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Ann Thorac Surg 2004;77:116-119
© 2004 The Society of Thoracic Surgeons

Original article: cardiovascular

Duplex ultrasonography predicts safety of radial artery harvest in the presence of an abnormal Allen test

Yasir Abu-Omar, MRCSa, Shafi Mussa, MA, MRCSa, Kyriakos Anastasiadis, MDa, Sarah Steel, BS(Hons)a,b, Linda Hands, MS FRCSb, David P. Taggart, MD, PhD FRCSa*

a Department of Cardiothoracic Surgery John Radcliffe Hospital, Oxford, England, UK
b Nuffield Department of Surgery, John Radcliffe Hospital, Oxford, England, UK

Accepted for publication July 25, 2003.

* Address reprint requests to Dr Taggart, Department of Cardiothoracic Surgery, John Radcliffe Hospital, Headley Way, Headington, Oxford, England, UK
e-mail: david.taggart{at}orh.nhs.uk


   Abstract
Top
 Abstract
Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
 References
 
BACKGROUND: The Allen test is commonly used to assess collateral hand circulation before radial artery harvest for coronary artery bypass grafting. However there is no consensus as to whether an abnormal Allen test is an absolute or relative contraindication to radial artery harvesting. We assessed the safety of harvesting the radial artery using arterial duplex ultrasonography in patients with an abnormal Allen test.

METHODS: Two hundred and eighty-seven consecutive patients scheduled for total arterial coronary revascularisation underwent preoperative Allen tests over a 34-month period. Patients with an abnormal Allen test underwent duplex ultrasonography preoperatively to assess the adequacy of the ulnar collateral supply and the suitability of the radial artery for harvesting.

RESULTS: Two hundred and forty-four patients (85%) had a normal left Allen test and proceeded directly to radial artery harvest. Forty-three patients (15%) with an abnormal left Allen test underwent duplex ultrasonography scans and of those, 5 patients had an abnormal scan. These patients underwent scanning of the contralateral forearm. Three patients had a normal right forearm arterial duplex scan and the right radial artery was harvested. The mean diameter of the radial and ulnar arteries was not significantly different between the patients with normal and abnormal duplex ultrasonograms. There were no ischemic hand complications in this series.

CONCLUSIONS: The Allen test is a quick, easy, and reliable screening test before radial artery harvesting in the majority of patients. Duplex ultrasonography predicts safe radial artery harvest in the majority of patients with an abnormal Allen test.


   Introduction
Top
 Abstract
 Introduction
Material and methods
 Results
 Comment
 Acknowledgments
 References
 
Superior patency rates and improved patient survival make the internal mammary arteries (IMA) the conduits of first choice for coronary revascularization [1, 2]. The radial artery (RA) is currently the third most commonly used arterial conduit. It is a versatile conduit that can be harvested easily, has handling characteristics superior to other conduits, and comfortably reaches any coronary target [3]. The RA has good early and midterm results and patency rates that appear superior to those of vein grafts [4, 5]. Improved harvesting techniques [6, 7] and the topical application [8, 9] and long-term oral administration [10] of vasodilator drugs to prevent arterial spasm have contributed to the current favorable outcome. Midterm angiographic data showed RA graft patency rate of up to 100% at 4 years [11]. Use of the RA also has the benefit of avoiding leg wound morbidity in association with saphenous vein harvesting and therefore promotes early postoperative mobilization [3].

However, successful RA harvest is contingent on adequate ulnar artery (UA) collateral circulation to avoid hand ischemia [12, 13]. The simplest and most practical method to assess collateral hand circulation in clinical practice is the Allen test. Edgar Allen described a noninvasive evaluation technique of arterial patency of hand circulation in patients with thromboangiitis obliterans in 1929 [14]. The Allen test was then modified in the early 1950s to assess collateral circulation before arterial cannulation. This test has now been widely adopted to screen patients undergoing coronary artery bypass grafting (CABG) before RA harvesting [15]. Despite its widespread use, recent studies have questioned its reliability [16]. Furthermore, there is no clear consensus in the literature as to whether an abnormal Allen test is an absolute or relative contraindication to radial artery harvest.

Based on our experience of RA use in more than 280 patients undergoing total arterial CABG we used the Allen test in combination with forearm arterial duplex ultrasonography to optimize the safe use of this valuable conduit in CABG patients.


