Vascular Health and Risk Management Dovepress open access to scientific and medical research Open Access Full Text Article Original Research Variation in the choice of elective surgical procedure for abdominal aortic aneurysm in Spain This article was published in the following Dove Medical Press journal: Vascular Health and Risk Management M Jesús Quintana 1,2 Objective: The two main surgical treatments for abdominal aortic aneurysm (AAA) are open Ignasi Gich 1–3 surgical repair (OSR) and endovascular aneurysm repair (EVAR). The aim of this study was to Julián Librero 4,5 analyze variation among Spanish hospitals in the use of OSR or EVAR for AAA. A secondary Sergi Bellmunt-Montoya 6,7 aim was to assess changes in preferences for these two procedures over time. Methods: This was a retrospective longitudinal study based on discharge data from public José R Escudero 3,8,9 hospitals in Spain during 2002–2012. Patient inclusion criteria were: age >18 years, elective Xavier Bonfill 1–3,10 admission, primary diagnosis of unruptured AAA, and surgical treatment with OSR or EVAR. On behalf of the AAA The characteristics of the treating center, patients, and in-hospital mortality were recorded. Spanish Study Group Results: We included 16,737 patients from 114 hospitals; 6,809 (40.7%) underwent EVAR and 9,928 (59.3%) underwent OSR. The total volume of surgeries increased throughout the period, 1 Department of Clinical Epidemiology and Public Health, University and the probability that any given procedure was EVAR increased by 20% per year (OR 1.20, Hospital de la Santa Creu i Sant P<0.001). The volume and distribution of the two procedures varied highly across the partici- Pau (IIB Sant Pau), Barcelona, Spain; 2 CIBER of Epidemiology and Public pating hospitals. Overall, in-hospital mortality rate was 3.6% and it decreased during the study Health (CIBERESP), Barcelona, Spain; period (5.3% in 2002 and 3.2% in 2012), mainly due to a decrease in OSR-related mortality, 3 Universitat Autònoma de Barcelona, despite a slight increase in EVAR-related mortality. Hospitals with higher surgical volumes Barcelona, Spain; 4Navarrabiomed- UPNA -Departamento de Salud, were more likely to use EVAR and have lower in-hospital mortality rates. IDISNA, Pamplona, Spain; 5Red de Conclusion: This study reveals high variability in the surgical treatment of unruptured AAA Investigación en Servicios de Salud en across Spanish hospitals. The number of interventions has increased in recent years, with EVAR Enfermedades Crónicas (REDISSEC), Bilbao, Spain; 6Department of Angiology, accounting for a growing percentage of these surgical procedures. Overall in-hospital mortality Vascular and Endovascular Surgery, rates decreased significantly during this period, mainly due to lower mortality among patients Vall d’Hebron University Hospital, Barcelona, Spain; 7Vall d’Hebron undergoing OSR. In-hospital mortality rates were lower in higher-volume centers, regardless Research Institute (VHIR), Barcelona, of the surgical approach used. Further research on variability and appropriateness of surgical Spain; 8Joint Service of Angiology, management of AAA is required to assess the suitability of concentrating elective AAA repair Vascular and Endovascular Surgery, Sant Pau-Dos de Maig Hospital, in more experienced centers to potentially achieve better outcomes. Barcelona, Spain; 9CIBER Cardiovascular Keywords: abdominal aortic aneurysm, open surgical repair, endovascular aneurysm repair, Diseases (CIBERCV), Barcelona, Spain; variability 10 Iberoamerican Cochrane Centre, Barcelona, Spain Introduction Abdominal aortic aneurysm (AAA) is a very severe pathology that presents a high Correspondence: Xavier Bonfil risk of mortality in case of rupture.1 Open surgical repair (OSR) has long been the Department of Clinical Epidemiology and Public Health, University Hospital de primary treatment option to repair an intact AAA; however, endovascular repair la Santa Creu i Sant Pau (IIB Sant Pau), (EVAR) – a minimally invasive procedure – has largely replaced OSR in many Iberoamerican Cochrane Centre, C/ Sant Antoni Maria Claret, 167, Pavelló 18, hospitals.2–6 Indeed, due to recent technological advances, many authors and centers planta 0, Barcelona CP: 08025, Spain now consider EVAR the procedure of choice for surgical repair of AAA.7,8 In recent Tel +34 93 553 7808 Fax +34 93 553 7809 years, several studies have been conducted to assess trends in the surgical treatment Email xbonfill@santpau.cat of AAA. Those studies have found a persistent increase in surgical procedure rates submit your manuscript | www.dovepress.com Vascular Health and Risk Management 2019:15 69–79 69 Dovepress © 2019 Quintana et