| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Ann Thorac Surg 1998;66:139-143
© 1998 The Society of Thoracic Surgeons
a Cardiac Surgical Research Center, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, USA
b Division of Laboratory Medicine and Pathology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, USA
c Section of Cardiovascular Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, USA
Accepted for publication March 3, 1998.
Address reprint requests to Dr Dearani, Section of Cardiovascular Surgery, Mayo Clinic and Mayo Foundation, 200 First St SW, Rochester, MN 55905
e-mail: (jdearani{at}mayo.edu)
 |
Abstract |
|---|
 TopFootnotes Abstract IntroductionMaterial and methodsResultsCommentAcknowledgmentsReferences |
|---|
Methods and Results. Porcine veins were harvested in either an endoscopic or open fashion. Superfusion bioassay from endoscopic veins had a similar basal secretion as control veins (6.5% ± 1.5% versus 3.2% ± 2.2%, respectively; n = 5, p = 0.39). Calcium ionophore A23187 stimulation was similar in both groups (24.6% ± 5.1% versus 27.3% ± 9.6%; n = 5, p = 0.68). Light and electron microscopy documented a normal endothelial monolayer in both groups with no endothelial cell or connective tissue loss. Encouraged by these results, 38 patients have subsequently undergone this procedure at our institution. Total operative time for harvesting 35 to 45 cm of saphenous vein was 62.3 ± 5.3 minutes (range, 35 to 120 minutes). The procurement time in the most recent five patients was 41.6 ± 3.3 minutes. Patients had little incisional pain, but did have mild ecchymosis.
Conclusions. Endothelial release of vasoactive substances after endoscopic harvesting is similar to that after the traditional, extended incision technique, and microscopy confirmed similar histology. These laboratory findings support the satisfactory early clinical experience with endoscopic harvesting of saphenous veins.
|
Introduction |
|---|
|
TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsReferences |
|---|
Novel instrumentation has recently become available for endoscopic harvesting of the saphenous vein. The premise of this instrumentation is founded on endoscopic visualization of the vein, an extended retractor for skin elevation, and a modified Mayo vein stripper [4]. A vein stripper has been used by others in a blind fashion for saphenous vein procurement [5–7], but there is little information on the integrity of endothelial function after alternative vein harvesting. Therefore, the present study was designed to evaluate the endothelial release of vasoactive substances in endoscopically and openly excised vein segments in a pig model. After demonstration of endothelial integrity with endoscopic vein harvesting, the study was expanded to include our initial clinical experience.
|
Material and methods |
|---|
|
TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsReferences |
|---|
Harvesting of vein
Adult pigs weighing between 35 and 45 kg were anesthetized with a combination of xylazine (60 mg intramuscularly), Telazol (timetamine and zolzapam, 150 mg combined intramuscularly), and glycopyrrolate (1.8 mg intramuscularly). Anesthesia was maintained with inhalational halothane.
The superficial cranial epigastric vein was harvested, representing a porcine anatomic model of the human saphenous vein, with the Ethicon (Cincinnati, OH) Endopath Subcu-Retractor, Subcu-Dissector, and Vessel Dissector (endoscopic technique) [4]. Side branches were singularly ligated with endoscopic metallic clips and incised. The vein was immediately placed in oxygenated, cold (4°C), modified Krebs’ bicarbonate solution (in mmol/L: NaCl, 118.3; glucose, 11.1; KCl, 4.7; MgSO4, 1.2; KH2PO4, 1.2; CaCl2, 2.5; NaHCO3, 25.0; pH 7.4). The contralateral vein was removed by an extended incision (open technique) with metallic clip ligation of side branches under direct vision. After harvesting of both veins, the heart was rapidly excised and placed in modified Krebs’ solution. The order of vein harvesting, endoscopic followed by open and vice versa, was randomized between animals.
Superfusion bioassay of luminal secretion
The bioassay apparatus was fashioned as previously described [8]. In brief, the endothelium was mechanically denuded in a coronary artery ring (porcine proximal circumflex coronary artery) and mounted on a force transducer (biodetector ring) [9]. The biodetector ring was sequentially stretched to an optimal length–tension during perfusion with Krebs’ solution. Prostaglandin F2
(2 x 10-6 mol/L) was added to the perfusate to contract the biodetector ring. Confirmation of endothelial removal from the biodetector ring was documented by lack of response to bradykinin (10-6 mol/L).