   Material and methods
Top
 Abstract
 Introduction
 Material and methods
Results
 Comment
 Acknowledgments
 References
 
Preoperative screening
The Allen test was performed by the senior surgeon (D.P.T.) in all the patients. The left radial and ulnar arteries were occluded at the wrist between the surgeon's thumbs and fingers. The patient was asked to make a tightly clenched fist several times to exsanguinate the palmar skin. The patient then opened his or her fingers, avoiding hyperextension. The UA was then released and the time taken for adequate capillary refill was noted. The test was defined as "normal" if the capillary refill time was less than 5 seconds, and "abnormal" if more than 5 seconds. Patients with a normal test proceeded directly to radial harvesting.

Patients with abnormal Allen test underwent duplex ultrasonography using a Philips ATL HDI 5000 system with a 7 to 4 MHz linear transducer (Koninklijke Philips Electronics NV, Eindhoven, Netherlands) preoperatively to assess the adequacy of the ulnar collateral supply and the suitability of the radial artery for harvesting (Fig 1). With the hand in the relaxed position, brachial, UA, and RA anatomy (including diameter and intimal abnormalities) were recorded (Fig 2). In addition flow velocity and waveform patterns were recorded proximally (at the bifurcation of the brachial artery), distally (at the wrist), and half way between these two points. A two-fold increase in Doppler velocity was considered representative of 50% stenosis. An abnormal duplex result, namely occlusion or greater than 50% stenosis of either the RA or UA, precluded RA harvesting. These patients proceeded to assessment of the contralateral forearm.



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  		Fig 1. (A) Representative duplex ultrasonography image of the normal radial artery. (B) Doppler flow velocity of the normal radial artery.

 


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  		Fig 2. (A) Demonstration of wall calcification (arrow) of the ulnar artery. (B) Ultrasonography image of a normal radial artery (arrow) in the same patient.

 
Statistical analysis
Diameters of the radial and ulnar arteries are presented as mean ± standard deviations. Radial and ulnar artery diameters in patients with normal and abnormal duplex ultrasonograms were compared using an unpaired Student's t test. A probability value of 0.05 or less was considered as statistically significant.


   Results
Top
 Abstract
 Introduction
 Material and methods
 Results
Comment
 Acknowledgments
 References
 
Two hundred and eighty-seven consecutive patients scheduled for total arterial CABG underwent preoperative Allen tests over a 34-month period. Two hundred and forty-four patients (85%) had a normal left Allen test and proceeded directly to radial artery harvest. Forty-three patients (15%) had an abnormal left Allen test and subsequently had preoperative duplex ultrasound scans. Of these, 38 patients had normal duplex scans as defined by distal brachial, RA, and UA calibers, flow velocities, and structural features and proceeded to radial artery harvesting. The remaining 5 patients with abnormal left forearm duplex scans (namely > 50% stenosis or occlusion of the RA or UA) underwent scanning of the contralateral forearm. Three patients—1 with more than 50% stenosis of the left distal UA, 1 with evidence of proximal disease with poor flow into the left RA and UA, and 1 with 50% stenosis of the left proximal UA—had normal right forearm arterial duplex scans and right RAs were duly harvested. Two patients—1 with bilateral stenoses of the mid RA and 1 with bilateral distal RA stenoses, right distal UA stenosis, and left distal UA occlusion—did not have their RA harvested (Table 1).


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  		Table 1. Clinical (Allen Test) and Duplex Ultrasonography Findings in 287 Patients Scheduled for Total Arterial Coronary Artery Bypass Graft Surgery

 
Mean diameters of the radial and ulnar arteries were not significantly different between normal and abnormal duplex ultrasonograms, suggesting that the occurrence of stenosis was not influenced by the size of the artery (Table 2). There were no ischemic arm complications in the immediate postoperative period in any of the 285 patients undergoing radial artery harvesting using this screening protocol.


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  		Table 2. Radial and Ulnar Artery Diameters Measured During Duplex Scanning in Patients With an Abnormal Allen Test

 

   Comment
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
Acknowledgments
 References
 
Assessment of collateral hand circulation is mandatory to allow safe harvesting of the RA. The Allen test is commonly used for this purpose despite concerns regarding its reliability. We have safely used the Allen test as the primary method of assessment in more than 800 patients undergoing CABG and 280 CABG patients undergoing total arterial revascularization. Only 43 (15%) of these patients had an abnormal Allen test with the cut-off point at 5 seconds. Of these patients only 5 had structural arterial abnormalities demonstrated on duplex ultrasonography. Furthermore only 2 patients had bilateral abnormalities on duplex scanning and required use of an alternative conduit.

