Volume Standards for Open Abdominal Aortic Aneurysm Repair Are Not Associated With Improved Clinical Outcomes

A Patient-Centered Textbook Outcome Measure Effectively Discriminates Contemporary Elective Open Abdominal Aortic Aneurysm Repair Quality

INTRODUCTION

There is persistent controversy surrounding the merit of surgical volume benchmarks being used solely as a sufficient proxy for assessing the quality of open abdominal aortic aneurysm (AAA) repair. Importantly, operative volume quotas may fail to reflect a more nuanced and comprehensive depiction of surgical outcomes most relevant to patients. Accordingly, we herein propose a patient-centered "textbook outcome" (TO) for AAA repair that is analogous to other large magnitude extirpative operations performed in other surgical specialties, and test its feasibility to discriminate hospital performance using Society for Vascular Surgery (SVS) volume guidelines.

METHODS

All elective open infrarenal AAA repairs (OAR) in the SVS-Vascular Quality Initiative were examined (2009-2022). The primary end-point was a TO, defined as a composite of no in-hospital complication or re-intervention/re-operation, length of stay ≤ 10-days, home discharge and 1-year survival. The discriminatory ability of the TO measure was assessed by comparing centers that did or did not meet the SVS annual OAR volume threshold recommendation (high-volume ≥ 10 OARs/year; low-volume <10 OARs/year). Logistic regression and multivariable models adjusted for patient and procedure-related differences.

RESULTS

A total of 9,657 OARs across 198 centers were analyzed (mean age-69.5±8.4, female-26%, non-white-12%). A TO was identified in 44% (N = 4,293) of the overall cohort. The incidence of individual TO components included: no in-hospital complication (61%), no in-hospital re-intervention/re-operation (92%), LOS ≤ 10-days (78%), home discharge (76%), and 1-year survival (91%). Median annual center volume was 6 [IQR 3, 10] and a majority of centers did not meet the SVS volume suggested threshold (<10 OARs/year: N = 148 [74%]). However, most patients (N = 6,265 of 9,657 [65%]) underwent OAR in high-volume hospitals. When comparing high and low-volume centers, a TO was more likely to occur in high-volume institutions: ≥10 OARs/year, 46% vs. <10 OARs/year, 42%; P=.0006. The association of a protective effect for higher center volume remained after risk adjustment: OR 1.1, 95%CI 1.05-1.26; P=.003.

CONCLUSIONS

Textbook outcomes for elective OAR reflect a more nuanced and comprehensive patient centered proxy to measure care delivery consistent with other surgical specialties. Surprisingly, a TO was achieved in < 50% of elective AAA cases nationally. Though the likelihood of a TO appears to correlate with SVS center volume recommendations, it more importantly reflects elements which may be prioritized by patients and thus offers insights into further improving real-world AAA care.

2023 Update on Vascular Anesthesia

The authors thank thank the editors for this opportunity to review the recent literature on vascular surgery and anesthesia and provide this clinical update. The last in a series of updates on this topic was published in 2019.1 This review explores evolving discussions and current trends related to vascular surgery and anesthesia that have been published since then. The focus is on the major points discussed in the recent literature in the following areas: carotid artery surgery, infrarenal aortic surgery, peripheral vascular surgery, and the preoperative evaluation of vascular surgical patients.

Low-Volume Elective Surgery and Outcomes in Medicare Beneficiaries Treated at Hospital Networks

Importance

Minimum volume standards have been advocated as a strategy to improve outcomes for certain surgical procedures. Hospital networks could avoid low-volume surgery by consolidating cases within network hospitals that meet volume standards, thus optimizing outcomes while retaining cases and revenue. The rates of compliance with volume standards among hospital networks and the association of volume standards with outcomes at these hospitals remain unknown.

Objective

To quantify low-volume surgery and associated outcomes within hospital networks.

Design, Setting, and Participants

This cross-sectional study used Medicare Provider Analysis and Review data to examine fee-for-service beneficiaries aged 66 to 99 years who underwent 1 of 10 elective surgical procedures (abdominal aortic aneurysm repair, carotid endarterectomy, mitral valve repair, hip or knee replacement, bariatric surgery, or resection for lung, esophageal, pancreatic, or rectal cancers) in a network hospital from 2016 to 2018. Hospital volume for each procedure (calculated with the use of the National Inpatient Sample) was compared with yearly hospital volume standards for that procedure recommended by The Leapfrog Group. Networks were then categorized into 4 groups according to whether or not that hospital or another hospital in the network met low-volume standards for that procedure. Data were analyzed from February to June 2023.

Exposure

Receipt of surgery in a low-volume hospital within a network.

Main Outcomes and Measures

Primary outcomes were postoperative complications, 30-day readmission, and 30-day mortality, stratified by the volume status of the hospital and network type. The secondary outcome was the availability of a different high-volume hospital within the same network or outside the network and its proximity to the patient (based on hospital referral region and zip code).