al. This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms. http://dx.doi.org/10.2147/VHRM.S191451 php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (https://www.dovepress.com/terms.php). Quintana et al Dovepress for AAA – likely due to population aging, among other OSR or EVAR. The following patient and treatment-related factors.9,10 Other studies have shown that EVAR accounts data were registered: surgical hospital, gender, age at the time for a growing proportion of surgical procedures for AAA of surgery, and mortality at hospital discharge. The Charl- repair, while OSR is in relative decline.11 Similarly, some son Comorbidity Index (CCI; using secondary diagnoses studies have shown wide variability in the criteria used to included in the CMBD) was also calculated and recorded. select the surgical technique. While selection of the specific Exclusion criteria were: patients diagnosed with tho- surgical approach generally depends on the characteristics racic or thoracoabdominal AA (codes: 441.1, 441.2, 441.4, of the patient and the aneurysm itself, the unique charac- 441.7) or aortic dissection (441.00, 441.01, 441.02, 441.03). teristics of the treating hospital and the health care system We also excluded patients who underwent both EVAR and may also play a role. This explains, in part, why treatment OSR during a single intervention, patients with ruptured selection can be highly variable.12–14 Notwithstanding the AAA (codes: 441.3, 441.5, and 441.6), and patients with aforementioned reports, relatively few studies have analyzed emergency admission. variability among hospitals in selection of the specific sur- gical approach for AAA.15–18 Such data would be valuable Statistical analyses to identify differences among hospitals and countries with A descriptive analysis of the main characteristics of the two regard to the treatment options offered to patients with surgical procedures was performed. Student’s t-test was used similar characteristics. to compare quantitative variables, while the chi-squared test In this context, the research group “Atlas de Variabilidad or Fisher’s exact test was used, as appropriate, to compare de la Práctica Médica” (Atlas of Variations in Medical Prac- categorical variables. We used generalized linear mixed tice; VPM in Spanish) carried out a study to assess the risk models (multivariate logistic regressions with hospital ran- of death after surgery for AAA in-hospitals in the Spanish dom effect) to examine interhospital variation. These models National Health Care System; this group also sought to iden- were run with and without adjustments to account for factors tify differences in mortality rates among those hospitals.19,20 independently associated with surgical technique selection Using the data obtained by the VPM, we evaluated variation and in-hospital mortality. Three multivariate models that among Spanish hospitals with regard to the treatment of included temporal and hospital effects were developed. The unruptured AAA. Specifically, we sought to identify current first model included adjusted variables; the second model also preferences among Spanish hospitals for OSR or EVAR and considered a potential time trend (year of surgery); and the to determine changes in these preferences over the course of third model added surgical volume (ie, number of procedures) the study period (2002–2012). performed at each hospital. The results were adjusted for individual factors (age, gender, and comorbidities) to assess Methods the influence of surgical volumes and compare improvement Study design, participants, and variables of the goodness of fit of the model (Hosmer–Lemeshow test). This was a retrospective, longitudinal study based on data Graphically, both the variation and the potential effect from the year 2002 to 2012 in the database “Minimum Basic of surgical volumes were expressed using a funnel plot.21 Dataset at Hospital Discharge” (in Spanish: “Conjunto Three statistical approaches were used to register variation: Mínimo Básico de Datos al Alta Hospitalaria” [CMBD- 1) intraclass correlation coefficient, using the latent variable AH]). This database – which was provided to us by the approach to express the proportion of total variance explained VPM – contains data on patients discharged from Spanish by the treating center, 2) the median OR, and 3) the change public hospitals. Specifically, we evaluated discharge data in discriminatory power (receiver operating characteristic for patients >18 years old with a primary diagnosis of aor- with area under the curve [AUC]) when using the center as tic aneurysm (AA) according to the ICD, Ninth Revision, the explanatory level. Clinical Modification. The corresponding surgical procedure The fixed effect of the