Radial arteries are commonly utilised for coronary artery bypass grafts. The laboratory routinely assesses the arteries before surgery, especially with positive or equivocal Allens test results. The technique involves duplex scanning of the radial and ulnar arteries and assessing the adequacy of the Palmar arch circulation. The test is simple, accurate, and provides useful information to show whether or not the artery is suitable for harvesting. There is usually good circulation in the hand between the radial and ulnar arteries. There is still however, the slight risk of claudication or even ischaemia of the hand following removal of the radial artery, if vascular communication between the lateral and medial sides of the hand is incomplete. The radial and ulnar arteries are scanned on both sides using a 7.5MHz linear transducer. The arterial walls are examined for calcification or atheroma, and their diameters are noted (needs to be > 2mm). Doppler signals are taken in both arteries although these arteries show a wide variance in normal Doppler waveforms. The Ulnar artery is usually the more dominant of the two. The distal radial artery at the ‘Snuffbox’ (the gap between the Extensor pollicis longus and brevis tendons) is scanned using colour Doppler. The proximal radial artery is compressed and dynamically occluded by the sonographer. Reverse flow should be seen (with colour) in the distal radial artery suggesting adequate Palmar arch circulation. If the artery does not show reverse flow, then probable inadequate Palmar arch circulation is indicated.
Duplex scan assessment of the radial arteries prior to coronary artery bypass surgery
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