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Ann Thorac Surg 1999;68:2107-2110
© 1999 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Endoscopic versus open saphenous vein harvest: the effect on postoperative outcomes

^a Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA

Address reprint requests to Dr Hayward, Department of Surgery, Duke University Medical Center, PO Box 31091, Durham, NC 27710;
e-mail: haywa001{at}mc.duke.edu

Presented at the Forty-fifth Annual Meeting of the Southern Thoracic Surgical Association, Orlando, FL Nov 12–14, 1998.

	Abstract

Top Abstract Introduction Material and methods Results Comment References

 
Background. Endoscopic vein harvest (EVH) has been promoted as a possible solution to the wound complications, incisional pain, and prolonged convalesce associated with open vein harvesting (OVH). The purpose of this study was to objectively compare the two techniques.

Methods. One hundred patients were prospectively randomized to EVH or OVH. Primary outcomes were wound complications, pain (Medical Outcomes Study Pain Survey), and general health (SF-12). Secondary outcomes were operative times and patient preferences. Patients were assessed at hospital discharge, 3, and 6 weeks postdischarge.

Results. No significant differences were detected in the primary outcomes: leg infection (p = 0.75), incisional pain (p = 0.74), physical health (p = 0.84), mental health (p = 0.47), and postoperative length of stay (p = 0.74). However, patient preference for EVH was highly significant (p < 0.01).

Conclusions. EVH does not demonstrate significant differences compared with OVH. This, coupled with higher operating room costs, should limit its use until clinical benefit is shown. However, strong patient preference and demand for EVH overshadow equivocal clinical outcomes.

	Introduction

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Coronary artery bypass grafting (CABG) is one of the most common surgical procedures in the U.S. Therefore, any modification to the operative technique or strategy has substantial implications for U.S. healthcare, healthcare institutions, and individual physicians. One of the components of CABG currently being reassessed is the need for the long incision for the harvest of the greater saphenous vein. Vein harvesting is a long underappreciated component of CABG and is associated with its own complications and postoperative morbidity [1, 2]. In an attempt to reduce this morbidity, several companies have developed products to perform this procedure via minimal access techniques.

The technical details of endoscopic vein harvest (EVH) have been described elsewhere [3]. A low rate of complications and the absence of major complications from early graft closure have also been reported [4, 5]. As with any new surgical procedure, the benefit the new technology might have over the standard therapy, open vein harvest (OVH), must be proven through scientific methodology before it can be recommended for widespread clinical use.

	Material and methods

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In order to determine if clinical outcomes improved with EVH, we enrolled patients in a prospective randomized trial at one tertiary academic center between February 1997 and August 1997. Patients who elected to participate were randomized to either the open or endoscopic group, each of which had 50 patients per arm. All data were analyzed on an "intent to treat" basis. This trial complied with ethical guidelines covering the treatment of patients involved in human investigative studies and was approved by the human research institutional review board in September of 1996. The criteria for inclusion in the trial were as follows: patients who were scheduled for a CABG operation for whom a trained physician assistant was available. The criteria for exclusion from the trial were as follows: patients who were not scheduled to have saphenous vein harvested, patients who did not have a greater saphenous vein on either side, patients who were on an intraaortic balloon pump until surgery, or patients who underwent emergency revascularization. The later two groups were excluded not because of perceived limitations of the device, but rather for the logistical difficulties of obtaining informed consent.

One physician assistant (PA-C) performed all of the vein harvests in the clinical trial. This physician assistant had more than 10 years experience as a cardiac surgery PA-C, had attended the corporate sponsored training session and local training sessions on the use of laproscopic equipment, and had performed 20 vein harvests before the start of the clinical trial. The Endovein Vein Harvest Kit (Ethicon Endosurgery, Cincinnati, OH) was used for the trial. The equipment was Ethicon’s first-generation device with separate Subcu-Dissector and Subcu-Retractor, and a Allport 5-mm clip applier. The saphenous vein harvest sites were drained for 24 to 72 hours with a closed drainage system if oozing was noted at the completion of the harvest. Every reasonable attempt to harvest the saphenous vein through as few and as small incisions as possible was made. However, in order to have the vein available on time, multiple incisions were often made on EVH patients to expedite vein harvesting.

Patients were assessed through surveys administered either in person or over the telephone at hospital discharge, 3 weeks, and 6 weeks postdischarge. Conversion was determined by having an incision length to vein harvested length (I/V ratio) more than or equal to 0.75. The length of stay (LOS) was determined from the time of surgery until discharge from the hospital.

