The potential role of external venous supports in coronary artery bypass graft surgery†

Abstract

Despite the apparent superiority of arterial conduits for coronary artery bypass grafting (CABG), the long saphenous vein remains the most commonly used graft. The high failure rate of long saphenous vein grafts (SVGs) over time is therefore an important limiting factor for the long-term outcomes of CABG. Various methods to improve SVG patency have been proposed, although few have had a significant impact on clinical practice. External SVG supports have been a focus of research over the past 50 years, with their use intended to minimize well-documented pathophysiological changes that occur in the SVG following implantation into the coronary circulation. These devices have been trialled extensively in animal models to assess their impact on both the morphology and the function of vascular conduits. Recently, a number of studies have been conducted in patients, leading to a substantial development in their design and the accumulation of a large body of evidence attesting to their potential benefit in CABG. In this review, we briefly discuss the proposed mechanism of action of external SVG supports and then evaluate the results from animal studies and more recent research assessing their use in CABG patients. Finally, we conclude that newer models of external stents have the potential to improve long-term outcomes in SVG.

Twenty-Five Years of No-Touch Saphenous Vein Harvesting for Coronary Artery Bypass Grafting: Structural Observations and Impact on Graft Performance

“…A number of mechanisms have been identified that are suggested to explain the superior performance of SVs harvested by the NT technique [60] . Most mechanisms are related to preservation of the outer cushion of fat of the SV acting as 'natural support' and therefore sharing the same beneficial properties as those proposed for the various external stents described in the recent review by Mawhinney, Mounsey, and Taggart [58] , as seen in Figure 4 from Rueda et al, 2008 [36] , and Mawhinney et al, 2017 [58] .…”

“…outermost tissue removed (Rueda et al [36] , 2008). Insert, examples of DacronTM 'EXTENT' and 'VEST' external supports (Mawhinney et al [58] , 2017). B) An example of a no-touch (NT) harvested SV with external tissue intact (Rueda et al [36] , 2008).…”

“…B) An example of a no-touch (NT) harvested SV with external tissue intact (Rueda et al [36] , 2008). C) Angiogram of an SV with VEST at 12-month follow-up (Mawhinney et al [58] , 2017). D) NT SV harvesting prevents kinking of excessively long graft (Rueda et al [36] , 2008).…”

“…More recently, an external support made from braided cobalt-chromium-nickel-molybdenum-iron alloy fibers [55][56][57] has been tested. Based on the results from animal studies, a recent review discusses the proposed mechanisms of action of external SV supports in CABG patients [58] . For example, studies into the effect of external synthetic stents and sheaths in a pig model of vein into artery interposition grafting suggest that this form of support has a profound effect on vein graft remodelling and thickening.…”

“…Disappointingly, when the results of the 'EXTENT' randomized trial on a small number of CABG patients were analysed, all 'EXTENTED' grafts were thrombosed whereas all LIMA grafts and non-stented SVGs remained patent [51] . The most recent encouraging data for external vein supports describes the use of braided durable, kink-resistant 'VEST' external stents made of plastically deformable cobalt-chrome wires [58] . Here, the placement of VESTs resulted in a significant decrease in mean intimal-medial area with a small decrease in intimal thickness between the stented and control groups.…”