Increased Contractile Function of Human Saphenous Vein Grafts Harvested by “No-Touch” Technique

Abstract

Saphenous vein grafts are the most common conduits used for coronary artery bypass grafting (CABG); however, no more than 60% of vein grafts remain open after 10 years and graft failure is associated with poor clinical outcome. The “no-touch” harvesting technique—where a sheet of perivascular tissue is retained around the vein—improves graft patency to over 80% after 16 years of follow-up, but the mechanism for the improved patency rate is unclear. In this study, we investigated acute functional differences between vein grafts harvested conventionally and by “no-touch” technique and explored the importance of perivascular tissue for reducing surgical trauma, minimizing excessive distension, and releasing vasoactive paracrine factors. Segments of human saphenous veins were obtained from CABG surgery and their functional properties investigated by isometric and isobaric myography. We found a broad diameter-tension relationship for human saphenous veins, with peak capacity for active tension development at diameters corresponding to transmural pressures around 60 mmHg. Across the investigated transmural pressure range between 10 and 120 mmHg, maximal tension development was higher for “no-touch” compared to conventionally harvested saphenous veins. Contractile responses to serotonin, noradrenaline, and depolarization induced with elevated extracellular [K+] were significantly larger for saphenous veins harvested by “no-touch” compared to conventional technique. Conventional vein grafts are routinely pressurized manually in order to test for leaks; however, avoiding this distension procedure did not change the acute contractile function of the conventionally excised saphenous veins. In contrast, even though surgical removal of perivascular tissue during conventional harvesting was associated with a substantial decrease in force development, removal of perivascular tissue by careful dissection under a stereomicroscope only marginally affected contractile responses of veins harvested by “no-touch” technique. In conclusion, we show that saphenous veins harvested by “no-touch” technique have greater contractile capacity than veins harvested by conventional technique. The different capacity for smooth muscle contraction is not due to vasoactive substances released by the perivascular tissue. Instead, we propose that the larger tension development of saphenous veins harvested by “no-touch” technique reflects reduced surgical damage, which may have long-term consequences that contribute to the superior graft patency.

Saphenous Vein Vasa Vasorum as a Potential Target for Perivascular Fat-Derived Factors

“…Such issues may be difficult to address when using organ bath studies as described by Yamada et al [ 1 ] and others [ 4 , 6 , 7 ] , but they may perhaps be elucidated using the myograph preparation, although this is technically more challenging. In fact, using this technique, Vestergaard et al [ 44 ] showed a tendency toward improved vasorelaxation of NTSV compared to CTSV ( Figure 3 ), but this improvement was just below statistical significance. However, as some NTSVs examined were manually distended (no details provided) and some were not distended, it is not clear if both distended and non-distended NTSVs were analysed together as one group.…”

“…The vein grafts (n = 13-14) were stretched to an internal diameter corresponding to a transmural pressure of 20 or 100 mmHg, pre-contracted with 10 µM serotonin, and exposed to 10 µM methacholine. It is acknowledged that this diagram is from the Open Access article Vestergaard et al [ 44 ] , 2018. PVT=perivascular tissue.…”

Clinical Outcomes After Surgical Revascularization Using No-Touch Versus Conventional Saphenous Vein Grafts: Mid-Term Follow-Up of Propensity Score Matched Cohorts

“…2,5À7 Histological and immunohistochemical studies have demonstrated improved integrity of endothelium and smooth muscle cells. 8,9 Furthermore, NT-SVGs have been shown to preserve contractile function in contrast to C-SVGs in myographic studies. 10 A recent network meta-analysis of randomized controlled trials comparing patency of second conduit grafts encouraged the use of NT-SVGs over arterial grafts.…”

Stable Hemodynamics within “No-Touch” Saphenous Vein Graft

“…6) Previous study showed "no-touch" harvest vein grafts presented with tone regulation on the vascular wall in vitro. 7) However, little is known about its altered vasomotor performance in vivo experiment and consequences of different vein harvest techniques for vasomotor development after intraluminal administration of anti-spastic medication have not been previously evaluated. We proposed that higher baseline blood flow and less dynamic fluctuations were associated with the superior anti-spastic and distension-tolerant function of "no-touch" vein grafts in CABG surgery.…”