In order to have comparable comorbidities, the Charlson Comorbidity Index was used. This is a prospectively applicable method for classifying comorbid conditions that might alter the risk of mortality for use in longitudinal studies [6]. In order to standardize the risk of wound infection, the modified National Noscomial Infections Surveillance (NNIS) risk index was used. This index stratifies risk as determined from a database of 49,333 clean operations [7]. The risk index gives 1 point for an American Society of Anesthesiologists Scale (ASA) score greater than 2, 1 point for operating room time greater than 75th percentile of time (5 h for CABG), and 1 point for contaminated wound status. In order to compare body habitus between groups in this study, the body mass index (BMI = weight in kilograms divided by height in meters squared) was used. The BMI not only relates body weight to height, but can also be used to access the magnitude of potential health risks from obesity [8].

Wound infection was determined by a physician as pus draining from the wound as documented, positive wound cultures, or a clinical diagnosis of infection that required specific wound management strategies (ie, opening of the wound or prescribing a course of antibiotics). Cellulitis was defined as redness at the incision site without objective evidence of infection. Hematoma was defined as a palpable collection of blood clot subcutaneously, and ecchymosis as any discoloration of the skin at discharge from the hospital.

The Medical Outcomes Study pain measures were used to quantify postoperative leg incision pain. It is a reliable (internal consistency of 0.91) and valid method of pain measure (correlations with physical assessment 0.52 to 0.68), and measures the severity, duration, and effects of pain on behavior before compiling these measures into a summary index score [9]. The index score is then standardized to a mean of 0 and standard deviation of 1. Thus, a score of -1 represents 1 standard deviation less pain than the study average, and a score of +1 represents 1 standard deviation more pain than the study average.

In order to measure the convalescence period, the SF-12, a multipurpose measure of general health, was used. The SF-12 is a reliable (internal consistency of physical component summary [PCS] = 0.89 and mental component summary [MCS] = 0.76) and valid (correlations with physical assessment PCS = 0.43 to 0.78 and MCS = 0.93 to 0.98) measure of health and gives two scores: PCS and MCS [10]. The two components of the SF-12 score are able to reproduce the results of the longer SF-36 with an accuracy of 90% or better [11].

Student’s nonpaired t test, ² analysis, and Kruskall-Wallis analysis of variance were applied where appropriate. Statistical analysis was performed using the Statistica (StatSoft, Inc, Tulsa, OK). A p value of 0.05 was considered significant.

	Results

Top Abstract Introduction Material and methods Results Comment References

 
The OVH group contained 13 females and 37 males, while the EVH group contained 9 females and 41 males. The mean age of the OVH group was 65.6 years vs 63.8 years in the EVH group. Both groups were racially identical, with 43 Caucasians, 4 African-Americans, and 3 Native American in each group.

Baseline assessments comparing comorbidities, wound infection risk, and standardized body habitus were performed on all patients in the trial. The average number of cardiac risk factors was 3.82 for the EVH group and 3.88 for the OVH group (p = 0.88). The average Charlson Comorbidity score was 2.1 for the EVH group and 2.28 for the OVH group (p = 0.29). The average ejection fraction in the EVH group was 54% and 43% for the OVH group (p = 0.90). The NNIS class for measuring wound infection risk was 1.1 for the EVH group and 1.14 for the OVH group (p = 0.54). The BMI for the EVH group was 28.3 and for the OVH group was 28.2 (p = 0.96). In the EVH group, 32% were diabetic, and in the OVH group, 28% were diabetic (p = 0.67). The length of bypass was 104 minutes for the EVH group and 115 min for the OVH group (p = 0.18). The cross-clamp time was 45 minutes for the EVH group and 47 minutes for the OVH group (p = 0.46). Therefore, differences in baseline characteristics between the EVH and OVH groups are not a probable explanation for any results either observed or not observed in this trial.

While it does take longer to perform than OVH, EVH significantly reduces the length of incisions on a patient’s body (see Table 1). The amount of vein obtained by either technique is adequate and grossly similar in quality, with two 7-0 Prolene repairs being required in the EVH group and one in the OVH group. The longer preparation time needed for EVH was associated with typing off all side branches, a physician preference. The maximum number of venous bypasses was four in both groups.

The primary outcomes of this trial, wound complications, pain levels, and general health status, are summarized in Tables 2 to 4. The LOS from surgery until discharge from the hospital was not significantly different between the two groups, with an LOS of 5.6 ± 1.1 days for the EVH group and an LOS of 6.0 ± 2.9 days for the OVH group (p = 0.714). However, patients preferred EVH over OVH overwhelmingly: 100% vs 0% of the patients (p < 0.01). Additionally, 23 EVH patients versus 12 OVH patients perceived the cosmetic result of the leg incision(s) as very good or excellent (² = 4.64, p = 0.03).

