclavian, axillary, brachial, radial and ulnar arteries; for the proximal (retroclavicular) subclavian a curvilinear transducer 2–5 MHz, or an angled approach with the linear probe, may help, given the greater depth and the acoustic shadow of the clavicle.
- Patient supine, the limb slightly abducted and externally rotated, palm upwards for the distal segment.
- The examination is always bilateral and comparative: asymmetry between the two sides is often the most informative finding.
Systematic scanning
3.1 · Subclavian artery
A supraclavicular approach for the proximal segment (arising on the right from the brachiocephalic trunk, and directly from the aorta on the left) and an infraclavicular approach for the distal segment. Document calibre, patency and flow profile: a high-resistance monophasic pattern with loss of the negative diastolic component suggests proximal stenosis.
3.2 · Axillary and brachial arteries
These are followed in the longitudinal plane along the medial bicipital groove to the antecubital fossa, where the brachial artery divides into the radial and ulnar arteries. Document any plaque and any post-traumatic or iatrogenic stenosis (puncture sites, previous catheterisation).
3.3 · Radial and ulnar arteries
Superficial in course and easily assessed as far as the wrist. Pay particular attention to the radial artery if it is a candidate for harvest for coronary bypass or for cannulation: an acceptable minimum calibre, absence of diffuse wall calcification, and patency of the palmar arch (see section 5).
Manoeuvres for thoracic outlet syndrome
The Doppler sample volume is placed on the distal subclavian or axillary artery and the signal is observed at rest and during the provocative manoeuvres, comparing the two sides:
- Adson manoeuvre: the head is rotated towards the side being examined, with neck extension and a held deep inspiration.
- Costoclavicular manoeuvre: the shoulders are drawn downwards and backwards (the "military brace" position).
- Hyperabduction manoeuvre: the arm is elevated beyond 180°.
A significant reduction or disappearance of the Doppler signal during one or more manoeuvres, reproducible and consistent with the patient's symptoms, supports a diagnosis of dynamic thoracic outlet compression. Mild attenuation of the signal in asymptomatic subjects is a common finding and not necessarily pathological: it must always be correlated with the clinical picture.
Ultrasound Allen test (patency of the palmar arch)
Before radial artery harvest or prolonged radial cannulation, the patency of the palmar arch and the adequacy of ulnar collateral supply are checked:
- The radial artery is compressed manually at the wrist.
- Colour Doppler is used to observe flow in the superficial palmar arch and/or a digital artery, which must remain patent thanks to the ulnar supply.
- The test is repeated compressing the ulnar artery, to check the radial supply in the same way.
What to measure and document
- PSV at the sites of suspected stenosis, with the velocity ratio against the normal proximal segment (a PSV ratio > 2 suggests significant stenosis).
- Flow profile (triphasic, biphasic or monophasic) in each segment.
- The result of the dynamic thoracic outlet manoeuvres, side by side.
- Patency of the palmar arch, where requested.
- Any plaque, calcification, sequelae of puncture or catheterisation, and aneurysms.