Reply to the Editor:

Abstract

I thank Drs Peng and Sarkar for their comments regarding the importance of awareness of radial artery (RA) anomalies when considering harvesting the conduit for coronary artery bypass grafting. Although the incidence of RA anomalies reported by McCormack and colleagues1McCormack L.J. Cauldwell E.W. Anson B.J. Brachial and antebrachial arterial patterns. A study of 750 extremities.Surg Gynecol Obstet. 1953; 96: 54Google Scholar in a study of 750 cadaveric limbs was on the order of 18%, most of these were due to high origin of the RA from the axillary (11.5%) or brachial artery (77%). In contrast, the anomaly reported in our study, an abnormally low origin of the RA behind the pronator teres muscle, is rare, with a prevalence of probably less than 0.01%. McCormack and colleagues1McCormack L.J. Cauldwell E.W. Anson B.J. Brachial and antebrachial arterial patterns. A study of 750 extremities.Surg Gynecol Obstet. 1953; 96: 54Google Scholar and Weathersby2Weathersby H.T. Anomalies of brachial and antebrachial arteries of surgical significance.South Med J. 1956; 49: 46-49Crossref PubMed Scopus (29) Google Scholar encounter this form of anomaly in a total of 1158 limbs studied. In the anomaly that we have reported, the full length of the RA, albeit shorter than normal, can still be harvested by dividing the pronator teres and following the artery behind the muscle up to its origin from the brachial artery. Faced with a shortened conduit, one solution would be to alter the grafting strategy by grafting the conduit to a more proximal coronary lesion, such as a proximal stenosis in the diagonal artery, or by anastomosing the proximal end of the RA to the internal thoracic artery as a T, inverted T, or Y graft.3Tashiro T. Nakamura K. Iwakuma A. Zaitu R. Iwahashi H. Murai A. et al.Inverted T graft: novel technique using composite radial and internal thoracic arteries.Ann Thorac Surg. 1999; 67: 629-631Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar Alternatively, the shortened graft can be used in a horseshoe anastomotic configuration with the internal thoracic artery.4Aguero O.R. Navia J.L. Navia J.A. Mirtzouian E. A new method of myocardial revascularization with the radial artery.Ann Thorac Surg. 1999; 67: 1817-1818Abstract Full Text Full Text PDF PubMed Scopus (14) Google Scholar Of more importance are the anomalies of RA or ulnar artery aplasia and incomplete superficial (13% of 650 dissected hand specimens) or deep palmar (3% of 200 dissected hand specimens) arches.5Coleman S.S. Anson B.J. Arterial patterns in the hand based upon a study of 650 specimens.Surg Gynecol Obstet. 1961; 113: 409-424PubMed Google Scholar In most of these cases of anatomic forearm and hand anomalies, a modified Allen test should allow detection of the vascular insufficiencies. With a cutoff point of 5 seconds, the modified Allen test has sensitivity and specificity of 65.8% and 81.6%, respectively, with a diagnostic accuracy of 80%.6Jarvis 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: 1362-1365Abstract Full Text Full Text PDF PubMed Scopus (121) Google Scholar With a cutoff limit longer than 6 seconds, the modified Allen test has a poorer sensitivity of 54.5%, a better specificity of 91.7%, and a somewhat lower diagnostic accuracy of 78%.6Jarvis 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: 1362-1365Abstract Full Text Full Text PDF PubMed Scopus (121) Google Scholar I therefore recommend using a cutoff point of 5 seconds. The presence of a more proximally arising superficial palmar branch of the RA, however, may yield a false-negative result. To avoid such a false-negative result, I recommend performing the modified Allen test with three fingers to occlude the RA and ulnar artery, as shown in Figure 1. This modification, which is commonly performed in our unit, ensures occlusion of a proximally arising superficial palmar branch from the RA. Various other methods have been reported to improve diagnostic accuracy, such as digital plethysmography to measure pulse-volume recording or digital-brachial index, duplex Doppler ultrasonography with dynamic Doppler, or arteriography to assess anatomy and flow. A simple intraoperative assessment of sufficiency of ulnar collateralization of the palmar circulation is to check the distal stump pressure or to feel for a pulse when occluding the proximal RA with a bulldog vascular clamp before division of the RA. Because the prevalence of clinically relevant RA and ulnar artery anomalies is probably less than 0.01%, the routine use of arteriography is not recommended. A properly performed modified Allen test, with or without digital plethysmography supplemented by duplex Doppler ultrasonography in marginal cases, may be sufficient to detect vascular anomalies that are relevant. The addition of intraoperative stump pressure assessment should further help to reduce the incidence of postoperative hand ischemia.