Coronary artery bypass grafting (CABG) has become

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1 Leg Wound Infection After Coronary Artery Bypass Grafting: A Meta-Analysis Comparing Minimally Invasive Versus Conventional Vein Harvesting Thanos Athanasiou, PhD, Omer Aziz, MBBS, Petros Skapinakis, MS, PhD, Branco Perunovic, MD, Jonathan Hart, MBBS, Mary-Claire Crossman, MRCS, Vassilis Gorgoulis, PhD, Brian Glenville, FRCS, and Roberto Casula, FECTS The National Heart and Lung Institute, Imperial College of Science, Technology and Medicine, Department of Cardiothoracic Surgery, St. Mary s Hospital, London, United Kingdom The great saphenous vein remains the most commonly harvested conduit for revascularization in coronary artery bypass grafting (CABG). Our aim is to compare minimally invasive vein harvest techniques to conventional vein harvest with regards to leg wound infection rates. A meta-analysis of identified randomized controlled trials, reporting a comparison between the two techniques published between 1965 and 2002, was undertaken. The outcome of interest was leg wound infection. Fourteen randomized studies were identified and included in the meta-analysis. Our study revealed that Address reprint requests to Dr Athanasiou, Department of Cardiothoracic Surgery, 70 St. Olaf s Road, Fulham, London SW6 7DN, UK; tathan5253@aol.com. wound infection was significantly lower in the minimally invasive vein harvest group (odds ratio 0.22 with 95% confidence intervals of 0.14 to 0.34). Our study suggests that using minimally invasive techniques might reduce leg wound infection rate following great saphenous vein harvesting for CABG. Further research is required to evaluate the potential benefits of minimally invasive vein harvesting techniques on the cost of postoperative care and quality of the harvested vein. (Ann Thorac Surg 2003;76:2141 6) 2003 by The Society of Thoracic Surgeons Coronary artery bypass grafting (CABG) has become one of the most common operations in cardiac surgery. Although the use of arterial conduits has been increasing in light of evidence of more favorable outcome and longer-term patency, the great saphenous vein (GSV) remains the most commonly harvested conduit for revascularization. Conventional vein harvesting (CVH) uses standard surgical instrumentation and direct visualization through a longitudinal or skin-bridging technique to harvest the vein. Although wound-healing disturbances make up the majority of complications from CVH, there are also reports of more serious adverse events such as sepsis and limb amputation [1]. Wound infections can result in a delayed discharge from the hospital, increasing the need for additional interventions such as debridement, antibiotic therapy, and dressing changes. This results in an increased cost of postoperative care, while also reducing patient satisfaction. Figures for the overall incidence of wound-related complications from vein harvesting range from 1% to 43.8% [2 5]. Minimally invasive vein harvest (MIVH) techniques have been used in surgical practice since 1996, with mixed results [6]. The development of these techniques has resulted in the modification of several instruments (both nonendoscopic and endoscopic), in order to improve visualization and reduce the length of skin incisions. Some groups have shown a reduction of postoperative leg complications with MIVH, recommending it for either routine use [7, 8] or selectively in patients at high risk of developing wound infections [9]. Others have shown no benefit in comparison to conventional techniques [10]. Given this uncertainty, we carried out a meta-analysis of published randomized trials reporting a comparison between MIVH and CVH techniques. The outcome of interest was leg wound infection. Material and Methods Literature Search A literature search (using MEDLINE) was performed, looking for all studies published between 1965 and 2002, and reporting on minimally invasive vein harvesting for CABG with emphasis on comparison between MIVH and CVH techniques. The following search headings were used: minimally invasive vein harvesting, endoscopic and great saphenous vein harvest, and coronary artery bypass grafting. We also searched for the terms endoscopic versus conventional vein harvesting and minimally invasive versus conventional vein harvesting.. All the abstracts, studies, citations, and related articles found were reviewed. Data Extraction Data extraction was conducted by two reviewers (A.T. and A.O.). In the case of a discrepancy, the decision was taken by consensus. The following information was extracted from each study: first author, year of publication, 2003 by The Society of Thoracic Surgeons /03/$30.00 Published by Elsevier Inc doi: /s (03)