individual and context variables codes were also included and grouped as either OSR (codes were expressed as OR with 95% CIs. Statistical significance 38.34, 38.44, 38.84, 39.25, 39.29, 39.23, 39.26, 39.51, 39.52, was set at P<0.05. The statistical analysis was performed 39.57, 39.56, 39.58, 38.46, 38.66, 38.86, and 38.64.) or with the IBM-SPSS statistical software package, v25.0 (IBM EVAR (codes 39.71, 39.73, 39.79, 39.90, 00.55, and 39.50). Corp., Armonk, NY, USA), the Stata Statistical Software, Inclusion criteria were as follows: 1) primary diagnosis of release 15.2017 (Stata Corp.), and the R Core Team 2018 unruptured AAA, 2) elective admission, and 3) treated with (R Foundation for Statistical Computing, Vienna, Austria). 70 submit your manuscript | www.dovepress.com Vascular Health and Risk Management 2019:15 Dovepress Dovepress Quintana et al Ethics approval and consent to inclusion criteria. A total of 6,809 patients (40.7%) underwent participate EVAR and 9,928 (59.3%) patients underwent OSR. Most Data used in the study were approved by the ethics commit- patients were men (16,185; 96.7%). The mean age was 71.4 tees of the participating institutions: “Atlas de Variaciones years (SD 7.8). The mean CCI was 0.7 (SD 0.98). Variability en la Práctica Médica” (Instituto Aragonés de Ciencias de la among the participating centers in surgical volumes was high: Salud) and University Hospital de la Santa Creu i Sant Pau the mean number of procedures per center during the study (IIB Sant Pau). Informed consent was waived because we period was 328.2 (SD 159.25; range 1–682). Of the 16,737 used anonymized retrospective data. patients, 601 died during the hospital stay, for an overall in- hospital mortality rate of 3.6% (Table 1). Results The total volume of surgical procedures at the participat- A total of 30,372 patients underwent EVAR or OSR at 117 ing hospitals increased from 1,132 procedures in 2002 to hospitals in Spain during the study period. Of these, 16,737 1,859 in 2012, which represents a 64% increase overall and an patients (55.1%) (Figure 1) from 114 centers met the study annual increase of 5.8%. The number of surgical ­procedures AA N=30,372 AA other AAA than abdominal N=26,906 (88.6%) N=3,466 (11.4%) Dissection No dissection N=94 N=26,812 (99.7%) (0.3%) >1 surgery type 1 surgery type N=2,428 (9.1%) N=24,3704 (90.9%) Urgent Elective N=7,438 (30.5%) N=16,922 (69.4%) Ruptured Ruptured Unruptured Unruptured AAA AAA AAA AAA N=3,776 N=185 N=3,662 N=16,737 (50.8%) (1.1%) (49.2%) (98.9%) Patients included in the analysis Open surgery N=9,928 (59.3%) Included N=16,737 Excluded EVAR N=6,809 (40.7%) (55.1% of the initial population) Figure 1 Selection process for study inclusion. Note: Patients diagnosed with unruptured AAA, undergoing EVAR or OSR with an elective admission during the study period 2002–2012. Abbreviations: AA, aortic aneurysm; AAA, abdominal aortic aneurysm; EVAR, endovascular aneurysm repair; OSR, open surgical repair. Vascular Health and Risk Management 2019:15 submit your manuscript | www.dovepress.com 71 Dovepress Quintana et al Dovepress per year increased progressively from 2002 to 2009, after relation between surgical volumes and the use of EVAR. which the volume stabilized. More specifically, the higher the volume, the greater the Patients undergoing OSR were significantly younger than probability that the endovascular approach was used (OR those treated with EVAR (OR 1.08, P<0.001) and also had 1.09, P<0.001; Table 2). Nonetheless, there was substantial a significantly lower CCI (OR 1.16, P<0.001). There was variability between surgical volume at any given hospital no significant association between gender and treatment and the proportion of endovascular surgeries: in some cases, selection (OR 1.14, P=0.148). However, there was a direct EVAR accounted for a relatively small percentage of pro- cedures at high-volume hospitals, but a high percentage of AAA surgeries at hospitals with lower volumes (Figure 2A). Table 1 Characteristics of patients undergoing elective surgical Overall, the probability that any given procedure was EVAR repair for unruptured AAA in Spanish hospitals between 2002 increased by ~20% annually (OR 1.20, P<0.001; Figure 2B). and 2012 The overall in-hospital mortality rate in 2002 was 5.3%, Included patients (N=16,737) which declined to 3.2% in 2012 (OR 0.94, P<0.001), showing n % an annual decrease of 7% (Figure 3). This decrease in mortal- Age (years) ity rates was due primarily to the decrease in O ­ SR-related Mean (SD) 71.4 (7.8) mortality, with mortality rates falling from 6.3% in 2002 Median (min–max) 72 (25–96) to 5.4% in 2012 (OR 0.98, P=0.235); by contrast, the in- Gender hospital mortality increased slightly (but not