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Ruptured Abdominal Aortic Aneurysms: Endovascular Repair versus Open Surgery—Systematic Review¹

¹ From the Departments of Epidemiology and Biostatistics (J.J.V., T.H.H., M.G.M.H., J.L.B.), Radiology (J.J.V., M.G.M.H., J.L.B.), and Surgery (J.J.V., M.R.H.M.v.S.), Erasmus MC, Dr Molewaterplein 40, Room Ee21-40B, 3015 GD Rotterdam, the Netherlands; Department of Health Policy and Management, Harvard School of Public Health, Boston, Mass (M.G.M.H.); and Institute of Technology Assessment, Massachusetts General Hospital, Harvard Medical School, Boston, Mass (J.L.B.). Received July 12, 2006; revision requested September 14; revision received November 13; accepted December 18; final version accepted February 20, 2007. Supported in part by an Erasmus University Medical Center Health Care Efficiency grant and an unrestricted educational grant from the Lijf en Leven Foundation. Address correspondence to J.L.B. (e-mail: j.l.bosch{at}erasmusmc.nl).

	ABSTRACT

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Purpose: To perform a systematic review of studies in which endovascular repair was compared with open surgery in the treatment of patients with a ruptured abdominal aortic aneurysm (AAA).

Materials and Methods: A search of the English-language literature from January 1994 until March 2006 was performed. Inclusion criteria for studies were that they were about a comparison between patients who underwent endovascular repair and patients who underwent open surgery, that each treatment group included at least five patients, that information about patients' hemodynamic condition at presentation was reported, and that 30-day mortality was reported for each treatment group. Two reviewers independently extracted the data, and discrepancies were resolved by an arbiter. Random-effects models and meta-regression analysis were used to calculate crude and adjusted odds ratios (ORs) for endovascular repair versus open surgery.

Results: Ten studies, in which the results of 478 procedures (n = 148 for endovascular repair, n = 330 for open surgery) were reported, met the inclusion criteria. All studies were observational; no randomized controlled trials were found. The pooled 30-day mortality was 22% (95% confidence interval [CI]: 16%, 29%) for endovascular repair and 38% (95% CI: 32%, 45%) for open surgery. The pooled rate for total systemic complications was 28% (95% CI: 17%, 48%) for endovascular repair and 56% (95% CI: 37%, 85%) for open surgery. The crude OR for 30-day mortality for endovascular repair compared with open surgery was 0.45 (95% CI: 0.28, 0.72). After adjustment for patients' hemodynamic condition, the OR was 0.67 (95% CI: 0.31, 1.44).

Conclusion: In this systematic review, after adjustment for patients' hemodynamic condition at presentation, a benefit in 30-day mortality for endovascular repair compared with open surgery for patients with a ruptured AAA was observed, but it was not statistically significant.

Supplemental material: http://radiology.rsnajnls.org/cgi/content/full/245/1/122/DC1

© RSNA, 2007

	INTRODUCTION

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Open surgery has traditionally been the approach to treat ruptured abdominal aortic aneurysms (AAAs). In 1994, endovascular repair became available (1). Since then, this technique has increasingly been used to treat ruptured AAAs (2). The initial results are very promising (3–5), and many hospitals have implemented the policy to treat patients with a ruptured AAA with endovascular repair, provided the anatomy is suitable. Recently, however, results of published randomized trials in which elective endovascular repair was compared with elective open surgery in patients with an asymptomatic AAA indicated that there is only a short-term advantage of endovascular repair in these patients (6,7); in the long term (ie, 4 years), they found that endovascular repair offers no survival advantage compared with open surgery (7). To our knowledge, no randomized controlled trials in which endovascular repair and open surgery in patients with a ruptured AAA were compared have been published.