2 2142 REVIEW ATHANASIOU ET AL Ann Thorac Surg LEG WOUND AFTER CABG: MIVH VERSUS CVH 2003;76: study population characteristics, study design (prospective, retrospective, or other), selection criteria and exclusion criteria, number of subjects operated on with each technique, time of follow-up, and conversion rate from MIVH to CVH. Studies were evaluated according to the criteria proposed by Heyland and colleagues and graded on an ordinal 14-point scale, with higher scores representing studies of higher quality [11, 12]. The parameters that were used to evaluate the quality of the studies included: randomization, blinding, intention to treat, patient selection, compatibility of compared groups, extent of followup, description of treatment protocol, cointerventions, and description of outcomes. The quality of each study was graded as follows: level 1 (1 to 5 marks), level 2 (6 to 10 marks), and level 3 (11 to 14 marks). Using this score, level 3 studies were deemed to be of a greater quality than level 1. Inclusion Criteria The following criteria were used in order to include studies into our analysis: (1) A randomized controlled study design. (2) Where several articles reported on the same patient material, the most recent article was included. (3) Care was taken to avoid inclusion of any double publications. (4) Studies from single institutions were included. (5) The term minimally invasive was used for endoscopic and nonendoscopic minimally invasive techniques. The nonendoscopic techniques included in the MIVH group used three types of instrument modifications: (a) Mini-Harvest System (Autosuture; USSC, Norwalk, CT); (b) SaphLITE System (Genzyme Surgical Products, Cambridge, MA); (c) Aesculap Retractor (Aesculap AGCoKG, Tutligen, Germany). Exclusion Criteria The following criteria were used in order to exclude studies from our analysis: (1) Studies reporting partially randomized trials. (2) Studies in which the mode of harvesting could not be extracted. (3) Studies in which the outcome for comparison of both techniques was not reported or it was not possible to calculate this from the published results. (4) Studies that contained a zero for the outcome of interest in two cells of the cross-tabulation tables for both CVH and MIVH groups. Outcome of Interest Definitions Minimally invasive vein harvest and CVH were compared with leg wound infection being the only outcome of interest. We did not focus on the different MIVH techniques (endoscopic and nonendoscopic) used by different surgeons. Leg wound infection following harvesting of the great saphenous vein was diagnosed by the studies in our meta-analysis as follows: (1) The drainage of pus from the wound. (2) Documented wound infection with positive wound cultures. (3) The requirement for additional treatment (surgical or medical as, for example, prescription of antibiotics). We thus extracted wound infection figures from the studies, where the terms wound infection,, antibiotic requirement,, or inflammation were used at the time of follow-up of outcome assessment. Table 1 shows the definition of wound infection used in each study included in our meta-analysis. Analysis Statistical analysis was carried out using the odds ratio as the summary statistic. This represents the odds of an adverse event occurring in the treatment group compared with the reference group. The group where CVH was used was considered as the reference group, and that in which MIVH was used, the treatment group. An odds ratio of less than one favors the treatment group, and the point estimate of the odds ratio is considered statistically significant at the p less than 0.05 level if the 95% confidence interval does not include the vertical bar 1. Aggregation of the overall rates of the outcomes of interest was performed with the Mantel-Haenszel 2 test. Yate s correction was used for those studies that contained a zero in one cell for the number of events of interest in one of the two groups. In our study, we used both fixed and random effect models, if, for the outcome of interest, a statistically significant test of heterogeneity was identified. The fixed effects approach was used as has been described by Yusuf and collelagues, as well as Mantel and Haenszel [13, 14]. In our diagram (Fig 1), squares indicate point estimates of treatment effect (odds ratio), with the size of the square representing the weight attributed to each study and 95% confidence intervals indicated by horizontal bars. The diamond represents the summary odds ratio from the pooled studies with 95% confidence intervals. Analysis was conducted by using the statistical software SPSS version 10.0 for Windows (SPSS Inc, Chicago, IL, USA), Review Manager Version 4.1 (The Cochrane Collaboration, Software Update, Oxford), and the PS software (version ) for power analysis calculations. Sensitivity Analysis Sensitivity analysis was performed by reanalyzing the data, using different statistical approaches (eg, using a random effects model instead of a fixed effect model), and by funnel plots to evaluate asymmetry [15 17]. Subgroup analysis was performed in order to evaluate if there is a difference in leg wound infection rate when different types of MIVH techniques were used (endoscopic or nonendoscopic). Sample Size Considerations Because wound infection is not a frequent categorical outcome, a large sample of patients would be required to have sufficient power to exclude difference between the two groups. The incidence of leg wound infection between studies ranged from 1% to 42%, allowing us to assume a baseline wound infection rate of 12%. In order to rule out a 50% relative risk reduction (from 12% to 6%), with a 5% significance level and 80% power, a traditional randomized controlled trial would require 389 patients in each arm.