significantly) Male 16,185 96.7 Female 552 3.3 in the EVAR group, from 0% in 2002 to 1.5% in 2012 (OR Charlson Index 0.97, P=0.344). Mean (SD) 0.7 (0.98) At hospital discharge, the in-hospital mortality rate was Median (min–max) 0 (0–10) significantly lower in the EVAR group vs OSR (1.2% vs Type of intervention EVAR 6,809 40.7 5.2%; OR 4.34, P<0.001). Two variables – age (OR 1.03, OSR 9,928 59.3 P<0.001) and the CCI score (OR 1.26, P<0.001) – were Surgical volumes for AAA repair per significantly associated with in-hospital mortality. There was hospital through the study period Mean (SD) 328.2 (159.25) no significant association between gender and mortality (OR Median (min–max) 306 (1–682) 1.11, P=0.672). Higher annual surgical volumes were associ- In-hospital mortality rates ated with lower mortality rates (OR 0.89, P<0.001; Table 3). Yes 601 3.6 Variability among the participating hospitals was high No 16,136 96.4 for the main study variables, which included the distribu- Abbreviations: AAA, abdominal aortic aneurysm; EVAR, endovascular aneurysm repair; OSR, open surgical repair. tion of EVAR/OSR, in-hospital mortality rates, and surgical Table 2 Characteristics of patients undergoing surgical repair for AAA: OSR vs EVAR Included patients (N=16,737) EVAR (n=6,809) OSR (n=9,928) OR 95% CI P-value n % n % Age Mean (SD) 73.8 (7.4) 69.7 (7.6) 1.08 (1.07–1.08) <0.001 Median (min–max) 75 (29–96) 71 (25–94) Gender Male 6,568 40.6 9,617 59.4 1 (0.96–1.35) 0.148 Female 241 43.7 311 56.3 1.13 Charlson Index 1.16 (1.13–1.20) <0.001 Mean (SD) 0.8 (1.04) 0.6 (0.93) Median (min–max) 0 (0–8) 0 (0–10) Intervention volume per hospital throughout the period/100 Mean (SD) 341.2 (160.70) 319.2 (157.64) 1.09 (1.07–1.11) <0.001 Median (min–max) 319 (1–682) 304 (1–682) Abbreviations: AAA, abdominal aortic aneurysm; EVAR, endovascular aneurysm repair; OSR, open surgical repair. 72 submit your manuscript | www.dovepress.com Vascular Health and Risk Management 2019:15 Dovepress Dovepress Quintana et al 100.0 600 500 80.0 Surgical procedures (n) 400 60.0 % EVAR 300 40.0 200 20.0 100 0 0 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 97 101 105 109 113 Hospital 60.0 6.0 50.0 5.0 40.0 4.0 EVAR (%) Death (%) 30.0 3.0 20.0 2.0 10.0 1.0 0 0 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Years Figure 2 Volume of AAA surgeries performed in the hospitals participating in the study from 2002 to 2012, distribution of the two types of procedures and evolution of mortality. Notes: (A) Number of surgical procedures performed at each participating hospital during the study period and the proportion of these interventions in each center. (B) EVAR as a proportion of surgical procedures to treat AAA from 2002 to 2012 at all participating hospitals. The mortality is also shown for the same period. Abbreviations: AAA, abdominal aortic aneurysm; EVAR, endovascular aneurysm repair. Vascular Health and Risk Management 2019:15 submit your manuscript | www.dovepress.com 73 Dovepress Quintana et al Dovepress 1.0 1.0 0.9 0.9 0.8 0.8 Probability of in-hospital death 0.7 0.7 Probability of EVAR 0.6 0.6 0.5 0.5 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0.0 0.0 0 200 400 0 200 400 n AAA n AAA Figure 3 Funnel plot: probability of in-hospital mortality and surgery by EVAR, according to the volume of procedures performed in the hospitals participating in the study. Abbreviations: AAA, abdominal aortic aneurysm; EVAR, endovascular aneurysm repair. Table 3 Mortality rates at discharge among patients undergoing surgical repair for AAA during the study period Included patients (N=16,737) Mortality Yes (n=601) No (n=16,136) OR 95% CI P-value n % n % Age (years) Mean (SD) 73.1 (6.64) 71.3 (7.80) 1.03 (1.02–1.04) <0.001 Median (min–max) 74 (48–94) 72 (25–96) Gender Male 583 3.6 15,602 96.4 1 (0.69–1.79) 0.672 Female 18 3.3 534 96.7 1.11 Charlson Index Mean (SD) 0.9 (1.14) 0.7 (0.97) 1.26 (1.17–1.34) <0.001 Median (min–max) 1 (0–10) 0 (0–10) Type of intervention EVAR 85 1.2 6,724 98.8 1 (3.44–5.47) <0.001 OSR 516 5.2 9,412 94.8 4.34 Intervention volume per hospital throughout the period/100 Mean (SD) 300.2 (149.59) 329.2 (159.51) 0.89 (0.84–0.94) <0.001 Median (min–max) 276 (1–682) 314 (1–682) Abbreviations: AAA, abdominal aortic aneurysm; EVAR, indicates endovascular aneurysm repair; OSR, open surgical repair. volumes. Variability in preferences for EVAR or OSR was The multivariate analysis, which was based on the three particularly high, with a large percentage of values falling different models, revealed a significant and increasing trend outside the expected range. Mortality, however, did not show over time toward the greater use of EVAR vs OSR (OR 1.25). such a high variability (Figure 3). Nevertheless, despite