In vivo human lower extremity saphenous vein bypass grafts manifest flow mediated vasodilation

• Published in: Journal of vascular surgery 2009-11, Vol.50 (5), p.1063-1070
• Main Authors: Owens, Christopher D., MD, MSc, Wake, Nicole, BS, RVT, Conte, Michael S., MD, Gerhard-Herman, Marie, MD, Beckman, Joshua A., MD
• Format: Article
• Language: English
• Subjects: Administration, Oral; Biological and medical sciences; Blood and lymphatic vessels; Brachial Artery - diagnostic imaging; Brachial Artery - physiopathology; Cardiology. Vascular system; Cohort Studies; Diseases of the peripheral vessels. Diseases of the vena cava. Miscellaneous; Endothelium, Vascular - drug effects; Endothelium, Vascular - metabolism; Endothelium, Vascular - pathology; Endothelium, Vascular - transplantation; Enzyme Inhibitors - administration & dosage; Femoral Artery - physiopathology; Femoral Artery - surgery; Humans; Hyperemia - physiopathology; Infusions, Intravenous; Lower Extremity - blood supply; Medical sciences; Nitric Oxide - metabolism; Nitric Oxide Synthase Type III - antagonists & inhibitors; Nitric Oxide Synthase Type III - metabolism; Nitroglycerin - administration & dosage; omega-N-Methylarginine - administration & dosage; Peripheral Vascular Diseases - metabolism; Peripheral Vascular Diseases - physiopathology; Peripheral Vascular Diseases - surgery; Popliteal Artery - physiopathology; Popliteal Artery - surgery; Regional Blood Flow; Saphenous Vein - diagnostic imaging; Saphenous Vein - drug effects; Saphenous Vein - metabolism; Saphenous Vein - physiopathology; Saphenous Vein - transplantation; Surgery; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Time Factors; Treatment Outcome; Ultrasonography, Doppler; Vascular Patency; Vascular surgery: aorta, extremities, vena cava. Surgery of the lymphatic vessels; Vasodilation; Vasodilator Agents - administration & dosage
• ISSN: 0741-5214; 1097-6809
• DOI: 10.1016/j.jvs.2009.06.022

Objective As in arteries, venous endothelium modulates vessel homeostasis and tone. The effect of an arterialized environment on venous endothelial function remains poorly understood. In particular, regulation of saphenous vein graft (SVG) blood flow and lumen caliber remains undefined. We hypothesized that mature SVGs would exhibit endothelium-dependent, flow-mediated vasodilation (FMD). We further hypothesized that endothelium-derived nitric oxide (NO) was an important mediator. Methods Patients with femoral to popliteal artery SVGs that had maintained primary patency and were at least 1 year from surgery were enrolled. High-resolution, B-mode ultrasound scans were used to measure vein graft diameter before and 1 minute after reactive hyperemia (RH) to determine FMD. RH was created through application of 220 mm Hg to the calf for 5 minutes with a sphygmomanometric cuff. After a 10-minute recovery period, nitroglycerin-mediated, endothelium-independent vasodilation was measured 3 minutes after administration of nitroglycerin 0.4 mg sublingually. Brachial artery FMD was determined by validated techniques. L-NG monomethyl arginine (L-NMMA; 1 mg/kg infusion over 10 minutes) was used in a subset of patients (n = 6) to competitively inhibit endothelial NO synthase. Results Nineteen subjects were enrolled. The median age of the SVGs was 34.6 (21.0-49.7) months. SVG flow-mediated, endothelium-dependent vasodilation was measured at 5.28% ± 3.1% mean change in lumen diameter (range, 1.99%-9.36%; P < .0001 for diameter change). Nitroglycerin-mediated vasodilation was 3.7% ± 1.0%, (range, 16%-10.04%; P < .005). Intravenous administration of L-NMMA abolished SVG FMD (5.7 ± 1.4% before L-NMMA vs 0.01 ± 0.01% during L-NMMA infusion; P = .0088) and attenuated brachial artery FMD (7.54% ± 1.0% vs 5.7 ± 1.4; P = .05). Conclusion SVGs manifest flow-mediated, endothelium-dependent, and nitroglycerin-mediated endothelium-independent vasodilation. Vein graft endothelium-dependent FMD is likely mediated by NO. Further investigation will be required to determine the role of endothelial function in vein graft patency.