Seven Ways To Improve Radial Artery Harvest Techniques And Outcomes
Michelle Olivia Dao.
Cedars Sinai Medical Center, Los Angeles, CA, USA.
BACKGROUND: Coronary artery bypass grafting (CABG) is a procedure for a patient with severe coronary artery disease and is the most common cardiac surgery procedure. There are over 18 million adults in the United States that have coronary artery disease.1 The left internal mammary artery (LIMA), right internal mammary artery (RIMA), greater saphenous vein (GSV), and radial artery (RA) are the most common conduits for this procedure. The radial artery is preferred over the greater saphenous vein due to long-term patency with arterial graft. In 1968, Dr. George Green performed the first LIMA to the left anterior descending artery (LAD) anastomosis in the United States, and since then, has become the gold standard as it has strongly correlated with improved outcome, long-term patency, and survival.1 There are multiple case studies and meta-analysis research that has demonstrated the superiority of using the radial artery over the greater saphenous vein, as well as the right internal mammary artery when looking at graft patency rates and long-term survival rates.1 Radial artery graft is superior to saphenous vein graft with better patency rates when target vessels are greater than 90% stenosis.2
There are two approaches to harvesting the RA, with the traditional approach of open radial artery harvesting (ORAH), and then the newly accepted and growing popularity of the endoscopic radial artery harvest (ERAH) technique which was adopted in the early 2000s.1 According to the Society of Thoracic Surgeons National Database from 2008 to 2018, it was discovered that across the nation, ORAH continuously is the radial artery harvest approach of choice with 56.8% of surgeons who utilize this approach, however, the ERAH approach is not far with 43.2% of those who have adopted this approach.1 ERAH has been highly accepted due to insignificant differences in patency rates amongst the traditional open approach, but also the benefit of smaller incision leading to lower wound infection and neurological injury, cosmetically appealing, and an increase in patient satisfaction.2The concern with ERAH is that it requires more manipulation of the radial artery than compared with ORAH, therefore leading to an increased risk of endothelium injury that could lead to graft spasm, thrombosis, and occlusion, causing an increased risk for cardiac events.1 However, there has been an ongoing debate with multiple analyses that showed conflicting results on whether there are significantly different outcomes between the two techniques.In a recent prospective randomized trial, REGROUP showed that the outcome of the radial artery conduit was primarily influenced by the harvester’s experience and that the endoscopic harvesting approach was not associated with higher rates of poor outcomes or risk for cardiac events.3 Endoscopic harvesting techniques are found to be safe and have become the recommended standard of care for radial artery procurement in patients who benefit from arterial graft for re-vascularization and meet criteria.3 This review looks at methods, techniques, and approaches to endoscopic radial artery harvesting that may improve a harvester’s ERAH skill and practices to minimize post-operative complications and endothelial injury. METHODS: As ERAH has gained popularity, there are various strategies have been practiced such as sealed, where CO2 insufflation is activated, versus non-sealed system does not require CO2 insufflation.3 It has been hypothesized that CO2 could lead to functional and structural damage to the endothelium.3 However, these endothelium injuries were considered microscopic and there are no significant data that shows long-term detrimental adverse effects or cardiac events. The endoscopic harvesting technique utilizes CO2 insufflation at a target pressure of 5-15 mmHg in the tunnel to help with visualization.3 In Samano N, et al. the insufflation of CO2 can cause a considerable amount of vascular trauma.4 Naik et al. describe that CO2 insufflation reduces spasms in the artery.5Additionally, a popular debate in the endoscopic harvesting world is the no-touch approach for similar reasons of avoiding any micro and macroscopic injury to the endothelium and as a result, improving patency rates.4 In a recent review article that researched the no-touch method of harvesting in the span of 25 years, revealed a significant improvement in both, the patency rates and left ventricular ejection fraction with short and long-term follow-up, up to 16 years postoperatively.4 More impressively was that the no-touch saphenous vein graft displayed a patency rate comparable to LIMA at 16 years follow up