In vivo early and mid-term flow-mediated endothelial function of the radial artery used as a coronary bypass graft.

Objectives: We sought to evaluate the in vivo endothelial function of the radial artery (RA) used as a coronary graft.

Background: The RA is becoming a recognized alternative coronary bypass conduit. In vivo endothelial function is a possible predictor of long-term performance.

Methods: Sixty consecutive patients underwent coronary artery bypass graft surgery (CABG); all received RA and left internal mammary artery (LIMA) grafts. Three weeks after CABG, 36 patients underwent angiography under basal conditions, during pacing and after intragraft injection of glyceryl trinitrate (GTN). Angiography was repeated at six months in 20 patients.

Results: The estimated mean difference of 66 segments of the radial graft on the first QCA study was 0.170 mm (95% confidence interval [CI] 0.101 to 0.258, p < 0.001) between baseline and pacing, and 0.310 mm (CI 0.225 to 0.401, p < 0.001) between baseline and GTN. At six months, the differences between baseline and pacing and baseline and GTN were 0.112 mm (CI 0.062 to 0.162, p < 0.001) and 0.274 (CI 0.192 to 0.353, p < 0.001), respectively. The difference between baseline values at three weeks and six months was 0.416 mm (CI 0.236 to 0.603, p < 0.001). In the LIMA segments, the difference between baseline and pacing and baseline and GTN were 0.206 mm (CI 0.136 to 0.278, p < 0.001) and 0.304 mm (CI 0.213 to 0.396, p < 0.001), respectively. At six months, the differences between baseline and pacing and baseline and GTN were 0.098 mm (CI 0.014 to 0.173, p < 0.001) and 0.218 mm (CI 0.130 to 0.298, p < 0.001). The difference between baseline values at three weeks and six months was 0.061 mm (CI 0.064 to 0.176, p > 0.05).

Conclusions: In vivo flow-mediated dilation of the RA is comparable to that of pedicled LIMA. The increased dilation both at baseline and after pacing at six months represents a time-related improvement in the vasomotor function of the RA, which could have implications for its performance as a coronary conduit.