Advertisement

Editor's Choice – Systematic Review and Meta-Analysis of the Impact of Institutional and Surgeon Procedure Volume on Outcomes After Ruptured Abdominal Aortic Aneurysm Repair

Open ArchivePublished:August 09, 2021DOI:https://doi.org/10.1016/j.ejvs.2021.06.015

      Objective

      To investigate whether there is a correlation between institutional or surgeon case volume and outcomes in patients with ruptured abdominal aortic aneurysm (rAAA).

      Data Sources

      The Healthcare Database Advanced Search interface developed by the National Institute of Health and Care Excellence was used to search MEDLINE, Embase, CINAHL, and CENTRAL.

      Review Methods

      The systematic review complied with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines with the protocol registered in PROSPERO (CRD42020213121). Prognostic studies were considered comparing outcomes of patients with rAAA undergoing repair in high and low volume institutions or by high and low volume surgeons. Pooled estimates for peri-operative mortality were calculated using the odds ratio (OR) and 95% confidence intervals (CI), applying the Mantel-Haenszel method. Analysis of adjusted outcome estimates was performed with the generic inverse variance method.

      Results

      Thirteen studies reporting a total of 120 116 patients were included. Patients treated in low volume centres had a statistically significantly higher peri-operative mortality than those treated in high volume centres (OR 1.39; 95% CI 1.22 – 1.59). Subgroup analysis showed a mortality difference in favour of high volume centres for both endovascular aneurysm repair (EVAR; OR 1.61, 95% CI 1.11 – 2.35) and open repair (OR 1.50, 95% CI 1.25 – 1.81). Adjusted analysis showed a benefit of treatment in high volume centres for open repair (OR 1.68, 95% CI 1.21 – 2.33) but not for EVAR (OR 1.42, 95% CI 0.84 – 2.41). Differences in peri-operative mortality between low and high volume surgeons were not statistically significant for either EVAR (OR 1.06, 95% CI 0.59 – 1.89) or open surgical repair (OR 1.18, 95% CI 0.87 – 1.63).

      Conclusion

      A high institutional volume may result in a reduction of peri-operative mortality following surgery for rAAA. This peri-operative survival advantage is more pronounced for open surgery than EVAR. Individual surgeon caseload was not found to have a significant impact on outcomes.

      Keywords

      Institutional and surgeon volume metrics have been discussed widely, but there has been no systematic review compiling data on ruptured abdominal aortic aneurysm (rAAA) repair. Meta-analysis of 13 studies reporting a total of 120 116 patients with rAAA showed that patients treated in low volume institutions have a higher peri-operative mortality that those treated in high volume institutions. Adjusted analysis showed a benefit of treatment in high volume centres for open, but not for endovascular, repair. Surgeon caseload did not have a significant impact on outcomes. The results have important implications for vascular service alignment and AAA care provision.

      Introduction

      Volume metrics have been discussed widely in the literature as a potential index of hospital or individual surgeon performance for a wide range of surgical procedures.
      • Schwartz D.M.
      • Fong Z.V.
      • Warshaw A.L.
      • Zinner M.J.
      • Chang D.C.
      The hidden consequences of the volume pledge: “No Patient Left Behind”?.
      • Lillemoe K.D.
      Surgical volume/outcome debate.
      • Finks J.F.
      • Osborne N.H.
      • Birkmeyer J.D.
      Trends in hospital volume and operative mortality for high-risk surgery.
      Efforts to identify quality measures that could improve surgical outcomes in the USA are illustrated in the work of a consortium of large corporations and public agencies recommending minimum volume standards for surgical procedures.
      • Milstein A.
      • Galvin R.S.
      • Delbanco S.F.
      • Salber P.
      • Buck Jr., C.R.
      Improving the safety of health care: the leapfrog initiative.
      Such an approach is based on published data indicating significant associations between operative outcomes and institutional and/or surgeon caseload for almost every surgical procedure, although the magnitude of effect may vary. Two landmark studies by Birkmeyer et al. suggested that for patients undergoing cardiovascular or cancer operations, the peri-operative mortality risk can be significantly reduced in high volume institutions, and this benefit is largely attributed to the superior performance of high volume surgeons.
      • Birkmeyer J.D.
      • Siewers A.E.
      • Finlayson E.V.
      • Stukel T.A.
      • Lucas F.L.
      • Batista I.
      • et al.
      Hospital volume and surgical mortality in the United States.
      ,
      • Birkmeyer J.D.
      • Stukel T.A.
      • Siewers A.E.
      • Goodney P.P.
      • Wennberg D.E.
      • Lucas F.L.
      Surgeon volume and operative mortality in the United States.
      In this work, elective surgery for abdominal aortic aneurysm (AAA) was shown to have almost half the peri-operative mortality in high volume institutions vs. low volume institutions.
      Subsequent studies examining the effect of institutional caseload on outcomes of AAA repair suggest a significant association, with higher volume centres demonstrating better performances, as indicated by lower peri-operative morbidity and mortality.
      • Phillips P.
      • Poku E.
      • Essat M.
      • Woods H.B.
      • Goka E.A.
      • Kaltenthaler E.C.
      • et al.
      Procedure volume and the association with short-term mortality following abdominal aortic aneurysm repair in European populations: a systematic review.
      • Paraskevas K.I.
      The effect of centralization of abdominal aortic aneurysm repair procedures on perioperative outcomes.
      • Patterson B.O.
      • Holt P.J.E.
      High volume aortic practices demonstrate benefits crossing healthcare boundaries.
      As a result, clinical practice guidelines have recommended minimum numbers of AAA repair for vascular centres to be able to offer such surgery.
      • Chaikof E.L.
      • Dalman R.L.
      • Eskandari M.K.
      • Jackson B.M.
      • Lee W.A.
      • Mansour M.A.
      • et al.
      The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm.
      ,
      • Wanhainen A.
      • Verzini F.
      • Van Herzeele I.
      • Allaire E.
      • Bown M.
      • Cohnert T.
      • et al.
      Editor's Choice – European Society for Vascular Surgery (ESVS) 2019 Clinical Practice Guidelines on the management of abdominal aorto-iliac artery aneurysms.
      Most research investigating volume outcome associations has largely focused on elective AAA cases.
      • Marlow N.E.
      • Barraclough B.
      • Collier N.A.
      • Dickinson I.C.
      • Fawcett J.
      • Graham J.C.
      • et al.
      Effect of hospital and surgeon volume on patient outcomes following treatment of abdominal aortic aneurysms: a systematic review.
      • Henebiens M.
      • van den Broek T.A.
      • Vahl A.C.
      • Koelemay M.J.
      Relation between hospital volume and outcome of elective surgery for abdominal aortic aneurysm: a systematic review.
      • Holt P.J.
      • Poloniecki J.D.
      • Gerrard D.
      • Loftus I.M.
      • Thompson M.M.
      Meta-analysis and systematic review of the relationship between volume and outcome in abdominal aortic aneurysm surgery.
      Potential associations in the emergency setting for AAA surgery could have implications for vascular service provision, structure and configuration, and utilisation of resources. The objective of this systematic review was to test the hypothesis that institutions or surgeons with higher AAA case volumes confer improved outcomes for patients with ruptured AAA (rAAA).

      Methods

      Design

      The objectives and methodology of this review were pre-specified in a protocol that was registered in PROSPERO (International Prospective Register of Systematic Reviews in Health and Social Care) with the registration number CRD42020213121. The review was developed in line with principles described in the Cochrane Handbook for Systematic Reviews of Interventions.
      Reporting of the review complied with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines.
      • Liberati A.
      • Altman D.G.
      • Tetzlaff J.
      • Mulrow C.
      • Gøtzsche P.C.
      • Ioannidis J.P.
      • et al.
      The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration.

      Criteria for considering studies

      Types of studies

      Prognostic studies of any design comparing outcomes of patients with rAAA undergoing repair in high and low volume institutions or by high and low volume surgeons were considered for inclusion in qualitative and quantitative synthesis. When two or more studies reported overlapping patient cohorts, the sample size and/or study period (i.e., the largest and/or most recent study) were considered for study selection. Studies published before 2000 were not included, because they were considered outdated, and not representative of current clinical practice.

      Types of participants

      Participants were male or female patients of any age undergoing emergency surgery, either endovascular aneurysm repair (EVAR) or open surgical repair, for ruptured infrarenal or juxtarenal AAA. Patients with symptomatic but not rAAA were not included, as were patients with ruptured pararenal, suprarenal, or thoraco-abdominal aortic aneurysm treated by complex endovascular or open surgery.

      Types of prognostic factor

      The primary prognostic factor of interest was institutional caseload. Caseload was defined as the number of emergency operations for rAAA, the number of emergency or urgent operations for ruptured or symptomatic (not ruptured) AAA, the number of elective AAA repairs, or the total number of AAA operations performed in a single institution over a certain period of time (e.g., 12 months). The definition of institutional high (or low) volume used in the individual studies was used for the purposes of the analysis.
      The secondary prognostic factor was surgeon case volume, defined as the number of open or endovascular AAA repairs performed by a single surgeon over a certain period. Again, the definition of high or low surgeon volume was that used in individual studies.
      When a study divided patient cohorts into more than two groups, the lowest and highest volume groups were considered for the purposes of the analysis.

      Types of outcome measures

      Primary outcome

      Peri-operative mortality was defined as death occurring within 30 days from surgery or during the hospital stay.

      Secondary outcome

      Length of hospital stay.

      Search methods for identification of studies

      The literature search strategy was developed by a review author (G.A.) with experience in outreach, knowledge, and evidence search. Relevant studies were identified by searching electronic information sources and bibliographic reference lists of articles.

      Electronic sources

      The Healthcare Databases Advanced Search (HDAS) interface developed by the National Institute for Heath and Care Excellence (NICE) was used to interrogate the following electronic bibliographic databases: MEDLINE (Medical Literature Analysis and Retrieval System Online), Embase (Excerpta Medica Database), CINAHL (Cumulative Index to Nursing and Allied Health Literature), and CENTRAL (Cochrane Register of Studies). A combination of thesaurus and free text terms was used to search electronic literature sources. Thesaurus headings, search operators, and search limits in each of the above databases were adapted accordingly. The search of MEDLINE, Embase, and CINAHL was last run on 1 September 2020, and that of CENTRAL on 2 September 2020. The electronic search strategy is presented in Appendix S1 (Supplementary Material).

