Vascular Anastomotic Techniques and Exposures
The need for practical training in vascular anastomotic techniques is well recognised by the surgical community.
This section is designed to provide an introductory guide on anastomotic techniques, and a summary of the popular techniques used for future reference.
Vascular surgery requires a highly meticulous technique. The consequences of technical failure are often extreme, ranging from catastrophic haemorrhage to loss of limb, and since many patients are elderly with concomitant cardiac disease, prolonged or repeated surgery may result in significant morbidity. Careful and controlled surgery with particular attention to detail is essential, and adherence to the following principles will form the basis for the development of a proficient technique.
- Arteries should be handled gently. Do not pick up the artery with forceps, but lift it with a sling or use the adventitia for traction.
- Prepare the artery thoroughly by dissecting onto the correct plane, and clearing the artery of all other tissue.
Sutures are often delicate and will easily break. They should never be grasped between forceps. Always insert the suture at right angles to the artery, from inside the artery to the outside - this will prevent the development of an intimal flap. Always ensure that the suture has penetrated the full thickness of the arterial wall so that all layers are held together, and pull the thread in the direction in which the suture was placed so that a “cheesewire effect” does not occur.
The knot must be a carefully laid “reef knot”, with 4 or 5 throws for braided material and 6 or more for monofilament. The knot should be pushed down onto the anastomosis with a finger, since any upward pull will cause the suture to cut through the artery. The ends should be left long, especially with monofilament sutures, to avoid unravelling.
- A stenosis at the anastomosis must be avoided at all costs. Beware of the “purse string effect” of a continuous suture, and the potential for narrowing following direct suture of an arteriotomy. The poor shaping and suturing of the graft in an end-to-side anastomosis is a common cause of stenosis.
- Surfaces must be everted by the suture which ensures that intima to intima or intima to new graft surface contact is achieved. Contact between the adventitia and blood is prevented and turbulent blood flow is minimised.
Correct size matching of graft to the artery and the formation of a tension free anastomosis are critical to the overall success of the repair.
- Before beginning the anastomosis, ensure that everything has been well prepared; you will then be able to develop a rhythm as you work. For accuracy and comfort, the surgeon should remain relaxed and employ pronation as opposed to supination sewing.
All of these factors contribute towards precise anastomotic techniques.
All clamps will damage an artery. Atheroma may be dislodged, calcified material disrupted, or the arterial wall crushed. Use only vascular clamps and apply them gently. If there is hard plaque, place the clamps as shown so that the plaque is not crushed.
Avoid excessive movement of clamps by fixing them to drapes etc. Eccentric plaque formation often on the posterior wall requires the use of an inserted pledget between the jaws of the clamp and the arterial wall ensuring haemostasis.
Before completion of the anastomosis, it is important to flush the artery to remove air and any debris, which would otherwise embolise distally. Do this by briefly releasing then reclamping the proximal arterial clamp, then removing the distal clamp and tying the suture. Arterial pressure will also distend the anastomosis to its maximum - this should be allowed to occur before the final knot is tied.
The suture is passed through the graft, into the arterial lumen, and out through the wall of the artery. It is important that adequate but not excessive tension is maintained on the suture.
This technique is useful at the heel of an anastomosis where it may be difficult to place sutures accurately. Three or four loose sutures are placed using a monofilament double-ended suture, then tightened by gently drawing each end tight.
Interrupted sutures are especially useful at the apex of an anastomosis, to enable accurate placement, correct tensioning and the avoidance of stenosis. Once all the sutures have been placed, they are tied.
An alternative to the parachute stitch at the heel is the mattress suture - this should only be used at the heel of an anastomosis in large vessels. Using a double-ended suture, this allows suturing to be carried out from within the artery with both ends, thus minimising the risk of generating an intimal flap. This suture will also aid eversion between graft and artery.
Types of Anastomosis
This technique is used to prevent stenosis when closing an arteriotomy, such as a carotid endarterectomy. Synthetic material or vein may be used. The patch is cut in an elliptical as opposed to a diamond shape. Each apex is well rounded to prevent narrowing and is initially left long, and trimmed when one end has been sutured in position.
The anastomosis is carried out using a continuous double-ended suture.
This method is used to suture an inlay graft to the aorta or to join two arterial ends. Although the ends may be left at 90o, they are commonly cut obliquely which increases the anastomotic area and decreases the risk of stenosis.
