Continuing Education Activity

Endoscopic vein harvesting (EVH) is a procedure to harvest the greater saphenous vein (GSV), the most widely used conduit in coronary artery bypass graft surgery. This procedure is performed by making small incisions and using an endoscopic camera like a blunt dissector to create a subcutaneous tissue tunnel under the skin. The activity outlines the main steps of the procedure and explains the role of the healthcare team who perform this procedure.

Objectives:

• Describe the anatomy of the greater saphenous vein in detail.
• Review the steps of endoscopic vein harvesting and explain the importance of preoperative venous mapping.
• Outline the advantage of endoscopic vein harvesting in comparison to the conventional (open) technique.
• Explain the importance of collaboration and communication amongst the interprofessional team to ensure appropriate selection of candidates for endoscopic vein harvesting and to enhance outcomes.

Introduction

Over the last decade, endoscopic vein harvesting (EVH) has been the method of choice to harvest the greater saphenous vein (GSV), which is the most widely used conduit in coronary artery bypass graft (CABG) surgery. The saphenous veins often are used due to their ease of harvesting and length. The global demand for CABG surgery, as well as the increasing need for patients to require multiple coronary artery bypasses in the same procedure, have increased the demand for more and better conduits.[1] 

In the past, the conventional open technique of GSV harvesting involved a long skin incision, which often carries a higher incidence of wound complications, and pain. This is often coupled with increased length of hospital stay and a decrease in patient satisfaction. The endoscopic vein harvesting technique has evolved and developed to improve the above-mentioned drawbacks of the open procedure.[2]

A recent review of approximately 28000 patients from 22 studies found that mid and long term patency of vein conduits harvested by the endoscopic technique was lower than the open technique. However, this study was limited to one year. The researchers concluded that growing surgical experience in the EVH might be associated with better outcomes.[3]

Although long-term patency of conduits harvested by EVH has been questioned, many studies show that the patency of vein grafts harvested by EVH technique is similar to the patency reported using the conventional method.[4]

Anatomy and Physiology

The greater saphenous vein is the longest vein in the body. It emerges from the dorsal foot veins medially and runs anteriorly to the medial malleolus. It continues on the medial side of the leg along the tibial side of the calf region beside the edge of the tibia up to the knee. The GSV then runs in a direction posterior and medial to the knee curving behind the medial femoral condyle.

Above the knee, it returns to a more medial position through the medial aspect of the thigh before draining into the common femoral vein at the saphenofemoral junction. Through the whole course of the GSV, it runs in a superficial plane to the muscles and deep fascia of the lower limb. The saphenous nerve runs along the vein at the lower two-thirds of the leg. This orientation makes it more susceptible to injury, to postoperative pain and paresthesias.[5]

Indications

The main indication for endoscopic vein harvesting is coronary artery bypass grafting as a conduit. Other vessels that could qualify for bypass include the internal mammary artery and the radial arteries. The saphenous vein has also found use as a conduit for arteriovenous grafts for dialysis fistulas, peripheral vascular bypass interventions, and cerebral bypass surgeries.[6]

Contraindications

From a technical point of view, there are no absolute contraindications for endoscopic vein harvesting. However, there are some reservations on harvesting the saphenous vein in general, especially in patients with extensive varicosities, deep venous thrombosis, and those where the vessel is of poor quality and would not function as an adequate conduit.[7]

Equipment

Specific devices should be available and working efficiently to perform the endoscopic vein harvesting procedure. Including a zero-degree endoscopic lens connected through a cable to a high definition monitor video display. A light source unit needs to be wired to the lens to provide illumination. A source of carbon dioxide is necessary to insufflate and keep the EVH tunnel open during the procedure. Finally, a ready-made single-use kit which comes as a package to provide housing for the endoscope and electrocautery probe. Different manufacturing companies supply the above-mentioned equipment with similar mechanisms with minor design differences.[8] 

Personnel

In the operating theatre, a surgeon and a surgical scrub nurse are necessary. A surgical technician should be available in the operating theatre as well for any technical or equipment related problems.

Preparation

There is no specific preparation for the endoscopic vein harvesting procedure. However, preoperative bedside venous doppler mapping is of great importance before harvesting. Many centers consider this test mandatory as it provides crucial information regarding the location and quality of the greater saphenous vein as a conduit. The scan provides measurements typically within margin of 95% confidence level of the predicted conduit diameter.[9]

The vein course, size, and quality undergo inspection to asses which side to be harvested or even aborting the procedure entirely in cases of small vein diameter (less than 1.5 to 2 mm), grossly dilated veins, and extensive varicosities. This test is noninvasive and is typically performed in under ten minutes.

