INVITED COMMENTARY

Abstract

Coronary artery bypass grafting (CABG) with saphenous vein conduits is one of the most commonly performed surgical procedures worldwide. Unfortunately, saphenous vein graft patency is only 50% at 10 years. As a result, there has been a growing interest in the use of arterial conduits, particularly the radial artery (RA), as excellent midterm patency results of more than 90% have been reported. Nevertheless, concerns have been raised about decreased blood flow to the hand with potential morbidity after RA harvesting. This paper by Knobloch and colleagues describes a novel combined laser-Doppler flowmeter system that can be used to measure palmar microcirculation in attempts to avoid ischemic complications of the hand. Palmar circulation was evaluated using the laser-Doppler flowmeter before and 2 days after RA harvesting. Patients were tested for either complete suprasystolic occlusion of the brachial artery or alternate occlusion of the radial and ulnar arteries. As expected, changes in both blood flow and tissue oxygenation saturation decreased with various occlusive maneuvers. After RA harvest, tissue flows and saturations were the same as for the nondonor hand. This “proof-of-concept” study is small with only 15 patients, all of whom were less than 60 years of age. One wonders how well this system would work in the elderly, smoking, or diabetic population with small vessel occlusive disease. By including more patients and then applying a subgroup analysis, the authors might have answered this question. The Allen test is simple and safe, and is performed commonly to assess palmar circulation. Unfortunately, the authors make no mention of whether concomitant Allen testing was performed in any of these patients. Furthermore, there are no comparative results or descriptions of how the device might be more reliable than the Allen test. Correlation with the laser-Doppler flowmeter system would have been interesting and would have validated the utility. Nevertheless, one of the more interesting points of the paper was that despite reduction in palmar blood flow and tissue oxygen saturation with RA harvesting, 2 days postoperatively both tissue oxygen saturation and blood flow were not reduced compared with the other hand and, more importantly, compared with preoperative values. Potential mechanisms might include increased compensatory blood flow from the remaining artery or the opening of small collaterals within the palmar arch hand. This finding raises a critical point in the use of this new technology. Should decreases in blood flow and tissue oxygen saturation be disregarded as they return to baseline 2 days after RA harvest, or is there some dangerous threshold before RA harvesting that can be detected by this new method? In summary, further work will need to include a wider patient population to determine whether this technology can add more clinical information for patients whose RA is harvested. Moreover, will this device predict and detect who may have postoperative ischemic complications? This important question must be answered before surgeons can conclude that the laser-Doppler flowmeter will add functional information that goes beyond the Allen test.