this clear trend toward the use of this 74 submit your manuscript | www.dovepress.com Vascular Health and Risk Management 2019:15 Dovepress Dovepress Quintana et al minimally invasive technique, we did not observe any cor- growing proportion of those surgical procedures. Overall responding decrease in in-hospital deaths among patients in-hospital mortality rates decreased during the study period, treated with EVAR compared to those treated with OSR (OR primarily due to a decrease in OSR-related mortality, suggest- 0.98). Higher-volume hospitals were more likely to perform ing improved safety. Not surprisingly, higher-volume centers EVAR (OR 1.38), and mortality rates were lower in the high- had better results in terms of lower in-hospital mortality volume hospitals (OR 0.87; Table 4). rates, which was independent of the predominant surgical The hospital effect – the influence that the variable “hos- technique at the institution. These results are consistent with pital” itself had on the choice of surgical technique – was previous reports,9 thus confirming the growing number of highly relevant, accounting for almost 20% of the variance surgical indications for patients with AAA and the increasing in this variable. However, this same effect accounted for only preference for EVAR vs OSR.11 slightly over 2% of the differences in in-hospital mortality. During the 11-year study period, the volume of elective In other words, the influence of hospital characteristics is AAA procedures conducted in Spanish public hospitals (not much greater on determining the type of surgical procedure including emergency procedures and cases with ruptured that is performed than on patients’ mortality. The median OR AAA) increased by 64%. While EVAR accounted for 38% of for the hospital effect on treatment selection was 2.4, with all AAA procedures performed during the study period, the an OR of 1.3 for immediate mortality. Overall, the capacity use of EVAR increased by 40% from 2002 to 2012, was 16% of the model to discriminate for mortality was good (AUC at the beginning of the period, and eventually accounted for =0.74); by contrast, the discriminatory capacity for treatment >56% of all surgical procedures for AAA in the year 2012. selection was poor (AUC=0.50), as shown in Table 4. Factors such as older age, more comorbidities, and elective admission all increased the likelihood that a patient would Discussion undergo EVAR rather than OSR. In general, EVAR was more The present study was carried out to analyze variation among common than OSR in higher-volume hospitals, although this Spanish hospitals in the choice of treatment – OSR or EVAR was highly variable, as some high-volume centers presented – for elective AAA surgery and to assess changes over time in a low EVAR to OSR ratio. This is an important finding, as it these preferences. Our findings showed that both the surgical indicates high inter-center variability in the selection of the approach and surgical volumes vary widely across Spanish surgical procedure. hospitals. During the study period, the overall number of Surgical volumes varied widely among the participating elective surgical procedures for AAA increased by 64%, hospitals, ranging from as low as only a single AAA surgery an annual increase of 5.8%, with EVAR ­accounting for a at one hospital to as many as 682 surgeries at the most active Table 4 Multilevel logistic regression analysis of surgery selection and in-hospital mortality in public hospitals in Spain, 2002–2012 Selection of EVAR In-hospital mortality Model 1 Model 2 Model 3 Model 1 Model 2 Model 3 Specific individual average effects Age (years) 1.90 (1.82–1.97) 1.93 (1.85–2.01) 1.89 (1.82–1.97) 1.58 (1.43–1.74) 1.58 (1.43–1.74) 1.58 (1.43–1.74) Female vs male 1.02 (0.84–1.23) 0.94 (0.77–1.15) 1.02 (0.84–1.24) 0.89 (0.55–1.44) 0.90 (0.55–1.46) 0.89 (0.55–1.44) Charlson Index 1.14 (1.10–1.18) 1.12 (1.08–1.16) 1.13 (1.10–1.18) 1.27 (1.19–1.37) 1.28 (1.20–1.37) 1.27 (1.19–1.37) EVAR vs OSR -------- -------- -------- 0.17 (0.13–0.22) 0.18 (0.14–0.22) 0.17 (0.14–0.22) Year 1.25 (1.23–1.26) 0.98 (0.95–1.01) Specific contextual average effects Volume of intervention 1.38 (1.14–1.67) 0.87 (0.79–0.97) General contextual effects ICC (%) 21.04 22.27 19.89 2.86 2.86 2.31 Median OR 2.44 2.56 2.37 1.35 1.35 1.30 AUC 0.51 (0.49–0.53) 0.48 (0.46–0.50) 0.51 (0.49–0.53) 0.74 (0.72–0.76) 0.74 (0.72–0.76) 0.74 (0.72–0.76) Goodness of fit DIC 19,649.96 18,361.55* 19,640.54 4,827.75 4,827.94 4,824.34* Notes: Values are given as OR with 95% CI, unless stated otherwise. The intercept is not shown in the table. *Significant change relative to model 1 (likelihood ratio: P<0.05). Abbreviations: AUC, area under the receiver operating