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Ann Thorac Surg 2000;70:487-491
© 2000 The Society of Thoracic Surgeons

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Original articles: cardiovascular

Histologic evidence of the safety of endoscopic saphenous vein graft preparation

^a Departments of Surgery and Pathology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA
^b Dallas Veterans Administration Medical Center, Dallas, Texas, USA
^c Guidant Corporation, Cardiac and Vascular Surgery, Menlo Park, California, USA

Address reprint requests to Dr Meyer, Department of Thoracic and Cardiovascular Surgery, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75235–8879
e-mail: dan.meyer{at}email.swmed.edu

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
Background. Endoscopic methods of saphenous vein procurement have recently been introduced. These techniques have been successful in limiting pain and wound complications, but less information on assessing potential trauma to the harvested vein segment is available.

Methods. Fourteen male patients undergoing coronary artery bypass grafting were included in the study. Nine patients underwent endoscopic procurement of saphenous vein whereas 5 patients underwent procurement using standard open techniques. Histologic appearance and immunohistochemical studies (factor VIII:vWF [von Willebrand factor protein] and CD34) of the vein segments were reviewed in a blinded fashion.

Results. On histologic analysis, no differences in the intima, media, or adventitia were found between endoscopically and conventionally obtained vein segments. Immunohistochemical staining for factor VIII:vWF and CD34 showed no differences between veins harvested by the two techniques.

Conclusions. Endoscopic saphenous vein harvesting does not appear to traumatize the vessel wall any more than open techniques. Longitudinal assessment is necessary to evaluate long-term patency in vein grafts procured using this method.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
Less invasive approaches to coronary artery bypass grafting (CABG) surgery are currently being investigated with intense interest. An important part of coronary surgery involves harvesting and preparation of venous and arterial conduits. Efforts to limit postoperative pain and offer the patient a more aesthetic surgical wound have prompted evaluation of endoscopic techniques for saphenous vein harvest [1, 2]. Early reports of these techniques have suggested that they offer a reduced incidence of wound complications and a superior cosmetic result [3, 4]. However, although vein grafts can be procured by endoscopic techniques, few data are available on the condition of the harvested conduits. The goal of this study was to assess the degree of vascular trauma sustained by saphenous vein conduits prepared by an endoscopic technique compared with those harvested by conventional open methods.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

 
Fourteen men aged 52 to 71 years undergoing elective coronary artery bypass grafting at the Dallas Veterans Administration Medical Center were included in this study. All patients had multivessel coronary artery disease and were scheduled for CABG to include grafts of the left anterior descending coronary artery (LAD) with the left internal thoracic artery (LITA) and grafts of all other vessels with greater saphenous vein. Patient histories were reviewed for the presence of diabetes, peripheral vascular disease, and any history of congestive heart failure, edema, or prior venous disease. Saphenous vein was dissected by one of the two techniques described below.

Endoscopic saphenous vein dissection
Endoscopically-harvested vein segments were procured from 9 of 14 patients undergoing CABG. Dissection was initiated at the level of the medial maleolus or medial epicondyle. A 15-mm vertical incision was made to expose the greater saphenous vein. After dissection in the visible periadventitial plane, a tapered-tip balloon dissection cannula (VasoView Balloon Dissection System; Guidant Corporation, Cardiac and Vascular Surgery, Menlo Park, CA) (Fig 1) was placed on the anterior surface of the exposed vein. The cannula was advanced in a proximal direction, inflating the balloon to form a perivascular endoscopic operating tunnel (Fig 2). The device was progressively advanced in 3-cm intervals before reinflation of the balloon. The transparent tapered tip transmits a distinct image of the vessel to the video monitor, as it lies in contact with the adventitial surface. Using this image as a roadmap, the cannula was passed the length of the vein. When tributaries were visualized, the cannula was redirected to the side of the vein opposite the tributary to enable passage down the main conduit.

View larger version (143K): [in this window] [in a new window]   Fig 1. Tapered-tip balloon dissecting cannula (VasoView Balloon Dissection System, Guidant Corporation, Cardiac and Vascular Surgery, Menlo Park, CA). The transparent tip allows for visualization during endoscopic dissection.

View larger version (74K): [in this window] [in a new window]   Fig 2. Dissecting the tunnel during endoscopic harvesting of the saphenous vein. The tapered-tip cannula is placed on the adventitial surface of the exposed vein. The cannula is advanced under continuous visualization, initially with the balloon deflated, to form a perivascular tract. After balloon inflation and insufflation, endoscopic instruments are inserted to isolate, ligate, and transect the vein tributaries.

