All or Nothing Saphenous Vein Graft Harvesting

SVGs are indispensable to CABG surgery and provide diverse advantages including: emergent ease of access, shorter harvesting times, and sufficient length to bypass multiple distal coronary targets.2 Additionally, clinical factors (i.e., advanced age) or emergent surgical interventions (i.e., aortic root or valve surgery requiring conduit to bypass acutely occluded coronary arteries) highlight situations where SVGs are suitable and readily available for immediate harvesting.2

Vascular Injury and Barotrauma

Clinical laboratory studies have demonstrated that damage to conduits during vessel harvesting and preparation influences both short and long-term patency.2,6 Traditional endoscopic vein harvesting (EVH) use of carbon dioxide (CO2) insufflation to maintain tunnel visualization has been shown to promote unfavorable local and systemic environments.10 The closed tunnel EVH permits passive systemic absorption of CO2, resulting in hypercarbia and tissue acidosis.10 The external pressurized CO2 (12-15 mmHg of insufflation) and endoscopic dissection further introduces extravascular stresses that could lead to detrimental changes in conduit integrity.10 Additionally, common SVG preparation consists of stripping vein conduits of its adventitial layer and vessel distention to overcome vascular spasms.6 The vascular manipulation and mechanical stress from these techniques can result in both intimal and luminal wall damage, predisposing the conduit to possible remodeling and accelerated intimal hyperplasia.6,11

To avoid vascular insult, the development of “ no-touch” saphenous vein harvesting was introduced.11 This technique involves harvesting a SVG pedicle (open harvesting, encompassing the saphenous vein and intact surrounding perivascular tissue), without direct vessel contact, which reduces vascular spasms and need for repeated pressure distention.11 The reduction of vascular distention decreases barotrauma and preserves luminal endothelium, retaining local nitric-oxide levels and slowing the development of intimal hyperplasia.2 Preservation of the perivascular tissue provides external structural support to prevent conduit kinking (preventing accelerated intimal hyperplasia and subsequent atherosclerosis) and retention of the vasa vasorum (retaining vessel wall perfusion and reduced ischemic damage).2 Perivascular adipose tissues anticontractile factors (i.e., nitric oxide, leptin) may also provide additional anti-spasmatic properties to preserve graft patency, which can significantly benefit patients with poor coronary anatomy (i.e., small coronary artery targets with poor distal runoff).2

Figure 1. Histological, cellular, and ultrasound comparison of no-touch (NT) and conventional (C) saphenous vein graft harvesting.

Upper panel: Transverse NT vs. C saphenous vein that were prepared for coronary artery bypass surgery. NT intima is thrown into folds around the lumen (L), vein wall media remains thick with smooth muscle cells, and intact adventitia (red arrow indicating vasa vasorum). C intima folds are absent with a thinner media wall secondary to distention, and absence of adventitia due to its removal. Lower panel: Damage comparison in NT vs. C saphenous vein. Panel A (NT) shows an intact endothelial lining, compared to D (C) minimal lining. Panel B (NT) shows uniformly shaped and distributed smooth much versus E (C) variable smooth muscle distribution. Panel C (NT) displays intact vasa vasorum (Arrow-lumens), while F (C) shows only remnants of this layer.12

Optimizing Conduit Patency Rates

CABG surgery continues to be the most common procedure performed in adult cardiac surgery and remains the standard of care for patients with complex coronary artery lesions.5,13 The weak point of this procedure remains to be the limited long-term patency rates of saphenous vein grafts.5,14 Alternative conduits, such as arterial grafts, have been investigated in the literature. Gaudino et al. literature review of six randomized, controlled trials analyzing the long-term (>2 years) outcomes among patients that were randomly assigned to undergo either radial artery (RA) grafting or SVG to supplement the LIMA graft during isolated CABG surgery, found that longterm patency rates and mortality benefits were more commonly seen among RA conduits.7 Even with supportive evidence favoring arterial grafts, limitations for their use still exist: prolonged harvesting time, increased bleeding, limited graft length, compromised collateral flow leading to ischemia, limiting graft durability secondary to severe peripheral arterial disease, graft spasms, delayed sternal healing, and diminished post-operative motor and/or sensory strength surrounding anatomic harvest site.6,15,16 With these benefits and limitation considered, the long saphenous vein remains the preferred conduits in CABG surgery.11,15 Saphenous vein’s superficial anatomical position expedites harvesting time, decreases the incidence of bleeding, and provides adequate length to bypass multiple distal culprit lesions, which makes this conduit essential to CABG surgery.2,13,14

