What is EVAR?
Endovascular aneurysm repair (EVAR) is a type of minimally-invasive surgery that involves inserting a stent graft to repair an aortic aneurysm, which is a bulge in the aorta. A stent graft is a metal skeleton (the ‘stent’) sewn (or glued) to one or more fabric tubes (the ‘graft’).
The stent graft comes loaded into a delivery system of similar width to a pen. This allows the stent graft to be inserted through the arteries in one or both groins.
The stent graft is positioned using x-rays and deployed using the delivery system, which is then removed.
The aim is to only allow blood to flow within the fabric tubes (the ‘graft’) and not into the bulging sac of the aortic aneurysm.
The sac is no longer under pressure.
In this way we ‘exclude’ the aneurysm and reduce the risk of it rupturing.
Why use a ‘complex’ stent graft?
A standard aortic stent graft seals below the arteries to the kidneys. If there is not enough normal aorta below the arteries to the kidneys, including when an aneurysm extends into the chest, a standard stent graft is not an option. The aneurysm is complex.
In the UK, around 65% of planned (elective) AAA repairs are done using standard aortic stent grafts and a smaller number using complex aortic stent grafts.
A complex stent graft may be a safer for you than having open surgery if your fitness raises concerns over an open operation, or the shape of your aneurysm is more challenging.
People who have previously had an aneurysm repaired and have further growth of their aorta may also be suitable for a complex aortic stent graft.
Planning and manufacture
Complex aortic stent grafts usually have one or more elements ‘custom-made’. Using measurements from your CT scan and working with the planning centre, a technical drawing of the custom grafts is made.
Your specialist will check these plans carefully before ‘signing off’ the design. The graft will then be custom made, mostly by hand, to fit your aorta and its branches.
There is a delay caused by the planning and manufacturing process. This delay is usually around three months from your CT scan being sent to the planning centre to the graft being delivered to the hospital for your operation.
Fenestrated and branched aortic stent grafts
Custom aortic stents are made with holes (‘fenestrated’ or FEVAR), branches (‘branched’ or BEVAR) or a combination of both. The holes and branches are placed in the exact position where each artery comes off the aorta. This is so that the main stent ‘seals’ your aneurysm, whilst at the same time the blood supply to your vital organs is maintained.
The procedure itself
Anaesthetics are used during procedures to numb sensation so you don’t feel pain during the operation. There are different types of anaesthetic this operation can be performed under:
- General anaesthetic – asleep on a ventilator
- Spinal anaesthetic – injection in the back to numb the groin area and legs
- Local anaesthetic – injection to ‘freeze’ both groin areas
We will make an incision to gain access to the arteries to put the stent into the aorta. We usually use arteries in the groins (the ‘common femoral arteries’):
- Surgical incision – this allows the team to see the artery, puncture it, and stitch it to repair the hole.
- Percutaneous – the artery is punctured using ultrasound, a smaller incision, and special devices (Proglide) used to place stitches through the artery wall. At the end, the stitches are used to close the hole left in the artery.
Your specialist team will assess you, and your arteries on CT, to decide the most appropriate method of ‘arterial access’ to use.
Axillary incision, a branched stent will need a further small cut under the collarbone to allow access from above to the stent branches.
The stenting procedure is done with the help of x-rays. This allows the team to accurately position the stent in the ideal position to treat your aortic condition.
To treat most complex AAAs, we use a combination of different grafts (a ‘fenestrated component’, a ‘bifurcated component’ and one or more ‘legs’ or ‘limbs’) to build up a repair inside the aorta.
It may be necessary in addition to place a more proximal ‘thoracic stent’ and this can require you undergoing more than one procedure.
- A stiff (‘guide wire’) is inserted from the groin up through the aorta and into the chest. This wire supports the stent delivery system as it is advanced through the arteries in the pelvis and into position in the aneurysm.
- From the other groin the we place a small tube (catheter) into the aorta. This catheter is used to perform an angiogram, where contrast is injected into your arteries whilst taking an x-ray. This is required to obtain a detailed map of your arteries because blood vessels do not show up on ordinary x-rays.
- Once we have a map of the arteries the first stent, usually the ‘fenestrated’, or ‘branched’, component can be opened up inside the aorta.
- This component is initially ‘constrained’ by a system that allows it to be moved once open in order that it is accurately aligned with the vital arteries to your liver, intestines and kidneys.
- Another sheath (tube) is inserted from the other groin (or incision under the collar bone) and smaller sheaths are advanced out into each of the aortic side branches. Into each smaller sheath we then advance a stent.
- The fenestrated or branched component is fully deployed, and balloons inflated in each of the branch stents to seal them in position. It may be necessary sometimes to extend the branch stents.
- Using more catheters and guide wires, the ‘limb’ stents are inserted and are then opened-up to seal the aneurysm below into one or both iliac arteries.
- A final angiogram is done to check that the blood is now flowing through the stents and down the legs rather than around the stent and into the aneurysm.
On the final angiogram the team also checks that there is blood flowing to all of the stented arteries and to the pelvic organs/buttocks (internal iliac arteries).
After the procedure
Patients are admitted to the intensive care unit. They are monitored for 24-48 hours for signs or symptoms of spinal cord injury or leg ischaemia. They then return to the vascular ward for 1-3 days (average 2 days).
Spinal cord injury
Probably the most devastating complication of a complex aortic stent is to lose the use and sensation in your leg. This happens when the blood supply to the spinal cord comes mainly from small arteries off the back of the aorta. Complex stent grafts cover these arteries and so the greater the amount of aorta covered, the greater the risk.