3 Table 1. Details of Randomized Control Trials No. Authors Date Study Quality MIVH/CVH Selection Criteria Matching Conversion Follow-up (Days) 1 Dusterhoft et al 2001 Level 2 128/127 1, 2, 3, 4, 10, 11 1, 3, 4, 5, 6, 10, 15, 16 Not recorded 14 Post-discharge 3 2 Hayward et al 1999 Level 2 50/50 1, 9, 12, 13 3, 4, 10, 12, 17, 18 22% 42 Post-discharge 2 3 Fabricius et al 2000 Level 2 62/30 5, 6 1, 2, 3, 4, 8 5% 3 & 6 Post-op 1 4 Folliguet et al 1998 Level 1 30/30 1, 5, 8, 14, 15 1, 2, 4, 8 Not recorded 7 & 10 Post-op 1 5 Puskas et al 1999 Level 2 47/50 1, 2, 7, 16 1, 2, 3, 4, 5, 6, 19, 20 6% 28 Post-op 2 6 Carpino et al 2000 Level 2 66/ , 3, % 14 Post-discharge 2 7 Tevaerai et al 1997 Level 2 15/15 Not recorded 1, 2, 3, 4, 5, 8 Not recorded 7 Post-op 1 8 Allen et al 1998 Level 2 54/58 1, 3, 4 1, 2, 3, 4, 5, 11, 21, 22, % 42 Post-op 3 9 Kiaii et al 2002 Level 2 69/65 5, 18, 19 1, 2, 3, 4, 5, 6, 7, 9, 13, Not recorded 42 Post-op 2 15, 24, 25, 26, Black et al 2002 Level 2 22/18 1, 6, 20 1, 2, 3, 4, 11, 14 18% 42 Post-op 3 11 Cisowski et al 2000 Level 2 45/15 1, 3, 5 1, 2, 3, 4, 5 Not recorded 7 Post-op 1 12 Bonde et al 2001 Level 2 30/30 1, 4, 5, 7, 9, 21, 1, 3, 4, 5, 6, 7, 9, 12, 13, 6% 42 Post-op 3 22, 23 14, 23, 28, 29, Schurr et al 2002 Level 2 80/60 1, 5, 8 1, 2, 3, 4, 5, 31 6% 5 Post-op 3 14 Isgro et al 1999 Level 1 103/ , 2, 3, 4, 5 2% Not recorded 2 Selection Criteria 1. Emergency operation 2. Conversion to open 3. Decubitus leg ulcers 4. Presence of active infection 5. G. saphenous/extensive varicosities 6. Peripheral vascular disease 7. Previous G. saphenous vein harvest 8. Exclusive arterial re-vascularzation 9. Pre-op intraaortic balloon pump 10. Ejection fraction Veins from both legs used 12. No vein required 13. No vein on either side 14. Prior bilateral vein stripping 15. Pre-op continuous IV therapy 16. Insufficient subcutaneous tissues for endoscopic instrument insertion 17. High wound infection risk 18. Patient refusal 19. Unable to give consent 20. At least two venous grafts required 21. Hemodynamically unstable 22. Previous deep venous therapy 23. Leg dermatitis CVH conventional vein harvesting; MIVH minimally invasive vein harvesting. Matching Criteria 1. Age 2. Sex 3. Obesity 4. Diabetes 5. Peripheral vascular disease 6. Hypertension 7. Smoking 8. Harvest site 9. High cholesterol 10. Ejection fraction 11. Albumin 12. Cross-clamp time 13. Non-elective operation 14. New York Heart Association status 15. Renal failure 16. Chronic steroid use 17. Cardiac risk factors 18. Infection risk 19. Pre-operative creatinine 20. Ankle brachial pressure index 21. Anemia/Hemoglobin 22. Parsonnet score 23. Cleveland Clinic score 24. Liver failure 25. Arthritis 26. Skin disorder 27. Gout 28. Euro Score 29. Chronic obstructive pulmonary disease 30. Bypass time 31. Complex surgery Definition of Leg Infection Definition of Leg Infection 1. Inflammation 2. Infection 3. Use of antibiotics Ann Thorac Surg REVIEW ATHANASIOU ET AL 2003;76: LEG WOUND AFTER CABG: MIVH VERSUS CVH 2143

4 2144 REVIEW ATHANASIOU ET AL Ann Thorac Surg LEG WOUND AFTER CABG: MIVH VERSUS CVH 2003;76: Fig 1. Meta-analysis of minimally invasive versus conventional vein harvesting for wound infection rates. (CI confidence interval; OR odds ratio.) Results Randomized Controlled Trials Selected Fifteen randomized controlled trials comparing MIVH versus CVH techniques were identified [9, 10, 18 29, 30]. One study, by Morris and colleagues, was excluded because it was partially randomized [29]. Characteristics of the fourteen remaining studies including quality score