Harvesting of the saphenous veins can be performed by direct visualization (open-harvest) or by minimally invasive EVH.13 Open harvest allows for quicker access and shorter harvesting time with direct visualization and mobilization of the saphenous vein.13 Due to the large open incision, this technique incurs a greater risk for wound complications and possible increase in length

of hospital stay.13 EVH’s minimally invasive approach has abundant evidence to support its improved wound-related outcomes due to its minimal incisional approach, with comparable “short-term” patency rates to open-harvest techniques.13,15 Kodia et al. systematic review evaluating “long-term” patency (>1 year) rates in patients that underwent CABG surgery (n=18,131) with either open (n=10,873) or endoscopic SVG harvesting (n=7,258) found graft patency beyond one year was significantly higher among open saphenous vein harvest as compared to EVH (Open 82.3% versus EVH 75.1%, OR 0.61 (CI, 0.43-0.87), P=0.01).13

Among clinical trials, the Randomized Endovein Graft Prospective (REGROUP) multicenter, randomized clinical trial (n=1150) investigated saphenous vein graft harvesting techniques (Open (n=574) versus EVH (n=576)) effect on long-term adverse cardiac events (death from any cause, nonfatal myocardial infarction, repeat revascularization).17 The REGROUP clinical trial accounted for harvester experience and techniques in order to limit variability.17 Expert endoscopic veingraft harvesters were required to have a minimal of >100 EVH cases, certified low conversion rate (<5%) to open harvesting, and > 2-year experience to participate.17 The results of the study ultimately found that the risk of major cardiac events between open and endoscopic SVG harvesting were not significantly different (Open 15.5% versus EVH 13.9%, hazard ratio 1.12, (CI, 0.83-1.51), P=0.47).17 Both large-scale systematic review and clinical trial suggest that open SVG harvesting confer similar clinical outcomes and long-term patency as EVH among patients undergoing CABG surgery 13, 17 To further optimize open saphenous vein harvesting, utilization of the “ no-touch” pedicle technique could possibly provide additional multifactorial benefits and prolong long-term SVG patency rates.2,16

Figure 2: Endoscopic versus open saphenous vein harvesting approach

Left panel is a transverse section of saphenous vein prepared with endoscopic vein harvesting (EVH). Arrow indicating intimal damage/tearing. Middle panel to the left shows EVH incisional access. Middle panel to the right shows the extended incision utilized for both open and NT harvesting. Right panel is a transverse section of NT harvested saphenous vein with intact and undamaged vascular layers.12

Extending Conduit Harvesting Choices

The long-term patency of SVG remains a major challenge in cardiothoracic surgery and various harvesting techniques reviewed in the medical literature shows great promise addressing this issue.6 Kodia et al. investigation of 18,131 patients undergoing CABG with either open or EVH techniques highlighted the benefits of open harvesting and the positive effect on long-term SVG patency.13 Open saphenous vein harvesting provides ease of access and shorter harvesting time that can prove to be beneficial in emergent situations.2 With the addition of “ no-touch” saphenous vein harvesting to existing open-harvest techniques, superior long-term SVG patency rates could possibly be achieved.

