Is the Allen’s test adequate to safely confirm that a radial artery may be harvested for coronary arterial bypass grafting?

May 30, 2005

May 30, 2005

Andrew Ronald, Anish Patel, Consultant Cardiac Anaesthetist (Department of Cardiac Anaesthesia, Aberdeen Royal Infirmary, Freeman Hospital, Newcastle-upon-Tyne and James Cook University Hospital, Middlesbrough)

Joel Dunning, Department of Cardiac Anaesthesia, Aberdeen Royal Infirmary, Freeman Hospital, Newcastle-upon-Tyne and James Cook University Hospital, Middlesbrough

In [patients undergoing CABG surgery using radial artery grafts] is the [Allen's test, plethysmography, Doppler ultra-sound or MRI imaging] the best method of assessing [ulnar artery or collateral flow]

You are at a clinical research meeting when you hear presentations comparing the use of magnetic resonance imaging (MRI), plethysmography and Doppler ultrasound techniques to assess adequacy of ulnar collateral flow in patients scheduled for radial artery graft conduit harvesting for CABG surgery. You decide to review the literature to identify just how good these techniques are and to find out whether they offer any advantage in identifying satisfactory collateral flow in the forearm over the Allen's test which you currently use in your own practice.

Medline 1966 to March 2005 using OVID interface
EMBASE 1980 to March 2005

[CABG.mp OR exp Thoracic Surgery/OR Coronary art$ bypass.mp OR Cardiopulmonary bypass.mp OR exp Cardiovascular Surgical Procedures/OR exp Thoracic Surgical Procedures/OR exp Coronary Artery Bypass] AND [exp Radial Artery/OR radial artery graft.mp] AND [Plethysmography.mp. OR exp Plethysmography/OR Magnetic resonance angiography.mp. OR exp Magnetic Resonance Imaging/OR exp Magnetic Resonance Angiography/OR Angiography/OR Allens test.mp. OR exp Ulnar Artery/OR Doppler ultrasonography.mp. OR exp Ultrasonography, Doppler] AND [collateral circulation.mp. OR exp Collateral Circulation/OR exp Regional Blood Flow/OR exp Ulnar Artery/OR exp Hand/OR ulnar blood flow.mp.]

A total of 176 papers were identified: 58 on Medline, 111 on Embase and 7 by hand searching of reference lists. Fifteen papers representing the best evidence on the subject are summarised below.

Definitions of hand/forearm ischaemia are subjective and variable but are low in patients with 'normal' Allen's tests. Agrifoglio reported no postoperative forearm or hand ischaemia, but 5.3% of their patients did not have radial artery harvest on the basis of Doppler assessment of hand flow during RA compression. However, papers by Sajja, Ruenaskulrach, Starnes and Abu-Omar report no ischaemic sequelae when using an Allen's test to guide suitability for RA harvest. The paper by Meharwal is perhaps the most reassuring in that it reported no acute ischaemic hand symptoms in a series of 4172 harvests in 3977 patients and whilst 5.2% complained of some hand weakness at 4 weeks, this had fallen to 0.4% beyond 3 months. Their incidence of numbness and paraesthesia although as high as 25% in the early postoperative period had fallen to 1.22% at 6 months. The decision to harvest in this series was based on preoperative Allen's test and intraoperative pulse oximetry studies. Of note cut-off points from 3 to 12 s are quoted as the time limit for return of palmar flush in these studies.

Several studies have compared the Allen's test to a 'gold standard'. Glavin demonstrated that the test was associated with both false positives and false negatives using a 6-s cut-off when compared to Doppler and that pulse monitor and pulse oximetry were also unable to identify the absence of ulnar flow demonstrated with Doppler. Johnson used pulse oximetry to identify return of perfusion to control levels during an Allen's test in 452-forearms using a 12-s cut-off time. Jarvis compared a modified Allen's test (MAT) to Doppler ultrasound assessment of collateral ulnar flow in CABG patients. By examining the receiver operating characteristics of the Doppler signal from the princeps pollicis artery of the thumb during release of ulnar artery compression they concluded that whilst a 3-s cut-off would give the highest sensitivity, the false positive rate would also be high with a diagnostic accuracy rate of only 52%. Maximum diagnostic accuracy was achieved with a cut-off point of 5 s although the sensitivity would fall. In response to this paper, Sajja published a case series of 241 patients in which the Allen's test with pulse oximetry (6-s cut-off) was used in combination with intraoperative assessment of distal RA pulse during proximal RA occlusion to assess efficacy of collateral blood flow. They quoted a false negative rate of 0.4%. In a smaller study, Ruengsakulrach studied the non-dominant arm of 71 patients undergoing CABG surgery with a modified Allen's test (10 s cut-off). They identified abnormal Doppler flow in patients with abnormal Allen's tests and concluded that their study confirmed the validity of the Allen's test and that absence of flow in the dorsal digital thumb artery was an absolute contraindication to RA harvest.

Some studies support the use of the RA even in the presence of an abnormal Allen's test. Starnes compared the modified Allen's test with Doppler ultrasound assessment of the superficial palmar arch blood flow during RA compression, to digital blood pressures before and after RA compression (P). They identified a false positive rate of 50% in their series, and defined 'maximum sensitivities' for P for both arms. RA harvest was performed in 52/129 patients with no ischaemic sequelae in 50/52 followed up. Abu-Omar used Duplex ultrasonography in the presence of an abnormal Allen's test in a subgroup of 43 out of 287 patients undergoing total arterial revascularisation who had an abnormal preoperative Allen's test (5 s cut-off). Duplex scanning was normal in 38 patients in this group and these together with a further 3 'Duplex abnormal' RA's were subsequently harvested without ischaemic sequelae.

