What is an aneurysm?
An aneurysm is a dilatation in any blood vessel, but almost invariably an artery and any artery can be involved. Arteries are elastic blood carrying tubes made up of a matrix of tissues including strong collagen and elastin and their function is to transmit oxygen and nutrients in blood to the peripheral tissues. This includes vital organs, muscles, skin, nerves and connective tissue. If the collagen degrades then the artery starts to dilate with the arterial blood pressure, much as a balloon does with air. Loss of collagen occurs commonly with age, but it can be an inherited problem. The wall will then dilate and the more dilated it is the weaker it is. Eventually it will dilate to a point of rupture. Arterial rupture needs urgent repair or usually death will follow.
The most common area for development of an aneurysm is the abdominal aorta, the so called AAA. Other common sites are the popliteal artery behind the knee, the femoral artery and the aorta in the chest.
How is it detected?
A larger aneurysm can be felt by abdominal examination or examination of the arteries behind the knee, but if the patient is obese, has multiple abdominal scars it can be difficult to feel. Hence, most aneurysms are diagnosed coincidentally by the use of ultrasound scans, CT or MRI when performed for investigation of other abdominal disorders.
How is the aneurysm assessed?
Assessment is by clinical means, ultrasound scan, CT-angiogram and/or MRI.
When does it need to be treated?
Abdominal aorta aneurysm is a rupture risk at greater than 5.5 cm, although the rupture risk at this size is relatively low, being about 10% per annum. To be safe, repair is advised when the aneurysm expands to 5 cm in diameter. The shape of the aneurysm can affect the likelihood of rupture and tenderness of the aneurysm suggests that rupture may be imminent.
So in summary, an abdominal aortic aneurysm usually warrants treatment when it reaches about 5 cm in maximum diameter.
How is an abdominal aorta aneurysm managed?
- Surveillance – usually on an annual basis by ultrasound when a small aneurysm is present.
- Repair
2A. Open repair.
2B. Endograft repair.
- Standard infrarenal endograft.
- Fenestrated endograft.
- Branched endograft.
If repair is planned then the patient will undergo a thorough medical workup which will look at cardiac, renal and respiratory function, as well as any other medical issue such as diabetes etc.
If the patient is deemed medically fit, then a decision will be made on the anatomy. This decision depends on CT Angiogram, which provides information to decide whether the Aneurysm is suitable for minimally invasive endovascular repair or requires open repair.
Most abdominal aneurysms at the present time are repaired by endovascular means – a minimally invasive procedure.
Occasionally aneurysms are not suitable for any of the various forms of minimally invasive procedure and require open repair, which means a midline abdominal incision or sometimes a transverse abdominal incision.
PROCEDURE
OPEN REPAIR OF ABDOMINAL AORTIC ANEURYSM
The patient is given a general anaesthesia and an arterial line, intravenous line, urinary catheter and usually a spinal anaesthetic is inserted for post operative pain relief. A midline incision is made from rib cage to pubic region. The aneurysm is exposed heparin given to prevent clotting and clamps are then applied to minimise bleeding while the aneurysmal artery is replaced by suitably sized dacron tube graft. This dacron graft is impervious to blood flow. Heparin which was given prior to clamping is reversed and the abdomen is closed.
During the procedure the anaesthetist will place a gastric tube to drain the stomach. A cell saver, blood harvesting system is used during the procedure and the blood is cleansed of impurities and reinfused. This minimises the amount of foreign or bank blood that is required.
The problems with the procedure are blood loss, temperature loss and clamp time and all of these need to be minimised for a rapid recovery.
Other issues which are important are maintenance of kidney function, restoration of blood flow to the legs and pelvis and post operative haemostasis.
Post operative care
The patient is usually taken to intensive care for 24 to 48 hours. The breathing tube is removed at the time of the operation. The important issues are blood replacement, fluid balance, electrolyte balance, respiratory care, blood pressure and renal support.
After 24-48 hours the patient then returns to the ward and usually spends a week to ten days post operatively in hospital.
Common problems post operatively are anaemia requiring re-transfusion, slow recovery of bowel function, wound haematoma, chest infection.
Uncommon problems in the early phase are bleeding, loss of blood supply to a limb, cardiac arrhythmia, deep venous thrombosis and pulmonary embolism.
Rare problems are wound breakdown, stroke and death.
Progress after discharge from hospital
Recovery is significantly slower after open surgery than endovascular surgery, because of the large abdominal incision, and extensive surgery which retards rapid restoration of gastrointestinal function and movement and although you will be walking after three or four days, it will be two to three months before you feel that you have reached a full range of activities. You will probably be driving a car after six weeks, but recovery to full range of physical function will be three to six months depending on the activity.
ENDOVASCULAR REPAIR
Who is suitable for this?
This procedure was originally designed for treatment of aneurysms in patients with difficult access to the aneurysm abdominally for open surgery. This meant old scars, obesity, colostomy etc. It was also designed for people who had multiple medical problems, such as cardiac respiratory and renal disease and were deemed unfit for open surgery.
However in time, endovascular repair has become the preferred mode of repair because of the refinement in the technique, which makes it as effective in treating the aneurysm and also offers a minimally invasive approach. This means lesser risk of complications, particularly major ones and a shorter hospital stay with rapid return to a full range of activities after a few weeks.
There are three basic types of endograft. These include simple endovascular aneurysm repair (EVAR), more complicated fenestrated EVAR (which is used to manage the patient with particular anatomical features on CT-scan) and the most complicated being a BEVAR which is a branched endograft for treatment of aneurysms of the thoracic and abdominal aorta.
