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

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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.

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