      Search of other sources

      A second level search was conducted by interrogating the bibliographic list of articles that qualified for inclusion in the review.

      Study selection and data management

      Two review authors (N.G. and E.A.) conducted the pre-specified literature searches and evaluated the eligibility of studies against the inclusion criteria independently. When disagreement arose, a third review author (N.K.) acted as arbitrator.
      Two review authors (N.G. and E.A.) extracted data from selected studies. The collected data were then cross checked by a third review author (N.K.). Retrieved data were entered into a spreadsheet. Only published material was considered. The following information was extracted from the individual studies:
      • Study related data: first author; journal and year of publication; study period; study design; single or multicentre study; sample size; definition of institutional or surgeon caseload (e.g., total number of AAA repairs or number of emergency AAA repairs over a certain period); definition of high and low institutional or surgeon volume; and potential confounders for which adjustments were made (for studies that performed such analyses).
      • Data pertaining to the risk of bias assessment.
      • Outcome data, as outlined above.

      Methods of study and evidence appraisal

      A modified Newcastle-Ottawa scale (NOS) was applied to assess the methodological quality of observational cohort studies (http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp). Using the tool, each study was judged on three domains: (1) the selection of the study groups; (2) the comparability of the groups; and (3) the assessment of outcome. Stars were awarded for each quality item. A maximum of nine stars could be awarded to the highest quality studies. The assessments were performed by two review authors (N.G. and E.A.) independently. In the event of disagreement, consensus was reached after discussion between the two.
      The quality of evidence for the primary prognostic factor was graded using the system developed by the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) working group and a summary of findings table was generated applying an online platform (https://gdt.gradepro.org/app/). The GRADE approach specifies four levels of quality of the body of evidence for each outcome, namely high, moderate, low, and very low, based on the following factors: limitations in the design and implementation; indirectness of the evidence; unexplained heterogeneity or inconsistency of results; imprecision of results; and probability of publication bias.
      • Antoniou S.A.
      • Antoniou G.A.
      The GRADE approach to appraising the evidence or how to increase the credibility of your research.

      Data synthesis

      Measures of treatment effect

      Pooled outcome estimates were calculated using the odds ratio (OR) or mean difference (MD) and associated 95% confidence interval (CI). When studies provided numbers of events and total numbers of patients in each group, the Mantel–Haenszel method was used, whereas when the primary studies reported only relative effect estimates (e.g., OR and 95% CI), the inverse variance method was employed. For continuous variables, when the mean value and standard deviation were not reported, they were calculated from median values and CI limits, standard error, or range values, as suggested by Hozo et al.
      • Hozo S.P.
      • Djulbegovic B.
      • Hozo I.
      Estimating the mean and variance from the median, range, and the size of a sample.
      Analysis of adjusted outcome estimates was performed with the generic inverse variance method.

      Assessment of heterogeneity

      Between study heterogeneity was examined with the Cochrane’s Q (chi square) test. Inconsistency was quantified and interpreted with the following guide: 0% – 40% might not be important; 30% – 60% may represent moderate heterogeneity; 50% – 90% may represent substantial heterogeneity; and 75% – 100% may represent considerable heterogeneity.
      • Langan D.
      • Higgins J.P.T.
      • Jackson D.
      • Bowden J.
      • Veroniki A.A.
      • Kontopantelis E.
      • et al.
      A comparison of heterogeneity variance estimators in simulated random-effects meta-analyses.
      ,
      • Deeks J.J.
      • Altman D.G.
      • Bradburn M.J.
      Statistical methods for examining heterogeneity and combining results from several studies in meta-analysis.

      Assessment of reporting bias

      For each study, the effect by the inverse of its standard error was plotted. For outcomes reported by at least 10 studies, the possibility of publication bias was assessed both visually, evaluating the symmetry of the funnel plot, and mathematically, using the Egger’s regression intercept.
      • Sterne J.A.C.
      • Sutton A.J.
      • Ioannidis J.P.A.
      • Terrin N.
      • Jones D.R.
      • Lau J.
      • et al.
      Recommendations for examining and interpreting funnel plot asymmetry in meta-analyses of randomised controlled trials.

      Missing data

      No attempt was made to contact the authors of included studies to enquire about missing or incomplete data.

      Statistical models

      Given the anticipated clinical, methodological, and conceptual heterogeneity, the summary estimates were calculated using the random effects models of DerSimonian and Laird.
      • Der Simonian R.
      • Laird N.
      Meta-analysis in clinical trials.
      A forest plot was created for each treatment effect.

      Sensitivity and subgroups analysis

      Studies that were judged to be high risk of bias (NOS score ≤ 6) were sequentially excluded and the analyses were repeated in order to assess whether studies deemed to be biased affected the final analysis. The analysis for each outcome was also repeated after removing one study at a time in order to assess each study’s impact on the overall results. Additional sensitivity analyses were performed by excluding (1) studies that included patients treated before 2000; (2) studies published from 2000 to 2010, in order to evaluate a more contemporaneous experience with endovascular techniques; and (3) studies that defined high and low volume institutions using criteria other than the number of rAAA cases (such as those that considered overall or elective AAA repairs, or hospital bed size).
      Subgroup analysis was performed for EVAR and open surgical repair of rAAA.

      Statistical software

      For data synthesis, the following software applications were used: (1) Review Manager (RevMan) computer program (Version 5.4; The Nordic Cochrane Centre, The Cochrane Collaboration, 2020); and (2) Comprehensive Meta-Analysis (CMA; Biostat, Englewood, NJ, USA).

      Results

      Literature search results

      A search of the literature applying pre-specified strategies retrieved 3 005 reports. Of these, 13 met the inclusion criteria and were included in the qualitative and quantitative synthesis.
      • Dimick J.B.
      • Stanley J.C.
      • Axelrod D.A.
      • Kazmers A.
      • Henke P.K.
      • Jacobs L.A.
      • et al.
      Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age.
      • Holt P.J.
      • Poloniecki J.D.
      • Loftus I.M.
      • Michaels J.A.
      • Thompson M.M.
      Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005.
      • Greco G.
      • Egorova N.
      • Anderson P.L.
      • Gelijns A.
      • Moskowitz A.
      • Nowygrod R.
      • et al.
      Outcomes of endovascular treatment of ruptured abdominal aortic aneurysms.
      • Giles K.A.
      • Hamdan A.D.
      • Pomposelli F.B.
      • Wyers M.C.
      • Dahlberg S.E.
      • Schermerhorn M.L.
      Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
      • McPhee J.
      • Eslami M.H.
      • Arous E.J.
      • Messina L.M.
      • Schanzer A.
      Endovascular treatment of ruptured abdominal aortic aneurysms in the United States (2001–2006): a significant survival benefit over open repair is independently associated with increased institutional volume.
      • Chen C.K.
      • Chang H.T.
      • Chen Y.C.
      • Chen T.J.
      • Chen I.M.
      • Shih C.C.
      Surgeon elective abdominal aortic aneurysm repair volume and outcomes of ruptured abdominal aortic aneurysm repair: a 12-year nationwide study.
      • Dua A.
      • Furlough C.L.
      • Ray H.
      • Sharma S.
      • Upchurch G.R.
      • Desai S.S.
      The effect of hospital factors on mortality rates after abdominal aortic aneurysm repair.
      • Karthikesalingam A.
      • Wanhainen A.
      • Holt P.J.
      • Vidal-Diez A.
      • Brownrigg J.R.
      • Shpitser I.
      • et al.
      Comparison of long-term mortality after ruptured abdominal aortic aneurysm in England and Sweden.
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      • Trenner M.
      • Kuehnl A.
      • Salvermoser M.
      • Reutersberg B.
      • Geisbuesch S.
      • Schmid V.
      • et al.
      Editor's Choice – High annual hospital volume is associated with decreased in hospital mortality and complication rates following treatment of abdominal aortic aneurysms: secondary data analysis of the Nationwide German DRG Statistics from 2005 to 2013.
      • Greenleaf E.K.
      • Hollenbeak C.S.
      • Aziz F.
      Outcomes after ruptured abdominal aortic aneurysm repair in the era of centralized care.
      • Tripodi P.
      • Mestres G.
      • Riambau V.
      Vascular Advisory Committee – Catalan Health Service
      Impact of centralisation on abdominal aortic aneurysm repair outcomes: early experience in Catalonia.
      • Sawang M.
      • Paravastu S.C.V.
      • Liu Z.
      • Thomas S.D.
      • Beiles C.B.
      • Mwipatayi B.P.
      • et al.
      The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
      The PRISMA flowchart is presented in Fig. S1 (Supplementary Material).

