Innovations: Technology & Techniques in Cardiothoracic & Vascular Surgery:
A Meta-Analysis of Endoscopic Versus Conventional Open Radial Artery Harvesting for Coronary Artery Bypass Graft Surgery
Cao, Christopher MBBS*†‡; Tian, David H. BMed*; Ang, Su C. MBBS*‡; Peeceeyen, Sheen MCh‡; Allan, James MBBS*; Fu, Benjamin BDS*; Yan, Tristan D. MD, PhD*
From The *Collaborative Research (CORE) Group, Macquarie University, †The Baird Institute for Applied Heart and Lung Surgical Research, and ‡Department of Cardiothoracic Surgery, St. George Hospital, Sydney, Australia.
Accepted for publication January 8, 2014.
Disclosure: The authors declare no conflicts of interest.
Address correspondence and reprint requests to Christopher Cao, MBBS, The Systematic Review Unit, The Collaborative Research (CORE) Group, 2 Technology Place, Macquarie University, NSW 2109, Sydney, Australia. E-mail: firstname.lastname@example.org.
Objective: The radial artery has been demonstrated to provide superior long-term patency outcomes compared with saphenous veins for selected patients who undergo coronary artery bypass graft surgery. Recently, endoscopic radial artery harvesting has been popularized to improve cosmetic and perioperative outcomes. However, concerns have been raised regarding the effects on long-term survival and graft patency of this relatively novel technique. The present meta-analysis aimed to assess the safety and the efficacy of endoscopic radial artery harvesting versus the conventional open approach.
Methods: A systematic review of the current literature was performed on five electronic databases. All comparative studies on endoscopic versus open radial artery harvesting were included for analysis. Primary endpoints included mortality and recurrent myocardial infarction. Secondary endpoints included graft patency, wound infection, hematoma formation, and paresthesia.
Results: Twelve studies involving 3314 patients were included for meta-analysis according to predefined selection criteria. There were no statistically significant differences in overall mortality, recurrent myocardial infarction, or graft patency between the two surgical techniques. However, patients who underwent endoscopic harvesting were found to have significantly lower incidences of wound infection, hematoma formation, and paresthesia.
Conclusions: Current literature on endoscopic harvesting of the radial artery for coronary artery bypass graft surgery is limited by relatively short follow-up periods as well as differences in patient selection and surgical techniques. In addition, there are currently no randomized controlled trials to provide robust clinical data. However, the available evidence suggests that the endoscopic approach is associated with superior perioperative outcomes without clear evidence demonstrating compromised patency or survival outcomes.
Coronary artery bypass graft surgery (CABG) remains to be the standard of care for selected patients with ischemic heart disease. Patients with complex lesions such as left main coronary artery disease and triple-vessel disease have significantly lower incidences of major adverse cardiac and cerebrovascular (MACCE) outcomes after CABG compared with drug-eluting stents.1,2 The left internal mammary artery has long been established as the best conduit for CABG.3 With respect to the second best conduit, a number of studies have recently demonstrated superior outcomes for the radial artery compared with the saphenous vein at short- and mid-term follow-up.4–7
To minimize trauma and improve patient satisfaction, an endoscopic approach to harvesting the radial artery has been developed in recent years. Despite encouraging immunohistochemical results, there are limited clinical data comparing endoscopic versus conventional open surgical techniques.8,9 Proponents of the relatively novel endoscopic procedure emphasize the superior cosmetic and perioperative outcomes associated with minimally invasive surgery, whereas skeptics cite the lack of robust clinical data on the safety of the endoscopic approach, especially in regard to graft patency. The present meta-analysis aimed to identify all relevant data from the current literature to compare the safety and the efficacy of radial artery harvesting for CABG by endoscopic and open approaches. Primary endpoints included mortality and recurrent myocardial infarction. Secondary endpoints included graft patency, wound infection, hematoma formation, and paresthesia.
PATIENTS AND METHODS
Literature Search Strategy
An electronic search was performed using Ovid MEDLINE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, American College of Physicians Journal Club, and Database of Abstracts of Review of Effectiveness from their date of inception to December 2012. To achieve maximum sensitivity of the search strategy and to identify all relevant studies, we combined the terms endoscopy or minimally invasive and radial and coronary artery bypass graft or CABG or coronary as either key words or MeSH terms. The reference lists of all retrieved articles were reviewed for further identification of potentially relevant studies. All selected articles were assessed with application of the predefined inclusion and exclusion criteria.
