This review assessed elective endovascular aneurysm repair in the management of infrarenal abdominal aortic aneurysms. The authors concluded that it was associated with reduced peri-operative morbidity and mortality rates in comparison with open repair. However, further research with longer term follow-up is required. This was a relatively well-conducted systematic review and the authors' conclusions are likely to be reliable.

To assess the recent evidence for the safety and efficacy of elective endovascular aneurysm repair (EVAR) in the management of infrarenal abdominal aortic aneurysms (AAAs).

MEDLINE, EMBASE, BIOSIS Previews, CINAHL, the Cochrane CENTRAL Register, the Science Citation Index, the Social Sciences Citation Index, the Cochrane Database of Systematic Reviews, and the Centre for Reviews and Dissemination's databases were searched in March 2005. Examples of search terms were stated and the authors referred readers to their previous review for copies of the search strategies used in the major databases (see Other Publications of Related Interest). Only English language articles were sought. The previous review was restricted to papers published since the year 2000; it was unclear whether this update was also restricted by year of publication.

Randomised controlled trials (RCTs), controlled clinical trials, comparative observational studies, case-series studies comprising 50 patients or more and at least 5 outcome measures of interest, and population-based registry data were eligible for inclusion.

Comparisons of elective EVAR and open repair of AAAs were eligible for inclusion in the review.

Studies of adults with asymptomatic infrarenal AAAs were eligible for inclusion in the review. Studies of patients with thoracic and thoraco-abdominal aortic aneurysms, symptomatic aneurysms, or ruptured aneurysms were excluded. Where reported, the mean age of the patients in the studies ranged from 65 to 85 years.

Studies that assessed the efficacy and/or safety of EVAR were eligible for inclusion. A full list of efficacy and safety outcomes of interest were listed in the report. The outcomes assessed in the review included mortality, success rate, aneurysm rupture, primary and delayed conversion rate to open procedure, changes in aneurysm size, blood loss, length of stay in the intensive treatment unit and hospital, and complications.

The authors did not state how the papers were selected for the review, or how many reviewers performed the selection. For studies with multiple publications, the publication with the greatest number of participants, longest follow-up or latest publication with the most outcome data were included.

For the assessment of case-series studies, non-randomised controlled trials and comparative observational studies, quality assessment checklists were designed by adapting the checklists of the Centre for Reviews and Dissemination and Downs and Black. A modified version of Verhagen and colleagues' Delphi List was used to assess the quality of RCTs. One reviewer undertook the quality assessment.

A data extraction form was designed specifically for the review. One reviewer undertook the data extraction and another reviewer checked it for accuracy. The reviewers were not blinded to authorship, institution or source of publication.

For binary outcomes, the pooled odds ratio (OR) or hazard ratio (HR) and 95% confidence interval (CI) were calculated using a fixed-effect model. Where significant heterogeneity was indicated the results were recalculated using a random-effects model.

For continuous outcomes, a weighted mean difference (WMD) and 95% CI were calculated. When standard deviations were not reported, they were estimated from the interquartile range (if available) in order to calculate a WMD. If neither the standard deviation nor interquartile range were reported, the studies were not combined in the meta-analysis.

For studies that did not include a comparison group, the overall mean and 95% CI were calculated.

Heterogeneity was assessed using the chi-squared test and I-squared statistic.

The authors stated that, in addition to the studies included in the previous review, 78 studies (n=33,664) were identified for inclusion : 4 RCTs (6 publications), 17 non-randomised controlled trials, 22 comparative observational studies, 28 case series and 6 registry publications. They presented details of 78 studies in their table of included studies. However, in the table there were 6 RCTs, 16 non-randomised controlled trials, 20 comparative observational studies, 32 case series, and 4 case series that were registry publications.

The quality of three of the 4 included RCTs was high. The non-randomised controlled trials, comparative observational studies and case-series studies were poorer in quality and more prone to bias.

EVAR versus open repair.

EVAR was associated with a statistically significant lower 30-day mortality rate compared with open repair (3 RCTs; OR 0.33, 95% CI: 0.17, 0.64). This result was supported by data from 17 non-randomised controlled trials (OR 0.31, 95% CI: 0.25, 0.39). There was no significant heterogeneity between the studies. However, 2 RCTs that reported 2-year and 4-year follow-up indicated that the early survival benefit was lost by the end of the first year.

The primary conversion rate to open repair was 0.8% and 1.8% in the 2 RCTs, a mean of 2.4% (95% CI: 1.8, 3.0; range: 0 to 7.3) in the 12 non-randomised controlled trials, and a mean of 1.2% (95% CI: 1.0, 1.4) in the case series.