characteristic curve; DIC, Bayesian deviance information criterion; EVAR, endovascular aneurysm repair; ICC, intraclass correlation coefficient; OSR, open surgical repair. Vascular Health and Risk Management 2019:15 submit your manuscript | www.dovepress.com 75 Dovepress Quintana et al Dovepress center. Similarly, preferences for EVAR vs OSR were also et al.23 That study analyzed data from vascular surgery records highly variable. EVAR accounted for anywhere from 0% to in eleven countries, finding that OSR-related mortality had 100% of all elective AAA surgeries, depending on the hospital. increased during the study period, whereas EVAR-related These heterogeneous findings are consistent with the results mortality rates had decreased. Although the reason for the of a large international study12 that found that the therapeutic differences between the two studies is not clear, perhaps these management of AAA varies widely from country to country contrasting findings could be explained (at least partially) and even across regions within the same country. Consistent by differences in the sources of information used (a large with our findings, that study showed wide variability between database from the Ministry of Health vs medical records) or hospitals in terms of both surgical volumes and in the propor- the criteria used to select the surgical technique. tion of patients undergoing EVAR. This wide variability is To better understand how temporal factors or surgical somewhat surprising, given the similarity of the clinical practice volumes influence treatment-related outcomes, we performed recommendations published by most professional societies.12 a multilevel analysis adjusted for patient characteristics. This Inter-center variability in the surgical approach (ie, EVAR analysis showed that the volume of surgical procedures at the vs OSR) is probably due to differences in selection criteria. treating center was independently associated with a prefer- It seems likely that the choice of technique could affect ence for EVAR. In other words, the greater the volume, the outcomes, primarily complication and mortality rates. The higher the probability of selecting EVAR. Higher surgical selection of one technique or another typically depends on volumes were also associated with lower in-hospital mortal- patient characteristics and on the anatomic characteristics ity rates: centers that performed more surgical procedures of the aneurysm itself; however, treatment selection also (EVAR or OSR) had lower in-hospital mortality rates. This depends on the treating center and on the surgeons’ expertise, association between a higher volume of AAA procedures which is why variability can be wide.22 and better treatment outcomes is consistent with previous The findings of the present study are consistent with reports.24,25 Both our findings and those of other studies show previous reports that have found EVAR to be associated with that immediate mortality rates are lower in higher volume lower in-hospital mortality rates than open surgery. Several hospitals, regardless of the specific surgical procedure. Some factors are associated with an increased risk of mortality, studies have even demonstrated a clear relationship between including age, female gender, presence of comorbidities, the number of surgeries performed by the surgeon and mor- and a low surgical volume at the treating center. The ATLAS tality rates, regardless of the specific number of surgeries VPM group conducted a study that was similar to the present performed annually at the center.12,22,24,25 study, but with fewer hospitals and patients and with a shorter It has long been known that centers with higher volumes follow-up.20 Not surprisingly – given that both studies were achieve better results overall, especially in complex, high- based on a similar data set – the demographic characteristics risk, and uncommon surgeries (particularly in cardiology and and distribution of the two types of surgery in that study were oncology).26 Mortality rates are lower and overall outcomes similar to our data. However, whereas we found that hospital are better in patients treated in-hospital with a large number volume independently (ie, regardless of the mix of surgical of patients with the same condition compared to those treated techniques) affected in-hospital mortality (adjusted by age, in less-experienced centers.27,28 In the context of surgical gender, and comorbidity), the ATLAS VPM study found that treatment of AAA, our findings – and those of other studies – lower mortality rates were mainly attributable to the use of support the implementation of policies to concentrate elective EVAR, and that this decrease was independent of