Comparison of three contemporary risk scores for mortality following elective abdominal aortic aneurysm repair

Preoperative and ICU Scoring Models for Predicting the In-Hospital Mortality of Patients With Ruptured Abdominal Aortic Aneurysms

OBJECTIVES

This study's objective was to compare several preoperative and intensive care unit (ICU) prognostic scoring systems for predicting the in-hospital mortality of ruptured abdominal aortic aneurysms (RAAAs).

DESIGN

Retrospective cohort study.

SETTING

Single tertiary university center.

PARTICIPANTS

The study comprised 157 patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 157 patients (82% male) presented with RAAA at Charité University Hospital from January 2011 to December 2020. The mean age was 74 years (standard deviation ten years). In-hospital mortality was 29% (n = 45), of whom nine patients (6%) died en route to the operating room, 13 (8%) on the operating table, and 23 (15%) in the ICU. A total of 135 patients (86%) were admitted to the ICU. All six models demonstrated good discriminating performance between survivors and nonsurvivors. Overall, the area under the curve (AUC) for RAAA preoperative scores was greater than those for ICU scores. The largest AUC was achieved with the Vascular Study Group of New England (VSGNE) RAAA risk score (AUC = 0.87 for all patients, AUC = 0.84 for patients admitted to the ICU), followed by Hardman Index (AUC = 0.83 for all patients, AUC = 0.81 for patients admitted to the ICU), and Glasgow Aneurysm Score (AUC = 0.74 for all patients, AUC = 0.83 for patients admitted to the ICU). The largest AUC for ICU scores (only patients admitted to the ICU) was achieved with Simplified Acute Physiology Score II (0.75), followed by Sepsis-related Organ Failure Assessment (0.73), and Acute Physiology and Chronic Health Evaluation II (0.71).

CONCLUSIONS

Preoperative and ICU scores can predict the mortality of patients presenting with RAAA. In addition, the discriminatory ability of preoperative scores between survivors and nonsurvivors was larger than that for ICU scores.

The fate of patients with large abdominal aortic aneurysms referred for consideration for elective repair

BACKGROUND

The premise of the Vascular Services Quality Improvement Programme (VSQIP) in management of patients with asymptomatic large abdominal aortic aneurysms (AAA) is reducing mortality from ruptured AAA in a sustainable way without introducing excessive procedure related mortality. Inevitably a proportion of patients are deemed unfit for elective repair. The aim of this study was to report outcomes of patients who were referred with large asymptomatic AAAs including those turned down for elective repair and identify independent risk factors for being turned down for elective open or endovascular repair of AAA.

METHODS

Consecutive patients referred to a regional vascular center with a large AAA (greater than 55 mm) between 1^st January 2008 and 31^st March 2018 were included. All patients underwent the nationally agreed VSQIP pathway which included preoperative cardio-pulmonary exercise testing and contrast enhanced CT scan of aorta. The decision to repair and the modality of repair were made through a Multi-Disciplinary Team MDT process on each patient. Patients were classified into two groups; those managed non-operatively and those offered elective repair. Survival was assessed using Kaplan-Meier analysis. Factors associated with non-operative management were examined using multivariate analysis.

RESULTS

A total of 876 patients of whom 768 were men and 108 were women with a mean age of 74 years (SD: 7.2) and a diagnosis of a large asymptomatic AAA were assessed. One hundred and seventy-four patients (19.9%) were turned down for elective repair and 702 (80.1%) underwent repair [Open: 244(34.8%), EVAR: 458 (65.2%] with perioperative and 30 day mortality of 1.13% (8 patients). Median duration of follow-up was 1530 days (51 months), (inter quartile range: 1714 days). Patients who underwent repair had significantly higher survival rates compared with those who were turned down (P<0.0001). Risk factors for being turned down for elective AAA included anaerobic threshold <8 mL kg^-1 min^-1 [OR: (95% CI): 2.27 (1.31-3.92)], (P=0.0005), Age>80 yrs. [OR (95% CI): 1.32 (1.012-1.52], (P=0.0203), complex aneurysm morphology [OR (95% CI): 3.70 (2.82-4.87], (P<0.0001), Female gender: [OR: (95% CI): 2.41 (1.32-3.92)], (P<0.0001) and being classed high or very high risk for open AAA repair OR: (95% CI): 6.48 (4.01-10.49)], (P<0.0001).