Results

In all, data were analyzed for 950 079 Medicare fee-for-service beneficiaries (mean [SD] age, 74.4 [6.5] years; 621 138 females [59.2%] and 427 931 males [40.8%]) who underwent 1 049 069 procedures at 2469 hospitals within 382 networks. Of these networks, 380 (99.5%) had at least 1 low-volume hospital performing the elective procedure of interest. In 35 137 of 44 011 procedures (79.8%) that were performed at low-volume hospitals, there was a hospital that met volume standards within the same network and hospital referral region located a median (IQR) distance of 29 (12-60) miles from the patient's home. Across hospital networks, there was 43-fold variation in rates of low-volume surgery among the procedures studied (from 1.5% of carotid endarterectomies to 65.0% of esophagectomies). In adjusted analyses, postoperative outcomes were inferior at low-volume hospitals compared with hospitals meeting volume standards, with a 30-day mortality of 8.1% at low-volume hospitals vs 5.5% at hospitals that met volume standards (adjusted odds ratio, 0.67 [95% CI, 0.61-0.73]; P < .001).

Conclusions and Relevance

Findings of this study suggest that most US hospital networks had hospitals performing low-volume surgery that is associated with inferior surgical outcomes despite availability of a different in-network hospital that met volume standards within a median of 29 miles for the vast majority of patients. Strategies are needed to help patients access high-quality care within their networks, including avoidance of elective surgery at low-volume hospitals. Avoidance of low-volume surgery could be considered a process measure that reflects attention to quality within hospital networks.

Decreasing prevalence of centers meeting the Society for Vascular Surgery abdominal aortic aneurysm guidelines in the United States

OBJECTIVE

Based on data supporting a volume-outcome relationship in elective aortic aneurysm repair, the Society of Vascular Surgery (SVS) guidelines recommend that endovascular aortic repair (EVAR) be localized to centers that perform ≥10 operations annually and have a perioperative mortality and conversion-to-open rate of ≤2% and that open aortic repair (OAR) be localized to centers that perform ≥10 open aortic operations annually and have a perioperative mortality ≤5%. However, the number and distribution of centers meeting the SVS criteria remains unclear. This study aimed to estimate the temporal trends and geographic distribution of Centers Meeting the SVS Aortic Guidelines (CMAG) in the United States.

METHODS

The SVS Vascular Quality Initiative was queried for all OAR, aortic bypasses, and EVAR from 2011 to 2019. Annual OAR and EVAR volume, 30-day elective operative mortality for OAR or EVAR, and EVAR conversion-to-open rate for all centers were calculated. The SVS guidelines for OAR and EVAR, individually and combined, were applied to each institution leading to a CMAG designation. The proportion of CMAGs by region (West, Midwest, South, and Northeast) were compared by year using a χ2 test. Temporal trends were estimated using a multivariable logistic regression for CMAG, adjusting by region.

RESULTS

Overall, 67,865 patients (49,264 EVAR; 11,010 OAR; 7591 aortic bypasses) at 336 institutions were examined. The proportion of EVAR CMAGs increased nationally by 1.7% annually from 51.6% (n = 33/64) in 2011 to 67.1% (n = 190/283) in 2019 (β = .05; 95% confidence interval [CI], 0.01-0.09; P = .02). The proportion of EVAR CMAGs across regions ranged from 27.3% to 66.7% in 2011 to 63.9% to 72.9% in 2019. In contrast, the proportion of OAR CMAGs has decreased nationally by 1.8% annually from 32.8% (n = 21/64) in 2011 to 16.3% (n = 46/283) in 2019 (β = -.14; 95% CI, -0.19 to -0.10; P < .01). Combined EVAR and OAR CMAGs were even less frequent and decreased by 1.5% annually from 26.6% (n = 17/64) in 2011 to 13.1% (n = 37/283) in 2019 (β = -.12; 95% CI, -0.17 to -0.07; P < .01). In 2019, there was no significant difference in regional variation of the proportion of combined EVAR and OAR CMAGs (P = .82).

CONCLUSIONS

Although an increasing proportion of institutions nationally meet the SVS guidelines for EVAR, a smaller proportion meet them for OAR, with a concerning downward trend. These data question whether we can safely offer OAR at most institutions, have important implications about sufficient OAR exposure for trainees, and support regionalization of OAR.

Reliability of hospital-level mortality in abdominal aortic aneurysm repair

OBJECTIVE

The relationship between volume and surgical outcomes has been shown for a variety of surgical procedures. The effects in abdominal aortic aneurysm repair have continued to be debated. Reliability adjustment has been used as a method to remove statistical noise from hospital-level outcomes. However, its impact on aortic aneurysm repair is not well understood.