Early medical literature from Souza et al. mirrored these benefits in their 2006 randomized longitudinal clinical trial comparing graft patency among conventional (n=52, SVG harvested with vein stripping, distention, and stored in normal saline) and no-touch harvesting (n=52, SVG removed with surrounding peri-vascular tissue, not distended, and stored in heparinized blood).6 The post-operative angiographic results from their study found superior post-operative graft patency rates among no-touch groups at both 18 months (89%: Conventional. 95%: No-Touch) and 8.5 years (76%: Conventional. 90%: No-Touch. P=0.01).6 Similar results were seen among Samano et al. 2015 single center randomized clinical trial (Conventional harvest: n=52, SVG stripped & distended. No-touch harvest: n=52, pedicle & without distention) data that found SVG patency at a mean 16 year post-operative angiographic follow up to be 64% in conventional group versus 83% in no-touch group (P=0.03).18 More recent 2021 multicenter randomized, controlled trial (n=2655) data by Tian et al. comparing conventional (n=1318) and no-touch (n=1337) saphenous vein graft harvesting found no-touch groups to have significantly lower rates of vein occlusion at both 3 months (2.8% no-touch versus 4.8% conventional, OR 0.57 (95% CI, 0.410.80), P<0.001) and 12 months (3.7% no touch versus 6.5% conventional, OR, 0.56 (95% CI, 0.410.76), P<000.1) by CT angiography.19 This chronological review of medical literature demonstrates repeated benefits supporting the use of no-touch harvesting. Currently, open harvest notouch technique is recognized as Class IIaB (Class IIa: weight of evidence in favor of efficacy, Level B: data derived from single randomized clinical trial or large non-randomized studies) recommendation, while EVH is Class IIaA (Level A: data derived from multiple randomized clinical trials or meta-analysis) among the 2018 European Society of Cardiology and the European Association for Cardiothoracic Surgery guidelines on myocardial revascularization.12, 20

As clinical literature continues to investigate “ no-touch” saphenous vein harvesting, the advantages surrounding its ability to preserve and extend graft patency have been well documented since its introduction in 1996.19 With average vein graft occlusion rates ranging from 5% to 13% at 1 month and 10% to 15% within 1 year after CABG surgery, strategies to optimize harvesting techniques remain paramount.19 The no-touch pedicle approach serves as an excellent alternative to arterial conduits, forgoing the complication and limitations surrounding arterial graft harvesting and candidacy.21 Application of the no-touch technique in selected patients undergoing open vein harvesting shows promise in synergistically improving both their long-term and postoperative mortality after CABG surgery.

References

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Copyright

Figure 1 & 2: This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Additional References Utilized:

9. Cancelli G, Audisio K, Chadow D, Soletti GJ, Gaudino M. The evidence for radial artery grafting: When and when not?. JTCVS Tech. 2021;10:114-119. Published 2021 Sep 24. doi:10.1016/j.xjtc.2021.09.039 10. Krishnamoorthy B, Critchley WR, Nair J, et al. Randomized Study Comparing the Effect of

Carbon Dioxide Insufflation on Veins Using 2 Types of Endoscopic and Open Vein Harvesting.

Innovations (Phila). 2017;12(5):320-328. doi:10.1097/IMI.0000000000000405 17. Zenati MA, Bhatt DL, Bakaeen FG, et al. Randomized Trial of Endoscopic or Open Vein-Graft

Harvesting for Coronary-Artery Bypass. N Engl J Med. 2019;380(2):132-141. doi:10.1056/

NEJMoa1812390. 19. Tian M, Wang X, Sun H, et al. No-Touch Versus Conventional Vein Harvesting Techniques at 12 Months After Coronary Artery Bypass Grafting Surgery: Multicenter Randomized, Controlled

Trial. Circulation. 2021;144(14):1120-1129. doi:10.1161/CIRCULATIONAHA.121.055525 21. Dreifaldt M, Mannion JD, Geijer H, Lidén M, Bodin L, Souza D. The no-touch saphenous vein is an excellent alternative conduit to the radial artery 8 years after coronary artery bypass grafting: A randomized trial. J Thorac Cardiovasc Surg. 2021;161(2):624-630. doi:10.1016/ j.jtcvs.2019.09.177