CONCLUSIONS

A significant cohort of patients with large asymptomatic AAA is turned down for elective AAA repair. These patients appear to have significantly lower survival rates than those who are treated. Information on patients turned down for elective AAA repair should be routinely reported.

[The DIGG risk score : A risk predictive model of perioperative mortality after elective treatment of intact abdominal aortic aneurysms in the DIGG register]

OBJECTIVE

The aim of the study was to develop a specific risk score for the aortic register of the German Institute for Vascular Health Care Research (DIGG) of the German Society for Vascular Surgery and Vascular Medicine (DGG) for the prediction of postoperative mortality in elective treatment of intact abdominal aortic aneurysms (iAAA). The score should also enable a risk-adjusted presentation of the register results in the near future.

METHODS

The method of binary logistic regression analysis was used to calculate the model. The data from 10,404 patients were included in the analysis, of whom 7870 (75.6%) were treated by endovascular (EVAR) and 2534 (24.4%) by open (OR) aortic repair. It was examined which factors have an independent influence on hospital mortality and the effect size was determined as a score.

RESULTS

For EVAR, the influencing factors with their effect sizes (score in brackets) were: age >85 years (2), female gender (2), juxtarenal AAA (5), maximum diameter >65 mm (2), diabetes mellitus (2), American Society of Anesthesiologists (ASA) score >3 (2), cardiac comorbidities (3) and renal insufficiency stage >3 (5). For OR the factors were: age >80 years (2), female gender (2), juxtarenal AAA (2), ASA score >3 (3), previous myocardial infarction (2), renal comorbidities (3) and previous stroke (2). The estimated hospital mortality was calculated for the individual case from the sum of the risk factors (scores). The accuracy of the model (correlation between observed and expected results) was determined using the receiver operating characteristic (ROC) curve. An area under the curve (AUC) of 0.817 (confidence interval 0.789-0.844) demonstrated an excellent discrimination. In a validation group of 3831 patients, the good agreement between observed and calculated results was confirmed.

CONCLUSION

The DIGG risk score can predict risk-adjusted hospital mortality after EVAR and OR of iAAA in the DIGG register. Improvements with respect to the prediction are desirable for OR and should be strived for by extending the model in the future.

Outcome after Turndown for Elective Abdominal Aortic Aneurysm Surgery

OBJECTIVES

The aim was to assess the survival of patients who had been turned down for repair of an abdominal aortic aneurysm (AAA) and to examine the factors influencing this.

METHODS

This was a retrospective observational study of a prospectively maintained database of all patients turned down for AAA intervention by the Black Country Vascular Network multidisciplinary team (MDT) from January 2013 to December 2015. Data on AAA size, cardiopulmonary exercise testing (CPET) and cause of death were recorded.

RESULTS

There were 112 patients. The median age at turndown was 83.9 years (IQR 10.2 years). The median AAA size at turndown was 63 mm (IQR 16.7 mm). The median follow-up time after turndown was 324 days (IQR 537.5 days). Sixty-four patients (57.1%) were deceased after 2 years, with a median survival time of 462 days (IQR 579 days). Patients who died had a significantly larger AAA dimension (median 65 mm, IQR 18.5 mm) than those surviving to date (median 59 mm, IQR 10 mm, p = .004). Using Cox regression analysis, the probability of 1 year survival in the whole population was 0.614. The probability of 2 year survival was 0.388. When accounting for age, gender, AAA dimension, and British Aneurysm Repair risk score, no factors had significant influence over survival. Of the 64 deceased patients, 30 had an accessible cause of death: 36.7% of these were due to ruptured AAAs. There was no significant difference in AAA size between those dying of ruptures and those dying of other causes (p = .225, mean 74 mm and 67 mm respectively).

CONCLUSIONS

Being turned down for AAA repair carries a significant short-term risk of mortality. Those turned down for repair carried significant levels of comorbid disease but no factors considered were found to be independently predictive of the length of survival.