METHODS

We used prospectively collected data from the Vascular Quality Initiative to identify all patients who had undergone abdominal aortic aneurysm repair from 2003 to 2019. We first calculated the hospital-level risk-adjusted 30-day mortality rates. We subsequently used hierarchical logistic regression modeling to adjust for measurement reliability using empirical Bayes techniques. The effect of volume on risk- and reliability-adjusted mortality rates was then assessed using linear regression.

RESULTS

Between 2003 and 2019, 67,073 abdominal aortic aneurysms were repaired, of which 11,601 (17.3%) were repaired with an open approach. The median annual volume was 7.4 (interquartile range, 3.0-13.3) for open repairs and 35.4 (interquartile range, 18.8-59.8) for endovascular repairs. Of the 223 hospitals that had performed open repairs during the study period, only 11 (4.9%) had performed ≥15 open repairs annually, and the risk-adjusted mortality rates varied from 0% to 75% across all centers. After reliability adjustment, the variability of the risk-adjusted mortality rates had decreased significantly to 1.3% to 8.2%. The endovascular repair risk-adjusted mortality rate variability had decreased from 0% to 14.3% to 0.3% to 2.8% after reliability adjustment. A decreasing trend in mortality was found with increasing an annual case volume for open repair with each additional annual case associated with a 0.012% decrease in mortality (P = .05); however, the relationship was not significant for endovascular repair (P = .793).

CONCLUSIONS

We found that most hospitals do not perform a sufficient number of annual cases to generate a reliable center-specific mortality rate for open aneurysm repair. Center-specific mortality rates for low-volume centers should be viewed with caution, because a substantial proportion of the variation for these outcomes will be statistical noise rather than true center-level differences in the quality of care.

Surgeon experience versus volume differentially affects lower extremity bypass outcomes in contemporary practice

BACKGROUND

Calls for minimum case thresholds to guide surgeon credentialing paradigms are increasing in contemporary practice. To date, the volume-outcome relationship and the role of surgeon experience as a proxy for quality have remained primarily focused on nonvascular extirpative surgery and aneurysm repair. However, it is unclear whether these data can be rightly extrapolated to predict lower extremity bypass (LEB) outcomes. Thus, the purpose of the present study was to examine whether the annualized case volume vs surgeon experience is more consequential in predicting for successful LEB reconstruction.

METHODS

A total of 25,852 procedures with sufficient 1-year follow-up data from the Society for Vascular Surgery Vascular Quality Initiative infrainguinal bypass registry (2003-2019) were reviewed for chronic limb threatening ischemia among patients undergoing infrageniculate reconstruction. The procedures were categorized according to surgeon years of practice experience at surgery (ie, 0-5, 6-10, 11-15, >15 years) and the number of LEB procedures performed by the surgeon during the year of surgery (volume quartiles: 1-8, 9-14, 15-21, and >21). Mixed effects logistic and Cox regression models were used to assess the effects of experience, volume, and their interaction on outcomes.

RESULTS

Increasing practice experience was more significantly associated with a reduction of in-hospital complications (odds ratio, 0.97; 95% confidence interval [CI], 0.96-0.99; P = .002) and the risk of major adverse limb events (odds ratio, 0.94; 95% CI, 0.92-0.97; P < .0001) compared with the volume. Increasing experience and volume were both associated with increased freedom from thrombosis (hazard ratio, 0.95; 95% CI, 0.93-0.98; P = .001). In contrast, neither experience nor volume had any significant association with early mortality. However, a higher volume was associated with diminished long-term survival (hazard ratio, 1.04; 95% CI, 1.0-1.1; P = .01). The most experienced surgeons (>15 years' experience) were significantly more likely to perform LEB for rest pain (P < .0001). No significant differences were found in the bypass rates among patients with tissue loss. The most experienced and highest volume surgeons were more likely to use an autogenous and/or composite conduit, in situ reconstruction, and/or pedal targets (P < .05). Similarly, more experienced and higher volume surgeons had less blood loss and shorter procedure times (P < .0001). Overall, the most experienced surgeons (>15 years' experience) were significantly more likely to have a higher volume with a diminished risk for all LEB outcomes.

CONCLUSIONS

Surgeon experience appears to have the most important role in predicting for overall LEB performance with improved in-hospital outcomes and major adverse limb events. The more experienced surgeons performed more complex reconstructions with fewer complications. These findings have significant clinical and educational implications as our most experienced surgeons approach retirement. Mentorship strategies to facilitate ongoing technical development among less experienced surgeons are imperative to sustain optimal limb salvage outcomes and have significant ramifications regarding expectations for regulatory and credentialing paradigms.