      Description of studies

      All studies had a retrospective design and were published between 2002 and 2020. They reported a total of 120 116 patients with rAAA who underwent either open or endovascular repair. Of them, 40 218 were treated in low volume centres and 43 080 in high volume centres. The remainder were treated in intermediate volume centres and were not included in the comparison. Of the patients who had EVAR, 3 453 were treated in low and 5 251 in high volume centres. Of those who underwent open surgical repair, 35 682 were treated in low volume and 26 727 in high volume centres. Study related information is summarised in Table 1. Seven studies provided adjusted outcomes,
      • Dimick J.B.
      • Stanley J.C.
      • Axelrod D.A.
      • Kazmers A.
      • Henke P.K.
      • Jacobs L.A.
      • et al.
      Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age.
      ,
      • Holt P.J.
      • Poloniecki J.D.
      • Loftus I.M.
      • Michaels J.A.
      • Thompson M.M.
      Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005.
      ,
      • Giles K.A.
      • Hamdan A.D.
      • Pomposelli F.B.
      • Wyers M.C.
      • Dahlberg S.E.
      • Schermerhorn M.L.
      Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
      • McPhee J.
      • Eslami M.H.
      • Arous E.J.
      • Messina L.M.
      • Schanzer A.
      Endovascular treatment of ruptured abdominal aortic aneurysms in the United States (2001–2006): a significant survival benefit over open repair is independently associated with increased institutional volume.
      • Chen C.K.
      • Chang H.T.
      • Chen Y.C.
      • Chen T.J.
      • Chen I.M.
      • Shih C.C.
      Surgeon elective abdominal aortic aneurysm repair volume and outcomes of ruptured abdominal aortic aneurysm repair: a 12-year nationwide study.
      ,
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      ,
      • Sawang M.
      • Paravastu S.C.V.
      • Liu Z.
      • Thomas S.D.
      • Beiles C.B.
      • Mwipatayi B.P.
      • et al.
      The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
      and the factors for which adjustments were made are listed in Table S1 (Supplementary Material).
      Table 1Characteristics of included studies comparing outcomes of patients with ruptured abdominal aortic aneurysm undergoing repair in high and low volume institutions or by high and low volume surgeons and number of patients treated
      Author, journal, yearStudy periodType of studyPatients in low / high volume centres – nPatients treated by EVAR in low / high volume centres – nPatients treated by OSR in low/high volume centres – n
      Dimick, Ann Vasc Surg, 2002
      • Dimick J.B.
      • Stanley J.C.
      • Axelrod D.A.
      • Kazmers A.
      • Henke P.K.
      • Jacobs L.A.
      • et al.
      Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age.
      1996–1997Registry1 219 / 813NR1 219 / 813
      Holt, Br J Surg, 2007
      • Holt P.J.
      • Poloniecki J.D.
      • Loftus I.M.
      • Michaels J.A.
      • Thompson M.M.
      Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005.
      2000–2005Registry1 312 / 1 353NR1 312 / 1 353
      Greco, J Vasc Surg, 2006
      • Greco G.
      • Egorova N.
      • Anderson P.L.
      • Gelijns A.
      • Moskowitz A.
      • Nowygrod R.
      • et al.
      Outcomes of endovascular treatment of ruptured abdominal aortic aneurysms.
      2000–2003Registry2 823 / 2 975194 / 962 629 / 2 879
      Giles, J Endovasc Ther, 2009
      • Giles K.A.
      • Hamdan A.D.
      • Pomposelli F.B.
      • Wyers M.C.
      • Dahlberg S.E.
      • Schermerhorn M.L.
      Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
      2001–2006Registry11 272 / 8 378795 / 82810 477 / 7 550
      McPhee, J Vasc Surg, 2009
      • McPhee J.
      • Eslami M.H.
      • Arous E.J.
      • Messina L.M.
      • Schanzer A.
      Endovascular treatment of ruptured abdominal aortic aneurysms in the United States (2001–2006): a significant survival benefit over open repair is independently associated with increased institutional volume.
      2001–2006Registry18 407 / 4 1201 394 / 1 12517 013 / 2 995
      Chen, World J Surg, 2013
      • Chen C.K.
      • Chang H.T.
      • Chen Y.C.
      • Chen T.J.
      • Chen I.M.
      • Shih C.C.
      Surgeon elective abdominal aortic aneurysm repair volume and outcomes of ruptured abdominal aortic aneurysm repair: a 12-year nationwide study.
      1998–2009Registry135 / 11120 / 19115 / 92
      Dua, J Vasc Surg, 2014
      • Dua A.
      • Furlough C.L.
      • Ray H.
      • Sharma S.
      • Upchurch G.R.
      • Desai S.S.
      The effect of hospital factors on mortality rates after abdominal aortic aneurysm repair.
      1998–2011Registry1 062 / 10 868NRNR
      Karthikesalingam, Br J Surg, 2016
      • Karthikesalingam A.
      • Wanhainen A.
      • Holt P.J.
      • Vidal-Diez A.
      • Brownrigg J.R.
      • Shpitser I.
      • et al.
      Comparison of long-term mortality after ruptured abdominal aortic aneurysm in England and Sweden.
      Reporting 90 day outcomes.
      2003–2012Registry809 / 6 00870 / 779739 / 5 229
      Meltzer, J Vasc Surg, 2017
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      2000–2011Registry598 / 552208 / 204390 / 348
      Trenner, Eur J Vasc Endovasc Surg, 2018
      • Trenner M.
      • Kuehnl A.
      • Salvermoser M.
      • Reutersberg B.
      • Geisbuesch S.
      • Schmid V.
      • et al.
      Editor's Choice – High annual hospital volume is associated with decreased in hospital mortality and complication rates following treatment of abdominal aortic aneurysms: secondary data analysis of the Nationwide German DRG Statistics from 2005 to 2013.
      2005–2013Registry893 / 6 43545 / 1 511848 / 4 923
      Greenleaf, J Vasc Surg, 2020
      • Greenleaf E.K.
      • Hollenbeak C.S.
      • Aziz F.
      Outcomes after ruptured abdominal aortic aneurysm repair in the era of centralized care.
      2003–2017Registry760 / 586353 / 434407 / 152
      Tripodi, Eur J Vasc Endovasc Surg, 2020
      • Tripodi P.
      • Mestres G.
      • Riambau V.
      Vascular Advisory Committee – Catalan Health Service
      Impact of centralisation on abdominal aortic aneurysm repair outcomes: early experience in Catalonia.
      2009–2017Multicentre study21 / 233NRNR
      Sawang, Eur J Vasc Endovasc Surg, 2020
      • Sawang M.
      • Paravastu S.C.V.
      • Liu Z.
      • Thomas S.D.
      • Beiles C.B.
      • Mwipatayi B.P.
      • et al.
      The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
      2010–2016Multicentre study907 / 648374 / 255533 / 393
      EVAR = endovascular aneurysm repair; NR = not reported; OSR = open surgical repair.
      Reporting 90 day outcomes.
      Five studies used the number of rAAA cases to define high and low volume centres,
      • Holt P.J.
      • Poloniecki J.D.
      • Loftus I.M.
      • Michaels J.A.
      • Thompson M.M.
      Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005.
      ,
      • Giles K.A.
      • Hamdan A.D.
      • Pomposelli F.B.
      • Wyers M.C.
      • Dahlberg S.E.
      • Schermerhorn M.L.
      Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
      ,
      • Karthikesalingam A.
      • Wanhainen A.
      • Holt P.J.
      • Vidal-Diez A.
      • Brownrigg J.R.
      • Shpitser I.
      • et al.
      Comparison of long-term mortality after ruptured abdominal aortic aneurysm in England and Sweden.
      ,
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      ,
      • Sawang M.
      • Paravastu S.C.V.
      • Liu Z.
      • Thomas S.D.
      • Beiles C.B.
      • Mwipatayi B.P.
      • et al.
      The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
      four studies used the total number of elective and urgent/emergency AAA repairs,
      • Greco G.
      • Egorova N.
      • Anderson P.L.
      • Gelijns A.
      • Moskowitz A.
      • Nowygrod R.
      • et al.
      Outcomes of endovascular treatment of ruptured abdominal aortic aneurysms.
      ,
      • Trenner M.
      • Kuehnl A.
      • Salvermoser M.
      • Reutersberg B.
      • Geisbuesch S.
      • Schmid V.
      • et al.
      Editor's Choice – High annual hospital volume is associated with decreased in hospital mortality and complication rates following treatment of abdominal aortic aneurysms: secondary data analysis of the Nationwide German DRG Statistics from 2005 to 2013.
      ,
      • Greenleaf E.K.
      • Hollenbeak C.S.
      • Aziz F.
      Outcomes after ruptured abdominal aortic aneurysm repair in the era of centralized care.
      ,
      • Tripodi P.
      • Mestres G.
      • Riambau V.
      Vascular Advisory Committee – Catalan Health Service
      Impact of centralisation on abdominal aortic aneurysm repair outcomes: early experience in Catalonia.
      and one study used the number of elective AAA cases only.
      • Dimick J.B.
      • Stanley J.C.
      • Axelrod D.A.
      • Kazmers A.
      • Henke P.K.
      • Jacobs L.A.
      • et al.
      Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age.
      One study used hospital bed number,
      • Dua A.
      • Furlough C.L.
      • Ray H.
      • Sharma S.
      • Upchurch G.R.
      • Desai S.S.
      The effect of hospital factors on mortality rates after abdominal aortic aneurysm repair.
      and another two
      • McPhee J.
      • Eslami M.H.
      • Arous E.J.
      • Messina L.M.
      • Schanzer A.
      Endovascular treatment of ruptured abdominal aortic aneurysms in the United States (2001–2006): a significant survival benefit over open repair is independently associated with increased institutional volume.
      ,
      • Chen C.K.
      • Chang H.T.
      • Chen Y.C.
      • Chen T.J.
      • Chen I.M.
      • Shih C.C.
      Surgeon elective abdominal aortic aneurysm repair volume and outcomes of ruptured abdominal aortic aneurysm repair: a 12-year nationwide study.
      used various volume metrics to define low and high volume centres, such as elective open aneurysm repair cases, elective EVAR cases, and rAAA repairs (Table 2). Information on definitions of individual surgeon procedure volumes are presented in Table S2 (Supplementary Material).
      Table 2Criteria used to define volume groups and thresholds in studies comparing outcomes of patients with ruptured abdominal aortic aneurysm undergoing repair in high and low volume institutions or by high and low volume surgeons
      AuthorDefinition of volumeVolume subgroupsPatients in each group – n
      Dimick
      • Dimick J.B.
      • Stanley J.C.
      • Axelrod D.A.
      • Kazmers A.
      • Henke P.K.
      • Jacobs L.A.
      • et al.
      Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age.
      Procedures per year (intact AAA)Low ≤ 30, high > 30Low = 1 219, high = 813
      Holt
      • Holt P.J.
      • Poloniecki J.D.
      • Loftus I.M.
      • Michaels J.A.
      • Thompson M.M.
      Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005.
      Procedures per year (AAA)Q1 = 0–2.8, Q2 = 2.9–5.6, Q3 = 5.7–9.2, Q4 = 9.3–13.2, Q5 > 13.2Q1 = 1 312, Q2 = 1 268, Q3 = 1 256, Q4 = 1 273, Q5 = 1 353
      Greco
      • Greco G.
      • Egorova N.
      • Anderson P.L.
      • Gelijns A.
      • Moskowitz A.
      • Nowygrod R.
      • et al.
      Outcomes of endovascular treatment of ruptured abdominal aortic aneurysms.
      Procedures per year (overall number of EVAR and overall number of OSR)Low ≤ 25, high > 25Low = 2 823, high = 2 975
      Giles
      • Giles K.A.
      • Hamdan A.D.
      • Pomposelli F.B.
      • Wyers M.C.
      • Dahlberg S.E.
      • Schermerhorn M.L.
      Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
      Procedures per year (rAAA)Low = 1–3, medium = 4–6, high = 7–25Low = 11 272, medium = 8 779, high = 8 378
      McPhee27
      Number of events was not provided when volume definition was based on number of rAAAs; therefore, for the purpose of the analysis, events were calculated based on elective EVAR volumes.
      Procedures per year (intact OSR, intact EVAR, ruptured AAA)
      The analysis was performed three times using different definitions for institutional caseload based on the total number of AAA cases, number of elective EVAR cases, and number of elective OSR cases.
      Low < 19, medium = 19–40, high > 40Low = 18 407, medium = 5 223, high = 4 120
      Chen
      • Chen C.K.
      • Chang H.T.
      • Chen Y.C.
      • Chen T.J.
      • Chen I.M.
      • Shih C.C.
      Surgeon elective abdominal aortic aneurysm repair volume and outcomes of ruptured abdominal aortic aneurysm repair: a 12-year nationwide study.
      Procedures per year (intact EVAR and intact OSR, ruptured EVAR and ruptured OSR)
      The analysis was performed several times using the number of elective EVAR cases, number of elective OSR cases, number of EVAR for rAAA, and number of OSR for rAAA as the variable to quantify institutional caseload. For the analysis, the definition of rAAA volume was used.
      Low < 1, medium 1–3, high > 3Low = 135, high = 111
      Dua
      • Dua A.
      • Furlough C.L.
      • Ray H.
      • Sharma S.
      • Upchurch G.R.
      • Desai S.S.
      The effect of hospital factors on mortality rates after abdominal aortic aneurysm repair.
      Hospital bed sizeSmall, medium, large depending on the location and teaching statusSmall = 1 062, medium = 2 817, large = 10 868
      Karthikesalingam
      • Karthikesalingam A.
      • Wanhainen A.
      • Holt P.J.
      • Vidal-Diez A.
      • Brownrigg J.R.
      • Shpitser I.
      • et al.
      Comparison of long-term mortality after ruptured abdominal aortic aneurysm in England and Sweden.
      Procedures per year (rAAA)Q1 = 1–4, Q2 = 5–7, Q3 = 8–11, Q4 = 12–16, Q5 > 16Q1 = 809, Q2 = 1 799, Q3 = 2 796, Q4 = 3 783, Q5 = 6 008
      Meltzer
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      Procedures per year (ruptured EVAR and ruptured OSR)EVAR: low < 9, medium = 10–26, high > 27