Technique or Treatment

Under general anesthesia with the patient positioned supine, the team identifies the surgical site and laterality. The information provided by the previous preoperative venous doppler mapping should be available. For better positioning, the clinician flexes the knee from 90 to 120 degrees with mild external rotation of the hip joint on the ipsilateral side. Towels should support the leg at the posterior aspect of the knee (popliteal region).[10]

The skin incision of approximately two centimeters is made on the medial side of the lower limb one inch above or below the medial tibial tuberosity based on surgeon preference and the mapping. Following identification of the GSV, regular surgical dissection occurs to free the proximal part of the vein and to double-check the suitability of the conduit before starting the procedure. A balloon port is advanced through the incision to seal the tunnel and to prevent the escape of carbon dioxide. The endoscope is introduced into the subcutaneous tissue tunnel created by the device carefully and under vision. Some centers highly recommend starting low dose heparin at this step to prevent thrombus formation inside the conduit.[11]

Carbon dioxide insufflation starts at between 10 and 13 mmHg to facilitate the dissection process and to keep the tunnel opened. The dissection should be gentle to avoid injuries of the wall of the conduit or avulsion of vessel branches. After completing the dissection above and below the knee (or as required) according to the requested number of conduits, the endoscopic electrocautery functions to cut and cauterize the venous tributaries and free the vein from the surrounding adventitia. Small incisions are made at the groin and above the medial malleolus to divide the conduit, allowing its extraction at the site of the original incision. Both proximal and distal ends of the GSV are transfixed with (3-0) silk sutures and clipped with medium titanium clips.[1]

The tunnel gets checked one last time for proper hemostasis. Then pack the tunnel with an antibiotic soaked swab for five minutes before the closure. Some centers routinely consider inserting a surgical drain in the tunnel, while others only use drains in emergencies, or in patients expected to bleed postoperatively. All wounds should get sutured appropriately using absorbable sutures and staplers. The limb should be tightly bandaged with an average amount of pressure to keep the field hemostatic.

Once outside the body, the vein should be cannulated and inspected precisely for any tears, thrombus, or avulsed branches. All branches should be clipped with small clips, while tears can be fixed with (7-0) nonabsorbable sutures. The conduit should be kept in a solution, typically heparinized saline, until the time it is ready to be used in the anastomosis.[12]

Complications

The main complication associated with endoscopic vein harvesting is wound infection. However, the rate of infection is minimal in comparison to the conventional technique. Hematoma, dehiscence, and infection are often managed conservatively, but additional surgery may be necessary for definitive correction.[13]

Saphenous nerve injury during the procedure leads to postoperative pain and altered sensation along the medial aspect of the lower limb. Parasthesias and hyperalgesia can occur at the skin above the harvest site, which is typically temporary. After open and even endoscopic saphenous dissection, it is not uncommon for patients to report having more pain from their leg than from their sternum in the early postoperative period. The proceduralist needs to be aware to avoid damage to the adjacent saphenous nerve by mechanical force or the diathermy heat, particularly in the lower part of the leg where the nerve is close to the great saphenous vein.[14]

Endoscopic vein harvesting insufflates carbon dioxide to facilitate vein exposure. Pneumoperitoneum, subcutaneous extravasation, and air embolism can occur as a result. Treatment typically involves stopping insufflation and supporting hemodynamic status until the carbon dioxide is absorbed.[15]

Clinical Significance

Endoscopic vein harvesting has become the preferred technique for the harvesting of the great saphenous vein to be used in multiple surgical interventions, specifically, coronary artery bypass graft surgery.

A recent meta-analysis of 43 randomized controlled trials (RCT) and observational studies (OT) of 27789 patients took place to compare the two techniques. Forty-six percent of them underwent EVH versus fifty-six percent for the conventional open procedure. The results supported the superiority of the EVH technique for multiple endpoints, including conduit failure, myocardial infarction, mortality, and wound infection.[16]

Enhancing Healthcare Team Outcomes

Greater saphenous vein harvesting is a crucial step in multiple procedures. Endoscopic vein harvesting techniques have resulted in comparable technical outcomes while also improving morbidity, wound infection, hospital stay, and patient satisfaction.  During the EVH procedure, cooperation between the surgeon, the nursing staff, and the radiologist leads to satisfactory results regarding patient care and overall prognosis.