In several nonrandomized studies, mortality and morbidity data for endovascular repair were compared with data for conventional open surgery in patients with a ruptured AAA (8–17). The matching criteria for endovascular repair and open surgery varied across the studies. As a result, investigators in these studies reported a wide range of estimates for short-term mortality and morbidity; for example, in patients with a ruptured AAA, short-term mortality estimates for endovascular repair varied between 10% and 29% (10,17), and those for open surgery varied between 15% and 54% (12,17). These studies were rather heterogeneous with respect to the inclusion of hemodynamically unstable patients in the open surgery group. To enable comparison of the results of endovascular repair with results of open surgery in patients with a ruptured AAA, it is important to systematically evaluate these published studies and to adjust for differences in inclusion criteria among the studies. Thus, the purpose of our study was to perform a systematic review of studies in which endovascular repair was compared with open surgery in the treatment of patients with a ruptured AAA.

	MATERIALS AND METHODS

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Data Sources and Extraction
To find the best available evidence, we formulated a PICO question (P represents the patient, population, or problem; I stands for the intervention or independent variable; C indicates the comparison; and O signifies the outcome of interest or dependent variable) (18). We asked this question: In patients with a ruptured AAA, would endovascular repair compared with open surgery lead to lower mortality and morbidity?

The literature was searched by using the MEDLINE database and the Cochrane Library for literature in which data about endovascular repair and open surgery in patients with a ruptured AAA were reported. The search was performed on March 2, 2006, by one of the authors (J.J.V.). We used keywords describing "ruptured AAA," "endovascular repair," "open surgery," and "outcome." Our search was limited to the English language and included studies published between January 1994 and March 2006. The search started in 1994, when Yusuf and colleagues (1) published a case report on endovascular treatment of ruptured AAA, and continued onward to 2006. To obtain additional references, articles that met our inclusion criteria were checked by one author (J.J.V.) by reviewing the reference list of each article. Furthermore, these articles were entered into the ISI WEB OF KNOWLEDGE: WEB OF SCIENCE database (19) to find where the articles that met our inclusion criteria were cited, so that related articles could be found. In addition, the computerized search strategy was validated by one author (J.J.V.) who performed a manual search of the journals that reported most frequently about the topic of interest. These journals were searched from 1994 to 2006 and included Radiology, Journal of Vascular and Interventional Radiology, Journal of Vascular Surgery, Journal of Endovascular Therapy, and European Journal of Vascular and Endovascular Surgery. Meeting abstracts, unpublished data, and theses were not included in our search.

Prospective, as well as retrospective, studies were included if: (a) patients who underwent endovascular repair were compared with patients who underwent open surgery, (b) each treatment group included at least five patients, (c) information about patients' hemodynamic condition at presentation to the hospital was reported, and (d) 30-day mortality was reported for each treatment group. If researchers in the studies reported results of current and historic control patients separately, we included the results of only current control patients. When multiple reports from one institution were retrieved, the most recent report was included to avoid double counting.

Two authors (J.J.V., M.R.H.M.v.S.) independently extracted data from each article by using a standard form. Each of these two authors independently reviewed all articles. The arbiter (J.L.B.) considered discrepancies. The following data were recorded: (a) number of patients in each treatment group; (b) reasons to treat patients with open surgery; (c) patient characteristics; (d) AAA morphology; (e) whether computed tomography (CT) was performed prior to the procedure; (f) procedure characteristics, such as type of anesthesia, type of graft, amount of blood loss, and procedure time; (g) mortality and morbidity rates during the hospital stay; and (h) aneurysm-related complications during follow-up.

