Risk prediction for perioperative mortality of endovascular vs open repair of abdominal aortic aneurysms using the Medicare population

Abstract

INTRODUCTION AND OBJECTIVES The impact of risk factors upon perioperative mortality might differ for patients undergoing open versus endovascular repair (EVAR) of abdominal aortic aneurysms (AAA). In order to investigate this, we developed a differential predictive model of perioperative mortality after AAA repair. METHODS A total of 45,660 propensity score matched Medicare beneficiaries undergoing elective open or endovascular AAA repair from 2001–2004 were studied. Using half the dataset we developed a multiple logistic regression model for a matched cohort of open and EVAR patients and used this to derive an easily evaluable risk prediction score. The remainder of the dataset formed a validation cohort used to confirm results. RESULTS The derivation cohort included 11,415 open and 11,415 endovascular repairs. Perioperative mortality was 5.3% and 1.8% respectively. Independent predictors of mortality (RR, 95% CI) were open repair (3.2, 2.7–3.8), age (71–75 years 1.2, 0.9–1.6; 76–80 years 1.9, 1.4–2.5; >80 years 3.1, 2.4–4.2), female sex (1.5, 1.3–1.8), dialysis (2.6, 1.5–4.6), chronic renal insufficiency (2.0, 1.6–2.6), congestive heart failure (1.7, 1.5–2.1), and vascular disease (1.3, 1.2–1.6). There were no differential predictors of mortality across the two procedures. A simple scoring system was developed from a logistic regression model fit to both endovascular and open patients (area under the ROC curve of 72.6) from which low, medium, and high risk groups were developed. The absolute predicted mortality ranged from 0.7% for an EVAR patient ≤ 70 years of age with no comorbidities to 38% for an open patient > 80 with all the comorbidities considered. Although relative risk was similar among age groups, the absolute difference was greater for older patients (with higher baseline risk). CONCLUSIONS Mortality after AAA repair is predicted by comorbidities, sex, and age and these predictors have similar effects for both methods of AAA repair. This simple scoring system can predict repair mortality for both treatment options and thus may help guide clinical decisions.

Survival Following Endovascular Aneurysm Repair in the Octogenarian

“…This is in keeping with the findings reported in previous series and is considered to reflect the general level of co-morbidities and reduced physiological reserve [3,4]. Postoperative renal dysfunction is a significant complication following EVAR and represents the most common post-operative complication in patients under and over 80 years of age (8.4% vs 14.6%) [13,14].…”

“…Further investigations or pre-operative interventions were carried out as necessary. Fifty-eight percent of our octogenarian population survived beyond 5 years, which compares favourably with general life expectancy amongst the population in our region although it is notably less than the 64 -92% 5-year survival reported in other studies (3,4,11,12).…”

“…This poses a clinical dilemma to clinicians. On one hand, we recognize increasing age as an independent predictor of mortality, postoperative complications, and the need for discharge to an extended care facility for both treatment options of AAA, open and Endovascular Aneurysm Repair (EVAR) not to mention the limited potential in remaining life years [3,4]. On the other hand, current evidences through randomized controlled trials do suggest safe EVAR use in octogenarians [5][6][7][8].…”

Calculating when elective abdominal aortic aneurysm repair improves survival for individual patients: development of the Aneurysm Repair Decision Aid and economic evaluation

“…Other models assessed as part of this study include V-POSSUM which was developed using data from 1313 patients who had a range of arterial surgery, 110 the VBHOM which was derived from an earlier cohort of patients in the NVD 111 and the Medicare model which was developed on 45,660 patients who had elective AAA repair between 2001 to 2004 in the USA. 112 Both the V-POSSUM and VBHOM were previously validated. 109,113,114 In our validation, performed using 10,891 elective AAA repairs, the Medicare model was the only external model to demonstrate fair discrimination, with AUCs > 0.70; 54 the GAS, V-POSSUM and VBHOM were developed from elective and emergency data, and all achieved lower discrimination, with AUCs of 0.60-0.65, which is considered to be poor.…”

Mortality variability after endovascular versus open abdominal aortic aneurysm repair in a large tertiary vascular center using a Medicare-derived risk prediction model

“…Several algorithms to predict mortality have been developed in an attempt to risk-stratify patients considering surgical repair for AAA, including the Glasgow Aneurysm Score, Leiden Score, Society for Vascular Surgery/American Association for Vascular Surgery Comorbidity Scoring System, Hardman Index, Eagle Score, and Vascular Governance NorthWest model. [14][15][16][17][18][19][20] However, these models were developed based on data only from patients undergoing open AAA repair and have been shown to overpredict mortality in the EVAR population. 18,20 A more recent model proposed by Giles et al 15 used data from 45,660 Medicare beneficiaries to develop a scoring algorithm to predict perioperative (30-day) mortality after EVAR or open AAA repair.…”