Open operations for abdominal aortic aneurysms (AAAs) are more major and extensive than EVAR with higher risks of serious problems at the time of the operation. However, the expectation thereafter is for a good permanent result and there should be no need for scans or other checks in the longer term, unlike EVAR (endovascular aneurysm repair).
An additional reason for keeping a check on stent grafts after EVAR and not on grafts after an open operation is that EVAR was developed only during the 1990s and stent grafts have been used on a widespread scale only since the millennium. We therefore do not know exactly how well they work in the long term, or how many will develop problems over the years.
By contrast, Dacron grafts have been inserted at open operation since the 1950s and have been used in significant numbers since the 1960s, so their performance and the very low risk of problems in the longer term are well documented.
Some problems can only occur after one or other kind of procedure (for example, endoleaks after EVAR) but most of the possible complications can happen after either.
Possible problems at the time of the operation (or shortly afterwards)
Open AAA repair
All these problems are uncommon after planned replacement of an aneurysm: they are more common after emergency operation for aneurysms that have ruptured.
Infection of the abdominal wound is a small risk. Antibiotic treatment may be all that is necessary to settle redness (cellulitis). If there is pus under the skin, however, the stitches need to be cut to let the pus drain out and the wound will require dressings.
Infection of the bypass graft is a very uncommon complication (less than 1 per cent risk). Many precautions are taken to guard against infection, including antibiotics at the time of operation. If infection ever does develop on an aortic graft, this is a very serious matter and the graft may need to be replaced.
Heart problems, including heart attacks, abnormal rhythms requiring treatment and heart failure are all possible risks of aortic surgery. Heart problems are the most common cause of death after aortic surgery.
Kidney failure (sometimes requiring dialysis but recovering within a week or two) is another occasional complication.
Chest problems, including pneumonia and respiratory failure (requiring artificial ventilation), are risks.
Disturbance of blood flow to the gut can result in gangrene of part of the bowel, which is a very grave problem, and disturbed blood flow to the brain can result in stroke.
In men there is a risk of about 1 in 5 (20 per cent) of disturbed sex function (difficulty with erection, ejaculation and having intercourse) as a result of open surgery. This is because the nerves controlling sex function cross the front of the aorta and its branches. Care is taken to avoid these nerves, but they are difficult to see and the tissue in which they lie may need to be pulled aside or divided to do the operation.
Legs and feet
Any kind of aortic surgery poses very small but serious risks to the legs and feet. Very rarely small blood clots can pass from the aneurysm during surgery to the toes and feet, resulting either in a period of poor blood supply to the toes that gradually recovers, or sometimes in the loss of one or more toes. Whether or not the toes recover depends on how many of the little arteries in them have become blocked. If too many have become blocked, then tissues die. If enough arteries remain unblocked then the tissues stay alive while the blood flow improves (by enlargement of the arteries that remain).
If the blood supply to a leg becomes seriously disturbed by blood clots then amputation may be necessary. Less serious disturbance of blood flow to a leg can result in pain in the calf or thigh on walking a certain distance.
Very rarely the blood supply to the spinal cord can be damaged resulting in paralysis of the legs. All these problems are extremely uncommon (a risk of less than 1 in 100).
Deep vein thrombosis
Deep vein thrombosis (DVT), with the risk of blood clots passing to the lung (pulmonary embolism), is an occasional complication of aortic aneurysm surgery.
Aortic surgery has a risk of death, particularly because of the strain it can place on the heart. Overall the risk is about 5 per cent (one in twenty) for planned (elective) open surgery, but the risk is lower in people who are relatively young and fit, and higher in those who are elderly and have other medical problems. The risk of death after EVAR is lower – about one per cent.
Almost all the possible problems described above can occur after EVAR, but the risks are lower. Infection of the groin wounds is a small risk. Stent graft infection is very rare.
Organ failure can occur (heart, kidneys, lungs or a stroke) but the risks are very low, even in relatively unfit patients, whose risks might be high at the time of open repair. The risk of damage to the kidneys is a reason for avoiding EVAR in patients whose scans show atheroma or blood clots near the arteries to the kidneys at the ‘neck’ of the aneurysm.
The possibility of blood blots passing to the legs or feet exists at the time of EVAR, but as with open repair this possibility is remote. DVT is a small risk after EVAR.
The risk of death after EVAR is lower than after open AAA repair, but this is still a possibility, especially when EVAR is used to treat patients with serious medical problems, who would be considered unfit for open repair.