Several techniques are utilized to minimize this risk:
- Your procedure is planned to reduce the risk as far as possible
- The risk is reduced through staging some procedures i.e. repairing the aorta in two or more operations
- The risk is reduced through careful monitoring using a ‘Spinal Cord Protection Protocol’
- If you develop some weakness in your legs, there are a number of ways we can try to increase the spinal cord blood supply to try and reverse the symptoms.
When on the High Dependency Unit, it is quite common to need some medication to support your blood pressure. This has been shown to reduce your risk of Spinal Cord Ischaemia while the spinal cord blood supply adapts over the two days after surgery.
More information on preparing for your surgery, your admission to hospital and recovery afterwards are explained in the information booklet ‘Coming in for your aortic surgery’.
Potential early (first 30 day) risks
At NBT, 1 in 16 patients has a complication:
- Death (2.4%)
- Readmission to hospital (8.3%)
- Return to theatre (3.8%)
- Chest infection or breathing problem (1.7%)
- Problem with blood supply to leg(s) (1.2%)
- Heart problem (1.1%)
- Kidney problem (0.9%) – people rarely need to go onto temporary or permanent dialysis.
- Problem with bleeding (0.7%)
- Stroke – this can be caused by wire manipulation in the aoritc arch. The risk is higher for branched aortic stent grafts
- Paraplegia – related to the length of aorta stented, it can occasionally be reversed by inserting a ‘spinal drain’
- Reduced blood supply to the pelvis and buttocks – this is sometimes done intentionally when we treat an aneurysm that extends down into the pelvis. The most common problem seen is lower back or buttock pain on walking (buttock claudication). This may be for weeks, months or be permanent. Very rarely, the blood supply to the skin around the buttock can be lost.
- Reduced blood supply to the bowel in the colon – this leads to inflammation in the bowel (ischaemic colitis) which can progress to the bowel bursting. It is very uncommon for patients to have problems with the bowel in planned operations (1%).
- Reduced blood supply to the spinal cord or nerves – this can result in weakness in one or both legs (paraplegia) but it is very rare (0.2%) in patients having standard AAA repair.
- You may require a blood transfusion.
- The incisions in the groin may cause problems, like bleeding from or blockage of the artery in the groin, burning pain in the thighs due to bruising of nerves or wound infection, fluid discharge or ‘lumpiness’
- Reduced sexual function – this is common and men with AAA may already have experienced some loss of sexual function.
- Clots in the legs or lungs – as with any major surgery there is a risk of Deep Vein Thrombosis (DVT) or Pulmonary Embolus (PE). Whilst in hospital you will receive daily injections in your tummy to reduce this risk. You will also be encouraged to start to walk.
- Complications of anaesthesia – your anesthetist will talk to you about these in the pre-operative assessment clinic and on the day of your surgery.
Potential later problems (from 30 days)
- Reintervention (25%) – we rarely need to convert to an open surgical repair
- The aneurysm sac can rupture (2% per year) – this is only likely to occur if the aneurysm has started to grow again.
- Stents can block unexpectedly causing one or both legs to lose the blood supply, if this happens then it requires emergency surgery or another stent.
- Aortic graft infection (0.2% over 10 years)
- It is possible for stent grafts to pick up bugs from the skin at the time of the operation or for bugs to stick to the fabric graft when you have an infection in the blood stream at some later time (e.g. a chest infection).
- These bugs slowly multiply over time and can weaken the aorta or cause a collection of fluid around the graft.
- Such infection can be difficult to diagnose; symptoms can range from feeling tired with flu-like symptoms to being very unwell with bleeding problems.
- We rarely need to convert to open surgical repair as we can only 100% treat infection by removal of the stent graft.
- Good dental care may reduce the risk of an aortic graft infection.
- Aorto-enteric fistula – a very rare complication where the stent graft erodes into the bowel. This can cause life threatening bleeding with infection. This complication is more often seen after open AAA repair.
After an aortic stent graft long-term check-ups (surveillance), with a combination of CT, ultrasound, and plain x-rays is advised at least once a year to check:
- stent graft remains in the correct place
- stent graft is not blocked, kinked or broken
- the aneurysm sac has not started to grow
- no blood is flowing outside of the stent and into the aneurysm sac – an ‘endoleak’
This is a poor choice of word to use, as there is no actual ‘leak’. What the term actually means is that blood is flowing into and out of the aneurysm sac despite the stent graft.
This can be through smaller arteries as shown in the picture.
An endoleak through small arteries may not matter. Multiple arteries can come off the aneurysm sac and these often remain open even with a stent graft in place.
We only treat this type of endoleak (type 2) if the AAA starts to grow.
An aneurysm can start to grow again because blood is getting:
- around the side of the stent graft at the top or bottom (type 1)
- through one of the joins or a hole in fabric of the graft (type 3)
- through the fabric of the graft (type 4)
- for no immediately obvious cause (type 5)
We usually treat these types of endoleak, unless the stent graft has recently been implanted in case we may wait to see if the endoleak will settle.
The risk of a serious endoleak leading to AAA rupture is the reason why you are advised to have regular scans after an aortic stent graft.
You should consider carefully what a 1 in 5 chance of requiring at least one reintervention to prevent a late rupture means to you.
For some people ‘doing nothing’ or undergoing open surgical repair is a better option for treating their aneurysm.
Where can I find out more about treatment?
The Circulation Foundation
The Vascular Society of Great Britain & Ireland
Society for Vascular Surgery (USA)
National Institute for Clinical Excellence (NICE)
Abdominal Aortic Aneurysm and Dissection
AAA Screening Info
If you or the individual you are caring for need support reading this leaflet please ask a member of staff for advice.
How to contact us:
Vascular clinical nurse specialists: 0117 414 5302/3/4
AAA screening programme: 0117 414 8610
Patient pathway coordinators: 0117 414 0798
© North Bristol NHS Trust. This edition published September 2020. Review due September 2022. NBT003115