Endo-Vascular Infra-Renal Abdominal Aortic Aneurysm repair (EVAR)
Introduction
What is it?
The abdominal aortic aneurysm (AAA) is a pathological dilatation of the aorta (major arterial conduit conveying blood from the heart to the systemic circulation) when of that dilatation is over 1.5 times its expected diameter (1). Strong risk factors for AAA development are smoking, advanced age, hypertension, hypercholesterolemia, peripheral vascular disease, coronary artery disease, white race, positive family history and male gender (2, 3).
Why is it done?
Aneurysms are generally asymptomatic and diagnosed during abdominal imaging for unrelated conditions. Occasionally, patients may feel a ‘’pulse’’ in their abdomen or palpate a pulsatile mass. Large aneurysms may give chronic back pain or abdominal pain, which is vague and difficult to locate.
Rarely, large aneurysms can cause symptoms from local compression on duodenum, ureter and iliac vein. Acute symptoms of aneurysms are related to either emboli from the aortic thrombus, which may cause acute limb ischaemia or thrombosis of aneurysm and combined rate of occurrence is 2 – 5% (3). Abdominal aortic aneurysm becomes symptomatic due to the rupture or acute expansion.
AAA size remains widely accepted clinical predictor of rupture, which is 5% annual risk for size of 5 cm, 10% - for size of 6 cm and 20% - for the size of 7 cm (1). Growth rate of AAA is a marker for rupture as well and surgery is indicated if size increases 10mm/year (4). When aneurysm exceeds the size of 5.5 cm elective repair is indicated.
Two randomised control studies carried out in UK (UKSAT – UK Small Aneurysm Trial) and USA (ADAM – The Aneurysm Detection and Management) showed lack of benefit of early surgery for abdominal aortic aneurysms with size 4cm to 5.5 cm (3).
Treatment of abdominal aortic aneurysm can be open or endovascular. Endovascular approach is one of the treatment modalities offered to patients whose aneurysms have suitable morphology. Before the procedure measurements of the aneurysm anatomy are obtained to ensure appropriate size of the graft is used (diameter and length of the aortic neck, proximal and distal landing zones, length of the main body and limbs. EVAR can be performed on elective basis as well as an emergency case. The intended benefit is to prevent disastrous and often lethal rupture, which is a natural course of untreated aneurysm.
Will I need to do any preparation?
Before surgery, you may be asked to undergo clinical assessment and a battery of tests designed to assess how well your body is able to withstand the stress of the surgery. It is on the basis of these tests and your teams assessment that you should do well from surgery that the operation will be considered.
You will need to fast before the operation (Six hours for food and two hours for clear liquids). Your recovery after surgery will be greatly enhanced by your state of health before the procedure. The stronger and fitter you are able to get before the procedure, the better the likely outcome and recovery. This approach is sometimes called pre-habilitation as opposed to rehabilitation (which happens afterwards).
Technique
Anaesthesia
Anaesthesia for EVAR can be General, Spinal or even local anaesthesia on some occasions. You may be awake or asleep for the operation depending on your personalised situation. Often the anaesthetist will add a Spinal or Epidural Anaesthetic (needle in the back to number your lower half) to help with pain relief during the surgery and also for the first few days after the operation.
What does it involve?
A typical EVAR device has a main body which consists of a tube with one 'leg' attached. There is a hole in the main tube to allow for the other leg to be connected to the main tube via the other leg. Sometimes an EVAR is done by inserting a simple tube from the aorta to one leg artery. Blood flow to the other leg is maintained by a separate pipe taking blood from one leg to the other in the lower part of the belly.
The standard operation can be subdivided into a number of steps: 1. Access to the blood vessels in the groin; 2. Insertion of main body of the EVAR device; 3. Insertion of the 'Contra-lateral' limb of the EVAR device; 4. Quality control check; 5. Closure of the access blood vessels in the groin.
1. Access to the blood vessels in the groin.
The Common Femoral arteries in the groin are accessed by either an incision or via a needle being inserted through the skin.
2. Insertion of main body of the EVAR device.
The main body (tube) and attached single leg are inserted from one of the groin arteries. The top of the device is positioned just beneath where the kidney arteries come off the aorta.
3. Insertion of the 'Contra-lateral' limb of the EVAR device.
The 'other' leg is inserted from the other groin and 'docked' into the main body. This can be technically challenging as the two separate pieces have to be joined inside the body.
4. Quality control check.
Once the connection has been made, a quality control angiogram is performed to ensure that the aneurysm is well sealed.
5. Closure of the access blood vessels in the groin.
If cuts have been made in the groins, the arteries are closed with stitched as are the tissues above including the skin.
If access has been done through the skin with a needle then the arteries need to be closed under the skin with a 'closure device'. There are a number of types of device available to try to achieve a water tight closure. When this is successfully done then the operation can be achieved without any significant cuts at all.
How long does it take?
The operation usually takes around two hours, however there will be time taken to prepare for
anaesthesia as well as time in recover afterwards.
Post procedure course (follow-up)
Following surgery, you can return to the ward or spend some time in the High Dependancy Unit (HDU) depending on your individual circumstances.
It may be that a number of tubes are attached to you to help you over the first few days. There may be a tube in your back providing pain relief. There may be a tube in your bladder to allow free drainage of urine.
The advantage of EVAR is that the procedure is far less demanding on your body around the time of surgery. Once the procedure is successfully completed, you will need lifelong follow up with regular scan. This is because this operation is not as durable as conventional open surgery. If the seal to the aneurysm breaks down it will require re-intervention to prevent the aorta again being at risk of rupture.
How long will I stay in hospital?
Providing you do not develop complications, you can expect to be home pithing 1-4 days from surgery.
What care will I need at home?
Recovery should be relatively quick as the surgery has been carried out with access only from the groin arteries.
Will I need someone to stay with me?
This may be helpful however you should be relatively independent as the cuts made are relatively small.
Will I need any special equipment when I go home?
Occupational Therapists and Physiotherapists assess your individual needs before being discharged and advice on what if anything is required.
What follow up care is needed?
You will need to be regularly followed up with scans, once the repair is stable the frequency can reduce to annual or sometimes every two years.
