A note on Allen's test and Cardiac bypass surgery (CABG)
The radial artery is occasionally used as a conduit for bypass surgery, and its patency lasts longer in comparison to the saphenous veins. Prior to heart bypass surgery, Allen's test is performed to assess the suitability of the radial artery to be used as a conduit. A result of less than 3 seconds is considered as good and suitable. A result of between 3-5 seconds is equivocal, whereas the radial artery will not be considered for grafting if the result is longer than 6 seconds.
A negative Allen’s test is safe to harvest the radial artery.
Is the Allen test reliable enough? - Eur J Cardiothorac Surg (2007) 32 (6): 902-905.