Stent-graft placement in abdominal aortic aneurysm

Stent–graft placement is used to treat aneurysms of the abdominal aorta. Weakening of the wall of the aorta can lead to widening of the vessel, or aneurysm. Aneurysms may rupture causing internal bleeding which, if untreated, is usually fatal.

The standard treatment for abdominal aortic aneurysm is open surgical repair. The aneurysm is opened and a graft is then sewn in above and below the weakened area to allow normal blood flow.

Stent–graft placement is a minimally invasive alternative to open repair. The graft is mounted on a stent, which is inserted into the aorta via catheters in the femoral arteries. The stent–graft is deployed under X-ray guidance and positioned across the aneurysm. Additional endovascular or surgical interventions may be necessary to complete the procedure, such as insertion of stents into the iliac arteries, occlusion of selected arteries and femoro-femoral bypass grafts.

A systematic review of the published evidence on this procedure was commissioned by the Institute and completed in June 2005. A total of 77 studies were identified for inclusion. This comprised: four randomised controlled trials (RCTs) including the EndoVascular Aneurysm Repair (EVAR) 1 trial comparing stent–graft placement and open surgical repair, and the EVAR 2 trial comparing stent–graft placement in patients considered unfit for surgical repair with standard medical care; 17 non-randomised controlled trials; 22 comparative observational studies; 28 case series and 6 registry publications.

Data from the EVAR 1 trial at a median follow-up of 35 months reported an aneurysm rupture rate of 0.9% (5 of 543) following endovascular repair, compared with 0.2% (1 of 539) following open repair. Early aneurysm rupture rates of 0.2% (1 of 534) and 0.3% (13 of 3,859) were reported in 1 non-randomised controlled trial and 7 case series, respectively.

In the EVAR 1 trial, 16% (85 of 529) of patients required secondary intervention following stent–graft placement, compared with 7% (36 of 519) of patients following open repair. From the non-randomised controlled studies, secondary intervention rates were 20% following stent–graft placement and 6% following open repair.

The EVAR 2 trial reported that at 4 years, 26% of the group who had had stent–graft placement had required at least 1 additional intervention compared with 4% of the group who had received standard medical care. However, if crossovers are considered a secondary intervention, then the secondary intervention rate in the group that received standard medical care became comparable (approximately 30%). For more details, refer to the sources of evidence.

From a meta-analysis of data from 3 RCTs, stent–graft placement was associated with a 30‑day mortality rate of 2% (12 of 759 patients) compared with 5% (33 of 709 patients) for open repair. In patients considered unfit for surgery, the 30‑day mortality following stent–graft placement was 9% (13 of 150 patients).

During more prolonged follow-up to 4 years, the EVAR 1 trial reported no significant difference between the all-cause mortality rate in the group that had had stent–graft placement and the group that had had open repair.

The most common adverse event following stent–graft placement was endoleak originating from retrograde collateral flow into the aneurysm sac via aortic branches (type II). This occurred in 19% of patients at 1 year. Recent developments have led to a lower incidence of procedural and post-procedural complications. The incidence of pulmonary complications and haemorrhagic events was significantly lower in the stent–graft placement group than in the open repair group.

Technical complications included stent migration, which happened in 1% of patients within the first year, and stent wire fracture, which happened in 3% of patients within the first year. For more details, refer to the sources of evidence.

It was noted that these procedures are rapidly evolving.

The follow-up phase of the EVAR trials continues, and long-term results are expected to be published in 2010.