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MedWire News: Radial artery (RA) bypass conduits grafted to single coronary territories have better 5-year flow-mediated vasodilatory properties than do saphenous vein (SV) conduits, UK researchers report.
This “may at least partly explain the more favorable patency of RA grafts over SV grafts in aortocoronary bypass surgery,” say Carolyn Webb (Imperial College London) and colleagues.
For the study, the team measured the blood flow velocity and volumes of RA (n=15) or SV (n=12) conduits in 27 patients. All conduits were grafted to the native left circumflex heart territory 5 years previously.
The blood flow velocity and volume of each graft was calculated by Doppler and coronary angiography, before and after infusion with adenosine, acetylcholine, or isosorbide dinitrate.
The findings, published in the journal Circulation, show that at rest, RA grafts had a significantly smaller diameter but a larger blood flow velocity than SV grafts, at 2.6 versus 3.2 mm (p=0.029) and 16.9 versus 10.8 cm/second, respectively (p=0.008). Blood flow volumes were similar in both graft types.
RA grafts significantly dilated in response to adenosine and isosorbide nitrate by approximately 0.4 and 0.3 mm, respectively (p<0.05), but SV grafts did not, with diameter decreases of approximately 0.1 and 0.2 mm, respectively. Neither graft type significantly dilated when exposed to acetylcholine.
In addition, the blood flow volumes and velocities of RA and SV grafts increased by similar amounts in response to adenosine, acetylcholine, and isosorbide dinitrate, at 37 versus 35 ml/min, 6 versus 1 ml/min, and 30 versus 25 ml/min, respectively.
Webb and colleagues explain that these findings imply that “dysfunctional endothelium [which] is an initiator of atherosclerosis,” is most likely present in SV but not RA grafts.
They add: “Endothelial function is a predictor of coronary events in patients with coronary artery disease and is associated with short-term coronary graft performance.”
In a related commentary, Mark Slaughter (University of Louisville, Kentucky, USA) wrote that although these findings shed new light on the physiologic actions of different biologic conduits, they do not provide definite answers about the best choice of conduit for grafting.
He therefore advised: “The choice of radial artery versus saphenous vein should be individualized for each patient.”
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