Editor's Choice - Optimal Threshold for the Volume-Outcome Relationship After Open AAA Repair in the Endovascular Era: Analysis of the International Consortium of Vascular Registries

OBJECTIVE

As open abdominal aortic aneurysm (AAA) repair (OAR) rates decline in the endovascular era, the endorsement of minimum volume thresholds for OAR is increasingly controversial, as this may affect credentialing and training. The purpose of this analysis was to identify an optimal centre volume threshold that is associated with the most significant mortality reduction after OAR, and to determine how this reflects contemporary practice.

METHODS

This was an observational study of OARs performed in 11 countries (2010 - 2016) within the International Consortium of Vascular Registry database (n = 178 302). The primary endpoint was post-operative in hospital mortality. Two different methodologies (area under the receiving operating curve optimisation and Markov chain Monte Carlo procedure) were used to determine the optimal centre volume threshold associated with the most significant mortality improvement.

RESULTS

In total, 154 912 (86.9%) intact and 23 390 (13.1%) ruptured AAAs were analysed. The majority (63.1%; n = 112 557) underwent endovascular repair (EVAR) (OAR 36.9%; n = 65 745). A significant inverse relationship between increasing centre volume and lower peri-operative mortality after intact and ruptured OAR was evident (p < .001) but not with EVAR. An annual centre volume of between 13 and 16 procedures per year was associated with the most significant mortality reduction after intact OAR (adjusted predicted mortality < 13 procedures/year 4.6% [95% confidence interval 4.0% - 5.2%] vs. ≥ 13 procedures/year 3.1% [95% CI 2.8% - 3.5%]). With the increasing adoption of EVAR, the mean number of OARs per centre (intact + ruptured) decreased significantly (2010 - 2013 = 35.7; 2014 - 2016 = 29.8; p < .001). Only 23% of centres (n = 240/1 065) met the ≥ 13 procedures/year volume threshold, with significant variation between nations (Germany 11%; Denmark 100%).

CONCLUSION

An annual centre volume of 13 - 16 OARs per year is the optimal threshold associated with the greatest mortality risk reduction after treatment of intact AAA. However, in the current endovascular era, achieving this threshold requires significant re-organisation of OAR practice delivery in many countries, and would affect provision of non-elective aortic services. Low volume centres continuing to offer OAR should aim to achieve mortality results equivalent to the high volume institution benchmark, using validated data from quality registries to track outcomes.

Impact of Institutional Volume on Critical In-Hospital Complications Adjusted for Patient- and Limb-Related Characteristics: An Analysis of a Nationwide Japanese Registry of Endovascular Interventions for PAD

PURPOSE

To investigate the incidence and clinical predictors, including institutional annual case volume, of critical in-hospital complications after endovascular therapy (EVT) for peripheral artery disease (PAD).

MATERIALS AND METHODS

The data were extracted from the nationwide registry of peripheral interventions in Japan [Japanese EVT (J-EVT)] between 2012 and 2017. A total of 92,224 EVT cases either for chronic limb-threatening ischemia (CLTI) or intermittent claudication were included in the analysis. The primary outcome measure was critical in-hospital complications, which were defined as a composite of urgent surgery and in-hospital death within 30 days after EVT. The institutional volume was classified into quartiles. The association of institutional volume, as well as baseline characteristics, with the critical in-hospital complications was explored using a multivariable logistic regression model with multiple imputation for missing data. Results are presented as the adjusted odds ratio (OR) with the 95% confidence intervals (CI).

RESULTS

The estimated prevalence of critical in-hospital complications was 0.3% (95% CI 0.3% to 0.4%). The following 10 patient- and limb-related characteristics were identified as independent risk factors for critical in-hospital complications: (1) female sex (OR 1.75, 95% CI 1.36 to 2.25), (2) age ≥75 years (OR 1.60, 95% CI 1.06 to 2.40), (3) CLTI (OR 2.12, 95% CI 1.47 to 3.05), (4) nonambulatory status (OR 1.66, 95% CI 1.23 to 2.24), (5) regular dialysis (OR 1.35, 95% CI 1.02 to 1.77), (6) cerebrovascular disease (OR 1.76, 95% CI 1.33 to 2.33), (7) urgent revascularization (OR 5.10, 95% CI 3.64 to 7.13), (8) aortoiliac TASC II D lesion (OR 3.65, 95% CI 2.51 to 5.33), (9) femoropopliteal TASC II D lesion (OR 1.77, 95% CI 1.24 to 2.52), and (10) infrapopliteal TASC D lesion (OR 1.52, 95% CI 1.08 to 2.13). In addition, the 4th quartile of the institutional volume (≥158 cases/year), but not the 2nd or 3rd quartile, had a significantly and independently lower risk of critical in-hospital complications than the 1st quartile (OR 0.13, 95% CI 0.07 to 0.23).

CONCLUSION

After EVT for symptomatic PAD, 0.3% of the population encountered critical in-hospital complications. A higher institutional volume was significantly associated with a lower risk of critical in-hospital complications.