Doppler techniques (including duplex ultrasonography) [17, 18], thumb systolic arterial pressure measurement [19], pulse oximetry and plethysmography [20] have been used to assess the adequacy of collateral circulation to the hand and the suitability of the RA for harvesting. Duplex ultrasonography combines high resolution gray-scale imaging and pulsed Doppler spectral analysis to yield excellent anatomical and physiologic data. The major advantage of this technique is the ability to demonstrate the arterial anatomy along the entire length of the vessel, allowing an assessment of the quality of the RA (arterial caliber and severity and number of atherosclerotic lesions) to be used as a conduit. Stenotic lesions result in an increase in flow velocity at the lesion and decreased poststenotic systolic velocity. Exclusive use of the Doppler waveform may be misleading as the triphasic signal may be absent in the atherosclerotic patient population undergoing CABG. Anatomic variations such as RA or UA absence or malformations, dominant RA, and incomplete palmar arch may be factors contributing to an abnormal Allen test and are readily identifiable on duplex scanning.

Our approach has enabled use of 99% of all RAs as conduits, in contrast to the low reported usage rate in other studies. This is consistent with our previous study of histologic specimens of 177 RAs in which we found minimal disease in the majority [21]. Hosono and associates [22] excluded 27% of RAs owing to small arterial diameter, absent radial artery, poor vascular condition or interrupted palmar arch after preoperative assessment with duplex scanning. Rodriguez and colleagues [23] also excluded 27% of RAs after combined use of ultrasonography and digital plethysmography. Pola and colleagues [24] excluded 6% of RA after assessment with Doppler studies.

In contrast to the findings of Jarvis and coworkers [16] who reported the Allen test to be of severely limited use diagnostically, 85% of our patients had successful RA harvest with no ischemic postoperative complications after a normal Allen test. This finding suggests that it is safe to harvest the RA on the basis of a normal Allen test alone and is in agreement with Buxton's group [17, 25]. However in our series all Allen tests were conducted by a single senior surgeon, which may further enhance the reliability of this test. In addition our study demonstrates the value of the combined use of the Allen test and bilateral duplex scanning in maximizing the use of RA conduits in patients with an abnormal Allen test.

Based on these findings we have developed an algorithm to facilitate the maximal and safe use of radial artery conduits for CABG (Fig 3). We recommend that all patients with an abnormal Allen test should proceed to duplex ultrasonography for additional assessment of the forearm arterial system as this will maximize the use of the RA.



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  		Fig 3. Algorithm for the safe preoperative assessment of the collateral circulation before harvesting of the radial artery (RA) for coronary artery bypass graft surgery.

 
In conclusion the Allen test is a quick, easy, and reliable screening test before radial artery harvesting. Combination of clinical assessment with duplex ultrasonography affords safe maximal RA use.


   Acknowledgments
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
References
 
The authors would like to thank the Vascular Laboratory at the John Radcliffe Hospital for conducting the forearm duplex scanning and providing the images.


   References
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Acknowledgments
 References
 

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  9. Dipp M.A., Nye P.C., Taggart D.P. Phenoxybenzamine is more effective and less harmful than papaverine in the prevention of radial artery vasospasm. Eur J Cardiothorac Surg 2001;19:482-486.[Abstract/Free Full Text]
  10. Gaudino M, Glieca F, Luciani N, Alessandrini F, Possati G. Clinical and angiographic effects of chronic calcium channel blocker therapy continued beyond first postoperative year in patients with radial artery grafts: results of a prospective randomized investigation. Circulation 2001(Suppl I);104:I64–7
  11. Iaco A.L., Teodori G., Di Giammarco G., et al. Radial artery for myocardial revascularization: long-term clinical and angiographic results. Ann Thorac Surg 2001;72:464-469.[Abstract/Free Full Text]
  12. Denton T.A., Trento L., Cohen M., et al. Radial artery harvesting for coronary bypass operations: neurologic complications and their potential mechanisms. J Thorac Cardiovasc Surg 2001;121:951-956.[Abstract/Free Full Text]
  13. Greene M.A., Malias M.A. Arm complications after radial artery procurement for coronary bypass operation. Ann Thorac Surg 2001;72:126-128.[Abstract/Free Full Text]
  14. Allen E.V. Thromboangiitis obliterans: methods of diagnosis of chronic occlusive arterial lesions distal to the wrist with illustrative cases. Am J Med Sci 1929;178:237.
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  16. Jarvis M.A., Jarvis C.L., Jones P.R., Spyt T.J. Reliability of Allen's test in selection of patients for radial artery harvest. Ann Thorac Surg 2000;70:1362-1365.[Abstract/Free Full Text]
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