The paired vein segments, one endoscopic and the other open technique, were perfused at a constant flow (5 mL/min) at 37°C. There was a transient delay of less than 1 second before the effluent reached the biodetector ring. The basal release of vasoactive substances was documented by switching from perfusate through a stainless steel cannula to effluent from the veins. After stabilization of the biodetector-evoked response, calcium ionophore (10-6 mol/L) was administered proximal to the vein. Indomethacin (10-5 mol/L) was then added to the Krebs’ solution, the system was permitted to equilibrate for 40 minutes, and the above steps were repeated.
Histology
Ten saphenous vein segments from the five pigs were immediately fixed in 10% buffered formalin. Separate segments were fixed immediately in Trump’s solution (glutaraldehyde-based) for transmission and scanning electron microscopy. The formalin-fixed segments were embedded in paraffin, and standard glass slides were prepared with a transverse orientation. These were stained with either Verhoeff-van Gieson stain to show elastic fibers or hematoxylin and eosin. Segments from both the open and endoscopically obtained veins in each case were compared at the light microscopic level for significant morphologic injury or differences, such as endothelial denudation and elastic fiber disruption.
In veins fixed in Trump’s, transverse sections from each vein were postfixed in osmium tetroxide and embedded in a synthetic resin, and sections for transmission electron microscopy were prepared using an ultramicrotome. These sections were further stained with lead citrate and uranyl acetate and examined in a Phillips CM10 transmission electron microscope. The sections were assessed for differences in areas of endothelial denudation and qualitative changes in the endothelial cells themselves. Longitudinal sections from each of the veins were dehydrated in graded alcohols and transferred to a critical-point freeze-drying apparatus. They were then mounted on an aluminum stub and sputter-coated with gold/palladium. These preparations were examined in a Jeol 6400 scanning electron microscope, and assessed for endothelial denudation and qualitative changes in the endothelial cells and endothelial surface debris.
Drugs
Indomethacin, bradykinin, prostaglandin F2, calcium ionophore A23187, and dimethyl sulfoxide (DMSO) were obtained from Sigma Chemical (St. Louis, MO). All drugs were prepared daily with distilled water except for indomethacin, which was dissolved in sodium carbonate (10-5 mol/L), and calcium ionophore A23187, which was dissolved in 0.5% DMSO. These doses of sodium carbonate and DMSO have been previously documented to evoke no vascular effects [10]. The concentrations are expressed as final molar concentration in the perfusate.
Clinical experience
From August 1996 to April 1997, 38 patients underwent endoscopic harvesting of the greater saphenous vein graft at our institution. The procedure was attempted on three patients but was converted to a standard incision secondary to poor visualization; these patients are not further included in this report. The procedures were supervised by three surgeons (R.C.D., H.V.S., and J.A.D.) at the same institution. Clinical parameters for this patient cohort were as follows:
Surgical indication
During the developmental stage of endoscopic vein harvesting at our institution, no selection criteria were used to fully evaluate eventual clinical incorporation of this technique. Patients had coronary artery disease in which one or two vein grafts were used. Additional grafts harvested included internal mammary (left or right) and radial arteries.
Surgical technique
Our practice of endoscopic saphenous vein harvesting has previously been described [4]. In brief, the patient’s legs are prepared circumferentially and positioned in a "frog-leg" stance. Four finger-breadths posterior to the proximal margin of the patella, a 3- to 4-cm longitudinal incision is made, and the greater saphenous vein is identified. The subcutaneous retractor is inserted in the incision, and the vein is identified on the television monitor. The dissector is advanced along the proximal course of the saphenous vein, and a subcutaneous tunnel is subsequently fashioned. After the dissector has been advanced to the saphenofemoral junction, it is withdrawn and replaced with the subcutaneous retractor. Our customary practice is to advance the retractor to the limits of the groin and then insert the vein stripper. Gentle circumferential dissection with the stripper will identify lateral branches. These are clipped endoscopically. An endoscopic scissors is passed, and the branch is transected so the clip is retained in the body; the saphenous portion of the branch will venospasm and no bleeding will be noted.