	Comment

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The results of the pain survey over the postoperative period are mixed. The EVH group reported less pain at discharge, but more pain at 3 weeks and equivocal pain at 6 weeks. Several factors may contribute to the observed pattern. Because of the shorter length of incisions, EVH patients may have less incision pain at discharge. However, 3 weeks after surgery, some patients are in the process of recovering from wound complications, especially infection. With EVH, the surrounding cellulitis is much more severe and less easily dealt with than the opening and draining of the wound in the OVH group, possibly causing additional postoperative pain. Further, saphenous nerve injury may contribute to the increased postoperative discomfort the EVH group reports. At 6 weeks, most wounds have healed and postoperative inflammation subsided; thus, the groups would be expected to be comparable.

In has also been suggested that EVH will lead to faster recovery times because of reduced pain and complications. In this study, we found neither faster recovery times nor reduced pain, as measured by two reliable, and scientifically validated measures of functional status: the SF-12 score and the Medical Outcomes Study Pain Survey. Additionally, there is no randomized study to date that has shown these benefits with EVH [13, 14]. Therefore, improved functional outcome as an economic means of justifying the added expense of EVH remains unproven.

However, the suggestion that EVH results in a better cosmetic appearance and that those patients overwhelmingly prefer EVH to OVH is supported by the findings of this trial. Patients make the final decision on the acceptability or unacceptability of any surgical procedure, and whether science can explain the logic behind patient decisions and preferences is sometimes less important than the wishes themselves.

One of the difficulties with randomized clinical trials is that crossover between the arms of the study can create a statistical type II error, that is, not finding difference between groups when one does in fact exist. We experienced a high conversion rate of 22%, which could have led to the equivocal results reported. In order to further evaluate factors that led to conversion from an EVH to an OVH, univariate analysis was performed. From this analysis, it was determined that a BMI greater than 29 (morbid obesity) resulted in a relative risk of conversion of 2.8 (² = 8.26, p < 0.01), and a Charlson comorbidity index score greater than 2 resulted in a relative risk of conversion of 2.5 (² = 4.05, p = 0.04). The difficulty in completing EVH in obese patients was due to the decreased visibility from intruding fat; the additional weight upon the EVH device resulting in decreased mobility and the complete loss of positioning that resulted when the Subcu-Dissector was exchanged for the Subcu-Retractor. Unfortunately, the groups at highest risk for leg wound complications after an open harvest were the patients at the highest risk for conversion to OVH, thus blunting the ability to distinguish differences between the EVH and OVH groups.

The overall morbidity and convalescence of the CABG procedure itself also confounded measuring the functional recovery of CABG patients. It has been reported that older patients (age > 70 years) have not improved their functional status over their preoperative baseline as much as 6 months after surgery [15]. In this trial, 24% of patients were 70 years of age or older and 30% were retired before surgery. Therefore, isolating the functional improvement, if any, by changing the method of vein harvesting in CABG patients may not be possible.

EVH is gaining in acceptance and spreading in use largely because of its appeal to patients and the superior cosmetic results it offers. This growth is occurring with only minimal benefit regarding wound complications and a lack of clinical benefit regarding incisional pain, general health status, or length of hospital stay. Finally, the equivocal results observed in this trial might no longer be valid because of the substantial changes that have taken place with EVH technology since the completion of this trial. Therefore, continued analysis will be needed to determine the ultimate role of endoscopic vein harvesting.

	Acknowledgments

 
This research was supported by a grant from Ethicon Endo-Surgery, Inc, Cincinnati, OH and the Department of Surgery, Duke University Medical Center, Durham, NC.

	References

Top Abstract Introduction Material and methods Results Comment References

 

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6. Charlson M.E., Pompei P., Ales K.L. A new method of classifying prognostic comorbidity in longitudinal studies. J Chron Dis 1987;40:705-712.[Medline]
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9. Sherbourne C. Pain Measures. In: Stewart A.L., Ware J.E., eds. Measuring functioning and well-being. Durham, NC: Duke University Press, 1992:220-234.
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12. Utley J.R., Thomason M.E., Wallace D.J., et al. Preoperative correlates of impaired wound healing after saphenous vein excision. J Thorac Cardiovasc Surg 1989;98:147-149.[Abstract]
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