Anatomical severity score helps evaluate EVAR cost and use of adjunctive techniques

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A study utilising preoperative anatomical severity grading in patients undergoing abdominal aortic aneurysm repair has shown that high scores correlate with increased total cost and resource utilisation and the need for adjunctive procedures during endovascular aneurysm repair (EVAR). Because of these adjunctive techniques, the cost of EVAR was US$9,100 higher than open repair in patients with complex anatomies.

Currently over 70% of elective abdominal aortic aneurysms are treated with EVAR. However, EVAR is associated with increased rate of graft-related complications and endoleaks and late reinterventions. Complications and endoleaks can reach over 15% perioperatively and up to 38% at four years, whilst historical data demonstrates that long-term graft-related complications with open repair range between 2% and 4%, Khurram Rasheed, Division of Vascular Surgery, University of Rochester, Rochester, NY, USA, said at the Vascular Annual Meeting (17–20 June, Chicago, USA). “The potential cost-effectiveness of EVAR, compared with open repair, is offset by the use of intraoperative adjuncts and reinterventions,” he said.

In 2002, the Committee for Standardising Reporting Practice of the Society for Vascular Surgery defined and categorised the severity of anatomical factors for infrarenal abdominal aortic aneurysms. This grading scheme, the Anatomic Severity Grading (ASG), allows for preoperative assessment of aortic aneurysms and provides a quantitative and reproducible measure of anatomical complexity. The ASG is divided into three components: aortic neck, aortic aneurysm and iliac artery. It deals with parameters such as length, diameter, angle and presence of calcification and thrombus, and tortuosity. In total 16 parameters can be graded from zero (absent) to three (severe).

The purpose of the study presented from the University of Rochester was to determine if ASG was directly related to the use of intraoperative adjuncts and increased cost of aortic repair.

The investigators conducted a single institution retrospective review of elective open and endovascular abdominal aortic aneurysm repairs performed between 2007 and 2010. ASG scores were calculated manually by two blinded reviewers using three-dimensional reconstruction with 3D aortic reconstruction software. The variables collected included demographics, comorbidities, medical management, outcomes and cost.

The study population consisted of 140 patients (33 open repairs and 107 EVARs), the mean age was 81.2±9.7 years and 17.5% of the patients were women. Patients had a high incidence of smoking and hypertension and the medications most of the population was on at the time of the repair included betablockers (76.6%), aspirin (81.7%) and statins (76.6%).

The results showed that total cost and length of stay were significantly higher in the open repair cohort. The mean total cost was US$38,310±49,302 for open repair and US$24,701±13,012 (p=0.016), and the length of stay was 13.5±14.2 days for open repair and 3±4.4 days for EVAR (p=0.012). The ASG score also was greater in the open repair group (18.1±3.8 vs.  15.9±4.1, p=0.010). This was attributable to a more complex aortic neck anatomy (4.4±1.8 vs. 2.5±1.9, p=0.009).

Rasheed commented: “We did, however, notice that open repair cost was higher and this was contrary to what has been reported in the literature previously. This was driven by five patients in the open repair cohort who had lengths of stay that made them significant outliers and contributed to the cost. When adjusting for those outliers the total cost was lower than EVAR but the total ASG score and length of stay did not significantly change.”

In patients undergoing EVAR, 25.2% required intraoperative adjuncts (this was 6% in the open repair group). Adjuncts included proximal aortic cuff, branch vessel embolisation, distal limb extension, management of endoleak, repositioning of the graft, renal artery stenting, iliac artery angioplasty/stenting, endarterectomy of femoral/iliac artery and use of intravascular ultrasound.

An analysis of EVAR patients receiving adjunctive therapies revealed a mean total cost of US$31,509±15,996 and an ASG score of 18.5±3.7, which were statistically significant compared with cases without adjunctive procedures (p=0.009 and p<0.001, respectively). The anatomical difference was mainly attributable to aortic neck and iliac artery anatomy.

The investigators then sought to evaluate if ASG scores could be employed to predict the use of intraoperative adjuncts and found out that an ASG score of ≥15 was associated with an increased propensity for requiring intraoperative adjuncts (odds ratio, 5.75; confidence interval, 1.82–18.19). They then divided the entire cohort into two groups: those with ASG 15.

“We noted that within the EVAR group an ASG score of >15 was significantly associated with the use of adjuncts (p=0.003) and total cost (p=0.04). In the open repair group, the total cost was higher as was length of stay but this did not reach statistical significance. In addition, a multivariate analysis showed that ASG >15 was associated with chronic kidney disease (p=0.001), end-stage renal disease (p<0.001) and hypertension (p=0.049). Male gender was associated with lower complexity. Interestingly diabetes and angiotension blockade also trended towards lower anatomic complexity,” Rasheed said.

He noted that the limitations of the study include its retrospective design and also its relatively low power.

In summary, he said, high ASG scores correlate with increased total cost and resource utilisation and the need for adjunctive procedures during EVAR, resulting in a mean difference of US$9,100 per repair. He added, “Anatomic complexity does correlate with patient factors. Patient factors influence us to pursue a minimally invasive approach and also may pose anatomical challenges during the case. Anatomy is related to cost and we believe anatomy should be considered as a factor when calculating reimbursement. This is particularly important as we enter into value-based and bundled reimbursement paradigms.”

Moderator Ronaldo L Dalman, Stanford University, Stanford, USA, said: “This is an important problem. Hospital based reimbursement in the United States currently does not take into account anatomical complexity, only physiological risk, high or low risk patients for EVAR. This paper highlights that anatomical complexity does add significantly to the cost associated with the case. We could make a compelling case for CMS [Centers for Medicare and Medicaid Services] that there should be a component of anatomical complexity related to reimbursement for EVAR.”

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