age, comor- AAA surgical procedures at reference centers, which would bidities, or annual surgical volume at the treating center. ensure a higher volume of cases and better outcomes.24,29 We found that in-hospital mortality decreased over the 11-year study period, mainly attributable to the decrease Study strengths and limitations in mortality associated with OSR. These results probably An important limitation of the present study is that we were reflect improvements in the OSR technique or better patient unable to determine whether the selected procedure was selection. In terms of EVAR, we found a slight increase in appropriate for the patient based on clinical and anatomic mortality, perhaps due to the overuse of this technique related criteria. This determination was not possible because the data to the rapid and progressive expansion of the indications for set did not include the necessary information to assess this this procedure.1 Surprisingly, both of these findings contradict factor. Similarly, because the data set contained only data up to the results of an international study conducted by Budtz-Lilly hospital discharge, we were unable to perform any ­additional 76 submit your manuscript | www.dovepress.com Vascular Health and Risk Management 2019:15 Dovepress Dovepress Quintana et al follow-up analyses. In this regard, it would be valuable to 4. Multicentre Aneurysm Screening Study Group. Multicentre Aneurysm Screening study (MASS): cost effectiveness analysis of screening for perform a study in the future to determine the suitability of abdominal aortic aneurysms based on four year results from randomised the specific surgical technique used to treat patients with controlled trial. BMJ. 2002;325(7373):1135–1138. AAA. An important strength of this study is that the findings 5. Cosford PA, Leng GC. Screening for abdominal aortic aneurysm. Cochrane Database Syst Rev. 2007(2):CD002945. are based on consistent data from discharge data obtained 6. Svensjö S, Mani K, Björck M, Lundkvist J, Wanhainen A. Screening for from nearly all Spanish hospitals for a long period of time abdominal aortic aneurysm in 65-year-old men remains cost-effective with contemporary epidemiology and management. Eur J Vasc Endo- (11 years). Moreover, the study included >16,000 patients. vasc Surg. 2014;47(4):357–365. 7. Franks SC, Sutton AJ, Bown MJ, Sayers RD. Systematic review and Conclusion meta-analysis of 12 years of endovascular abdominal aortic aneurysm repair. Eur J Vasc Endovasc Surg. 2007;33(2):154–171. The present study shows that variability among Spanish 8. Blankensteijn JD, de Jong SECA, Prinssen M, et al; Dutch Randomized hospitals in terms of the surgical management of AAA Endovascular Aneurysm Management (DREAM) Trial Group. Two-year outcomes after conventional or endovascular repair of abdominal aortic repair is high. Surgical volumes and treatment selection are aneurysms. N Engl J Med. 2005;352(23):2398–2405. both highly variable among centers. The number of surgical 9. Drury D, Michaels JA, Jones L, Ayiku L. Systematic review of recent procedures to repair AAA increased substantially from 2002 evidence for the safety and efficacy of elective endovascular repair in the management of infrarenal abdominal aortic aneurysm. Br J Surg. to 2012, with EVAR comprising a growing proportion of all 2005;92(8):937–946. procedures. Overall in-hospital mortality decreased signifi- 10. Wendt K, Kristiansen R, Krohg-Sørensen K, Gregersen FA, Fosse E. Trends in abdominal aortic and iliac aneurysm repairs in Norway from cantly during this time period, mainly among patients treated 2001 to 2013. Eur J Vasc Endovasc Surg. 2016;51(2):194–201. with OSR. High-volume centers had better outcomes – both 11. Levin DC, Rao VM, Parker L, Frangos AJ, Sunshine JH. Endovascular for EVAR and OSR – with lower immediate mortality rates. repair vs open surgical repair of abdominal aortic aneurysms: comparative utilization trends from 2001 to 2006. J Am Coll Radiol. 2009;6(7):506–509. Ideally, controlled clinical trials should be conducted to 12. Schanzer A, Steppacher R, Eslami M, Arous E, Messina L, Belkin compare treatment outcomes achieved with new endovascular M. Vascular surgery training trends from 2001–2007: a substantial increase in total procedure volume is driven by escalating endovascu- devices vs those obtained with OSR. Data from such trials lar procedure volume and stable open procedure volume. J Vasc Surg. would be valuable to assess the suitability of concentrating 2009;49(5):1339–1344. elective AAA repair in more experienced centers to poten- 13. Beck AW, Sedrakyan A, Mao J, et al. Variations in abdominal aortic aneurysm care: a report from the International consortium of vascular tially achieve better outcomes. registries. Circulation. 