Data and Statistical Analysis
We assumed that the articles included in our systematic review were a random, unselected sample of a hypothetical population of studies in which endovascular repair was compared with open surgery in patients with a ruptured AAA. Therefore, to pool data, we used the random-effects model described by DerSimonian and Laird (20). With this model, we took into account between-study variability, as well as within-study variability. The pooled 30-day mortality, with the 95% confidence interval (CI), was calculated for both treatment groups. The total systemic complications were calculated as the sum of cardiac, pulmonary, cerebrovascular, and renal complications; multiorgan failure; and sepsis. These complications were based on those in the studies in which investigators reported systemic complications for each treatment group (8,11,13,15,17). The pooled rate of total systemic complications, with the 95% CI, was calculated for each treatment group. Furthermore, we calculated the weighted means, with the 95% CI, for the mean age, mean AAA diameter, mean infrarenal neck diameter, mean infrarenal neck length, mean days in the hospital, mean days in the intensive care unit, mean amount of blood loss, mean number of blood transfusions, and mean time of the procedure. The crude odds ratio (OR) for 30-day mortality, with the 95% CI, was calculated for endovascular repair versus open surgery (ie, an OR <1.0 favored endovascular repair). Furthermore, an OR for 30-day mortality adjusted for patients' hemodynamic condition at presentation in the hospital was calculated by performing a meta-regression analysis. In the regression model, we included the proportion of patients with low systolic blood pressures in each treatment group as covariate in the model.

Publication bias (ie, bias resulting from the greater likelihood of publishing favorable results) was detected by using a funnel plot (21). In the current study, we plotted the reciprocal of the standard error of the 30-day mortality OR of each study as a function of the natural logarithm of the 30-day mortality OR. If no publication bias is present, the data points are distributed in a symmetric fashion and shaped like an inverted V. Furthermore, to test for heterogeneity in patients' hemodynamic condition at presentation to the hospital across the studies, we used the ² test. A difference with P < .05 was considered statistically significant. Analyses were performed by using spreadsheet software (Microsoft Excel 2000; Microsoft, Redmond, Wash) and statistical software (SAS, version 8.2; SAS, Cary, NC).

	RESULTS

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Literature Search
A total of 402 articles were identified from the MEDLINE and ISI WEB OF KNOWLEDGE: WEB OF SCIENCE databases (Fig 1). No additional articles were retrieved from the Cochrane Library, the review of the reference list of each article, and the manual search. Of these 402 articles, 56 articles were retrieved in full, and 10 of them met our inclusion criteria (8–17). The total number of procedures was 478; 148 patients underwent endovascular repair and 330 patients underwent open surgery. Nine studies were performed in Europe and one in the United States (Table 1). The articles were published between June 2003 and January 2006; patients were enrolled from 1996 to 2004. All studies were observational and were performed in a single center; no randomized controlled trials were found. The size of the treatment groups varied between six and 25 for endovascular repair and between 10 and 172 for open surgery. Researchers in two studies did not report results for current and historic control patients separately for comparison with patients treated with open surgery. Therefore, we used the combined results (8,14).

View larger version (19K): [in this window] [in a new window] [Download PPT slide]   Figure 1: Flowchart of the study selection procedure, with criteria and numbers of studies.

Outcomes
In studies in which intraoperative mortality for the endovascular repair and the open surgery groups was reported, the intraoperative mortality was lower for patients treated with endovascular repair (Table E3 [http://radiology.rsnajnls.org/cgi/content/full/245/1/122/DC1]). In addition, all studies showed lower 30-day mortality rates for patients treated with endovascular repair compared with those patients who underwent open surgery. The pooled 30-day mortality was 22% (95% CI: 16%, 29%) for endovascular repair and 38% (95% CI: 32%, 45%) for open surgery. The crude OR for 30-day mortality of endovascular repair versus open surgery was 0.45 (95% CI: 0.28, 0.72). Heterogeneity was demonstrated for the patients' hemodynamic condition at presentation to the hospital across the studies for both treatment groups (P < .01). After adjustment for patients' hemodynamic condition at presentation to the hospital, the OR was 0.67 (95% CI: 0.31, 1.44; P = .37), and this finding indicates that the difference in 30-day mortality was, in part, explained by this variable (Fig 2).

View larger version (13K): [in this window] [in a new window] [Download PPT slide]   Figure 2: Comparative analysis of endovascular repair versus open surgery. Forest plot of ORs (with 95% CIs in square brackets) of reported and pooled 30-day mortality of each study included in the analysis. Random-effects model was used to pool data.

