The Use of Preoperative Noninvasive Vascular Studies for the Evaluation of Radial Artery Conduits for Coronary Artery Bypass Grafting

Abstract

Background: The increased use of the radial artery for coronary artery bypass conduits has heightened the awareness of potential resultant hand ischemia. The Allen test and subsequent modifications have been used to evaluate the patency of the superficial palmar arch (SPA). The purpose of this study was to determine if changes in blood flow patterns of the SPA assessed by the modified Allen test parallel changes in blood pressures of the first and second digits following radial artery occlusion. Methods: Continuous-wave Doppler ultrasound and photoplethysmography (PPG) were used to evaluate blood flow in the SPA and first and second digits, respectively, before and after manual occlusion of the radial artery in 60 extremities. A second continuouswave Doppler probe was used to ensure complete occlusion of the radial artery. Digit skin temperature was controlled between 36° and 37.5°0. A reduction of >20 mmHg in blood pressure was arbitrarily chosen to reflect a clinically significant change in digit arterial pressure. Results: Six of the 60 extremities (10%) studied showed a decrease in the audible Doppler signal over the SPA following radial artery occlusion. Reduction in digit arterial pressure following radial artery occlusion occurred in 13 of 60 extremities (21.7%). Digit arterial pressure reductions ranged from 20 to 58 mmHg (mean ±SD, 35.2 ±12.8 mmHg), demonstrating a 40% decrease in digital pressure. Changes in SPA flow did not parallel digital pressure changes following occlusion of the radial artery. Conclusion: Continuous-wave Doppler ultrasound of the SPA following radial artery compression alone does not accurately predict digit ischemia. Digit arterial pressure measurement of the first and second digits of upper extremities offers a relatively simple and objective method for evaluation of potential ischemic complications following radial artery harvest. This finding is important because many physicians only use a modified Allen test with radial artery compression to assess potential digit ischemia.

Noninvasive evaluation of hand circulation before radial artery harvest for coronary artery bypass grafting

“…[9][10][11][12] Previous work from our laboratory has demonstrated poor correlation of the modified Allen's test to predict a decrease in digit pressure with RA compression in healthy volunteers. 5 Fifty percent of extremities with an abnormal modified Allen's test had a digit ∆P of less than 40 mm Hg with RA compression in this study. Therefore these patients would have been unnecessarily excluded from RA harvest for CABG based on the modified Allen's test.…”

“…A likely explanation for the high false-positive and false-negative rates for the modified Allen's test compared with digit pressure measurements may relate in part to the difficulty of accurately insonating the SPA with a continuous wave Doppler probe. 5 Similar audible Doppler signals may be obtained from the superficial palmar arch, deep palmar arch, common digital arteries, and the deep interosseus branch of the ulnar artery. Interpretation of changes in Doppler signals in these vessels during RA compression is potentially misleading.…”

“…3,4 Shortcomings of the Allen's test have been recognized. 5 The assessment of digit pressures with RA compression may represent a more objective test for determining collateral hand circulation. The purpose of this study was to compare the modified Allen's test with digit pressure measurements before and during RA compression in patients undergoing preoperative evaluation for RA harvesting.T he radial artery (RA) conduit for coronary artery bypass grafting (CABG) was introduced by Carpentier and colleagues in 1973.…”