Postoperative course
All patients had the lower extremity wrapped with elastic bandages after the endoscopic harvesting. This was maintained for the first 24 postoperative hours.
Statistical analysis
Results are expressed as mean ± standard error of the mean. In all experiments with animals, n refers to the number of animals in which vein segments were taken. Only paired segments, procured through an endoscopic and open approach, are reported. Relaxations are expressed as percent change in tension from the contraction of the bioassay ring to prostaglandin F2. Statistical evaluation of data was performed with two-tailed Student’s t test for paired observations. Values were considered to be statistically significant when p < 0.05.
|
Results |
|---|
|
TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsReferences |
|---|
Superfusion bioassay of luminal release of nitric oxide
Endoscopically harvested veins had a basal production of vasoactive substances such that the bioassay ring relaxed 6.5% ± 1.5% (Fig 1). Veins harvested in an open manner had a basal production of vasoactive substances such that the bioassay ring relaxed 3.2% ± 2.2% (p = 0.39). Calcium ionophore stimulation of endoscopically harvested veins relaxed the bioassay ring 24.6% ± 5.1%, whereas stimulation of veins harvested in an open manner evoked a 27.3% ± 9.6% relaxation (p = 0.68).
|
Histology
The sections examined under light microscopy showed no significant differences. In particular, both the openly harvested and endoscopically harvested vein sections showed minimal endothelial retraction and small intimal fissures. This was believed to be mostly preparation artifact. Endothelial denudation in each case was minimal and was limited to isolated cells. There were no significant areas of endothelial denudation. Those sections stained for elastic fibers again showed no obvious fiber disruption.
The sections examined with transmission electron microscopy were similar. Endothelial cell retraction, most likely artifact, was the same in each group, and all cases showed patches of endothelial denudation. Significant morphologic differences in the appearance of the endothelial cells themselves were not observed (Fig 2).
|
Intraoperative procurement
Thirty-eight patients underwent endoscopic saphenous vein harvesting, performed by six surgical technicians. However, one surgical technician was present during all procedures to provide continuity of technique. Three conversions to traditional harvesting were performed, two for avulsive injuries and one for difficulty in visualization. None jeopardized the coronary revascularization.
The procurement times of the remaining 35 patients who had successful endoscopic saphenous vein harvesting averaged 60 ± 3 minutes (range, 34 to 120 minutes). The total length of graft harvested was 44.5 ± 2.0 cm, providing a harvest time of 0.9 ± 0.1 cm/min. This was slightly swifter than that noted during the animal studies (0.7 ± 0.1 cm/min), as the greater length harvested negated some of the fixed preparation time, but considerably slower than veins harvested clinically in the traditional manner. However, the procurement time in the most recent 5 patients was only 41.6 ± 3.3 minutes, confirming a learning curve was indeed operative.
Postoperative management
The leg was wrapped with elastic bandages for 24 hours after vein harvest. The absence of incisional pain was universal in all patients with veins harvested by the endoscopic manner. Mild ecchymosis was noted in the majority of patients, but no hematomas, seromas, or infections were observed. One patient underwent exploration the first postoperative night for mediastinal bleeding; a suture had slipped from a large side branch of the vein graft.
|
Comment |
|---|
|
TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsReferences |
|---|
Vascular endothelium can produce several biologically active compounds, of which nitric oxide and prostacyclin are the predominant vasodilators. Nitric oxide is a ubiquitous vasodilator, produced by the vascular endothelium, that is capable of inhibiting platelet aggregation, smooth muscle proliferation, and leukocyte adhesion and scavenging superoxide anions [11–14]. Prostacyclin relaxes blood vessels, inhibits aggregation of platelets, and synergistically potentiates nitric oxide [11, 15, 16]. Preservation of either compound in coronary artery bypass conduits may improve both early and long-term patency results by their antithrombotic and antiproliferative properties. The present investigation demonstrated preservation of basal and stimulated release of vasoactive substances from endoscopically harvested veins. Indomethacin did not significantly attenuate this release, suggesting a predominant nitric oxide component. We did not further characterize the composition of these vasoactive substances as the porcine superficial cranial epigastric vein is not well described within the literature, abrogating comparison to published reports.
