Stent grafts for treating abdominal aortic aneurysm (EVAR)

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.

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.

EVAR

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 ‘main body’ and one or more ‘legs’ or ‘limbs’) to build up a repair inside the aorta.

  1. A stiff wire (‘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.
  2. From the other groin 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 provides a detailed ‘map’ of your arteries. This ‘map’ is needed because arteries, unlike bones, do not show up on plain x-ray.
  3. Once we have this ‘map’, the first stent (main body) can be opened up inside the aorta.
  4. Using more catheters and guide wires, the other stents (limbs) are inserted on delivery systems and are then opened up to seal the AAA below.
  5. A final x-ray is taken to check that the blood is now flowing properly (through the stents and down the legs rather than around the stent and into the aneurysm).

On the angiogram the team also check that there is blood flowing to the arteries supplying the kidneys and the
pelvic organs.

If the artery below the aorta (common iliac artery) is also large (aneurysmal) sometimes it is necessary to extend the stent further down towards the groin. This can mean closing off the artery to the pelvis/buttocks (internal iliac artery) or using a more complex type of stent graft (iliac branch).

More information on preparing for your surgery, your admission to hospital and recovery are explained in the booklet ‘Coming in for your aortic surgery’.

Potential early (first 30 day) risks

Almost 1 in 5 patients will get a complication while in hospital, according to data from the UK National Vascular Registry Report 2019:

  • Death (0.4%)
  • Readmission to hospital (5.5%)
  • Return to theatre (1.9%)
  • 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%)
  • 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 (20%) – 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.

Check-ups

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’

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.

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 AAA treatment?

The Circulation Foundation
www.circulationfoundation.org.uk

The Vascular Society of Great Britain & Ireland
www.vascularsociety.org.uk

Society for Vascular Surgery (USA)
https://vascular.org/patient-resources

National Institute for Clinical Excellence (NICE)
www.nice.org.uk

Where can I find out more about my vascular specialist?

North Bristol NHS Trust Website
www.nbt.nhs.uk/our-services/a-z-consultants
www.nbt.nhs.uk/our-services/a-z-services/vascular-surgery

Vascular Society of Great Britain & Ireland
www.vascularsociety.org.uk/patients/surgeons/default.aspx

Surgeon Outcomes
www.vsqip.org.uk/surgeon-outcomes/

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:

Brunel building
Southmead Hospital
Westbury-on-trym
Bristol
BS10 5NB

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. NBT002075

Stent grafts for treating abdominal aortic aneurysm (EVAR)