leading to its class IIa recommendation by the European Society of Cardiology as well as the European Association for Cardio-Thoracic Surgery.4 The study showed that the conventional method as well as distending the graft under high pressure caused microscopic trauma which was seen in all three layers; the intima, media, and adventitia, as well as the surrounding perivascular fat.4,6 This impacts the quality and performance of the graft and ultimately may lead to early graft failure.Another article published in Ann Thoracic Surgery is unique that it studies and screens the radial artery conduits quality intraoperatively before and after endoscopic and open radial artery harvest using catheter-based high-resolution optical coherence tomography (OCT) imaging.6 This technique was used to study intimal disruption and spasm that occurs in endoscopic radial artery harvest. Spasm is quantified by the percentage change in luminal volume.6 Intimal disruption was classified as minor or severe based on the defect to the branch ostia or involved luminal surface.6 Histology was used to confirm OCT findings. Luminal volume was no difference between the two groups. However, the initial injury was significant in the endoscopic harvest. Serial imaging revealed that 86% of ostial tears occurred in endoscopic techniques during the initial blunt dissection step.6 This study revealed that though there was an intimal injury found in ERAH, they were minor and involved the luminal surface of the radial artery.6 This is significant evidence that could benefit the artery quality by ensuring harvesters modify their blunt dissection technique to take caution when entering with the conical tip during initial dissection endoscopically. Due to the minimally invasive approach of ERAH, neurological complications are reduced when compared to open harvest. Open radial artery harvest requires a longitudinal incision along the forearm that extends from the wrist to approximately the antecubital fossa. The superficial radial nerve and the lateral antebrachial cutaneous nerve would possibly be injured by the forearm incision.7 In Naik et al. a study that compared ERAH with ORAH showed "major neurological complications, wound erythema, ecchymosis, mild numbness, or tingling to be significantly higher in open approach."5 In Huang et al. research article, it was shown that the ERAH groups found in nine studies had a significant reduction in the neurological complication of 59% when compared to the open approach.7 A prospective randomized trial published in the Journal of Cardiac Surgery, showed that 20% of those who underwent ORAH had post-operative major neuralgias, where 0% in the ERAH arm showed major neuralgia.2 Another concern with ERAH is limb ischemia and there is a continuous debate on the use of a tourniquet during ERAH. Abdelkarime et al., a very recent prospective clinical trial study investigates the effect of pneumatic tourniquet device deployment during endoscopic radial artery harvest and its effect on the patient’s hemodynamics.8 Pneumatic tourniquet deployment is commonly the standard practice for some institutions or harvesters when endoscopically harvesting the radial artery. During tourniquet inflation, there is ischemia of the forearm with subsequent cellular ischemic changes, such as cellular acidosis, cellular edema, and activation of cellular apoptosis.8 These changes in turn can affect not only the patient’s hemodynamics but possibly the radial artery’s endothelium or cellular ischemic changes.8 Vasospasm is one of the most common risks and largest concerns in the use of radial artery grafts for CABG procedures. The radial artery has a thick tunica media which is associated with increased spasm.5 Therefore some surgeons have adopted the use of pharmacological prophylaxis protocols intraoperatively and/or post-operatively to avoid vasospasm of the artery. Various combinations have been recommended such as a calcium channel blocker with or without a long-acting nitrate or nitroglycerine has been used as a vasospasm prophylaxis.5 Patients are initiated with these drugs intra-operatively during ERAH and/or immediately post-operative for a duration that ranges from six months to a year.5,9 However, there are still disputing studies that show no benefit from antispasmodic pharmacological therapy. Therefore, it is the discretion of the surgeon to implement this practice with the consideration of the patient’s tolerance to the therapy. RESULTS: Though radial artery graft has only been around as a reliable graft for CABG and found to be superior to the saphenous vein graft since the 1990s, some studies suggest there is no statically significant difference in patency rate when compared to the saphenous vein.2 Studies have shown comparable