Comparative Analysis of Saphenous VeinConduit Harvesting Techniques for CoronaryArtery Bypass Grafting – EndoscopicTechnique versus the Open Technique

Abstract

Since the introduction of saphenous vein grafting by René Favaloro in the 1968, coronary artery bypass grafting (CABG) surgery has become one of the most common surgical procedures performed. Although approximately 15% to 20% of vein grafts occlude in the first year with an annual occlusion rate of 1% to 2% in the first six years and 4% to 5% from 6 to 10 years, the greater saphenous vein continues to be the most commonly used bypass conduit. The saphenous vein used for coronary artery bypass grafting (CABG) procedures is traditionally harvested by means of the open technique, and as a consequence, lower limb wound complications are an important source of morbidity after CABG, occurring in about 15% of cases. Complications such as hematoma, dehiscence, skin necrosis, or wound infection increase the length of stay and delay rehabilitation, ambulation, and exercise training. With vein harvest being such a critical part of this operation it deserves greater attention in order to reduce morbidity from this component of the operation. Minimally invasive techniques have been developed in order to reduce the significant morbidity associated with the extensive incisions made during a traditional approach to vein harvest. Minimally invasive endoscopic saphenous vein harvesting was introduced by Lumsden in 1995. Ever since it has been increasingly investigated in order to reduce the morbidity associated with conventional open vein harvesting, which requires long incisions, and thus postoperative leg wound complications, pain and patient dissatisfaction. EVH appears to be a safe technique for harvesting veins for CABG surgery, in comparison with OVH, there is a demonstrated benefit in the categories of postoperative pain and wound infection. Additionally, patient satisfaction and overall wound complications have been reported to be superior with EVH. No significant difference could be detected in the outcomes of postoperative MI, mid-term MI, mid-term mortality, recurrence of angina and repeat revascularization. Endoscopic vein harvest has become increasingly used as an alternative to the open technique. The advantages of this technique includes reduced leg wound complications, postoperative pain, required analgesia and incision length. One disadvantage has been the learning curve for endoscopic vein harvest with an increased operative time for the vein harvest compared to the open technique reported in several studies. A further disadvantage of endoscopic vein harvest is the risk of carbon dioxide (CO2) embolism during CO2 insufflation. Lin et al showed the incidence of significant CO2 embolism during endoscopic vein harvest with CO2 insufflation procedures was >4%. However, there have been no documented mortalities as a result of CO2 embolism following endoscopic vein harvest. The comparison and discussion of EVH vs. CVH results often neglects to consider the impact of the use of endoscopic devices for vein harvesting which differ both for dissection technique and usage of CO2. An immediate satisfaction is important when assessing the vein harvesting techniques; however, the conduit quality and the prognostic implications must be the primary outcome. As now, the evidence for short-term patient benefits in reducing infections and operative complications while improving patient mobility and satisfaction is sufficiently replete, including the conclusion that wound complication management following EVH requires significantly less resource utilization than for CVH and thus increase its cost-effectiveness. The mid- and long-term outcome are instead still controversial issues. This may be partly due to the fact that the event-free survival rate over periods from 2 to 5 years is commonly taken as a surrogate marker for graft failure, since postoperative angiographic studies, the gold standard to evaluate the long-term influence of vein harvest technique on graft patency, are not widely used owing to their low practicality and high costs. Furthermore, there are little data regarding the long-term patency rates of veins harvested by the endoscopic technique. The device used and all the related technicalities with the ongoing improvements over the years may well be the divide among different evaluations. Further research is needed to adequately address confounding variables contributing to graft failure, and therefore permit a more accurate assessment of the impact of harvest technique on graft patency. The study should recording operative procedure including; type of harvesting device used, operator experience with the device, documentation of heparin administration prior to vein harvest, storage solution of conduit prior to anastomoses, quality of conduit as assessed by a standardized method, and quality of target vessel as assessed by the operating surgeon. Post-operative documentation should include a list of concomitant medications maintained through the conclusion of the trial. Angiographic follow-up should be performed at six months post-surgery and again at 18 months post-surgery, A trial with adequate power including these confounding variables would more accurately assess the link between graft patency and harvesting technique. The limited state of current research has failed to demonstrate significant harm that may otherwise persuade the Society for Thoracic Surgery and the Association of Physician Assistants in Cardiovascular Surgery (APACVS) to negate the important proven benefits of EVH over OVH. These benefits are landmark in their own right. As mentioned previously they include; decreased wound morbidity, decreased infection rates, and decreased length of hospital stay. The APACVS, in a meeting held in January of 2010, noted a need for more randomized clinical trials utilizing so-called “best practices” that address the confounding variables. It was noted that in general “best practices” would include: an experienced vein harvester, utilization of veins in the lower leg, pre-heparinization prior to vein harvest, non-thermal side branch ligation, prevention of over- distension of the conduit through use of a pressure pop-off syringe, minimization of traction on the harvested vein, and demonstrated patience by the operating cardiothoracic surgeon. Widespread adaptation of best practices may more easily allow for an angiographic patency comparison between EVH and OVH to be completed across multiple surgical centers. More importantly, the adaptation of best practices will ultimately contribute to better patient outcomes. Until further research is completed, EVH remains the preferred method of saphenous vein harvest.