      OSR: low < 27, medium = 28–81, high > 81
      Low = 598, medium = 574, high = 552
      Trenner
      • Trenner M.
      • Kuehnl A.
      • Salvermoser M.
      • Reutersberg B.
      • Geisbuesch S.
      • Schmid V.
      • et al.
      Editor's Choice – High annual hospital volume is associated with decreased in hospital mortality and complication rates following treatment of abdominal aortic aneurysms: secondary data analysis of the Nationwide German DRG Statistics from 2005 to 2013.
      Procedures per year (overall AAA)Q1 = 1–5, Q2 = 6–14, Q3 = 15–30, Q4 > 30Q1 = 893, Q2 = 1 565, Q3 = 2 875, Q4 = 6 435
      Greenleaf
      • Greenleaf E.K.
      • Hollenbeak C.S.
      • Aziz F.
      Outcomes after ruptured abdominal aortic aneurysm repair in the era of centralized care.
      Procedures per year (overall EVAR, overall OSR)EVAR: Q1 < 30, Q2 = 31–47, Q3 = 48–71, Q4 > 71

      OSR: Q1 < 10, Q2 = 10–19, Q3 = 20–35, Q4 > 36
      Q1 = 760, Q2 = 793, Q3 = 756, Q4 = 586
      Tripodi
      • Tripodi P.
      • Mestres G.
      • Riambau V.
      Vascular Advisory Committee – Catalan Health Service
      Impact of centralisation on abdominal aortic aneurysm repair outcomes: early experience in Catalonia.
      Procedures per year (overall AAA)Low ≤ 30, high > 30Low = 21, high = 233
      Sawang
      • Sawang M.
      • Paravastu S.C.V.
      • Liu Z.
      • Thomas S.D.
      • Beiles C.B.
      • Mwipatayi B.P.
      • et al.
      The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
      Procedures per year (ruptured EVAR and ruptured OSR)EVAR: Q1 < 19, Q2 = 19–24, Q3 = 25–33, Q4 = 34–45, Q5 = 46–95

      OSR: Q1 < 7, Q2 = 7–10, Q3 = 11–16, Q4 = 17–26, Q5 = 27–71
      Low (Q1–Q3) = 907, high (Q4–Q5) = 648
      AAA = abdominal aortic aneurysm; EVAR = endovascular aneurysm repair; OSR = open surgical repair; Q = quantile; rAAA = ruptured AAA.
      Number of events was not provided when volume definition was based on number of rAAAs; therefore, for the purpose of the analysis, events were calculated based on elective EVAR volumes.
      The analysis was performed three times using different definitions for institutional caseload based on the total number of AAA cases, number of elective EVAR cases, and number of elective OSR cases.
      The analysis was performed several times using the number of elective EVAR cases, number of elective OSR cases, number of EVAR for rAAA, and number of OSR for rAAA as the variable to quantify institutional caseload. For the analysis, the definition of rAAA volume was used.

      Results of study and evidence appraisal

      The median value of stars in the NOS across the included studies was seven (range 6 – 9). Several studies scored low in the selection domain, mainly because of inadequate definition and representativeness of cases. The study quality assessment is summarised in Table 3. The results of the GRADE assessment are presented in Table 4.
      Table 3Methodological quality assessment of studies comparing outcomes of patients with ruptured abdominal aortic aneurysm undergoing repair in high and low volume institutions or by high and low volume surgeons using the Newcastle-Ottawa scale
      Definition adequateRepresentativenessSelection of controlsDefinition of controlsComparabilityAscertainment of exposureSame methodNon-response rateTotal
      Dimick
      • Dimick J.B.
      • Stanley J.C.
      • Axelrod D.A.
      • Kazmers A.
      • Henke P.K.
      • Jacobs L.A.
      • et al.
      Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age.
      ∗∗7
      Holt
      • Holt P.J.
      • Poloniecki J.D.
      • Loftus I.M.
      • Michaels J.A.
      • Thompson M.M.
      Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005.
      6
      Greco
      • Greco G.
      • Egorova N.
      • Anderson P.L.
      • Gelijns A.
      • Moskowitz A.
      • Nowygrod R.
      • et al.
      Outcomes of endovascular treatment of ruptured abdominal aortic aneurysms.
      6
      Giles
      • Giles K.A.
      • Hamdan A.D.
      • Pomposelli F.B.
      • Wyers M.C.
      • Dahlberg S.E.
      • Schermerhorn M.L.
      Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
      ∗∗8
      McPhee
      • McPhee J.
      • Eslami M.H.
      • Arous E.J.
      • Messina L.M.
      • Schanzer A.
      Endovascular treatment of ruptured abdominal aortic aneurysms in the United States (2001–2006): a significant survival benefit over open repair is independently associated with increased institutional volume.
      ∗∗7
      Chen
      • Chen C.K.
      • Chang H.T.
      • Chen Y.C.
      • Chen T.J.
      • Chen I.M.
      • Shih C.C.
      Surgeon elective abdominal aortic aneurysm repair volume and outcomes of ruptured abdominal aortic aneurysm repair: a 12-year nationwide study.
      ∗∗8
      Dua
      • Dua A.
      • Furlough C.L.
      • Ray H.
      • Sharma S.
      • Upchurch G.R.
      • Desai S.S.
      The effect of hospital factors on mortality rates after abdominal aortic aneurysm repair.
      6
      Karthikesalingam
      • Karthikesalingam A.
      • Wanhainen A.
      • Holt P.J.
      • Vidal-Diez A.
      • Brownrigg J.R.
      • Shpitser I.
      • et al.
      Comparison of long-term mortality after ruptured abdominal aortic aneurysm in England and Sweden.
      6
      Meltzer
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      ∗∗7
      Trenner
      • Trenner M.
      • Kuehnl A.
      • Salvermoser M.
      • Reutersberg B.
      • Geisbuesch S.
      • Schmid V.
      • et al.
      Editor's Choice – High annual hospital volume is associated with decreased in hospital mortality and complication rates following treatment of abdominal aortic aneurysms: secondary data analysis of the Nationwide German DRG Statistics from 2005 to 2013.
      8
      Greenleaf
      • Greenleaf E.K.
      • Hollenbeak C.S.
      • Aziz F.
      Outcomes after ruptured abdominal aortic aneurysm repair in the era of centralized care.
      8
      Tripodi
      • Tripodi P.
      • Mestres G.
      • Riambau V.
      Vascular Advisory Committee – Catalan Health Service
      Impact of centralisation on abdominal aortic aneurysm repair outcomes: early experience in Catalonia.
      6
      Sawang
      • Sawang M.
      • Paravastu S.C.V.
      • Liu Z.
      • Thomas S.D.
      • Beiles C.B.
      • Mwipatayi B.P.
      • et al.
      The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
      ∗∗9
      Table 4Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) assessment of studies comparing outcomes of patients with ruptured abdominal aortic aneurysm undergoing repair in high and low volume institutions or by high and low volume surgeons
      Certainty assessmentPatients – nRelative effect (95% CI)Absolute effectCertaintyImportance
      StudiesStudy designRisk of biasInconsistencyIndirectnessImprecisionOther considerationsLow volume institutions – n (%)High volume institutions – n (%)
      Peri-operative mortality
       12Obs. studiesSerious
      Risk of confounding.
      Serious
      Different criteria were used to define control and experimental groups, and size thresholds are variable, resulting in high heterogeneity.
      Not seriousNot seriousNone17 048 / 39 311 (43.4)15 296 / 42 432 (36.0)OR 1.39 (1.22–1.59)79 more per 1 000 (from 47 more to 112 more)⨁◯◯◯