Eligible studies for the present meta-analysis included those that presented comparative outcomes for patients who underwent CABG using radial arteries that were harvested endoscopically or through open incision. Studies were excluded if these did not present any of the predetermined primary or secondary endpoints. When institutions published duplicate studies with accumulating numbers of patients or increased lengths of follow-up, only the most complete reports were included for quantitative assessment at each time interval. All publications were limited to human subjects and in English language. Abstracts, case reports, conference presentations, editorials, and expert opinions were excluded. Case reports and case series with fewer than 10 patients were also excluded.
Data Extraction and Critical Appraisal
Data were extracted from article texts, tables, and figures of the selected studies. Two investigators (D.H.T. and S.C.A.) independently reviewed each retrieved article. Discrepancies between the two reviewers were resolved by discussion and consensus. The final results were reviewed by the senior investigator (C.C.).
Meta-analysis was performed by combining the results of reported incidences of primary and secondary endpoints from individual studies. The relative risk (RR) was used as a summary statistic. The χ2 tests were used to study heterogeneity between trials. I2 statistic was used to estimate the percentage of total variation across studies, due to heterogeneity rather than chance. I2 can be calculated as: I2 = 100% × (Q − df)/Q, with Q defined as Cochran heterogeneity statistics and df defined as degree of freedom. An I2 value of greater than 50% was considered substantial heterogeneity. If there was substantial heterogeneity, the possible clinical and methodological reasons for this were explored qualitatively. All P values were two sided. A significant difference was defined as P < 0.05. All statistical analysis was conducted with Review Manager Version 5.1.2 (Cochrane Collaboration, Software Update, Oxford, United Kingdom).
Quantity and Quality of Trials
A total of 101 references were identified through the five electronic database searches. After exclusion of duplicate or irrelevant references, 43 potentially relevant articles were retrieved for more detailed evaluation. After applying the selection criteria, 12 comparative studies remained for assessment.10–21 Manual search of the reference lists did not identify any additional relevant studies. A summary of the search strategy is presented in Figure 1.22 All 12 studies included for meta-analysis were observational studies, involving 3314 patients who underwent CABG using the radial artery as a conduit, including 1376 patients who underwent endoscopic harvesting and 1938 who underwent the conventional open approach. Study characteristics, harvesting times, and follow-up periods varied between studies, as summarized in Table 1.
Assessment of Mortality and Myocardial Infarction
Mortality was defined as death within 30 days or during the same hospitalization. When patients who underwent CABG using endoscopic radial artery harvesting were compared with those who underwent conventional open approach, there was no statistically significant differences in regard to perioperative mortality [0.3% vs 0.5%; RR, 0.67; 95% confidence interval (CI), 0.17–2.55; P = 0.55; I2 = 0%; Fig. 2]. The incidence of myocardial infarction was also found to be similar between the endoscopic and open approaches (0.8% vs 1.0%; RR, 0.79; 95% CI, 0.30–2.04; P = 0.62; I2 = 0%; Fig. 3).
Assessment of Graft Patency
Graft patency was assessed in selected studies by coronary angiography or computed tomography angiography at the time of discharge or postoperative follow-up. When both investigations were performed, data from coronary angiography were selected for analysis because it remains to be the standard investigation to assess graft patency. A graft was considered “patent” as defined by individual studies, including those grafts that were perfectly patent, grafts that were patent with minor irregularities, or grafts that did not demonstrate occlusion or stenosis.10,12,15 Two studies reported graft patency outcomes according to the number of grafts (88.7% vs 85.8%; RR, 1.04; 95% CI, 0.97–1.12; P = 0.24; I2 = 0%), and two studies reported the number of patients who had patent grafts at follow-up (75.9% vs 78.1%; RR, 1.00; 95% CI, 0.83-1.21; P = 0.97; I2 = 0%, Fig. 4). Neither measurements reached statistical significance comparing endoscopic versus open techniques.
Assessment of Wound Infection, Hematoma Formation, and Paresthesia
In regard to perioperative morbidities, patients who underwent endoscopic radial artery harvesting had significantly lower incidences of wound infection (1.0% vs 4.0%; RR, 0.36; 95% CI, 0.16–0.82; P = 0.01; I2 = 0%; Fig. 5), hematoma formation (2.9% vs 4.0%; RR, 0.45; 95% CI, 0.26–0.77; P = 0.004; I2 = 43%; Fig. 6), and paresthesia (23.5% vs 30.9%; RR, 0.77; 95% CI, 0.61–0.99; P = 0.04; I2 = 42%; Fig. 7) when compared with patients who underwent the conventional open approach.