2016;134(24):1948–1958. 14. Fitridge RA, Boult M, Mackillop C, et al. International trends in patient Data sharing statement selection for elective endovascular aneurysm repair: sicker patients with safer anatomy leading to improved 1-year survival. Ann Vasc Surg. Please contact the corresponding author. 2015;29(2):197–205. 15. Schermerhorn ML, Buck DB, O’Malley AJ, et al. Long-term outcomes of abdominal aortic aneurysm in the Medicare population. N Engl J Acknowledgments Med. 2015;373(4):328–338. The authors would like to thank Andrea Cervera Alepuz and 16. Zettervall SL, Buck DB, Soden PA, et al; Society for Vascular Sur- gery Vascular Quality Initiative. Regional variation exists in patient Bradley Londres for their help in editing the final version of selection and treatment of abdominal aortic aneurysms. J Vasc Surg. the manuscript. This work was supported by a grant from the 2016;64(4):921–927. Instituto de Salud Carlos III (PI12/02530). The authors would 17. Zettervall SL, Soden PA, Buck DB, et al; Dutch Randomized Endovascu- lar Aneurysm Management (DREAM) Trial Group. Significant regional also like to acknowledge the AAA Spanish Study Group. variation exists in morbidity and mortality after repair of abdominal aortic aneurysm. J Vasc Surg. 2017;65(5):1305–1312. Disclosure 18. Tambyraja AL, Rodriguez-Lopez JA, Ramaiah V, Diethrich EB, Chalmers RT. Institutional differences in endovascular aneurysm The authors report no conflicts of interest in this work. repair and aneurysm morphology. World J Surg. 2012;36(11): 2738–2741. 19. VPM Atlas [homepage on the Internet]. Project VPM Atlas Variations References in Medical Practice in the National Health System. Available from: 1. Healey CT, Neilson M, Clark D, Schanzer A, Robinson W; Vascular http://www.atlasvpm.org/home. Accessed October 18, 2018 Study Group of New England None. Predicting mortality of ruptured 20. 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Holt PJE, Poloniecki JD, Gerrard D, Loftus IM, Thompson MM. 29. Eckstein HH, Bruckner T, Heider P, et al. The relationship between Meta-analysis and systematic review of the relationship between vol- volume and outcome following elective open repair of abdominal aortic ume and outcome in abdominal aortic aneurysm surgery. Br J Surg. aneurysms (AAA) in 131 German hospitals. Eur J Vasc Endovasc Surg. 2007;94(4):395–403. 2007;34(3):260–266. 26. Pieper D, Mathes T, Neugebauer E, Eikermann M. State of evidence on the relationship between high-volume hospitals and outcomes in surgery: a systematic review of systematic reviews. J Am Coll Surg. 2013;216(5):e18:1015–1025. 78 submit your manuscript | www.dovepress.com Vascular Health and Risk Management 2019:15 Dovepress Dovepress Quintana et al Supplementary material of ­Epidemiology and Public Health (CIBERESP), Spain: Nieves Plana, Alfonso Muriel, Borja Castejón. Hospital La AAA Spanish Study Group members Fe, Valencia, Spain: Manuel Miralles, Laura Gálvez Núñez. Hospital de la Santa Creu i Sant Pau, IIB Sant Pau, Bar- University of Valencia, Valencia, Spain. CIBER of Epide- celona, Spain. CIBER of Epidemiology and Public Health miology and Public Health (CIBERESP), Spain: Maria M (CIBERESP), Spain. Iberoamerican Cochrane Center, Bar- Morales-Suárez-Varela. Hospital 12 de Octubre, Madrid, celona, Spain: Xavier Bonfill, M Jesús Quintana. Hospital Spain: Inés Fernández de Valderrama, Ana Isabel Rodríguez. de la Santa Creu i Sant Pau, IIB Sant Pau, Barcelona, Spain. Hospital 12 de Octubre, Madrid, Spain. CIBER of Epidemiol- CIBER of Cardiovascular Diseases (CIBERCV), Spain: José ogy and Public Health (CIBERESP), Spain: Agustín Gómez R Escudero. Vall d’Hebron University Hospital, Barcelona, de la Cámara. Hospital Cruces, Barakaldo, Spain. Biocruces Spain. Vall d’Hebron Research Institute (VHIR), Barcelona, Health Research Institute, Barakaldo, Spain. CIBER of Spain: Sergi Bellmunt. Hospital Ramón y Cajal, Madrid, Epidemiology and Public Health (CIBERESP), Spain: José Spain. Health Research Institute (IRYCIS), Spain. CIBER Ignacio Pijoan; Eduardo Pérez. Vascular Health and Risk Management Dovepress Publish your work in this journal Vascular Health and Risk Management is an international, peer- metabolic disorders, particularly diabetes. This journal is indexed on reviewed journal of therapeutics and risk management, focusing on PubMed Central and MedLine. The manuscript management system concise rapid reporting of clinical studies on the processes involved is completely online and includes a very quick and fair peer-review in the maintenance of vascular health; the monitoring, prevention and system, which is all easy to use. 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