The long-term outlook
Whether you can expect any problems in the long term depends on the type of repair operation that was done. Dacron grafts used to repair AAAs tend not to deteriorate and normally serve patients well for the rest of their lives. It is not normal practice to perform any checks or scans once a patient has recovered fully from the operation. A single visit to hospital a few weeks after operation is usual, to check that all is well and to answer any queries.
By contrast, EVAR requires long-term follow-up. Stent grafts need to be checked by scans or X-rays in the long term (for life) because problems can occasionally develop in the months or years after they have been put in. These problems are described in the next section; the main ones that cause concern are:
• dislodgement of the stent graft
• development of endoleaks.
It is usual for a detailed scan (most often a CT scan) to be done a few weeks after EVAR and then for yearly checks by CT or X-rays (to show the position of the stent graft) and ultrasound scanning (to show the aneurysm sac around it). The aim of these checks is to be sure that the stent graft has not moved and that the aneurysm sac shrinks, and remains shrunken, without any blood flow into it.
Problems in the longer term after open operations
It must be remembered that all these complications are rare.
Infection of an aortic graft can become apparent months or years after the operation. This is a serious problem and may require replacement of the graft. Infection may occur because:
• bacteria introduced at the time of the original operation have lain dormant on the graft
• bacteria circulate in the bloodstream, settling on the graft
• the graft erodes into a part of the gut.
Erosion of the graft through to the gut (aortoenteric fistula)
If an aortic graft comes into contact with the gut (most likely the duodenum), it can erode into it and cause bleeding (vomiting blood or passing blood in the stool). If an aortic graft erodes into the gut then it is automatically infected. This rare situation requires major surgery for its correction.
Aneurysms above or below the graft
These can form because the aorta and other arteries continue slowly to dilate. If a further aneurysm becomes large enough to need treatment, this may be possible by insertion of an endovascular stent (similar to EVAR) or an open operation. Sometimes, aneurysms can form in the area where the graft has been stitched to the arteries: this was most typically seen when aortic grafts were stitched to the femoral arteries in the groins, which is not often done nowadays.
After open surgery, weakening of the deeper layers of the scar can occasionally result in bulging of the wound. Rarely, this becomes sufficiently troublesome to require repair, by insertion of a piece of mesh to strengthen the area.
Problems in the longer term after EVAR
Endoleaks have already been described in the previous section, because they may pose problems at the time of insertion of stent grafts. They can also occur unpredictably weeks, months, or even years after EVAR.
There should be a firm seal at the upper and lower ends of a stent graft, and any arteries through which blood might flow to enter the sac of the AAA should be sealed off and remain so. All this allows the sac of the AAA to ‘shrink’ around the stent graft and gradually to become adherent and scarred around it.
Type 1 endoleak
An endoleak means that blood is ‘leaking’ outside the stent graft and into the sac of the AAA. If blood leaks between the stent graft and the neck of the AAA, it is called a ‘type 1 endoleak’ and may occur because the aorta continues to dilate in the area where the stent graft has been attached inside it.
Type 2 endoleak
A ‘type 2 endoleak’ means that blood enters the sac of the aneurysm from a branch of the aorta. It is not clear why blood should ever start to flow back into the aneurysm sac through a smaller artery some time after EVAR, but occasionally it may start to do so.
Detection of endoleaks is an important reason for advising regular scans in the months and years after EVAR. Further procedures, such as insertion of additional stents, may be required to treat endoleaks.
Expansion of the aneurysm sac
The normal expectation is for the sac of the AAA to shrink around the stent graft. If scans show that it is expanding, this suggests that there is blood under pressure between the stent graft and the sac: this means that some kind of endoleak must be present.
Migration or breakage of the stent graft
This can occur if the fixation of the upper or lower ends of the stent graft becomes dislodged or if the stent portion of a stent graft breaks (fractures). The result is a significant ‘type 1 endoleak’, with blood flowing outside the stent graft into the sac of the aneurysm. It may be possible to correct the situation with further stenting, but a complex open operation may be necessary.
Some of the early models of stent graft were prone to breakage and migration, but advances in design and technology have made these rare problems now. Regular scans (or X-rays, which demonstrate the metallic stent) check that the stent remains intact and in the correct position.
Stent graft infection
This is a risk but is very rare indeed. Treatment is complex.
Aneurysms above or below the graft
These can form because the aorta and other arteries continue slowly to dilate. If an aneurysm becomes large enough to need treatment, this may be possible by insertion of a further stent graft or an open operation.