Systematic review of mortality risk prediction models in the era of endovascular abdominal aortic aneurysm surgery

BACKGROUND

The introduction of endovascular aneurysm repair (EVAR) has reduced perioperative mortality after abdominal aortic aneurysm (AAA) surgery. The objective of this systematic review was to assess existing mortality risk prediction models, and identify which are most useful for patients undergoing AAA repair by either EVAR or open surgical repair.

METHODS

A systematic search of the literature was conducted for perioperative mortality risk prediction models for patients with AAA published since 2006. PRISMA guidelines were used; quality was appraised, and data were extracted and interpreted following the CHARMS guidelines.

RESULTS

Some 3903 studies were identified, of which 27 were selected. A total of 13 risk prediction models have been developed and directly validated. Most models were based on a UK or US population. The best performing models regarding both applicability and discrimination were the perioperative British Aneurysm Repair score (C-statistic 0·83) and the preoperative Vascular Biochemistry and Haematology Outcome Model (C-statistic 0·85), but both lacked substantial external validation.

CONCLUSION

Mortality risk prediction in AAA surgery has been modelled extensively, but many of these models are weak methodologically and have highly variable performance across different populations. New models are unlikely to be helpful; instead case-mix correction should be modelled and adapted to the population of interest using the relevant mortality predictors.

Development and External Validation of a Model Predicting Death After Surgery in Patients With a Ruptured Abdominal Aortic Aneurysm: The Dutch Aneurysm Score

OBJECTIVE

The decision whether or not to proceed with surgical intervention of a patient with a ruptured abdominal aortic aneurysm (rAAA) is very difficult in daily practice. The primary objective of the present study was to develop and to externally validate a new prediction model: the Dutch Aneurysm Score (DAS).

METHODS

With a prospective cohort of 10 hospitals (n = 508) the DAS was developed using a multivariate logistic regression model. Two retrospective cohorts with rAAA patients from two hospitals (n = 373) were used for external validation. The primary outcome was the combined 30 day and in-hospital death rate. Discrimination (AUC), calibration plots, and the ability to identify high risk patients were compared with the more commonly used Glasgow Aneurysm Score (GAS).

RESULTS

After multivariate logistic regression, four pre-operative variables were identified: age, lowest in hospital systolic blood pressure, cardiopulmonary resuscitation, and haemoglobin level. The area under the receiver operating curve (AUC) for the DAS was 0.77 (95% CI 0.72-0.82) compared with the GAS with an AUC of 0.72 (95% CI 0.67-0.77). The DAS showed a death rate in patients with a predicted death rate ≥80% of 83%.

CONCLUSIONS

The present study shows that the DAS has a higher discriminative performance (AUC) compared with the GAS. All clinical variables used for the DAS are easy to obtain. Identification of low risk patients with the DAS can potentially reduce turndown rates. The DAS can reliably be used by clinicians to make a more informed decision in dialogue with the patient and their family whether or not to proceed with surgical intervention.

The Concept of Risk Assessment and Being Unfit for Surgery

The concept of risk assessment and the identification of surgical unfitness for vascular intervention is a particularly controversial issue today as the minimally invasive surgical population has increased not only in volume but also in complexity (comorbidity profile) and age, requiring an improved pre-operative selection and definition of high risk. A practical step by step (three steps, two points for each) approach for surgical risk assessment is suggested in this review. As a general rule, the identification of a "high risk" patient for vascular surgery follows a step by step process where the risk is clearly defined, quantified (when too "high"?), and thereby stratified based on the procedure, the patient, and the hospital, with the aid of predictive risk scores. However, there is no standardized, updated, and objective definition for surgical unfitness today. The major gap in the current literature on the definition of high risk in vascular patients explains the lack of sound validated predictive systems and limited generalizability of risk scores in vascular surgery. In addition, the concept of fitness is an evolving tool and many traditional high risk criteria and definitions are no longer valid. Given the preventive purpose of most vascular procedures performed in elderly asymptomatic patients, the decision to pursue or withhold surgery requires realistic estimates not only regarding individual peri-operative mortality, but also life expectancy, healthcare priorities, and the patient's primary goals, such as prolongation of life versus maintenance of independence or symptom relief. The overall "frailty" and geriatric risk burden, such as cognitive, functional, social, and nutritional status, are variables that should be also included in the analyses for stratification of surgical risk in elderly vascular patients.