Investigators in five studies reported complications for both endovascular repair and open surgery (Table E4 [http://radiology.rsnajnls.org/cgi/content/full/245/1/122/DC1]) (8,11,13,15,17). The pooled percentage of total systemic complications (ie, the sum of cardiac, pulmonary, cerebrovascular, and renal complications; multiorgan failure; and sepsis) was 28% (95% CI: 17%, 48%) for endovascular repair and 56% (95% CI: 37%, 85%) for open surgery.

Follow-up data were reported in five studies and only in patients treated with endovascular repair (8,9,11,13,17). Peppelenbosch et al (8) reported type 1 endoleaks in two patients and a type 2 endoleak in one patient during follow-up from 30 days to 14 months. Reichart et al (9) reported an additional endovascular procedure to exclude an iliac aneurysm in one patient during follow-up from 6 to 24 months. Alsac et al (11) reported a conversion to open surgery for endograft sepsis in one patient, type 1 endoleaks in three patients, and a second rupture in one patient during follow-up from 30 to 250 days. Castelli et al (13) reported occlusion of an iliac limb in one patient and type 2 endoleaks in two patients during follow-up from 4 to 24 months. Franks et al (17) reported type 2 endoleaks in four patients during follow-up from 7 to 106 months. It should be noted that Peppelenbosch et al and Franks et al did not report data on follow-up separately for patients with a symptomatic AAA and patients with a ruptured AAA.

Funnel Plot Evaluation
Publication bias was evaluated with a funnel plot (Fig 3). Figure 3 shows an asymmetrical distribution of the data points. In the lower right-hand corner, studies appear to be missing.

View larger version (6K): [in this window] [in a new window] [Download PPT slide]   Figure 3: Funnel plot shows the reciprocal of the standard error of the 30-day mortality OR for endovascular repair versus open surgery as a function of the natural logarithm of the 30-day mortality OR. The square with the horizontal bars indicates the natural logarithm of the pooled 30-day mortality OR with the 95% CI. The funnel plot shows an asymmetric distribution of the data points, indicating that publication bias may be present. In the lower right-hand corner, studies () appear to be missing. This suggests that small studies with higher mortality rates for endovascular repair than for open surgery are underrepresented.

	DISCUSSION

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Caution must be exercised when one interprets the results of this review. The principal limitation of our study was that no randomized controlled clinical trials were included and that only observational studies were available. Systematic reviews of observational studies may be a better representation of daily clinical practice than randomized controlled trials. In the comparison of therapies, however, including observational studies means that these studies may have been affected by selection bias (25–27). The decision to treat patients with a ruptured AAA with endovascular repair or open surgery was based on patients' hemodynamic condition at presentation to the hospital, anatomic considerations, or logistic reasons, such as availability of adequate endovascular equipment and sufficiently trained staff, or all of these factors. A selection based on patients' hemodynamic condition may result in poorer clinical outcomes for open surgery, which was confirmed by findings in our analysis in which we adjusted 30-day mortality for this condition. The effect of potential bias due to other selection criteria remains unknown but is likely to show that endovascular repair is favored.

Other major limitations of our review, as with many reviews, are variation in definitions and protocols across the studies and the quality of reported data. Across the studies in our review, procedure protocols varied, type of grafts used varied, definitions of characteristics and clinical outcomes varied, and sometimes definitions or data were not reported. This lack of standardization in treatment protocol and in reporting data complicated the comparison of endovascular repair and open surgery. In addition, over two times as many patients were treated with open surgery as were with endovascular repair. Furthermore, data about in-hospital complications for both treatment groups were reported in only five of 10 included studies, and data about follow-up were available only for patients treated with endovascular repair in five of 10 included studies. Nevertheless, showing the data of the studies in a systematic way and performing analyses with adjustment for a major confounder demonstrated current status of treatment management for patients with a ruptured AAA.