If additional vein was needed after isolation of the leg segment, the cannula was passed from the counterincision near the knee to expose the thigh vein. Once the vein was dissected free, it was ligated, transected at the ankle and the saphenofemoral junction, and removed. The vein segment was cannulated and gently distended with a solution of normal saline (250 mL), papaverine (15 mg), and heparin (2500 U), and stored in this solution at room temperature.

Conventional saphenous vein dissection
For 5 of the 14 patients, 10 vein segments were also prepared from saphenous vein harvested using a conventional open technique. In the open technique, incisions were made over the entire course of the dissected vein segment without any intervening skin bridges to allow maximal exposure in order to minimize trauma to the vein. Side branches, when encountered, were isolated and ligated with silk ligatures; and the vein was cannulated, removed and gently distended with the same solution and stored under identical conditions.

Evaluation of vein segments
Harvested saphenous vein segments were used for aortocoronary bypass grafts. After completing distal anastomoses but before completion of the proximal anastomoses, segments of excess vein were excised and submitted in 10% buffered formalin for histologic examination. Two-millimeter cross sections of each segment were processed and embedded in paraffin for routine light microscopy. Hematoxylin and eosin, Verhoeff’s elastic, and Gomori’s one-step trichrome stained sections were examined in a blinded fashion. Immunohistochemical stains for factor VIII:vWF (von Willebrand factor protein) and CD34, a 110 kD glycoprotein expressed on vascular endothelium, were also examined in cross-sections of vein segments to ascertain the status of the endothelium. The frequency of abnormalities in vein segments from the two groups were compared by Fisher’s exact test.

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
Patients in the two groups did not differ in terms of age or presence of diabetes or peripheral vascular disease. No patient had a history of congestive heart failure, peripheral edema, or known venous disease. Endoscopic saphenous vein harvesting was used to procure 20 vein segments in 9 patients undergoing coronary artery bypass grafting. In two segments submitted from 1 patient, insufficient vein material was provided for histologic review, leaving 18 segments for analysis. Vein procurement from the lower leg required two incisions in 8 patients, and three incisions in 1 patient, with an average incision length of 2.4 cm. Vein segments from the thigh were harvested via two incisions. The time required for saphenous vein harvesting averaged 55 minutes per leg or thigh segment.

A total of 10 vein segments from 5 patients were obtained by the open technique. All were adequate specimens. With this technique, a single skin incision was used that was, by design, much greater in length than those incisions used in the endoscopic approach. Time of harvesting was not recorded in the open group, but was shorter than in the endoscopic group.

Gross examination
In the endoscopically harvested veins, small tributaries were divided an average of 2.5 times per vein segment, requiring vascular clip placement. In 2 early cases, suture repair was used. The number of tributaries encountered in the veins harvested using the open technique was similar.

Histologic examination
Comparison of the histologic features of veins harvested by both the endoscopic and open techniques showed no differences in the frequency of abnormalities in the intimal, medial, or adventitial layers. There was no evidence of any significant vascular injury in these layers and no difference in elastic or connective tissues staining in the vein walls between in the two groups. There was strong immunohistochemical staining of the endothelium in both groups for factors VIII:vWF and CD 34 (Fig 3). Focal areas of minor separation between medial smooth muscle fibers were common in vein cross sections from both groups. These areas were occasionally associated with mild hemorrhage (Fig 4). When assessed in a blinded fashion no significant difference between groups was found in the fraction of samples exhibiting medial separation or hemorrhage (Table 1).

View larger version (131K): [in this window] [in a new window]   Fig 3. Verhoeff’s elastic stain of representative vein segments showing no abnormalities of the intimal, medial, or adventitial layers when procured using a conventional (A) or endoscopic (B) technique. The darkly stained irregular line in the upper portion of the figures (arrow) is the internal elastic lamina. The other darkly stained areas are elastic tissue in the underlying medial and adventitial layers. The insert displays an immunohistochemical stain for factor VIII:vWF showing strong staining of the endothelium, the dark line on the lumenal surface of the vein.

View larger version (146K): [in this window] [in a new window]   Fig 4. Verhoeff’s elastic stain of an endoscopically obtained vein segment showing a focal area of separation of the medial muscle fibers associated with a small amount of hemorrhage in the same area (arrow). This was noted frequently in both the endoscopic and conventionally obtained groups.

	Comment

Top Abstract Introduction Patients and methods Results Comment References

 
Many techniques are under development to enable coronary bypass operations under minimally invasive conditions. Most reports have focused on avoiding a median sternotomy incision or cardiopulmonary bypass (or both) but new endoscopic methods of conduit procurement have also been described. Although several studies have examined the effects of these harvesting techniques on wound sequelae, few data on the impact on the vein graft itself are available.

