Assessment of ulnar collateral circulation by the Allen test in patients undergoing radial artery harvest

Radial artery harvest, Allen test, Hand ischemia

I read with interest the article entitled ‘Is the Allen test reliable enough?’ written by Dr Kohonen and associates about the reliability of the Allen test to assess the adequacy of ulnar collateral circulation to avoid ischemic complications of the hand in patients scheduled for radial artery graft conduit harvesting for coronary artery bypass grafting surgery [1]. The authors have enrolled 145 patients in their study and performed the Allen test, Doppler ultrasonography and digital plethysmography. Seventy-seven percent of patients had a negative Allen test (111/144) and 23% (33 pts) had a positive Allen test in their study. Forty out of 145 patients (27.7%) had anatomical variations, pathological changes or abnormal circulatory findings that precluded radial artery harvest.

In our series of 555 patients considered for radial artery harvest, 527 patients underwent coronary artery bypass grafting using radial artery (RA) graft as one of the conduits to bypass a critically stenosed (>70%) non-left anterior descending (LAD) coronary artery. The RA graft was harvested using extrafascial technique from the non-dominant forearm as described earlier [2]. The radial artery harvest could not be done in 25 patients due to a positive Allen test. In three out of 530 patients with a negative Allen test the dissected radial artery pedicle was not divided and the RA was left in situ due to absence of pulsations in the distal part of radial artery after temporary occlusion of radial artery proximally in the forearm. With the use of a combination of three tests; negative Allen test, prompt reappearance of pulse wave on the pulse oxymeter screen (less than 6 s) after the release of radial compression and prompt reappearance of pulse (less than 6 s) in the distal radial artery following proximal occlusion of radial artery temporarily, none of the 527 patients had suffered ischemia of the hand or digits postoperatively following radial artery harvest, in concurrence with our earlier report [3]. We encountered false negativity of the Allen test soon after the completion of the dissection of radial artery in three patients (three out of 530) (0.56%).

We feel that a negative Allen test in combination with a prompt reappearance of pulse wave on pulse oxymeter screen and palpability of distal radial artery pulse after occlusion of radial artery proximally is quite reliable in assessing the adequacy of ulnar collateral circulation prior to RA harvest and only if the Allen test is positive, is further evaluation needed by ultrasonography, digital plethysmography or magnetic resonance imaging to ensure a safe harvest of the radial artery in those subjects.

We would appreciate if the authors could clarify

1. 1.

   How many patients with positive Allen test underwent radial artery harvest in their study because of demonstration of adequate ulnar collateral circulation by ultrasonography and/or digital plethysmography?

2. 2.

   How many patients with a negative Allen test did not undergo radial artery harvest in their study because of demonstration of inadequacy of ulnar collateral circulation by ultrasonography and/or digital plethysmography?