Ninety percent of endovascular repairs are by simple EVAR, which is basically placing the endograft beneath the kidney arteries and into the pelvic arteries to exclude the aneurysm and thus prevent rupture
The decision as to whether open repair or endograft repair is appropriate depends purely on the anatomical features of the abdominal aorta and the pelvic arteries. This is determined by CT Angiogram
EVAR PROCEDURE
Decision to undertake endograft repair of an abdominal aneurysm is based on the features of the aorta and pelvic arteries shown on the CT-angiogram and occasionally a catheter angiogram. If the anatomy appears suitable the EVAR is the preferred procedure to exclude the aneurysm from pressure and avoid rupture.
The endograft when deployed requires a two centimetre neck above the aneurysm and healthy pelvic arteries below to establish a seal above and below the aneurysm and to allow the blood to pass through the graft and not impinge upon the aneurysm wall.
Procedure
General anaesthetic or spinal anaesthetic is performed and usually a percutaneous approach is undertaken. Percutaneous means a one centimetre incision in the groin crease on each side and then a needle puncture with insertion of a sheath for access to the artery. The graft would have been pre-measured and designed to fit the anatomy of your arteries and this includes the length and diameter of the various sites of the artery where the endograft establishes a seal to exclude the aneurysm. This means the artery beneath the kidney arteries and the arteries in the pelvis which are above and below the aneurysm respectively. These measurements are taken usually by CT-angiogram and sometimes by a catheter based angiogram (in more complicated situations).
The endograft is essentially a three piece device, with a main body and two limbs into the pelvic arteries and these are all connected by overlapping and the overlap is significant to prevent dislodgement of the pieces over the following years. When the endograft has been inserted and the so called bifurcated graft is fully deployed it is then ballooned into final shape and an angiogram performed to confirm that all is well.
Intraoperative problems
The main operative problem is incomplete seal below the renal arteries or in the pelvic arteries. This is usually resolved with re-ballooning, but sometimes need deployment of an extra piece to establish a complete seal above or below the aneurysm.
Heparin is given during the procedure to eliminate the risk of clots forming and heparin is reversed at completion when the aneurysm procedure is deemed completed. The sheaths and wires are removed and the preplaced sutures are then tied to complete the procedure.
Post operative care
You will return to the ward after a half hour stay in the recovery unit and then the same evening in the standard ward you will be able to have a light supper and have toilet privileges. You may have had a catheter inserted, but probably not.
In the next two days you will gradually recover and about day three an ultrasound scan will be performed to assess the outcome. Following this you will be able to go home. It is recommended to take it easy around the house and for the next week and then start resuming activities. You should be able to drive a car about a week after the procedure.
Complications – all uncommon
- Groin haematoma – rarely requires surgical care
- Urinary tract problems
- Chest infection, cardiac problems, kidney complications are uncommon problems.
Rare complications are:
- Internal bleeding
- Graft blockage
- Deep vein thrombosis and pulmonary embolism (blood thinners are given post operatively to prevent this)
- Graft infection.
FEVAR
What is a fenestrated endograft?
Fenestrated EVAR is required when the Aorta has a short seal zone above the aneurysm. Aneurysm can still be treated by EVAR but by a modified EVAR – FEVAR. The modification is to allow use of the aorta above the kidney arteries to achieve endograft seal. However to maintain blood supply to the kidney arteries, the graft is modified with holes (fenestrations) cut in the graft to maintain blood flow into the kidney arteries These designs need to be precise and so computer based designs are essential. These designs are based on data received on CTA.
FEVAR is made in 4 pieces. The first piece is a tube with the fenestrations and the other 3 are very similar to the standard EVAR.
What is the procedure of FEVAR?
This is similar to the EVAR in regard to introducing the FEVAR device, but more time is required to introduce the fenestrated piece of the device into precisely the correct spot. Precision is required to position the fenestrations over the renal arteries and then to stent them into position to ensure blood flow into the renal arteries and avoid slippage of this vital component. Then the other components are added to complete the FEVAR.
What are the problems?
The main concerns are similar to those for an EVAR, but there is the added concern that blood supply to the kidney arteries and the bowel is maintained.
There is a wealth of experience with this procedure to demonstrate its safety and efficacy world wide, as well as in Australia, where the procedure was designed, developed and pioneered. So, FEVAR is the preferred method of treatment for abdominal aneurysm with a short neck because of lower mortality and complication rates when compared with the alternative which is Open repair. This demonstrates the benefit of the minimally invasive approach.
The risk to kidney and bowel blood supply is minimal and survival rates for this procedure are 98%.
Post operative care
You will be in hospital for 4 days, intensive care is not required.
Recovery is much the same as for EVAR and return to normal activities usually takes about 2 to 3 weeks and to more vigorous activities about 4 to 6 weeks. Recovery is much the same as with EVAR.
Is follow up required?
Initially a CT-angiogram will be performed on day 3 post op and you will have follow up ultrasound scans at 3, 6 and 12 month and continuing 12 monthly indefinitely.
You will also be assessed clinically on these occasions.
BEVAR
What is a branched endograft (BEVAR)?
Branched Endograft is a minimally invasive device specifically designed to treat the most complicated type of aneurysm namely the thoraco-abdominal aneurysm, which involves the thoracic and abdominal aorta. The risks of repairing this by conventional open means are very high. These risks include death, paraplegia, chest infection, cardiac complications etc.
The minimally invasive approach is to repair the Aneurysm by Branched Endograft and this is still a significant operation but has a much diminished risk of death and paraplegia as well as all complication etc., because of its minimally invasive nature. This approach allows repair of the aneurysm through a groin incision and an incision beneath the collar bone on the left side rather than the major surgery of opening the chest and abdomen.
I will be happy to explain all aspects of the procedure in detail as well as the problems that can be encountered.