Ultrasound of Hand arteries prior to coronary bypass surgery

R Ziegenbein, G Shardey, AV Gray,Monash Medical Centre, Clayton Vic

Radial arteries are becoming a preferred conduit for coronary bypass surgery since modification of the harvesting technique increased short term patency to more than 95% (1,2,3,4) compared to about 50% patency rate when radial arteries were first used as a graft (5). The long term patency of the radial artery graft is unclear, but if it proves to be a better quality and longer lasting graft than other graft types such as the long saphenous vein, it will be increasingly important to identify those patients who can have the radial artery safely removed without consequent hand ischaemia.

Contraindications for the use of the radial artery include past trauma, a fistula or proposed fistula formation for renal dialysis and inadequate collateral compensation in the hand. Inadequate collateral compensation in the hand is an 'absolute' contraindication (6) but the definition of inadequate compensatory flow and the most appropriate method to determine it varies from one study to another. The modified Allen test, angiographic studies and non-invasive tests involving digit pressures, pulse oximetry and Doppler have all been applied either singly or in various combinations to identify those patients who are likely to suffer from hand ischaemia once the radial artery is removed. The modified Allen test is the most common clinical assessment of adequate collateral circulation in the hand but suffers a high rate of false positive tests. This would needlessly exclude many people from radial artery harvesting, but the added benefit of non invasive tests is yet to be defined.

Conclusion
Duplex ultrasound appears to be a useful investigation in the assessment of hand blood flow when considering radial artery harvesting for coronary bypass surgery with the greatest benefit in those patients with a positive or equivocal Allen test. Flow reversal in the DPA is a safe criteria to determine the risk of hand ischaemia, but must be confirmed in each laboratory intending to perform this test. Alternate criteria such as the maintenance of digital artery flow has yet to be tested but may offer a further increase in the number of arteries which can be used for grafting.