Endovascular aneurysm repair
Endovascular aneurysm repair (EVAR) was introduced in the late 1990s as a way of treating aortic aneurysms. ‘Endo’ is Greek for ‘within’, so endovascular means that the operation is done ‘inside the arteries’.
EVAR involves introducing a specially packaged ‘stent graft’ into the aorta through the arteries in the groins. The special packaging allows the stent graft to be delivered to its intended site. The graft is made of durable fabric (like the graft used in open operations) and this is attached to an expandable metal stent, which holds it in place. The stent helps to form a ‘seal’ at the top and bottom end so blood flows through the graft and not through the aneurysm when the stent graft is properly in place.
The surgeons and X-ray specialists doing the operation use X-ray monitoring to place the stent graft accurately. Recovery is quicker than after an open operation, but not all aortic aneurysms are suitable for EVAR. After the procedure the stent graft needs to be checked year by year using scans or X-rays.
What is a stent graft?
Stent grafts are made of material such as Dacron, just like the grafts used in an open operation, but they are attached to rigid struts and to hooks or other fixing devices that are designed to fix the stent graft firmly to the wall of the aorta and keep it from becoming deformed or dislodged.
Stent grafts are ordered individually for each patient, based on measurements of the aorta and its branches made from scans. Each is supplied specially pre-packed in a long delivery sheath which is introduced through one of the femoral arteries in the groins, into the aorta.
Several different types and designs of stent graft are available. All of them have evolved over the years, based on experience and on technological developments. As they are specially made stent grafts are much more expensive than the kinds of graft inserted at open operation.
Who does EVAR?
EVAR is commonly done by a combined team of vascular surgeons and specialists in interventional vascular radiology (X-ray specialists). In some places EVAR is done by one of those specialties, without the other. But a combined approach to the care of the patient is generally regarded as ideal.
How is EVAR done?
EVAR may be done under a general anaesthetic or regional anaesthesia (spinal or epidural anaesthetic). Fewer lines and tubes are required than for an open operation, but it is usual to have:
• an intravenous drip
• a urinary catheter
• sensors attached to your skin for monitoring your heart and blood oxygen.
An incision is made in each groin (about 10 cm in length) and the femoral artery on each side is ‘controlled’ with clamps and slings. Clamps are applied to the branches of the femoral arteries, to prevent blood flowing out of them from the pelvis and the legs. Slings are elastic bands or tubes, which are passed around the arteries: they allow the arteries to be ‘lifted up’ to apply clamps and they are also used to ‘snug’ around the packaging of the stent graft to prevent blood flowing out around it during the operation. Fine tubes are inserted into the femoral arteries to inject contrast medium (a dye that shows up the arteries on X-ray). This allows the surgeon to accurately monitor the progress of the stent graft in the femoral artery.
Special guidewires are introduced through the femoral arteries and up into the aneurysm. Then the stent graft (which may consist of one or more components) is inserted through the femoral arteries, carefully manipulated into position by the guidewires and deployed from its packaging. A balloon is inserted up through the stent graft and inflated at the upper (and lower) end of the stent, to be sure that it is firmly fixed to the wall of the aorta, so that no blood can flow between the stent graft and the aortic wall, into the sac. All the blood should flow through the stent graft.
When the stent graft is properly in place, each femoral artery is repaired and the groin incisions are closed using two or more layers of stitches. The blood flow to each leg is checked at the end of the operation and an antibiotic is given to guard against the risk of graft infection.
Preventing problems
Depending on the extent of the aneurysm and on whether the iliac arteries are also aneurysmal, a number of additional procedures may need to be done, to be sure that blood cannot flow ‘backwards’ into the space between the stent graft and the aneurysm (an endoleak – see below) and that blood is able to flow properly to both legs and to the pelvis.
Occlusion of iliac arteries
One of the internal iliac arteries to the pelvis may need to be blocked off before inserting the stent graft so that blood does not flow back up it into the aneurysm sac (flow down just one internal iliac artery is normally quite sufficient).
Surgical bypass
It may be necessary to perform a surgical bypass from the femoral artery in one groin to the femoral artery in the other. This is done when the iliac artery to one leg needs to be blocked off in order to treat the aneurysm thoroughly.
Additional stenting
If one ‘limb’ of the stent graft turns out to be too short, or to have an inadequate seal against the wall of the iliac artery, an additional short stent graft may need to be inserted to complete the operation satisfactorily. This means that hospitals doing stent grafts need to have a variety of (expensive) extra components available in different sizes, in case they are suddenly required.
Endoleaks
Great care is taken to achieve a good seal at the upper end of the stent graft, so that no blood can leak past it into the aneurysm sac. If blood does leak between the stent graft and the neck of the aneurysm, this is called a ‘type 1 endoleak’ and needs to be dealt with by further attention to the stent graft. Any endoleak is shown up by injection of contrast (arteriography) which is done at various stages of the stent graft procedure, as a check. Stopping an endoleak may involve extra inflations of a balloon within the top part of the stent graft, to push it against the wall of the aorta, or even insertion of an additional stent.
A ‘type 2 endoleak’ means that blood continues to enter the aneurysm sac from branches of the aorta. Large type 2 endoleaks need to be stopped by injecting material into the relevant artery to block it off, or occasionally by tying the artery off at an open surgical operation. Small type 2 endoleaks from little arteries may sometimes stop without treatment.
Care after the operation
It is normal for patients to return to a vascular surgical ward after EVAR. Intensive care or high dependency is seldom required. With the help of painkillers for the groin wounds, patients can start walking within 24 hours of the operation. The intravenous drip and urinary catheter are usually removed within 48 hours. Patients can start to drink and eat as soon as they have recovered from the anaesthetic (after a few hours).
Coming out of hospital
Patients need to be walking with reasonable comfort and the groin wounds need to look healthy. Provided that there are no other problems and home circumstances allow, it is typical for patients to go home about three to six days after EVAR.
When you get home
Recovery after leaving hospital is normally quicker than after an open operation. Activity can be increased without restriction, dictated by how soon the groin wounds are comfortable. It is usual for patients to be walking normally within two weeks and to be back to full fitness within about a month.
Long term
Lifelong follow-up with scans (usually once a year) is needed to check that the stent graft has not become dislodged and that the sac of the aneurysm remains shrunken, without any blood flow into it.
On going home after an operation for aortic aneurysm, most people will continue with all the regular medicines that they were on before the operation. These normally include a low dose of aspirin and often a statin (which lowers blood cholesterol). Painkillers will be prescribed if you still need them (a mild painkiller such as paracetamol is often enough).