are summarized in Table 1. The studies dated from 1997 to 2002 and the total number of subjects included was 1527, of which 801 had MIVH (52%) and 726 had CVH (48%). On review of the data extraction there was 100% agreement between the two reviewers and the agreement on quality score of the individual studies was very high (weighted Kappa 0.92). Twelve out of fourteen studies were ranked at level 2 and two studies at level 1. There was one study (Carpino and colleagues) designed to document comparison between MIVH and CVH in patients found to be at risk for leg wound complications [9]. Conversion rate from MIVH to CVH techniques was reported in 8 out of 13 studies ranging from 5% to 22%. The outcome of interest was assessed at different follow-up end points between studies. In two studies, leg wound assessment was performed before the end of first postoperative week. Leg Wound Infection Meta-Analysis Five out of fourteen studies (Carpino and colleagues, Dusterhoft and colleagues, Fabricius and colleagues, Kiai and colleagues, and Schurr and colleagues) showed a statistically significant difference between the two groups [9, 18, 20, 24, 28]. Fourteen studies were included in the meta-analysis (Fig 1), which revealed a significant reduction of wound infection in the MIVH group (fixed-effect model calculated odds ratio 0.22, confidence intervals 0.14 to 0.34, and the 2 of heterogeneity with p value 0.53). The incidence of wound infection in the MIVH group was 27/801 (3%) versus 97/726 (13%) in the CVH group. Sensitivity Analysis Results We did not identify any significant differences in the odds ratios and heterogeneity for the outcome of interest using both random and fixed effect models. A funnel plot of the studies used in our meta-analysis is shown in Figure 2. This is a scatter plot of the treatment effects estimated from individual studies on the horizontal axis (odds ratio), against a measure of study size on the vertical axis (SE [logor]). The name funnel plot is based on the fact that the precision in the estimation of the underlying treatment effect will increase as the sample size of the component studies increases [15]. The plot in Figure 2 resembles a symmetrical inverted funnel (the 95% confidence interval), inside which are thirteen out of fourteen studies included in our meta-analysis. Meta-analysis on a subgroup was performed comparing solely endoscopic MIVH versus CVH techniques (Fig

5 Ann Thorac Surg REVIEW ATHANASIOU ET AL 2003;76: LEG WOUND AFTER CABG: MIVH VERSUS CVH 2145 Fig 2. Funnel plot. (SE[LOG OR] standard error [log odds ratio].) 3), which revealed a significant reduction of wound infection in the endoscopic MIVH group (fixed-effect model calculated odds ratio 0.22, confidence intervals 0.14 to 0.37, and the 2 of heterogeneity with p value 0.38). The incidence of wound infection in the endoscopic MIVH group was 20/590 (3%) versus 78/566 (14%) in the CVH group. The odds ratio of leg wound infection for the endoscopic MIVH versus the CVH group was almost identical to the MIVH (endoscopic and nonendoscopic) group versus the CVH group. Comment In this meta-analysis of all previous randomized control trials of MIVH versus CVH, we have found that MIVH techniques are associated with a reduced risk of leg wound infection. The evidence suggests that using MIVH techniques might reduce wound complication rates following great saphenous vein harvesting for CABG. For the wound infection data analyzed (Fig 1), the most extreme value of the odds ratio favoring the treatment group was almost 0.4 (within 95% CI), translating