Fifty Years After the Introduction of Vein Grafts for CABG: New Evidence for a No-Touch Harvesting Approach

Gry Dahle, MD, PhD; Jörg Kempfert, MD, Prof Dr Med

Disclosures

Circulation. 2021;144(14):1130-1132. 

Coronary artery bypass grafting (CABG) was introduced in a statement article by Favaloro in 1968, although, it was Garrett and colleagues who performed the first coronary bypass operation in 1964.[1] A decade later, Gruntzig introduced the concept of coronary angioplasty in 1977,[2] as an alternative to CABG. Since those early days of coronary revascularization, both approaches have evolved substantially.

To decide between the 2 options (CABG versus coronary angioplasty) in left main or multivessel coronary artery disease, the concept of a "heart team" was introduced, in part on the basis of the SYNTAX trial (Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery), in which a dedicated scoring system was suggested to assess the complexity of the individual anatomy.[3]

For CABG, many technical aspects have been the focus of extensive research. Topics like "on-pump" versus "off-pump" approaches, the sequential versus independent grafting technique,[4] the potential effect of incompleteness of revascularization,[3] or minimally invasive access versus conventional sternotomy have been discussed scientifically over the past decades.[5]

However, long-term outcomes associated with CABG are undoubtedly linked to the patency ("durability") of the grafts used for revascularization. On the basis of several randomized trials and matched analyses, the concept of multiarterial revascularization seems to outperform saphenous vein revascularization in general,[6] and is therefore recommended by both American and European guidelines.[7,8] In contrast with this evidence, at least 1 venous graft is still used in the majority of routine CABG cases. Potential reasons include ease of use, availability of graft material (ie, pathological Allen's test for radial artery use), potential risk of sternal wound infection in case of bilateral internal thoracic arteries harvest, and others. Hence, the optimal graft quality of a harvested saphenous vein remains a matter of utmost importance.

Even 50 years after the introduction of CABG using venous grafts, a scientific discussion on the optimal quality of vein conduits is still ongoing. Both graft patency and endothelial integrity have been used as surrogate markers for "graft quality" and seem to be influenced by the harvesting technique itself, the constitution of the storing solution, and the amount of fluid pressure applied to dilate the graft.[9]

The introduction of no-touch (NT) saphenous vein harvesting was first published in 1996 by Souza.[10] Its technique involves harvesting the saphenous vein with a surrounding layer of fat and fibrous tissue. Since then, several studies have been conducted to further explore this technique, and it seems that graft occlusion tends to be less frequent with the NT technique,[11] which led to a IIB recommendation in the recent European guidelines.[7] On the downside, the NT technique is more invasive, and associated with significantly higher rates of wound healing problems and infections. In contrast, endoscopic vein graft harvesting has been consistently shown to help prevent leg wound healing issues, leading to a IIA recommendation in the same guidelines. Unfortunately, the NT technique has not yet been shown feasible through a minimally invasive approach.

In this issue of Circulation, Tian et al present a multicenter randomized, controlled trial that included 2533 patients undergoing CABG at 7 hospitals in China, randomized 1:1 between NT and conventional harvested saphenous grafts (CVS).[12] Computed tomography angiography at 3 and 12 months was performed to assess vein graft occlusion rates. In addition, recurrent angina, major adverse cardiac and cerebrovascular events, and leg wound problems were quantified.

This study has several strengths. First, computed tomography scans were systematically performed at 3 and 12 months, with high follow-up rates of 91% and 93% for NT and CVS grafts. Second, the study was a large multicenter trial with graft data from >4000 grafts, in addition to clinical outcomes data. The key finding was a significant lower graft occlusion rate for NT versus CSV at 3 months (2.8% versus 4.8%) and at 12 months (3.7% versus 6.5%, NT versus CVS). Consistent with these imaging results, patients experienced a lower incidence of angina in the NT group (2.3 versus 4.1%; P<0.01). Compared with other similar trials,[11] the overall patency rates of vein grafts observed in this trial were extremely good. In this context, it should be mentioned that the population was Chinese, 78% male, of relatively young age (mean, 61 years), and with a low mean body mass index of only 26. In addition, all patients received dual antiplatelet therapy starting at postoperative day 1, which is not standard of care at most centers.[13]

The known disadvantage of the NT technique compared with CVS is a higher rate of wound exudation, numbness, and edema. Accordingly, in this trial, one-fifth of the patients with the NT technique had leg edema, and almost one-forth had numbness of the leg. For the CVS group, rates were significantly lower at 13% and 17%, respectively.

In conclusion, the trial presented here strengthens the evidence for improved vein graft patency if a NT harvesting technique is used, at the price of more frequent wound healing issues at the harvest site.

In this context, it is critical to point out that the NT technique used here consists of 2 components: the NT harvesting technique per se, and a policy to not distend the graft with syringe inflation to dilate and test the graft. From a scientific point of view, it would be of major importance to better understand the effect of both factors involved.

The negative effect of high-pressure fluid distension on endothelial integrity of vein grafts has been described multiple times in the literature.[14] There currently are studies evaluating a pressure-controlled syringe to limit distension of the vein.

A recently published study tried to further investigate the 2 components of the general concept of the NT harvesting technique: harvesting the graft with a surrounding tissue pedicle and avoiding high-pressure distension. Although this prospectively randomized trial included only a limited number of patients and graft quality was assessed by means of measuring wall thickness by intravascular ultrasound rather than patency, the results did at least highlight the need for a larger trial. On the basis of this preliminary work, it appears that low-pressure graft distension alone may yield similar results to a pedicled harvesting technique.[14,15]

From a clinical perspective, a "best of both worlds" scenario would be to improve saphenous vein graft patency (with a no-pressure dilation technique) with minimal wound healing problems (because of endoscopic harvesting technique).

Until there are more robust data on the exact mechanism of the NT vein graft harvesting concept, we must balance our decision-making about graft selection for CABG procedures by considering multiple variables. Overall, a complete arterial strategy appears to be associated with unsurpassed long-term patency. In the case of vein graft harvesting, the endoscopic technique has been shown to result in significantly less wound healing issues. As has been shown by the well-conducted trial of Tian et al published in this issue of Circulation, the concept of "NT vein graft harvesting" seems to be associated with improved midterm graft patency at the price of slightly increased wound healing issues. Further research will hopefully identify the exact root cause of graft quality preservation: the pedicled harvesting technique per se or other factors like the nondistension/dilation approach.

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