Scoring System Developed to Define High-Risk Patients for EVAR

December 3, 2009—The Society for Vascular Surgery announced that a new scoring system may help physicians determine risk levels in Medicare patients when considering endovascular repair for abdominal aortic aneurysms. Endovascular aneurysm repair (EVAR) is commonly used as a minimally invasive technique for repairing infrarenal aortic aneurysms; however, there have been recent concerns that a subset of high-risk patients experience unfavorable outcomes with this intervention. To determine whether such a high-risk cohort exists and to identify the characteristics of these patients, Natalia Egorova, PhD, MPH, et al analyzed the outcomes of Medicare patients treated with EVAR from 2000 to 2006. The investigators' findings were published in the Journal of Vascular Surgery (2009;50:1271-1279).

Dr. Egorova and her colleagues from the Mount Sinai School of Medicine in New York City, Columbia Weill Cornell Division of Vascular Surgery in New York, and the department of surgery at the University of Wisconsin School of Medicine and Public Health in Madison designed the system, which rated risk factors from one to seven, with seven being the highest number for predicting mortality for any one factor.

The investigators concluded that there is a high-risk cohort of patients that should not be treated with EVAR because of prohibitively high mortality but noted that this cohort is small. They stated that their scoring system, which is based on patient and institutional factors, provides criteria that can be easily used by clinicians to quantify perioperative risk for EVAR candidates.

“We believe that EVAR is safe and effective in the majority of the elderly population and even for those with multiple comorbidities,” commented Dr. Egorova, who is assistant professor in the department of health policy at Mount Sinai. “The scoring system we developed can be useful to perioperatively identify risk factors for older adults and those who may be unfit for even minimally invasive treatment of their aneurysm.”

As reported in the Journal of Vascular Surgery, the investigators identified 66,943 patients who underwent EVAR from the Inpatient Medicare database. The overall 30-day mortality rate was 1.6%. A risk model for perioperative mortality was developed by randomly selecting 44,630 patients; the other one-third of the dataset was used to validate the model. The model was deemed reliable (Hosmer-Lemeshow statistics were P = .25 for the development, P = .24 for the validation model) and accurate (c = 0.735 and c = 0.731 for the development and the validation model, respectively).

In the investigators' scoring system, where scores ranged between one and seven, the following were identified as significant baseline factors that predict mortality: renal failure with dialysis (score = 7); renal failure without dialysis (score = 3); clinically significant lower extremity ischemia (score = 5); patient age ≥ 85 years (score = 3), age 75 to 84 years (score = 2), 70 to 74 years (score = 1); heart failure (score = 3); chronic liver disease (score = 3); female gender (score = 2); neurological disorders (score = 2); chronic pulmonary disease (score = 2); surgeon experience in EVAR < 3 procedures (score = 1); and hospital annual volume in EVAR < 7 procedures (score = 1). The majority of Medicare patients who were treated (96.6%, n = 64,651) had a score of nine or less, which correlated with a mortality rate < 5%. Only 3.4% of patients had a mortality rate of ≥ 5%, and 0.8% of patients (n = 509) had a score of 13 or higher, which correlated with a mortality rate > 10%, the investigators reported.

According to the Society for Vascular Surgery, the study investigators said that there were some limitations in their current study: administrative datasets' knowledge of the severity of comorbidities is often lacking; diagnosis codes can be broad and vague and provide limited detail about a specific patient's disease state (eg, if a patient has a chronic condition between hospitalization or there is no code available); and there is a lack of information regarding a patient's complex arterial anatomy (eg, size of the aneurysms treated).

“However, our report of almost 67,000 EVAR procedures is one of the largest ever published,” commented Dr. Egorova. “It is based on a Medicare administrative database and is a true representation of clinical practice in the United States.”