Additional factors that might injure endothelium of vein grafts, aside from harvest trauma, include high-pressure distention, nonphysiologic pH of the preservation solution, and transient loss of luminal flow with resultant ischemia. The present study did not examine all of these variables as the purpose was limited to comparison of traumatic injury. Prior studies have demonstrated correlation between animal and human saphenous vein data in the superfusion bioassay preparation [17].
Histologic examination, both with light and electron microscopy, confirmed the preservation of endothelial integrity with endoscopic vein harvesting. Transmission electron microscopy demonstrated similar cell morphology for endocopically harvested veins compared with veins harvested in an open manner. As scanning electron microscopy and light microscopy demonstrated similar small patches of endothelial denudation and disruption of elastic fibers, the possibility of preparation artifact in these small regions of the vein must be entertained. Although a type II error may be present with the small sample size in the present study, the remarkable similarity in the two groups suggests a larger sample size would, at most, only detect a small difference that, although interesting, would not likely be clinically relevant.
Minimally invasive techniques have revolutionized surgical interventions. Smaller incisions and reduced dissection have affected postoperative morbidity in several surgical disciplines. However, the reduction in patient morbidity must be weighed against a perceived or real compromise in quality of the operative procedure. Certainly laproscopic cholecystectomies would not have reached widespread acceptance if an increased bile duct injury rate persisted after the initial learning curve. Analogously, an attempt to apply minimally invasive techniques to cardiac surgical procedures must be scrutinized for heightened morbidity. Therefore, greater saphenous vein harvesting must be evaluated for increased damage to the vein; it is surprising that several centers have incorporated this procedure into their routine practice without this information. The present study demonstrated comparable production of endothelial-derived vasoactive substances from porcine veins harvested endoscopically in comparison to the standard, "open" fashion.
The present report also demonstrated an acceptable learning curve to clinical application. Greater than 90% of patients could have successful endoscopic harvesting of veins. Although the procurement time was greater with endoscopic vein harvesting than with traditional methods, it would be reasoned that further experience and improved instrumentation could reduce the discrepancy. The larger issue at hand is the impact minimally invasive surgical procedures will have on the morbidity of cardiac operations. The traditional method of harvesting a vein for coronary revascularization, an extended lower extremity incision, is associated with morbidity rates as great as 24% [3]. However, many of these complications are well-tolerated in the postoperative convalescence and do not dramatically affect either the duration of hospitalization or total accrued costs of the procedure. Further documentation is required before minimally invasive cardiac surgery, be it endoscopic vein harvesting or coronary artery bypass grafting, can be uniformly endorsed.
Endothelial release of vasoactive substances after endoscopic harvesting of vein conduits is similar to the traditional, extended incision technique, and microscopy confirmed similar histology. These laboratory findings support the satisfactory early clinical experience with endoscopic harvest of saphenous veins.
|
Acknowledgments |
|---|
|
TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsReferences |
|---|
Supported in part by The Mayo Foundation. Performed during the tenure of D.G.C. as a Clinical Investigator Research Fellow.