to a relative risk reduction of at least 60%. As previously mentioned, the average incidence of leg wound infection after CVH was 12%. A 60% reduction would mean an incidence of wound infection of 4.8% with MIVH. Thus, the calculated absolute risk reduction would be 7.2% with MIVH, meaning the numbers needed to treat would be 14. This number would be less in patients at high risk for wound infection (female, obese, diabetic, peripheral vascular disease). In the studies we looked at, the conversion rate from MIVH to CVH varied from 5% to 22%. We believe that patients should be carefully selected to have MIVH and thus reduce the need to convert to CVH. Most of the randomized studies selected for our metaanalysis were of moderate quality, as has been previously emphasized for the majority of surgical trials [31]. Similar beneficial results favoring the MIVH group have been showed by previous nonrandomized studies [32]. A reduction in wound infection can potentially reduce postoperative morbidity, postoperative pain, length of stay, readmission rate, and postdischarge care. This, in turn, has an implication on not only the cost of postoperative care for these patients, but also patient satisfaction and quality of life due to an uncomplicated recovery. Although the cost of MIVH may be higher than CVH, we feel that the reduced morbidity associated with the minimally invasive technique may make it more affordable. Fig 3. Meta-analysis of endoscopic minimally invasive versus conventional vein harvesting for wound infection rates. (CI confidence interval; OR odds ratio.)

6 2146 REVIEW ATHANASIOU ET AL Ann Thorac Surg LEG WOUND AFTER CABG: MIVH VERSUS CVH 2003;76: Our meta-analysis had the following limitations. First, neither the allocation of treatment, nor the assessment of outcome was blinded. Second, it is important to keep publication bias in mind, as this meta-analysis relies on data from previously published studies. Positive results are more likely to be published than negative results (type I error). Third, there was variation in inclusion criteria, the type of randomization used, treatment protocols, and outcome assessment between studies. We feel that MIVH allows the harvesting of vein conduits for CABG, with reduced traumatic injury to surrounding tissues, fewer disturbances to skin vascularity, and a reduction in skin flap creation. This, in turn, results in a reduction of leg wound related infection, supporting the view that minimal access requires minimal wound care after CABG [32]. Finally, it is important to remember that there are other issues, relating to the comparison of MIVH and CVH techniques not covered by our study, that must also be considered. First, harvesting time required and the quality of the conduit must be looked at. Second, MIVH requires different equipment and procedures to CVH (lit retractors, endoscopic equipment, carbon dioxide insufflation), and the effect of these on clinical outcome has not been reviewed. Third is an actual comparison of the cost between the two techniques, including not only the cost of instruments, but also the cost of postoperative stay. Further research into these factors is required. References 1. Paletta CE, Huang DB, Fiore AC, Swartz MT, Rilloraza FL, Gardner JE. Major leg wound complications after saphenous vein harvest for coronary revascularization. Ann Thorac Surg 2000;70(2): L Ecuyer PB, Murphy D, Little JR, Fraser VJ. The epidemiology of chest and leg wound infections following cardiothoracic surgery. 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