In some patients with equivocal tests a 'non-Allen's test' may be required. These are principally Doppler-based and there are a number of papers reporting various techniques to identify adequate collateral circulation. Kupinski imaged forearm vessels with Duplex ultrasound and digital pulse volume recording at rest and during RA compression. They identified 'some postoperative symptoms of ischaemia...' in a small subgroup that had abnormal preoperative digital pulse volume recordings and evidence of 'perfusion defects' without symptoms of ischaemia in 10% of a follow-up group. Finally, Winkler used a 3-part radial artery mapping technique together with a 'RA removal simulation procedure' to assess circulation preoperatively. They reported that surgeons were least keen to proceed to RA harvest if the Allen's test was abnormal and most if only the Duplex scan was positive. They also followed up a small subgroup and whilst 32% of patients reported minor but resolving hand symptoms, they felt that there was no evidence of ischaemia.

Adding a second technique might significantly increase the number of arteries which could be harvested without adverse outcome. When Barbeau studied 1010 consecutive patients presenting to the Catheter Lab for transradial catheterisation they noted that 80% of the abnormal Allen's test group (52 out of 65 patients) had satisfactory plethysmography and pulse oximetry responses to RA compression. This decreased the potential 'RA rejection' rate from 6.4% (9-s Allen's test) to as little as 1.5%. Starnes reported a false positive rate as high as 50% in their series when they compared the Allen's test to a digital pressure change test.

Finally in 2001, Winterer compared Doppler assessment of blood flow velocity in the ulnar artery at the wrist to Gadolinium-enhanced MRI angiography in a series of 21 patients presenting for surgery. Three patients had a positive Doppler with no UA acceleration or flow decrease in one or more digital arteries during RA compression. Twenty patients (including all with positive Doppler's) proceeded to MRI which confirmed patent vessels between UA and RA in all the Doppler negative, and aberrant vessels/lack of collaterals in the Doppler positive patients. Whilst this study involved small numbers, it may represent a new ultimate 'gold standard' assessment modality.

A negative Allen's test safely selects patients for radial artery harvest, although the cut-off point is controversial. However, if the test is positive, then a 2nd test such as dynamic Doppler ultrasound or measurement of digital pressure changes with radial artery occlusion may allow safe harvest.

1. Glavin RJ, Jones HM.. Assessing collateral circulation in the hand – four methods compared.
2. Johnson WH 3rd, Cromartie RS 3rd, Arrants JE, Wuamett JD, Holt JB.. Simplified method for candidate selection for radial artery harvesting.
3. Jarvis MA, Jarvis CL, Jones PR, Spyt TJ.. Reliability of Allen's test in selection of patients for radial artery harvest.
4. Sajja LR, Mannam G, Sompalli S.. Is Allen's test not reliable in the selection of patients for radial artery harvest (letter)?
5. Ruengsakulrach P, Brooks M, Hare DL, Gordon I, Buxton BF.. Preoperative assessment of hand circulation by means of Doppler ultrasonography and the modified Allen test.
6. Agrifoglio M, Dainese L, Pasotti S, Galanti A, Cannata A, Roberto M, Parolari A, Biglioli P.. Preoperative assessment of the radial artery for coronary artery bypass grafting: Is the clinical Allen test adequate?
7. Starnes SL, Wolk SW, Lampman RM, Shanley CJ, Prager RL, Kong BK, Fowler JJ, Page JM, Babcock SL, Lange LA, Erlandson EE, Whitehouse WM Jr.. Noninvasive evaluation of hand circulation before radial artery harvest for coronary artery bypass grafting.
8. Abu-Omar Y, Mussa S, Anastasiadis K, Steel S, Hands L, Taggart DP.. Duplex ultrasonography predicts safety of radial artery harvest in the presence of an abnormal Allen test.
9. Meharwal ZS, Trehan N.. Functional status of the hand after radial artery harvesting: Results in 3977 cases.
10. Kupinski AM, Huang J, Khan AM, Zorn TJ, Mathus LH, Mick JA, Hoskins MS, Shah DM.. Noninvasive upper extremity arterial assessment in patients undergoing radial artery harvest.
11. Pola P, Serricchio M, Flore R, Manasse E, Favuzzi A, Possati GF.. Safe removal of the radial artery for myocardial revascularization: a Doppler study to prevent ischemic complications to the hand.
12. Rodriguez E, Ormont ML, Lambert EH, Needleman L, Halpern EJ, Diehl JT, Edie RN, Mannion JD.. The role of preoperative radial artery ultrasound and digital plethysmography prior to coronary artery bypass grafting
13. Winkler J, Lohr J, Bukhari RH, Hearn A, Goller R, Parlato D, Schmeltzer M, Van Wagenen T, Smith JM.. Evaluation of the radial artery for use in coronary artery bypass grafting.
14. Barbeau GR, Arsenault GF, Dugas L, Simard S, Lariviere MM.. Evaluation of the ulnopalmar arterial arches with pulse oximetry and plethysmography: comaprison with the Allen's test in 1010 patients.
15. Winterer JT, Ennker J, Scheffler K, Rosendahl U, Schafer O, Wanner M, Laubenberger J, Langer M.. Gadolinium-enhanced elliptically reordered three-dimensional MR angiography in the assessment of hand vascularization before radial artery harvest for coronary artery bypass grafting: First experience