Is the Allen's test adequate to safely confirm that a radial artery may be harvested for coronary arterial bypass grafting
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《血管的通路杂志》
Is the Allen's test adequate to safely confirm that a radial artery may be harvested for coronary arterial bypass grafting
Andrew Ronald, Anish Patel, Joel Dunning,
a Department of Cardiac Anaesthesia, Aberdeen Royal Infirmary, Aberdeen, AB25 2ZN, UK
b Department of Cardiothoracic surgery, Freeman Hospital, Newcastle-upon-Tyne, UK
c Department of Cardiothoracic Surgery, James Cook University Hospital, Middlesbrough, UK
Abstract
A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether the Allen's test, plethysmography, Doppler ultrasound or MRI imaging was the best method of assessing the presence of adequate collateral blood flow in the arm preoperatively prior to radial artery harvest for conduits during CABG surgery. Altogether 176 papers were identified using the reported search of which 15 represented the best evidence on the topic. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses were tabulated. We conclude that whilst there are theoretical limitations with the Allen's test, for most patients it is an adequate method of assessing collateral arm flow prior to radial artery harvest and several large studies have confirmed the absence of neurological and vascular adverse outcome with a modified Allen's test cut-off point of up to 12 s. However, if there are concerns about collateral flow then a second confirmatory test such as dynamic Doppler ultrasound or measurement of digital pressure changes with radial artery occlusion can also be used prior to harvest. Newer techniques such as Gadolinium-enhanced magnetic resonance angiography have also been described to confirm adequate collateral circulation prior to radial artery harvest for CABG conduit and whilst in time they might come to represent an ultimate ‘gold standard’ they are clearly too expensive and impracticable for everyday use.
Key Words: Allen's test; Radial artery
1. Introduction
A best evidence topic was constructed according to a structured protocol. This protocol is fully described in the ICVTS [1].
2. Clinical scenario
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.
3. Three-part question
In patients undergoing CABG surgery using radial artery grafts, is the Allen's test, plethysmography, Doppler ultrasound or MRI imaging the best method of assessing ulnar artery or collateral flow.
4. Search strategy
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.]
5. Search outcome
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.
6. Results
Definitions of hand/forearm ischaemia are subjective and variable but are low in patients with ‘normal’ Allen's tests. Agrifoglio [7] 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 [5], Ruenaskulrach [6], Starnes [8] and Abu-Omar [9] report no ischaemic sequelae when using an Allen's test to guide suitability for RA harvest. The paper by Meharwal [10] 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 [2] 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 [3] 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 [4] 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 [5] 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 [6] 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 [8] 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 [9] 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 [11] 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 [14] 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 [15] 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 [8] 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 [16] 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.
7. Clinical bottom line
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.
References
Dunning J, Prendergast B, Mackway-Jones K. Towards evidence-based medicine in cardiothoracic surgery: Best BETS. Interactive CardioVasc Thorac Surg 2003;2:405–409.
Glavin RJ, Jones HM. Assessing collateral circulation in the hand – four methods compared. Anaesthesia 1989;44:594–595.
Johnson WH 3rd, Cromartie RS 3rd, Arrants JE, Wuamett JD, Holt JB. Simplified method for candidate selection for radial artery harvesting. Ann Thorac Surg 1998;65:1167.
Jarvis MA, Jarvis CL, Jones PR, Spyt TJ. Reliability of Allen's test in selection of patients for radial artery harvest. Ann Thorac Surg 2000;70:1362–1365.
Sajja LR, Mannam G, Sompalli S. Is Allen's test not reliable in the selection of patients for radial artery harvest (letter) Ann Thorac Surg 2002;74:296.
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. J Thorac & Cardiovasc Surg 2001;121:526–531.
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 Ann Thorac Surg 2005;79:570–572.
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. J Thorac & Cardiovasc Surg 1999;117:261–266.
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. Ann Thorac Surg 2000;77:116–119.
Meharwal ZS, Trehan N. Functional status of the hand after radial artery harvesting: Results in 3977 cases. Ann Thorac Surg 2001;72:1557–1561.
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. J Vasc Technol 1998;22:187–191.
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. J Thorac & Cardiovasc Surg 1996;112:737–744.
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. Eur J Cardiothorac Surg 2001;19:135–139.
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. J Vasc Technol 1998;22:23–29.