|
Footnotes |
|---|
|
TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsReferences |
|---|
|
References |
|---|
|
TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsReferences |
|---|
This article has been cited by other articles:
|
|
 |
|
  L. J. Rousou, K. B. Taylor, X.-G. Lu, N. Healey, M. D. Crittenden, S. F. Khuri, and H. S. Thatte Saphenous Vein Conduits Harvested by Endoscopic Technique Exhibit Structural and Functional Damage Ann. Thorac. Surg., January 1, 2009; 87(1): 62 - 70. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. R Vaidyanathan, M. N Sankar, and K. M Cherian Endoscopic vs Conventional Vein Harvesting: a Prospective Analysis Asian Cardiovasc Thorac Ann, April 1, 2008; 16(2): 134 - 138. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. L. Yun, Y. Wu, V. Aharonian, P. Mansukhani, T. A. Pfeffer, C. F. Sintek, G. S. Kochamba, G. Grunkemeier, and S. Khonsari Randomized trial of endoscopic versus open vein harvest for coronary artery bypass grafting: Six-month patency rates J. Thorac. Cardiovasc. Surg., March 1, 2005; 129(3): 496 - 503. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. E. Hamner, P. Gloviczki, S. Meany, and R. O. De Jesus Endoscopic Vein Harvest and Minimal Incision Femoropopltal Saphenous Vein Bypass Graft Perspectives in Vascular Surgery and Endovascular Therapy, December 1, 2004; 16(4): 323 - 328. [Abstract] [PDF]
|
|
|
|
|
|
L.P. Perrault, H. Jeanmart, L. Bilodeau, J. Lesperance, J.-F. Tanguay, D. Bouchard, P. Page, and M. Carrier Early quantitative coronary angiography of saphenous vein grafts for coronary artery bypass grafting harvested by means of open versus endoscopic saphenectomy: A prospective randomized trial J. Thorac. Cardiovasc. Surg., May 1, 2004; 127(5): 1402 - 1407. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. C. Cook, C. M. Crowley, R. Hayden, M. Gao, L. Fedoruk, S. V. Lichtenstein, and C. van Breemen Traction injury during minimally invasive harvesting of the saphenous vein is associated with impaired endothelial function J. Thorac. Cardiovasc. Surg., January 1, 2004; 127(1): 65 - 70. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. T. Greenfield, W. A. Whitworth, L. L. Tavares, M. T. Wittenbraker, D. M. Wallace, J. A. Valdivia, K. Campbell, L. Williams, E. Black, R. Pillai, et al. Minimally invasive vein harvest and wound healing using the SaphLITE retractor system Ann. Thorac. Surg., September 1, 2001; 72(3): S1046 - 1049. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. A. Black, T. J. Guzik, N. E.J. West, K. Campbell, R. Pillai, C. Ratnatunga, and K. M. Channon Minimally invasive saphenous vein harvesting: effects on endothelial and smooth muscle function Ann. Thorac. Surg., May 1, 2001; 71(5): 1503 - 1507. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. M. Fabricius, A. Oser, A. Diegeler, T. Rauch, and F. W. Mohr Endothelial function of human vena saphena magna prepared with different minimally invasive harvesting techniques Eur. J. Cardiothorac. Surg., October 1, 2000; 18(4): 400 - 403. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. M. Fabricius, A. Diegeler, N. Doll, H. Weidenbach, and F. W. Mohr Minimally invasive saphenous vein harvesting techniques: morphology and postoperative outcome Ann. Thorac. Surg., August 1, 2000; 70(2): 473 - 478. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. M. Meyer, T. E. Rogers, M. E. Jessen, A. S. Estrera, and A. K. Chin Histologic evidence of the safety of endoscopic saphenous vein graft preparation Ann. Thorac. Surg., August 1, 2000; 70(2): 487 - 491. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Rinia-Feenstra, W. Stooker, R. de Graaf, J. J. Kloek, M. Pfaffendorf, B. A.J.M. de Mol, and P. A. van Zwieten Functional properties of the saphenous vein harvested by minimally invasive techniques Ann. Thorac. Surg., April 1, 2000; 69(4): 1116 - 1120. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. A. Carpino, K. R. Khabbaz, R. M. Bojar, H. Rastegar, K. G. Warner, R. E. Murphy, and D. D. Payne CLINICAL BENEFITS OF ENDOSCOPIC VEIN HARVESTING IN PATIENTS WITH RISK FACTORS FOR SAPHENECTOMY WOUND INFECTIONS UNDERGOING CORONARY ARTERY BYPASS GRAFTING J. Thorac. Cardiovasc. Surg., January 1, 2000; 119(1): 69 - 76. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Z. Hayward III, L. A. Hey, L. L. Newman, F. G. Duhaylongsod, K. A. Hayward, J. E. Lowe, and P. K. Smith Endoscopic versus open saphenous vein harvest: the effect on postoperative outcomes Ann. Thorac. Surg., December 1, 1999; 68(6): 2107 - 2110. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Coppoolse, W. Rees, R. Krech, M. Hufnagel, K. Seufert, and H. Warnecke Routine minimal invasive vein harvesting reduces postoperative morbidity in cardiac bypass procedures. Clinical report of 1400 patients Eur. J. Cardiothorac. Surg., November 1, 1999; 16(suppl_2): S61 - S66. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