The early aneurysm rupture rate was reported as 0.2% in one non-randomised controlled trial. There was no significant difference in delayed rupture rates between EVAR and open repair (OR 5.0, 95% CI: 0.58, 42.94). Of the 6 non-randomised controlled trials, five reported a 0% rupture rate for EVAR and one reported a 1.1% rate.

Two RCTs reported significantly higher secondary intervention rates following EVAR compared with after open repair (OR 2.57, 95% CI: 1.70, 3.87; HR 2.9, 95% CI: 1.1, 6.2).

The most common technical adverse event following EVAR was a type II endoleak, which occurred in 19.6% of patients at less than 30 days, 12.9% at 1 year and 11.7% beyond 1 year. Pulmonary complications, incidence of blood loss and haemorrhagic events were significantly lower in the EVAR group than in the open repair group. There was no significant difference in the rates of cardiac events, lower limb ischaemia, renal impairment, graft infection, colonic ischaemia or local wound complications. Total hospital stay was reduced for the EVAR group compared with the open repair group (3 RCTs). Three RCTs and 8 non-randomised controlled trials demonstrated a significant reduction in intensive treatment unit stay after EVAR compared with after open repair.

Further results were reported.

EVAR in high-risk patients.

One RCT evaluated EVAR compared with no intervention in a population who were deemed to be unfit for open repair. This RCT reported no statistically significant difference in aneurysm-related deaths between EVAR and no intervention (12% versus 12.8%, respectively; HR 1.00, 95% CI: 0.54, 1.84), or total mortality rates (44.6% versus 39.5%) during the follow-up period. The rupture rate was 2% in the first 30 days after EVAR, and 12.2% in the no intervention group. Conversion to open repair occurred in 0.6% of cases during the primary procedure and 1.2% during the follow-up period. The complication rate following EVAR was 32.6%. At 4 years, 26% required at least one re-intervention following EVAR, compared with 4% in the no intervention group (HR 5.8, 95% CI: 2.4, 14.0, P<0.001); however, if crossovers from the no intervention group were considered secondary interventions, the rate for the no intervention group rose to 30%.

EVAR is a less invasive technique which is associated with a reduction in peri-operative morbidity and mortality rates in comparison with open repair. However, there is a significant rate of re-intervention and the long-term success in preventing aneurysm-related mortality is unknown. No overall survival benefit following EVAR has been demonstrated in the medium term. Despite higher rates of morbidity and mortality found in an RCT comparing EVAR with best medical therapy in patients unfit for open repair, there may be a place for EVAR in the management of certain high-risk surgical candidates, as the risk of aneurysm-related death is likely to be higher than that found in the RCT. EVAR is a technique that is still developing and requires further research, with longer term follow-up, to determine its exact place in the management of AAAs.

The review question was clear in terms of the study designs, participants, intervention and outcomes of interest. Several relevant electronic databases were searched, but only English language publications were sought and no attempts were made to identify unpublished studies, thus increasing the potential for language and publication biases. The validity of the included studies was assessed using appropriate criteria. The data extraction was performed by one author and checked by a second, thus reducing the potential for reviewer error or bias. However, the validity assessment was only undertaken by one author and the procedure used for assessing the relevance of studies for inclusion was not reported; reviewer error or bias cannot, therefore, be ruled out for these stages of the review.

Adequate details of the included studies and the quality assessment exercise were presented. Heterogeneity was assessed and the methods of combining the studies seemed appropriate. The authors' conclusions appear to follow from the evidence presented and are likely to be reliable, although other relevant studies might have been missed.

Practice: Despite higher rates of morbidity and mortality found in an RCT comparing EVAR with best medical therapy in patients unfit for open repair, there may be a place for EVAR in the management of certain high-risk surgical candidates, as the risk of aneurysm-related death is likely to be higher than that found in the RCT.

Research: The authors stated that further research, with longer term follow-up, is required to determine the exact place of EVAR in the management of AAAs.

1. Drury D, Michaels J, Jones L, Ayiku L. A systematic review of the recent evidence for the safety and efficacy of elective endovascular repair in the management of infrarenal abdominal aortic aneurysms. London: National Institute for Health and Clinical Excellence; 2004. (accessed 30/05/2006). Available from: URL: http://www.nice.org.uk/page.aspx?o=234299 2. Drury D, Michaels J, Jones L, Ayiku L. Systematic review of recent evidence for the safety and efficacy of elective endovascular repair in the management of infrarenal abdominal aortic aneurysms. Br J Surg 2005;92:937-46.

This record is a structured abstract written by CRD reviewers. The original has met a set of quality criteria. Since September 1996 abstracts have been sent to authors for comment. Additional factual information is incorporated into the record. Noted as [A:....].