The two techniques of vein graft procurement have significant differences. The conventional (open) procedure is rapid and provides optimal visualization of the saphenous vein during harvest. However, it is invasive, requires a large incision and a longer period for wound closure, and results in a larger scar. In this study, endoscopic saphenous vein procurement was performed without complication in 9 patients. By employing continuous visualization of the vessel during cannula advancement, the described technique enabled isolation of the vein within the dissected cavity. Tributaries were easily delineated by the dissection cannula, decreasing the potential for avulsion during dissection. In contrast, previous minimally invasive methods of saphenous vein harvest dissected the vein in an axial fashion underneath interrupted skin bridges [5, 6], leaving tributaries obscured until exposed by blunt dissection. In the present study, the time required to procure the vein conduit was longer but decreased as experience was gained. The use of an operating endoscope may have helped facilitate the procedure, as fewer instrument exchanges were needed.

Maintaining the structural integrity of the vein is an important feature of any procurement technique. Studies examining the role of harvest techniques, vein preparation, or storage media have suggested that endothelial cell injury directly affects graft patency [7–9]. Preparation techniques described by Gundry and associates [7] demonstrated the importance of minimal manipulation of the vein graft on the integrity of the endothelium, intima, and media. Angelini and colleagues [8] found that surgical preparation by performance of the proximal venous anastomosis first, allowing the patient’s own blood pressure to distend the vein, preserved both medial and endothelial function. The activity of endothelium-dependent nitric oxide (known previously as endothelium-dependent relaxation factor) was found to be sensitive to preparation techniques when assessed in human saphenous vein segments [9]. In an animal study using endoscopic vein harvesting, endothelial release of vasoactive substances was similar after endoscopic or conventional techniques [10]. In the present study, the atraumatic nature of cannula passage was demonstrated by the presence of intact endothelium in samples examined histologically after endoscopic harvest. There appeared to be no differences in the light microscopic or immunohistochemical staining pattern of the endothelium in either endoscopic or conventionally procured saphenous vein segments in this study. Further evidence for the atraumatic nature of this procedure includes the absence of observed bleeding while negotiating past venous tributaries and the low incidence (1 patient) of hematoma formation on postoperative follow-up.

This study has several noteworthy limitations. The study size is small and statistical power is thereby limited. However, despite longer harvesting periods, greater tissue manipulation, and the application of forces to the external surface of the vein, no histologic changes consistent with endothelial damage were observed in any specimen. By these criteria, endoscopic saphenous vein harvesting appears safe. However, it should be noted that the durability of stainable molecular markers (such as factor VIII:vWF and CD34) on endothelial cells after damage or injury is not well described. Moreover, no biochemical markers of endothelial activity or integrity were studied. It is possible that other measurements such as production of prostacyclin or vasoactive changes induced by endothelial-derived or endothelial-independent factors may be more sensitive indicators of vascular damage. Also, sampling only one or two segments from harvested veins may miss areas of injury at other sites within the vein. Finally, although histologic differences were not seen, the relationship between histologic evidence of vein graft trauma and subsequent graft patency is not established. Longer-term follow-up with direct measurements of graft patency may be required to ultimately assess the efficacy of this, and other, minimally invasive techniques.

	Footnotes

 
Doctor Albert Chin is an employee of Guidant Corporation.

	References

Top Abstract Introduction Patients and methods Results Comment References

 

1. Tevaearai H.T., Mueller X.M., von Segesser L.K. Minimally invasive harvest of the saphenous vein for coronary artery bypass grafting. Ann Thorac Surg 1997;63:S119-S121.
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3. Allen K.B., Griffith G.L., Heimansohn D.A., et al. Endoscopic versus traditional saphenous vein harvesting. Ann Thorac Surg 1998;66:26-32.[Abstract/Free Full Text]
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7. Gundry S.R., Jones M., Ishihara T., Ferrans V.J. Optimal preparation techniques for human saphenous vein grafts. Surgery 1980;88:785-794.[Medline]
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9. Lawrie G.M., Weilbacher D.E., Henry P.D. Endothelium-dependent relaxation in human saphenous vein grafts. J Thorac Cardiovasc Surg 1990;100:612-620.[Abstract]
10. Cable D.G., Dearani J.A., Pfeifer E.A., et al. Minimally invasive saphenous vein harvesting. Ann Thorac Surg 1990;66:139-143.[Abstract/Free Full Text]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Dan M. Meyer Michael E. Jessen Aaron S. Estrera Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Meyer, D. M. Articles by Chin, A. K. Search for Related Content PubMed PubMed Citation Articles by Meyer, D. M. Articles by Chin, A. K.