      Very low
      Critical
      Adjusted peri-operative mortality
       5Obs. studiesNot seriousNot seriousNot seriousSerious
      Ninety-five per cent confidence around the pooled best estimate of effect includes both no effect and appreciable benefit or appreciable harm.
      None32 345 participants14 775 participantsOR 1.18 (0.99–1.4)NA⨁◯◯◯

      Very low
      Critical
      Length of hospital stay
       4Obs. StudiesSerious
      Risk of confounding.
      Serious
      Different criteria were used to define control and experimental groups, and size thresholds are variable, resulting in high heterogeneity.
      Not seriousSerious
      Ninety-five per cent confidence around the pooled best estimate of effect includes both no effect and appreciable benefit or appreciable harm.
      None12 200 participants9 259 participantsMD –3.06 (–8.21 lower to 2.1)MD 3.06 lower (8.21 lower to 2.1 higher)⨁◯◯◯

      Very low
      Important
      CI = confidence interval; MD = mean difference; NA = not available; Obs. = observational; OR = odds ratio.
      Risk of confounding.
      Different criteria were used to define control and experimental groups, and size thresholds are variable, resulting in high heterogeneity.
      Ninety-five per cent confidence around the pooled best estimate of effect includes both no effect and appreciable benefit or appreciable harm.

      Quantitative synthesis

      Primary and secondary outcomes

      Institutional volumes

      Peri-operative mortality for rAAA was reported by 12 studies,
      • Dimick J.B.
      • Stanley J.C.
      • Axelrod D.A.
      • Kazmers A.
      • Henke P.K.
      • Jacobs L.A.
      • et al.
      Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age.
      • Holt P.J.
      • Poloniecki J.D.
      • Loftus I.M.
      • Michaels J.A.
      • Thompson M.M.
      Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005.
      • Greco G.
      • Egorova N.
      • Anderson P.L.
      • Gelijns A.
      • Moskowitz A.
      • Nowygrod R.
      • et al.
      Outcomes of endovascular treatment of ruptured abdominal aortic aneurysms.
      • Giles K.A.
      • Hamdan A.D.
      • Pomposelli F.B.
      • Wyers M.C.
      • Dahlberg S.E.
      • Schermerhorn M.L.
      Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
      • McPhee J.
      • Eslami M.H.
      • Arous E.J.
      • Messina L.M.
      • Schanzer A.
      Endovascular treatment of ruptured abdominal aortic aneurysms in the United States (2001–2006): a significant survival benefit over open repair is independently associated with increased institutional volume.
      • Chen C.K.
      • Chang H.T.
      • Chen Y.C.
      • Chen T.J.
      • Chen I.M.
      • Shih C.C.
      Surgeon elective abdominal aortic aneurysm repair volume and outcomes of ruptured abdominal aortic aneurysm repair: a 12-year nationwide study.
      • Dua A.
      • Furlough C.L.
      • Ray H.
      • Sharma S.
      • Upchurch G.R.
      • Desai S.S.
      The effect of hospital factors on mortality rates after abdominal aortic aneurysm repair.
      • Karthikesalingam A.
      • Wanhainen A.
      • Holt P.J.
      • Vidal-Diez A.
      • Brownrigg J.R.
      • Shpitser I.
      • et al.
      Comparison of long-term mortality after ruptured abdominal aortic aneurysm in England and Sweden.
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      • Trenner M.
      • Kuehnl A.
      • Salvermoser M.
      • Reutersberg B.
      • Geisbuesch S.
      • Schmid V.
      • et al.
      Editor's Choice – High annual hospital volume is associated with decreased in hospital mortality and complication rates following treatment of abdominal aortic aneurysms: secondary data analysis of the Nationwide German DRG Statistics from 2005 to 2013.
      • Greenleaf E.K.
      • Hollenbeak C.S.
      • Aziz F.
      Outcomes after ruptured abdominal aortic aneurysm repair in the era of centralized care.
      • Tripodi P.
      • Mestres G.
      • Riambau V.
      Vascular Advisory Committee – Catalan Health Service
      Impact of centralisation on abdominal aortic aneurysm repair outcomes: early experience in Catalonia.
      with a total of 81 743 patients (39 311 treated in low and 42 432 in high volume centres). The pooled peri-operative mortality was 43% in low volume institutions and 36% in high volume institutions. Patients treated in low volume centres had statistically significantly higher peri-operative mortality compared with those treated in high volume centres (OR 1.39, 95% CI 1.22 – 1.59; p < .001) (Fig. 1A). The statistical between study heterogeneity was considerable (p < .001, I2 = 91%), but the publication bias was not statistically significant (p = .72). The GRADE level of evidence was judged to be very low.
      Figure 1
      Figure 1Forest plots of comparisons of high vs. low volume centres for (A) peri-operative mortality, (B) adjusted peri-operative mortality, and (C) length of hospital stay of patients with ruptured abdominal aortic aneurysm. The solid squares denote the odds ratios (ORs) or mean differences, the horizontal lines represent the 95% confidence intervals (CIs), and the diamonds denote the pooled ORs or mean differences. IV = inverse variance; SD = standard deviation; SE = standard error.
      Five studies reported adjusted OR for peri-operative mortality with a total of 47 120 patients (32 345 treated in low volume and 14 775 in high volume centres).
      • Dimick J.B.
      • Stanley J.C.
      • Axelrod D.A.
      • Kazmers A.
      • Henke P.K.
      • Jacobs L.A.
      • et al.
      Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age.
      ,
      • Holt P.J.
      • Poloniecki J.D.
      • Loftus I.M.
      • Michaels J.A.
      • Thompson M.M.
      Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005.
      ,
      • Giles K.A.
      • Hamdan A.D.
      • Pomposelli F.B.
      • Wyers M.C.
      • Dahlberg S.E.
      • Schermerhorn M.L.
      Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
      • McPhee J.
      • Eslami M.H.
      • Arous E.J.
      • Messina L.M.
      • Schanzer A.
      Endovascular treatment of ruptured abdominal aortic aneurysms in the United States (2001–2006): a significant survival benefit over open repair is independently associated with increased institutional volume.
      • Chen C.K.
      • Chang H.T.
      • Chen Y.C.
      • Chen T.J.
      • Chen I.M.
      • Shih C.C.
      Surgeon elective abdominal aortic aneurysm repair volume and outcomes of ruptured abdominal aortic aneurysm repair: a 12-year nationwide study.
      Meta-analysis of the adjusted OR for peri-operative mortality showed a higher mortality rate in low volume institutions vs. high volume institutions, with the difference lying at the margin of statistical significance (OR 1.18, 95% CI 0.99 – 1.40; p = .060) (Fig. 1B). The statistical heterogeneity was considerable (p < .001, I2 = 90%). The GRADE level of evidence was judged to be very low.
      Data on length of hospital stay were provided in three studies,
      • Giles K.A.
      • Hamdan A.D.
      • Pomposelli F.B.
      • Wyers M.C.
      • Dahlberg S.E.
      • Schermerhorn M.L.
      Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
      ,
      • Tripodi P.
      • Mestres G.
      • Riambau V.
      Vascular Advisory Committee – Catalan Health Service
      Impact of centralisation on abdominal aortic aneurysm repair outcomes: early experience in Catalonia.
      ,
      • Sawang M.
      • Paravastu S.C.V.
      • Liu Z.
      • Thomas S.D.
      • Beiles C.B.
      • Mwipatayi B.P.
      • et al.
      The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
      reporting a total of 21 459 patients (12 200 treated in low volume and 9 259 in high volume centres). Sawang et al. reported separate results for patients undergoing EVAR and open surgery.
      • Sawang M.
      • Paravastu S.C.V.
      • Liu Z.
      • Thomas S.D.
      • Beiles C.B.
      • Mwipatayi B.P.
      • et al.
      The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
      Meta-analysis showed that length of hospital stay was not statistically significantly different between low and high volume institutions (MD –3.06, 95% CI –8.21 – 2.10; p = .25) (Fig. 1C). Statistical heterogeneity was considerable (p < .001, I2 = 96%). The GRADE level of evidence was judged to be very low.

      Surgeon volumes

      Two studies reported the adjusted OR for peri-operative mortality in patients operated on by low and high volume surgeons.
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      ,
      • Sawang M.
      • Paravastu S.C.V.
      • Liu Z.
      • Thomas S.D.
      • Beiles C.B.
      • Mwipatayi B.P.
      • et al.
      The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
      Both reported data for EVAR and open surgical repair separately. The difference in peri-operative mortality between low and high volume surgeons was not statistically significant for EVAR (OR 1.06, 95% CI 0.59 – 1.89 [p = .85]; heterogeneity: p = .28, I2 = 13%) or open surgical repair (OR 1.18, 95% CI 0.87 – 1.63 [p = .27]; heterogeneity: p = .84, I2 = 0%) (Fig. 2A, B).
      Figure 2
      Figure 2Forest plots of comparisons of high vs. low volume surgeons for adjusted peri-operative mortality in patients undergoing (A) endovascular (EVAR) or open surgical repair (OSR) for ruptured abdominal aortic aneurysm. The solid squares denote the odds ratios (ORs), the horizontal lines represent the 95% confidence intervals (CIs), and the diamonds denote the pooled ORs. IV = inverse variance; SE = standard error.