outcomes in patency rates between the traditional open radial artery harvest and minimally invasive endoscopic harvest.12 Radial artery has been associated with a reduced risk of sternal wound infections and less blood transfusion requirement when compared to the right internal mammary artery, making it the preferred second conduit after the LIMA.9 Due to the overwhelming success, the minimally invasive endoscopic technique for harvesting has gained popularity as it has been considered safe and effective.9 However, the superior results with the endoscopic technique for radial harvesting are shown with a decrease in the risk of wound infection, improved cosmesis, pain reduction, lower neurological injuries, and increased overall patient satisfaction.9,11 Huang et al. shows that endoscopic radial artery harvesting can improve post-operative outcome without jeopardizing long-term survival, patency rate, or patient mortality.7Seven possible areas are studied with endoscopic radial artery harvesting that could improve or simulate similar outcomes to the traditional open harvest technique. When we look at the overall commonality, the no-touch approach is superior.10 However, modifications in the endoscopic technique can help improve the quality of the radial artery graft. The limitation of the endoscopic approach is the minimally invasive technique, therefore smaller incision and visualization. As a result, it has been the standard of care to use CO2 insufflation, similar to endoscopic saphenous vein harvesting, to increase the exposure of the tunnel for better visualization.10 The downfall that is shown in one article published in The Multimedia Manual of Cardio-Thoracic Surgery is that carbon dioxide may have a damaging impact on the endothelium.3 Perhaps lowering the insufflation pressure to minimize the endothelial exposure and pressure of carbon dioxide would remedy this issue.3 Additionally, it was found that most of the injuries were noted as ostial tears that occurred during the initial blunt dissection with the endoscopic tip.6 This discovery is significant to help tailor the technique used during ERAH. The limitation, however, with this study is that it is outdated and subjects were enrolled from June 2004 until May 2007.6 It would be advantageous to have a follow-up prospective study to determine where most of the injury occurred on the conduit.Additionally, the limitation in these studies is the variation in the harvester’s experience, skillset level, and volume of endoscopic radial artery harvests in the institution. There is a steep learning curve when learning ERAH, as it takes most individuals approximately 30 or more ERAHs to be proficient and requires continuous practice. Additionally, other factors can attribute to the quality of endothelial tissue such as storage in a crystalloid solution versus continuous perfusion of the graft using autologous blood.10 As a result, the outcome of the radial artery graft can vary due to multifactorial contributing factors that could be difficult to implement in case studies since the methodology and practices vary from surgeon to institution and the harvester’s experience level. CONCLUSIONS: With millions in the United States who have coronary artery disease aliment that could be life-threatening without any intervention, coronary artery bypass grafting outcome is significant in the field of cardiac surgery. Coronary artery bypass grafting is the most common cardiac surgical procedure in the world.1 Therefore, the long-term success rate and minimizing post-operative complications or cardiac events is prudent and could be directly correlated with the quality of the harvested radial artery conduits.Radial artery harvesting methodology reflects the quality of the conduit and therefore has a direct impact on the long-term patency rate and mortality rate. Endoscopic radial artery harvesting through a minimally invasive approach has some limitations. With increasing knowledge and attention to detail with the anatomy of the radial artery as well as the concerning microscopic injury to the endothelium, there is various modification in techniques that can circumvent these challenges. The top ways that endoscopic radial artery harvesting techniques could be improved or modified are minimal to no-touch technique, minimizing carbon dioxide exposure to the tissue, control of dilation of the conduit to minimize over distention, adopting the no tourniquet technique, careful blunt dissection, and the use of antispasmodic prophylaxis protocols. The endoscopic radial harvesting technique is superior to the conventional open harvest technique, and harvesters should seek opportunities to improve the minimally invasive approach.
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