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. Am Heart J 2004;147:489–493.
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. Investigat Radiol 2001;36:501–508.(Andrew Ronald, Anish Pate)
Andrew Ronald, Anish Patel, Joel Dunning,
a Department of Cardiac Anaesthesia, Aberdeen Royal Infirmary, Aberdeen, AB25 2ZN, UK
b Department of Cardiothoracic surgery, Freeman Hospital, Newcastle-upon-Tyne, UK
c Department of Cardiothoracic Surgery, James Cook University Hospital, Middlesbrough, UK
Abstract
A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether the Allen's test, plethysmography, Doppler ultrasound or MRI imaging was the best method of assessing the presence of adequate collateral blood flow in the arm preoperatively prior to radial artery harvest for conduits during CABG surgery. Altogether 176 papers were identified using the reported search of which 15 represented the best evidence on the topic. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses were tabulated. We conclude that whilst there are theoretical limitations with the Allen's test, for most patients it is an adequate method of assessing collateral arm flow prior to radial artery harvest and several large studies have confirmed the absence of neurological and vascular adverse outcome with a modified Allen's test cut-off point of up to 12 s. However, if there are concerns about collateral flow then a second confirmatory test such as dynamic Doppler ultrasound or measurement of digital pressure changes with radial artery occlusion can also be used prior to harvest. Newer techniques such as Gadolinium-enhanced magnetic resonance angiography have also been described to confirm adequate collateral circulation prior to radial artery harvest for CABG conduit and whilst in time they might come to represent an ultimate ‘gold standard’ they are clearly too expensive and impracticable for everyday use.
Key Words: Allen's test; Radial artery
1. Introduction
A best evidence topic was constructed according to a structured protocol. This protocol is fully described in the ICVTS [1].
2. Clinical scenario
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.
3. Three-part question
In patients undergoing CABG surgery using radial artery grafts, is the Allen's test, plethysmography, Doppler ultrasound or MRI imaging the best method of assessing ulnar artery or collateral flow.
4. Search strategy
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.]
5. Search outcome
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.
6. Results
Definitions of hand/forearm ischaemia are subjective and variable but are low in patients with ‘normal’ Allen's tests. Agrifoglio [7] 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 [5], Ruenaskulrach [6], Starnes [8] and Abu-Omar [9] report no ischaemic sequelae when using an Allen's test to guide suitability for RA harvest. The paper by Meharwal [10] 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 [2] 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 [3] 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 [4] 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 [5] 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 [6] 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 [8] 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 [9] 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 [11] 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 [14] 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 [15] 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 [8] 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 [16] 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.
7. Clinical bottom line
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.
References
Dunning J, Prendergast B, Mackway-Jones K. Towards evidence-based medicine in cardiothoracic surgery: Best BETS. Interactive CardioVasc Thorac Surg 2003;2:405–409.
Glavin RJ, Jones HM. Assessing collateral circulation in the hand – four methods compared. Anaesthesia 1989;44:594–595.
Johnson WH 3rd, Cromartie RS 3rd, Arrants JE, Wuamett JD, Holt JB. Simplified method for candidate selection for radial artery harvesting. Ann Thorac Surg 1998;65:1167.
Jarvis MA, Jarvis CL, Jones PR, Spyt TJ. Reliability of Allen's test in selection of patients for radial artery harvest. Ann Thorac Surg 2000;70:1362–1365.
Sajja LR, Mannam G, Sompalli S. Is Allen's test not reliable in the selection of patients for radial artery harvest (letter) Ann Thorac Surg 2002;74:296.
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. J Thorac & Cardiovasc Surg 2001;121:526–531.
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 Ann Thorac Surg 2005;79:570–572.
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. J Thorac & Cardiovasc Surg 1999;117:261–266.
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. Ann Thorac Surg 2000;77:116–119.
Meharwal ZS, Trehan N. Functional status of the hand after radial artery harvesting: Results in 3977 cases. Ann Thorac Surg 2001;72:1557–1561.
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. J Vasc Technol 1998;22:187–191.
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. J Thorac & Cardiovasc Surg 1996;112:737–744.
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. Eur J Cardiothorac Surg 2001;19:135–139.
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. J Vasc Technol 1998;22:23–29.
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. Am Heart J 2004;147:489–493.
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. Investigat Radiol 2001;36:501–508.(Andrew Ronald, Anish Pate)