      Subgroup analysis

      EVAR

      Eight studies reported comparative peri-operative mortality data in patients treated by EVAR in low and high volume institutions with a total of 8 075 patients (3 079 treated in low volume and 4 996 in high volume institutions).
      • Greco G.
      • Egorova N.
      • Anderson P.L.
      • Gelijns A.
      • Moskowitz A.
      • Nowygrod R.
      • et al.
      Outcomes of endovascular treatment of ruptured abdominal aortic aneurysms.
      • Giles K.A.
      • Hamdan A.D.
      • Pomposelli F.B.
      • Wyers M.C.
      • Dahlberg S.E.
      • Schermerhorn M.L.
      Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
      • McPhee J.
      • Eslami M.H.
      • Arous E.J.
      • Messina L.M.
      • Schanzer A.
      Endovascular treatment of ruptured abdominal aortic aneurysms in the United States (2001–2006): a significant survival benefit over open repair is independently associated with increased institutional volume.
      • Chen C.K.
      • Chang H.T.
      • Chen Y.C.
      • Chen T.J.
      • Chen I.M.
      • Shih C.C.
      Surgeon elective abdominal aortic aneurysm repair volume and outcomes of ruptured abdominal aortic aneurysm repair: a 12-year nationwide study.
      ,
      • Karthikesalingam A.
      • Wanhainen A.
      • Holt P.J.
      • Vidal-Diez A.
      • Brownrigg J.R.
      • Shpitser I.
      • et al.
      Comparison of long-term mortality after ruptured abdominal aortic aneurysm in England and Sweden.
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      • Trenner M.
      • Kuehnl A.
      • Salvermoser M.
      • Reutersberg B.
      • Geisbuesch S.
      • Schmid V.
      • et al.
      Editor's Choice – High annual hospital volume is associated with decreased in hospital mortality and complication rates following treatment of abdominal aortic aneurysms: secondary data analysis of the Nationwide German DRG Statistics from 2005 to 2013.
      • Greenleaf E.K.
      • Hollenbeak C.S.
      • Aziz F.
      Outcomes after ruptured abdominal aortic aneurysm repair in the era of centralized care.
      The pooled peri-operative mortality was 41.1% and 30.1% in low and high volume institutions, respectively. The mortality difference in favour of high volume centres was statistically significant (OR 1.61, 95% CI 1.11 – 2.35; p = .010) (Fig. 3A). The statistical between study heterogeneity was considerable (p < .001, I2 = 89%).
      Figure 3
      Figure 3Forest plots of comparisons of high vs. low volume centres for unadjusted peri-operative mortality (A and C) and adjusted peri-operative mortality (B and D) in patients undergoing endovascular aneurysm repair (EVAR, A-B) or open surgical repair (OSR, C-D). The solid squares denote the odds ratios (ORs), the horizontal lines represent the 95% confidence intervals (CIs), and the diamonds denote the pooled ORs. IV = inverse variance; SE = standard error.
      The adjusted ORs for peri-operative mortality in patients undergoing EVAR in low vs. high volume centres were reported in two studies.
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      ,
      • Sawang M.
      • Paravastu S.C.V.
      • Liu Z.
      • Thomas S.D.
      • Beiles C.B.
      • Mwipatayi B.P.
      • et al.
      The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
      Meta-analysis showed no statistically significant difference between low and high volume centres (OR 1.42, 95% CI 0.84 – 2.41; p = .20) (Fig. 3B), with no statistical evidence of between study heterogeneity (p = .69, I2 = 0%).

      Open surgical repair

      Ten studies reported peri-operative mortality data in patients treated by open surgery in low volume institutions vs. those treated by open surgery in high volume institutions with a total of 61 483 patients (35 149 treated in low and 26 334 in high volume centres).
      • Dimick J.B.
      • Stanley J.C.
      • Axelrod D.A.
      • Kazmers A.
      • Henke P.K.
      • Jacobs L.A.
      • et al.
      Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age.
      • Holt P.J.
      • Poloniecki J.D.
      • Loftus I.M.
      • Michaels J.A.
      • Thompson M.M.
      Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005.
      • Greco G.
      • Egorova N.
      • Anderson P.L.
      • Gelijns A.
      • Moskowitz A.
      • Nowygrod R.
      • et al.
      Outcomes of endovascular treatment of ruptured abdominal aortic aneurysms.
      • Giles K.A.
      • Hamdan A.D.
      • Pomposelli F.B.
      • Wyers M.C.
      • Dahlberg S.E.
      • Schermerhorn M.L.
      Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
      • McPhee J.
      • Eslami M.H.
      • Arous E.J.
      • Messina L.M.
      • Schanzer A.
      Endovascular treatment of ruptured abdominal aortic aneurysms in the United States (2001–2006): a significant survival benefit over open repair is independently associated with increased institutional volume.
      • Chen C.K.
      • Chang H.T.
      • Chen Y.C.
      • Chen T.J.
      • Chen I.M.
      • Shih C.C.
      Surgeon elective abdominal aortic aneurysm repair volume and outcomes of ruptured abdominal aortic aneurysm repair: a 12-year nationwide study.
      ,
      • Karthikesalingam A.
      • Wanhainen A.
      • Holt P.J.
      • Vidal-Diez A.
      • Brownrigg J.R.
      • Shpitser I.
      • et al.
      Comparison of long-term mortality after ruptured abdominal aortic aneurysm in England and Sweden.
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      • Trenner M.
      • Kuehnl A.
      • Salvermoser M.
      • Reutersberg B.
      • Geisbuesch S.
      • Schmid V.
      • et al.
      Editor's Choice – High annual hospital volume is associated with decreased in hospital mortality and complication rates following treatment of abdominal aortic aneurysms: secondary data analysis of the Nationwide German DRG Statistics from 2005 to 2013.
      • Greenleaf E.K.
      • Hollenbeak C.S.
      • Aziz F.
      Outcomes after ruptured abdominal aortic aneurysm repair in the era of centralized care.
      The pooled peri-operative mortality was 43.7% in low volume centres and 38.3% in high volume centres, with the difference being statistically significant (OR 1.50, 95% CI 1.25 – 1.81; p < .001) (Fig. 3C). The statistical between study heterogeneity was considerable (p < .001, I2 = 94%), but the publication bias was not significant (p = .67).
      The adjusted OR for peri-operative mortality in patients treated by open surgery in low vs. high volume centres were reported in two studies.
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      ,
      • Sawang M.
      • Paravastu S.C.V.
      • Liu Z.
      • Thomas S.D.
      • Beiles C.B.
      • Mwipatayi B.P.
      • et al.
      The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
      Meta-analysis showed a statistically significantly higher peri-operative mortality in patients treated in low volume centres (OR 1.68, 95% CI 1.21 – 2.33; p = .002) (Fig. 3D), with no statistical evidence of between study heterogeneity (p = .59, I2 = 0%).

      Sensitivity analysis

      Sensitivity analyses removing one study at a time affected the significance of the effect estimates for none of the outcomes expect for adjusted peri-operative mortality. Removing the study of Holt et al. resulted in a statistically significant difference in favour of high volume centres.
      • Holt P.J.
      • Poloniecki J.D.
      • Loftus I.M.
      • Michaels J.A.
      • Thompson M.M.
      Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005.
      When studies that included patients treated before 2000 were excluded, the significance of effect estimates did not change for any of the outcomes. Similarly, sensitivity analyses excluding reports that considered criteria other than number of rAAA cases to define volume groups found no difference in the significance of effect estimates for any of the outcomes. Additional sensitivity analyses, including only studies that were published after 2010, showed no change in the significance of effect estimates for overall mortality and mortality after open surgical repair, but the benefit of high volume centres for patients undergoing EVAR was lost. The results of sensitivity analyses are summarised in Table S3 (Supplementary Material).

