Does Periadventitial Fat-Derived Nitric Oxide Play a Role in Improved Saphenous Vein Graft Patency in Patients Undergoing Coronary Artery Bypass Surgery?

Abstract

Background/Aims: The saphenous vein is commonly used for coronary artery bypass surgery but its patency is poor. Vascular damage occurs during conventional surgery. However, patency improves when the graft is harvested with minimal surgical trauma, partly due to preservation of vascular endothelial nitric oxide synthase (eNOS) and tissue sources of nitric oxide (NO), a factor possessing both dilatory and anti-proliferative properties. Apart from these grafts exhibiting an intact luminal endothelium they are harvested complete with a surrounding cushion of tissue, much of which is fat. Methods: Immunostaining for eNOS was performed on vein graft sections and reverse-transcriptase polymerase chain reaction and Western blotting were used to identify eNOS mRNA and protein. NO synthase activity was measured using the citrulline assay. Results: Immunohistochemistry identified eNOS staining of vein graft segments, including dense staining of the cushion of perivascular fat and associated structures surrounding the vein. eNOS protein was confirmed in both the vein and surrounding fat by Western blot analysis. Using the citrulline assay, the perivascular fat and underlying vein possessed comparable NO synthase activity. Conclusions: Our observations suggest that perivascular fat-derived NO plays a beneficial role in saphenous veins harvested atraumatically and used as grafts in patients undergoing coronary artery bypass surgery.

Vascular Reactivity and Flow Characteristics of Radial Artery and Long Saphenous Vein Coronary Bypass Grafts

“…Conduit harvesting is known to damage the endothelium and may reduce endothelial nitric oxide synthase and nitric oxide release 24,25 ; however, careful surgical technique may minimize endothelial damage of coronary conduits. 26,27 Shear stress is also known to affect graft endothelial function, and reducing shear stress during graft preparation may preserve endothelial integrity. 24,28 Details of the harvesting techniques used in the RSVP trial have been published previously.…”

Effects of Removing the Adventitia on the Mechanical Properties of Ovine Femoral Arteries In Vivo and In Vitro

“…30 In addition, Dashwood et al reported that perivascular fat-derived nitric oxide had a beneficial role in vein grafts that had been atraumatically harvested. 31 Finally, Souza et al 32 demonstrated that harvesting saphenous vein to be used in coronary bypass with its intact adventitia and surrounding tissues was associated with high short-and long-term patency rates of the venous grafts. Consequently, nowadays several authors propose the use of a "non-touch" technique during venous procurement to avoid (a) adventitial disruption that occurs when conventional harvesting techniques are used, and (b) the detrimental changes on the venous graft's function.…”

Adipoparacrinology: an Emerging Field in Biomedical Research

“…Second, echocardiography, computer tomography, magnetic resonance imaging (MRI) and other non-invasive imaging of heart-and artery-associated adipose tissue may identify the high-risk population susceptible to metabolic syndrome (30) and atherosclerosis (41,42) and monitor vascular wall changes during follow-up studies and therapeutic trials. Third, the "non-touch harvesting technique" is an example of appreciation of adipoparacrinology in coronary artery bypass surgery (43,44). Fourth, PAAT/tunica adiposa may represent a new therapeutic target (2, 3, 12, 24, 31-33), in artery bypass surgery also (45).…”