Our study may have been affected by publication bias (ie, the greater likelihood of publication of positive results, such as lower mortality and complication rates, or results based on large sample sizes). To investigate this bias, we constructed a funnel plot. Our funnel plot was not symmetrically shaped; small studies with higher mortality rates for endovascular repair than for open surgery seemed to be underrepresented, which may have favored endovascular repair. It should be noted that our literature search was thorough; therefore, it is unlikely that we missed relevant articles. We did, however, limit our search to the English-language literature, on the basis of findings in a report that indicated that literature searches limited to the English-language literature often produce results that are close to results produced by comprehensive searches with no language restriction (28,29).

Unfortunately, the researchers in studies in our review did not report long-term follow-up results. Thus, uncertainty remains concerning the long-term effectiveness of endovascular repair for patients with a ruptured AAA. In the long term, threats to the effectiveness of endovascular repair are endoleaks, thrombosis, stenosis, and graft migration (30,31). Therefore, a clinical benefit caused by the favorable short-term results of endovascular repair compared with open surgery may be negated when long-term follow-up results are taken into account. Recently, this observation was demonstrated in randomized controlled trials in which clinical effectiveness of elective endovascular repair was compared with that of open surgery in patients with asymptomatic AAAs. The results of these trials suggested that the short-term reduction in mortality for patients treated with endovascular repair was not sustained after 2 years of follow-up (6,7). In addition, in a time of budget constraints, costs or cost-effectiveness of a new therapy compared with the traditional therapy may influence treatment policy. Of note, a recently performed study about the costs of endovascular repair versus those of open surgery in patients with acute AAAs showed that endovascular repair was cost saving compared with open surgery, even after 1-year follow-up (32).

Furthermore, to avoid selection bias and enhance the comparability between the two treatments, hemodynamically unstable patients should be excluded from the analysis. This will increase the homogeneity between patients treated with endovascular repair and patients treated with open surgery. Ideally, logistic reasons to treat patients with open surgery instead of endovascular repair should be avoided by having trained staff on call 24 hours a day 7 days per week and adequate endovascular equipment in stock. To enable combining results of different studies in which results of endovascular repair and open surgery were reported in patients with a ruptured AAA in a meta-analysis, we would recommend that researchers describe patient and procedure characteristics and selection criteria for endovascular repair in accurate detail (33–35).

In conclusion, after adjustment for patients' hemodynamic condition at presentation, a benefit in 30-day mortality for endovascular repair compared with open surgery for patients with a ruptured AAA was observed, but it was not statistically significant. For the decision whether patients with ruptured AAA should be treated with endovascular repair or open surgery, more research is needed, especially with larger series of patients and longer follow-up with adequate reporting of data.

	ADVANCE IN KNOWLEDGE

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• After adjustment for patients' hemodynamic condition at presentation, a benefit in 30-day mortality for endovascular repair compared with open surgery for patients with a ruptured abdominal aortic aneurysm (AAA) was observed, but it was not statistically significant (P = .37).
  

	IMPLICATION FOR PATIENT CARE

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• On the basis of current available evidence, both endovascular repair and open surgery are justified treatment options for patients with a ruptured AAA; it is likely, however, that patients treated with endovascular repair may have greater short-term survival.
  

	ACKNOWLEDGMENTS

 
We thank the members of the Assessment for Radiological Technology (ART) group for their comments and suggestions.

	FOOTNOTES

 

Abbreviations: AAA = abdominal aortic aneurysm • CI = confidence interval • OR = odds ratio

Authors stated no financial relationship to disclose.

Author contributions: Guarantors of integrity of entire study, J.J.V., J.L.B.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, J.J.V., M.R.H.M.v.S.; statistical analysis, J.J.V., T.H.H., M.G.M.H., J.L.B.; and manuscript editing, M.R.H.M.v.S., T.H.H., M.G.M.H., J.L.B.

	References

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