      Discussion

      Controversy surrounds the potential benefits of the centralisation of aortic services. Even though some evidence indicates that high volume institutions may achieve superior results, some reports suggest otherwise, including a 2019 study that showed no significant effect of the centralisation on outcomes after both elective and emergency AAA treatment.
      • Leighton P.
      • Doe M.
      • Pathak S.
      • AlDuwaisan A.
      • Brooks M.
      Immediate impact of centralization on abdominal aortic aneurysm repair outcomes for a Vascular Network in the South West of England: a retrospective cohort study.
      Opponents of centralisation raise issues regarding thresholds to define high volume institutions, the impact of individual surgeon experience, uncertainty about a correlation between infrastructure and outcomes, and the logistics of a centralised aortic service provision.
      • Thompson M.
      • Holt P.
      • Loftus I.
      • Forbes T.L.
      Debate: whether abdominal aortic aneurysm surgery should be centralized at higher-volume centers.
      A potential causal relationship between high institutional or individual surgeon caseload and improved outcomes or other quality indices in the setting of rAAA has not been quantified previously in a systematic review and meta-analysis.
      This analysis showed a clear peri-operative survival advantage in patients treated for rAAA in high volume institutions. This finding is supported by meta-analysis of studies that conducted regression analysis to account for potential confounders, albeit with a weaker effect estimate. Factors for which adjustments were made mostly concerned patient demographics and comorbidities, year of operation, and treatment at weekends or on weekdays.
      The external validity and applicability of the findings may be limited considering the between study heterogeneity as a result of different definitions of high and low institutional volumes employed by different studies. For instance, some studies applied the total number of AAA operations to define a high volume institution, while others used the number of emergency procedures for rAAA only. Although the present findings are suggestive of an inverse volume mortality correlation, a specific cutoff caseload to define a high volume institution remains to be determined. Furthermore, all studies included in this review were multicentre or presented administrative datasets, and reported no information on individual institution practices. Thus, it was not possible to stratify centres by the proportion of EVAR/open surgical repairs such centres were performing.
      Whether the survival benefit of emergency AAA treatment in high volume institutions is predominantly driven by EVAR or open surgical repair was also investigated. Subgroup analysis demonstrated lower peri-operative mortality in patients treated in high volume centres for both EVAR and open surgical repair. Notably, the pooled effect estimate was more pronounced in the open surgery subgroup. Two studies only reported adjusted mortality estimates for EVAR and open AAA repair subgroups, meta-analysis of which showed a significant effect for open surgical repair but not for EVAR. This finding is congruent with the results of a 2020 study demonstrating a volume outcome correlation in patients treated by open surgery for rAAA but not in those treated by EVAR.
      • Kontopodis N.
      • Galanakis N.
      • Antoniou S.A.
      • Tsetis D.
      • Ioannou C.V.
      • Veith F.J.
      • et al.
      Meta-analysis and meta-regression analysis of outcomes of endovascular and open repair for ruptured abdominal aortic aneurysm.
      Sensitivity analysis including only studies published after 2010, thereby representing contemporary clinical practices, did not show a significant peri-operative survival advantage of treatment in high volume centres for patients undergoing EVAR. This may be explained by the fact that even though a high annual caseload of rAAA cases treated by EVAR was important during an earlier phase of the development of endovascular techniques, this may not be the case in more contemporary studies, in which the annual caseload does not seem to affect outcomes significantly.
      The evidence regarding the potential impact of individual surgeon caseload on outcomes following surgery for rAAA is less robust, with only three studies providing relevant data and two included in adjusted analysis. The effect of surgeon volumes on outcomes following surgery for rAAA seems to be less pronounced than that of institutional volumes. Zettervall et al. found improved results in patients treated by high volume surgeons, with a greater benefit in patients undergoing open surgery.
      • ZettervallSL
      • Schermerhorn M.L.
      • Soden P.A.
      • McCallum J.C.
      • Shean K.E.
      • Deery S.E.
      • et al.
      The effect of surgeon and hospital volume on mortality after open and endovascular repair of abdominal aortic aneurysms.
      A recent report examining the relationship between volumes and outcomes in elective AAA surgery in England showed a significant effect of both institutional and individual surgeon volumes on outcomes for open AAA repair but not for EVAR.
      • Gray W.K.
      • Day J.
      • Horrocks M.
      Editor's Choice – Volume–outcome relationships in elective abdominal aortic aneurysm surgery: Analysis of the UK Hospital Episodes Statistics database for the Getting It Right First Time (GIRFT) programme.
      Meltzer et al. found that the significant effect of individual surgeon volume on outcomes after elective open AAA repair was more pronounced than that of institutional volume.
      • Meltzer A.J.
      • Connolly P.H.
      • Schneider D.B.
      • Sedrakyan A.
      Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
      In the same study, the opposite was found for ruptured cases, where centre, and not surgeon volume, significantly affected outcomes. It was found in the present study that the individual surgeon procedure volume did not have an impact on clinical outcomes. This may be the result of a type II error or because parameters other than surgeon volume may be more important in the setting of emergency AAA treatment, such as healthcare delivery infrastructure, the implementation of specific management protocols, and the availability of specialised expert multidisciplinary teams. The individual surgeon is a small (albeit significant) part in the patient’s journey, and the overall healthcare infrastructure may have a greater impact on clinical outcomes.
      These results have important implications for the future configuration of vascular services worldwide, given the changing epidemiology of AAA and the complexity of aortic pathologies. Centralisation of aortic services may have a profound impact on patient care, outcomes, and experience. Around the clock availability of aortic services requires changes in logistics, infrastructure, and healthcare delivery, including prehospital care, diagnostics, operating facilities (e.g., hybrid angiosuite), aortic endografts and ancillary equipment, post-operative intensive care management, and an expert vascular multidisciplinary team. Reconfiguration of aortic services will also have implications on surgical training and the development of expertise in open and endovascular aortic surgery. It may be argued, however, that transfer to a specialised aortic centre may take longer, which may affect overall mortality, as a number of patients may not receive prompt surgical treatment, resulting in a negative effect of centralisation with unintentional consequences.
      These findings should be interpreted carefully in the context of the study limitations. Definitions of high/low volume institutions/surgeons varied widely across the studies. Such inconsistency is reflected in the statistical heterogeneity for nearly all outcomes. Even though random effects statistical models were employed and sensitivity analyses performed to account for and explore heterogeneity as a result of different definitions, the findings should be interpreted cautiously and validated in well designed future prognostic research employing prospectively collected multi-institutional registry data. Furthermore, many patients included in the primary studies were excluded, because only high and low volume groups were considered for the purposes of the analysis, excluding intermediate size groups. A number of relevant studies investigating the research question were not included in quantitative synthesis because they did not report data suitable for meta-analysis.
      • Budtz-Lilly J.
      • Björck M.
      • Venermo M.
      • Debus S.
      • Behrendt C.A.
      • Altreuther M.
      • et al.
      Editor's Choice – The impact of centralisation and endovascular aneurysm repair on treatment of ruptured abdominal aortic aneurysms based on international registries.
      • Karthikesalingam A.
      • Holt P.J.
      • Vidal-Diez A.
      • Ozdemir B.A.
      • Poloniecki J.D.
      • Hinchliffe R.J.
      • et al.
      Mortality from ruptured abdominal aortic aneurysms: clinical lessons from a comparison of outcomes in England and the USA.
      • Ozdemir B.A.
      • Karthikesalingam A.
      • Sinha S.
      • Poloniecki J.D.
      • Vidal-Diez A.
      • Hinchliffe R.J.
      • et al.
      Association of hospital structures with mortality from ruptured abdominal aortic aneurysm.

      Conclusion

      A high institutional volume may result in a reduction in peri-operative mortality following surgery for rAAA. The peri-operative survival advantage of treatment in high volume centres is more pronounced in open surgery than in EVAR. Individual surgeon caseload was not found to have a significant impact on outcomes for either open or endovascular repair of rAAA. These findings have implications for vascular service provision, with an emphasis on the centralisation of aortic services and the potential to enhance clinical outcomes. Further research is required to determine volume thresholds for institutions to qualify for delivering specialised aortic services. Further studies should examine the effect of treatment in high volume institutions on long term outcomes after endovascular and/or open surgery for rAAA.

      Conflicts of interest

      None.

      Funding sources

      None.

      Appendix A. Supplementary data

      The following are the Supplementary data to this article:

