Complications and Patient Outcomes

Endoleak

The inability to obtain or maintain complete exclusion of the aneurysm sac from arterial blood flow, called endoleak, is a complication specific to endovascular aortic repair. The concern is that any pressurization of the aneurysm sac (i.e., endotension) can lead to aneurysm enlargement and rupture. Endoleaks can be detected by arteriography, computed tomographic scan, and duplex ultrasound scanning. A classification system has been developed for endoleak and describes four distinct types.^[456] Type I endoleak occurs when there is an inadequate seal between the endograft and the aortic wall at the proximal or distal attachment sites. Type II endoleak occurs when there is retrograde filling of the aneurysm sac from patent lumbar, intercostal, or inferior mesenteric arteries. Type III endoleak is caused by structural failure of the endograft that allows blood flow directly into the aneurysm sac. The structural failure may result from the tears in the graft fabric or separation of individual components of a modular endograft. Type IV endoleak is related directly to the porosity of the graft material and is usually self-limiting. Endoleaks are also classified as primary (after deployment) or secondary (after initial seal).

The rate of occurrence of endoleak depends on many factors, including the endograft device, method of deployment, vascular anatomy, and progression of disease. The management for endoleak after endograft placement is quite controversial and ranges from observation with periodic imaging surveillance to immediate endovascular or surgical correction. Type I and III endoleaks are associated with an increased risk of rupture^[457] and are often treated aggressively. Although type II endoleaks do not often require urgent treatment, they are associated with aneurysm enlargement.^[457] Endovascular extension grafts, coil embolization, and conversion to open repair have been used successfully to repair endoleaks.^[458] As endoleaks have a dynamic natural history with variable onset,^[459] periodic long-term endograft surveillance has been recommended.^{[431] [459]}

Morbidity and Mortality

A meta-analysis of 39 studies published between 1995 and 1999 reported perioperative (30 days, 2387 patients) and postoperative (>30 days, 1645 patients) complications after endovascular abdominal aortic repair.^[460] Mean follow-up was 13.9 months. The perioperative mortality rate was 3.7%, and the annual mortality rate was 5.0% per year. The rates of endoleak (13.1%) and conversion to open repair (5.0%) were higher in the perioperative period than postoperatively (5.4% and 1.4% per year, respectively). The European Collaborators on Stent-Graft Technique for Abdominal Aortic Aneurysm Repair (EUROSTAR) registry was established in 1996 to collect data on the outcome of endovascular repair of abdominal aortic aneurysm in Europe. In a publication from the EUROSTAR database involving 3222 patients who received a variety of endografts, the operative mortality rate was 2.0%.^[461] Mean follow-up was 13.7 months. Early conversion to open repair occurred in 1.5% of patients, and secondary interventions occurred at a rate of 10% per year (1% per year conversion to open repair and 9% per year revision). The risk of rupture was 0.46% per year, with an associated mortality rate of 56%. This database has confirmed the importance of endoleak, stent-graft failure, and stent-graft migration in the causation of aneurysm rupture.^[462]

The Cleveland Clinic group reported their experience involving 703 patients who underwent endovascular repair of abdominal aortic aneurysm using several devices.^[463] As with other reports, the average follow-up was just over 12 months. Overall, secondary procedures were required in 15% of patients, with a cumulative risk of 12% at 1 year, 24% at 2 years, and 35% at 3 years. The mortality rate associated with these secondary procedures

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Limited information is available regarding endovascular repair involving descending thoracic aorta. Although short-term results from small to moderate-sized retrospective series are encouraging,^{[433] [465] [466]} severe complications, including paraplegia, aortic rupture, stroke, renal failure, and respiratory failure, have been reported. ^[467] Major procedure-related or device-related complications occur in up to 38% of patients.^[468] A mortality rate of 6.2% has been reported for 642 patients treated worldwide.^[469] The long-term durability of endovascular repair of the descending thoracic aorta is unknown. Long-term endograft surveillance is required to detect device failure.

Comparison of Open and Endovascular Repair

A meta-analysis of nine studies involving 1120 patients (687 endovascular and 631 open procedures) compared published short-term results of elective endovascular and open repair of abdominal aortic aneurysm.^[470] The pooled estimate of 30-day mortality for endovascular repair (3.0%) was significantly less than that for open repair (4.0%). Cardiac (3% versus 11%), pulmonary (4% versus 13%), renal (5% versus 8%), bleeding (1% versus 2%), and gastrointestinal (0% versus 2%) complications occurred significantly less frequently after endovascular repair. Intensive care stays (0.5 versus 2.2 days) and hospital stays (3.9 versus 10.3 days) were significantly shorter after endovascular repair. Total complications (30% versus 53%) and systemic or remote complications (17% versus 44%) were significantly less after endovascular repair. Only the rate of arterial injury (2% versus 0%) was significantly higher after endovascular repair.

Results of a decision analysis model on the basis of data from EUROSTAR suggest that the primary difference between endovascular and open repair is the timing of the risk of death and adverse events. The early benefit of reduced perioperative morbidity and mortality associated with endovascular repair is offset by the inferior long-term durability.^[461] Quality of life in the first postoperative year after elective endovascular or open abdominal aortic aneurysm repair was evaluated in a randomized, controlled fashion.^[471] Although endovascular repair had a quality of life advantage in the early postoperative period, at 6 months and beyond patients reported better quality of life after open repair.

Ultimately, randomized controlled trials will be necessary to evaluate the effectiveness of endovascular aneurysm repair compared with open repair. Several randomized trials are underway in the United States and Europe.