Begin posteriorly, using a double-ended suture, which is tied outside the arterial lumen. The anastomosis is completed using a continuous over-and-over suture, and the two ends are tied anteriorly, again outside the lumen.
Stay sutures may be placed laterally before beginning the anastomosis. In small vessels, three stay sutures are placed (the “triangulation technique”) and interrupted sutures are used.
This is used to anastomose a vein or synthetic graft to an artery. It requires care to ensure that the integrity of the anastomosis is maintained, especially at the heel, while stenosis is avoided.
The anastomosis is constructed as follows:
The graft is cut obliquely at 45o, an S-shape is followed to increase the width of the heel of the apex.
A longitudinal incision is made on the native artery, using a scalpel then Potts scissors, taking care not to damage the posterior wall.
The graft is held against the native artery to ensure that the lengths match. At this stage, the arteriotomy could be left slightly short and subsequently lengthened, if required.
Begin suturing at the heel. Use of the parachute technique will enable accurate placement of heel sutures, which is important, since later modification will be difficult. Continue suturing the lateral wall using a continuous suture.
It is crucial to avoid a stenosis at the apex, particularly in small vessels. This may be achieved by placing several interrupted sutures (refer to diagram 6).
The remainder of the anastomosis is completed using a continuous suture.
Vein must be handled with extreme care. It may be helpful to use venous tributaries to handle the vein, or to leave tags which can be trimmed later.
Synthetic polyester grafts have been widely available as either knitted or woven products for a number of years. Initial designs required preclotting prior to implantation, however, the development of protein sealed grafts negated the need for this task to be undertaken.
Vascutek has a wide range of gelatin sealed vascular prostheses. The gelatin impregnation hydrolyses over a period of 14 days by a non-enzymatic mechanism which does not elicit a prolonged inflammatory reaction.
Vascutek’s grafts are crimped and will therefore elongate. This crimping feature serves two purposes:
- It provides the surgeon with a cylindrical structure rather than a flat tube to handle. Matching of diameters, cutting to shape and suturing are greatly helped if, during its adaptation to the host artery, the prosthesis has the shape it will assume once blood pressure is applied.
- It maintains a certain degree of longitudinal elasticity, even after the graft has been fully elongated and the correct tension applied. The marker lines on the Gelseal™ and Gelsoft™ products act as a “torque tension indicator” which assume a square pattern when the correct tension is applied.
The graft should be handled carefully and may be held with forceps.
The graft should be handled carefully and may be held with forceps as described in the products instructions for use.
This material is delicate and tears easily. Suture hole bleeding is a common problem which can be minimised by careful attention to suture technique, by the use of specialised sutures designed for use with PTFE and by using gelatin sealed ePTFE (eg. SEALPTFE™ and Taperflo™).
Unlike polyester crimped grafts, PTFE products do not retain their cylindrical shape prior to implantation. Choosing the correct diameter and “tailoring” it to the required shape, allowing a precise anastomosis to be formed, can sometimes prove more difficult. PTFE is a non-elastic material and must therefore be cut to the precise size.
Sutures used for vascular anastomosis should be non-absorbable. The main types of suture used are:
- Monofilament polypropylene
- Monofilament PTFE
- Braided polyester coated with silicone
Polypropylene and polyester sutures are used for polyester grafts. Polypropylene and PTFE sutures are commonly used with ePTFE grafts.
For arterial surgery, needles are available in either a tapered or round-bodied design. They may be curved into a semi or quarter circle. The optimum curvature used will depend on the size of the artery and ease of access.
Toughened needles are available for use in hard, calcified arteries where standard needles may bend.
For those who wish to study the subject of anastomotic techniques in more depth, an excellent publication is “Atlas of Vascular Surgery – Basic Techniques and Exposures” by Rutherford. Published by W B Saunders Co, 1993.
“All Vascutek Ltd Unsealed Vascular Prostheses are sterilised using Ethylene Oxide gas and are supplied sterile for single use only. However, should you choose to re-sterilise the prostheses use either steam or Ethylene Oxide, per the instructions provided by the manufacturer of the sterilisation equipment and established hospital procedures, where this is permissible under national legislation. In the event of re-sterilisation, the user accepts full responsibility for sterility, the burden of proof on sterility and full responsibility for any damage that may result to the product. DO NOT RESTERILIZE WITH ANY TYPE OF RADIATION EQUIPMENT. This will damage the device and render it unfit for its intended use, resulting in risk to the patient.”