      References

        • Schwartz D.M.
        • Fong Z.V.
        • Warshaw A.L.
        • Zinner M.J.
        • Chang D.C.
        The hidden consequences of the volume pledge: “No Patient Left Behind”?.
        Ann Surg. 2017; 265: 273-274
        • Lillemoe K.D.
        Surgical volume/outcome debate.
        Ann Surg. 2017; 265: 270
        • Finks J.F.
        • Osborne N.H.
        • Birkmeyer J.D.
        Trends in hospital volume and operative mortality for high-risk surgery.
        N Engl J Med. 2011; 364: 2128-2137
        • Milstein A.
        • Galvin R.S.
        • Delbanco S.F.
        • Salber P.
        • Buck Jr., C.R.
        Improving the safety of health care: the leapfrog initiative.
        Eff Clin Pract. 2000; 3: 313-316
        • Birkmeyer J.D.
        • Siewers A.E.
        • Finlayson E.V.
        • Stukel T.A.
        • Lucas F.L.
        • Batista I.
        • et al.
        Hospital volume and surgical mortality in the United States.
        N Engl J Med. 2002; 346: 1128-1137
        • Birkmeyer J.D.
        • Stukel T.A.
        • Siewers A.E.
        • Goodney P.P.
        • Wennberg D.E.
        • Lucas F.L.
        Surgeon volume and operative mortality in the United States.
        N Engl J Med. 2003; 349: 2117-2127
        • Phillips P.
        • Poku E.
        • Essat M.
        • Woods H.B.
        • Goka E.A.
        • Kaltenthaler E.C.
        • et al.
        Procedure volume and the association with short-term mortality following abdominal aortic aneurysm repair in European populations: a systematic review.
        Eur J Vasc Endovasc Surg. 2017; 53: 77-88
        • Paraskevas K.I.
        The effect of centralization of abdominal aortic aneurysm repair procedures on perioperative outcomes.
        Ann Transl Med. 2019; 7: S125
        • Patterson B.O.
        • Holt P.J.E.
        High volume aortic practices demonstrate benefits crossing healthcare boundaries.
        Eur J Vasc Endovasc Surg. 2018; 55: 195
        • Chaikof E.L.
        • Dalman R.L.
        • Eskandari M.K.
        • Jackson B.M.
        • Lee W.A.
        • Mansour M.A.
        • et al.
        The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm.
        J Vasc Surg. 2018; 67: 2-77
        • Wanhainen A.
        • Verzini F.
        • Van Herzeele I.
        • Allaire E.
        • Bown M.
        • Cohnert T.
        • et al.
        Editor's Choice – European Society for Vascular Surgery (ESVS) 2019 Clinical Practice Guidelines on the management of abdominal aorto-iliac artery aneurysms.
        Eur J Vasc Endovasc Surg. 2019; 57: 8-93
        • Marlow N.E.
        • Barraclough B.
        • Collier N.A.
        • Dickinson I.C.
        • Fawcett J.
        • Graham J.C.
        • et al.
        Effect of hospital and surgeon volume on patient outcomes following treatment of abdominal aortic aneurysms: a systematic review.
        Eur J Vasc Endovasc Surg. 2010; 40: 572-579
        • Henebiens M.
        • van den Broek T.A.
        • Vahl A.C.
        • Koelemay M.J.
        Relation between hospital volume and outcome of elective surgery for abdominal aortic aneurysm: a systematic review.
        Eur J Vasc Endovasc Surg. 2007; 33: 285-292
        • Holt P.J.
        • Poloniecki J.D.
        • Gerrard D.
        • Loftus I.M.
        • Thompson M.M.
        Meta-analysis and systematic review of the relationship between volume and outcome in abdominal aortic aneurysm surgery.
        Br J Surg. 2007; 94: 395-403
      1. Higgins J.P.T. Thomas J. Chandler J. Cumpston M. Li T. Page M.J. Cochrane Handbook for Systematic Reviews of Interventions Version 6.2. 2021 (Available at:)
        • Liberati A.
        • Altman D.G.
        • Tetzlaff J.
        • Mulrow C.
        • Gøtzsche P.C.
        • Ioannidis J.P.
        • et al.
        The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration.
        J Clin Epidemiol. 2009; 62: e1-e34
        • Antoniou S.A.
        • Antoniou G.A.
        The GRADE approach to appraising the evidence or how to increase the credibility of your research.
        Am J Surg. 2020; 220: 290-293
        • Hozo S.P.
        • Djulbegovic B.
        • Hozo I.
        Estimating the mean and variance from the median, range, and the size of a sample.
        BMC Med Res Methodol. 2005; 5: 13
        • Langan D.
        • Higgins J.P.T.
        • Jackson D.
        • Bowden J.
        • Veroniki A.A.
        • Kontopantelis E.
        • et al.
        A comparison of heterogeneity variance estimators in simulated random-effects meta-analyses.
        Res Synth Methods. 2019; 10: 83-98
        • Deeks J.J.
        • Altman D.G.
        • Bradburn M.J.
        Statistical methods for examining heterogeneity and combining results from several studies in meta-analysis.
        in: Egger M. Davey Smith G. Altman D.G. Systematic Reviews in Health Care: Meta-analysis in Context. 2nd edn. BMJ Publication Group, London2001: 285-312
        • Sterne J.A.C.
        • Sutton A.J.
        • Ioannidis J.P.A.
        • Terrin N.
        • Jones D.R.
        • Lau J.
        • et al.
        Recommendations for examining and interpreting funnel plot asymmetry in meta-analyses of randomised controlled trials.
        BMJ. 2011; 343: d4002
        • Der Simonian R.
        • Laird N.
        Meta-analysis in clinical trials.
        Control Clin Trials. 1986; 7: 177-188
        • Dimick J.B.
        • Stanley J.C.
        • Axelrod D.A.
        • Kazmers A.
        • Henke P.K.
        • Jacobs L.A.
        • et al.
        Variation in death rate after abdominal aortic aneurysmectomy in the United States: impact of hospital volume, gender, and age.
        Ann Surg. 2002; 235: 579-585
        • Holt P.J.
        • Poloniecki J.D.
        • Loftus I.M.
        • Michaels J.A.
        • Thompson M.M.
        Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005.
        Br J Surg. 2007; 94: 441-448
        • Greco G.
        • Egorova N.
        • Anderson P.L.
        • Gelijns A.
        • Moskowitz A.
        • Nowygrod R.
        • et al.
        Outcomes of endovascular treatment of ruptured abdominal aortic aneurysms.
        J Vasc Surg. 2006; 43: 453-459
        • Giles K.A.
        • Hamdan A.D.
        • Pomposelli F.B.
        • Wyers M.C.
        • Dahlberg S.E.
        • Schermerhorn M.L.
        Population-based outcomes following endovascular and open repair of ruptured abdominal aortic aneurysms.
        J Endovasc Ther. 2009; 16: 554-564
        • McPhee J.
        • Eslami M.H.
        • Arous E.J.
        • Messina L.M.
        • Schanzer A.
        Endovascular treatment of ruptured abdominal aortic aneurysms in the United States (2001–2006): a significant survival benefit over open repair is independently associated with increased institutional volume.
        J Vasc Surg. 2009; 49: 817-826
        • Chen C.K.
        • Chang H.T.
        • Chen Y.C.
        • Chen T.J.
        • Chen I.M.
        • Shih C.C.
        Surgeon elective abdominal aortic aneurysm repair volume and outcomes of ruptured abdominal aortic aneurysm repair: a 12-year nationwide study.
        World J Surg. 2013; 37: 2360-2371
        • Dua A.
        • Furlough C.L.
        • Ray H.
        • Sharma S.
        • Upchurch G.R.
        • Desai S.S.
        The effect of hospital factors on mortality rates after abdominal aortic aneurysm repair.
        J Vasc Surg. 2014; 60: 1446-1451
        • Karthikesalingam A.
        • Wanhainen A.
        • Holt P.J.
        • Vidal-Diez A.
        • Brownrigg J.R.
        • Shpitser I.
        • et al.
        Comparison of long-term mortality after ruptured abdominal aortic aneurysm in England and Sweden.
        Br J Surg. 2016; 103: 199-206
        • Meltzer A.J.
        • Connolly P.H.
        • Schneider D.B.
        • Sedrakyan A.
        Impact of surgeon and hospital experience on outcomes of abdominal aortic aneurysm repair in New York State.
        J Vasc Surg. 2017; 66: 728-734
        • Trenner M.
        • Kuehnl A.
        • Salvermoser M.
        • Reutersberg B.
        • Geisbuesch S.
        • Schmid V.
        • et al.
        Editor's Choice – High annual hospital volume is associated with decreased in hospital mortality and complication rates following treatment of abdominal aortic aneurysms: secondary data analysis of the Nationwide German DRG Statistics from 2005 to 2013.
        Eur J Vasc Endovasc Surg. 2018; 55: 185-194
        • Greenleaf E.K.
        • Hollenbeak C.S.
        • Aziz F.
        Outcomes after ruptured abdominal aortic aneurysm repair in the era of centralized care.
        J Vasc Surg. 2020; 71: 1148-1161
        • Tripodi P.
        • Mestres G.
        • Riambau V.
        • Vascular Advisory Committee – Catalan Health Service
        Impact of centralisation on abdominal aortic aneurysm repair outcomes: early experience in Catalonia.
        Eur J Vasc Endovasc Surg. 2020; 60: 531-538
        • Sawang M.
        • Paravastu S.C.V.
        • Liu Z.
        • Thomas S.D.
        • Beiles C.B.
        • Mwipatayi B.P.
        • et al.
        The relationship between operative volume and peri-operative mortality after non-elective aortic aneurysm repair in Australia.
        Eur J Vasc Endovasc Surg. 2020; 60: 519-530
        • Leighton P.
        • Doe M.
        • Pathak S.
        • AlDuwaisan A.
        • Brooks M.
        Immediate impact of centralization on abdominal aortic aneurysm repair outcomes for a Vascular Network in the South West of England: a retrospective cohort study.
        Ann Surg. 2019; 269: 172-176
        • Thompson M.
        • Holt P.
        • Loftus I.
        • Forbes T.L.
        Debate: whether abdominal aortic aneurysm surgery should be centralized at higher-volume centers.
        J Vasc Surg. 2011; 54: 1208-1214
        • Kontopodis N.
        • Galanakis N.
        • Antoniou S.A.
        • Tsetis D.
        • Ioannou C.V.
        • Veith F.J.
        • et al.
        Meta-analysis and meta-regression analysis of outcomes of endovascular and open repair for ruptured abdominal aortic aneurysm.
        Eur J Vasc Endovasc Surg. 2020; 59: 399-410
        • ZettervallSL
        • Schermerhorn M.L.
        • Soden P.A.
        • McCallum J.C.
        • Shean K.E.
        • Deery S.E.
        • et al.
        The effect of surgeon and hospital volume on mortality after open and endovascular repair of abdominal aortic aneurysms.
        J Vasc Surg. 2017; 65: 626-634
        • Gray W.K.
        • Day J.
        • Horrocks M.
        Editor's Choice – Volume–outcome relationships in elective abdominal aortic aneurysm surgery: Analysis of the UK Hospital Episodes Statistics database for the Getting It Right First Time (GIRFT) programme.
        Eur J Vasc Endovasc Surg. 2020; 60: 509-517
        • Budtz-Lilly J.
        • Björck M.
        • Venermo M.
        • Debus S.
        • Behrendt C.A.
        • Altreuther M.
        • et al.
        Editor's Choice – The impact of centralisation and endovascular aneurysm repair on treatment of ruptured abdominal aortic aneurysms based on international registries.
        Eur J Vasc Endovasc Surg. 2018; 56: 181-188
        • Karthikesalingam A.
        • Holt P.J.
        • Vidal-Diez A.
        • Ozdemir B.A.
        • Poloniecki J.D.
        • Hinchliffe R.J.
        • et al.
        Mortality from ruptured abdominal aortic aneurysms: clinical lessons from a comparison of outcomes in England and the USA.
        Lancet. 2014; 383: 963-969
        • Ozdemir B.A.
        • Karthikesalingam A.
        • Sinha S.
        • Poloniecki J.D.
        • Vidal-Diez A.
        • Hinchliffe R.J.
        • et al.
        Association of hospital structures with mortality from ruptured abdominal aortic aneurysm.
        Br J Surg. 2015; 102: 516-524

      Linked Article

      • Hospital Volume Counts for Ruptured Abdominal Aortic Aneurysm Repair: Evolving Data from a Meta-Analysis
        European Journal of Vascular and Endovascular SurgeryVol. 62Issue 3
        • Preview
          Kontopodis et al.1 provide a contemporary perspective on the volume outcome relationship with ruptured abdominal aortic aneurysm (AAA) repair. To date, several publications have examined centre and surgeon volume association with both elective and non-elective AAA repair outcomes. The importance of this issue is underscored by the fact that professional societies and watchdog organisations endorse specific and often conflicting volume thresholds for elective repair, presumptively to serve as proxies for high quality care, without recommendations for ruptured presentations (European Society for Vascular Surgery: surgeon ≥ 10, centre ≥ 30 procedures/year; International Consortium of Vascular Registries: surgeon not applicable, centre ≥ 13–16; Society for Vascular Surgery: surgeon not applicable, centre ≥ 10; Leapfrog Group: surgeon ≥ 10, centre ≥ 15).
        • Full-Text
        • PDF
        Open Archive

      Comments

      Commenting Guidelines

      To submit a comment for a journal article, please use the space above and note the following:

      • We will review submitted comments as soon as possible, striving for within two business days.
      • This forum is intended for constructive dialogue. Comments that are commercial or promotional in nature, pertain to specific medical cases, are not relevant to the article for which they have been submitted, or are otherwise inappropriate will not be posted.
      • We require that commenters identify themselves with names and affiliations.
      • Comments must be in compliance with our Terms & Conditions.
      • Comments are not peer-reviewed.