Since the introduction of antispasmodic medications and improvements in surgical techniques in the 1990s, there has been a growing interest in the use of the radial artery as a conduit for CABG. Although patients with less severe native coronary artery disease (<90% stenoses) have been shown to have worse patency outcomes,10,23 available evidence suggests that the radial artery is associated with superior angiographic outcomes at short-term and midterm follow-up compared with saphenous veins. Meta-analysis of randomized controlled trials have established higher incidences of complete patency as well as lower incidences of graft occlusion and graft failure after CABG using the radial artery.4,5 Nonetheless, concerns about the angiographic finding of the “string sign” persist, and patient selection in the randomized trials was strictly limited to severe (>70% stenoses) target vessel lesions.
Endoscopic harvesting of conduits attracted growing popularity since the first endoscopic saphenous vein harvest was performed in 1996.24 Encouraging data from institutional reports suggesting similar MACCE with improved perioperative morbidity outcomes through the endoscopic approach have resulted in the popularization of this technique during the past decade. Recent data from The Society of Thoracic Surgeons National Database reported that endoscopic harvesting was performed in up to 70% of CABG surgeries in the United States.25 However, a large retrospective analysis involving 3000 patients recently demonstrated that the endoscopic harvesting technique was associated with higher rates of vein graft failure at 12 to 18 months after surgery as well as higher incidences of mortality, myocardial infarction, or revascularization at 3 years.25
The results of the present study comparing endoscopic versus open techniques of harvesting the radial artery identified similar MACCE outcomes but superior morbidity outcomes for the minimally invasive approach. The incidences of mortality, myocardial infarction, and graft patency outcomes were similar between the two treatment groups, but patients who underwent endoscopic harvesting had significantly lower incidences of wound infection, hematoma formation, and paresthesia. Although the findings regarding MACCE outcomes are similar to previous individual reports, perioperative morbidities were consistently lower after endoscopic surgery in the present meta-analysis as compared with individual reports, possibly as a result of a larger number of patients analyzed. Our data suggest that patients who undergo endoscopic harvesting are less than half as likely to have hematoma formation and nearly a third as likely to have wound infection, when compared with the conventional open approach.
A number of limitations of the present meta-analysis should be acknowledged, and our results should be interpreted with caution. Firstly, none of the 12 selected studies included for analysis were randomized, and hence, these were subject to patient selection bias. Secondly, patient baseline characteristics, endoscopic harvesting techniques, and medication regimens varied among institutions. However, no statistically significant heterogeneity was identified from our analysis. Finally, the follow-up periods were relatively short or not specified, and outcomes such as graft patency were often measured only at the time of discharge. However, one study involving more than 200 patients who underwent angiography beyond 3 years demonstrated similar patency outcomes between the two surgical treatment groups.12 Overall, the results of the meta-analysis should be interpreted with caution because of the abovementioned limitations, and any superiority of the endoscopic approach should not be overstated because of the limited evidence.
In conclusion, existing evidence suggests that endoscopic harvesting of the radial artery is a safe procedure that can potentially offer superior perioperative outcomes related to wound infection, hematoma formation, and paresthesia, without clearly demonstrating any increased major adverse events such as mortality, myocardial infarction, and graft occlusion. However, future studies should aim to involve randomization with longer follow-up periods and a larger patient cohort to assess both angiographic and clinical outcomes to provide more robust evidence.
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3. Zeff RH, Kongtahworn C, Iannone LA, et al. Internal mammary artery versus saphenous vein graft to the left anterior descending coronary artery: prospective randomized study with 10-year follow-up. Ann Thorac Surg. 1988; 45: 533–536.
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This meta-analysis examined endoscopic versus conventional open radial harvesting for coronary artery bypass graft surgery. Twelve studies involving more than 3000 patients were examined. There were no significant differences in overall mortality, recurrent myocardial infarction, or graft patency between the two techniques. However, patients who underwent endoscopic harvesting were found to have a significantly lower incidence of wound infections, hematoma formation and paresthesias.
This meta-analysis suggests that the endoscopic approach has superior perioperative outcomes without compromising short-term results. However, there are weaknesses in this analysis. None of the studies that were examined were randomized, and hence, all may have been subjected to patient selection bias. Finally, the follow-up periods were relatively short, and only one of the studies looked at even medium-term outcomes. Keeping these limitations in mind, this study suggests that endoscopic harvesting of the radial artery is a safe procedure in the short-term and may offer superior perioperative outcomes in terms of wound complications. However, if there was a difference in long-term patency between these techniques, these advantages would be nullified. Future studies in this area are keenly anticipated.
Radial artery; Endoscopic; Coronary artery bypass graft surgery; Meta-analysis
©2014 by the International Society for Minimally Invasive Cardiothoracic Surgery
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