Flow-mediated dilation in lower-extremity vein grafts

Autogenous vein bypasses manifest a substantial late stenosis and occlusion rate due, at least in part, to the hostile conditions of the arterial mili eu. The present study was undertaken to evaluate flow-mediated dilation (FM D)-a putative measure of endothelial health and, potentially, long-term fun ction-in chronically implanted vein grafts performed for critical lower-ext remity ischemia. Eleven patients, four men, seven women (mean age: 64 +/- 1 4 years; range: 30 to 81 years), with saphenous vein bypasses performed for critical lower-extremity ischemia a mean of 346 +/- 457 days previously (r ange: 47 to 1640 days), had their grafts studied in the resting state, foll owing 5 minutes' tourniquet application to produce hyperemia, and following administration of nitroglycerin. Baseline and maximal postischemic brachia l artery and vein graft diameters were determined ultrasonographically. An Atherosclerosis Risk Score (ARS) was calculated by assigning one point for each of six established risk factors for atherosclerosis (smoking, diabetes , hypertension, hypercholesterolemia, male gender, and age >60 years). Vein graft flow and diameter increased significantly with hyperemia (20% +/- 23 %; p=0.04, and 3% +/- 3%; p=0.01 by paired t-test, respectively). Mean ARS was 3.6 +/- 1.2 (range: 2 to 5). FMD in vein grafts correlated inversely wi th ARS (r=-0.66, p=0.03). Seven of the 11 vein grafts demonstrated FMD grea ter than or equal to 1% of baseline diameter. No differences were observed between the seven patients with "reacting" grafts and four with '"non-react ing" grafts except in the mean ARS (2.9 +/- 0.9 vs. 4.3 +/- 0.5, respective ly, p=0.05) and in the frequency of diabetes (33% vs. 100%; p=0.05). Chronically implanted saphenous vein grafts performed for limb-threatening ischemia exhibit FMD, FMD in vein grafts appears to be influenced adversely by concurrent atherosclerotic risk factors, and is reduced compared to FMD reported in other vessels.