Advanced cross-sectional imaging and enhanced screening efforts have enabled physicians to identify abdominal aortic aneurysms (AAAs) with greater frequency. Several studies have compared the outcomes of open repair with endovascular aneurysm repair (EVAR) for the treatment of AAAs. Although much of the data have indicated that EVAR is associated with significant benefits, there have been concerns as to whether the procedure is a sufficiently low-risk surgery for all patients. Of particular concern is a subset of high-risk patients with prohibitively high mortality. “Every surgery requires a risk-benefit analysis before deciding whether or not to proceed,” explains K. Craig Kent, MD. “Aneurysms are incredibly lethal and have been associated with an 85% chance of death when ruptures occur. Few people make it to the hospital in time, and 50% of those who do have an aneurysm rupture die during emergency surgery. The goal in treating aneurismal disease is to prevent the aneurysm from rupturing. However, the challenge is deciding what aneurysms should be repaired based on individual patient characteristics.”

Assessing EVAR in High-Risk Patients

EVAR for AAA has been shown to offer significant advantages. As a minimally invasive procedure, EVAR does not always require general anesthesia or ICU admission postoperatively. The procedure also eliminates the need for laparotomy and associated complications, decreases blood loss compared with open repair, and avoids the major perioperative intravenous fluid shifts that are observed with open repair. Moreover, it significantly reduces perioperative morbidity and mortality, compared with traditional open surgery.

“Many patients who are at high risk for open repair can be safely treated with endovascular repair.”
— K. Craig Kent, MD

According to Natalia Egorova, PhD, MPH, the quick adoption of EVAR was similar to that of any new technology in medicine that is deemed successful in clinical trials. She says that significant benefits of EVAR may have encouraged physicians to become more aggressive in treating aneurysms in patients whose comorbidities would have otherwise precluded a traditional operation.

Recently, a study from England has brought into question the safety of EVAR, suggesting that patients who were at high risk for open aneurysm repair who undergo the minimally invasive alternative have an incredibly high mortality, with a death rate as high as 7%. These authors concluded that no surgical intervention is warranted for high-risk AAA patients.

Despite some valuable insights from that data, Dr. Kent and Dr. Egorova (along with other co-investigators) had a study published in the December 2009 Journal of Vascular Surgery in which they analyzed nearly 67,000 patients who had EVAR. Contrary to findings from the English study, the overall 30-day mortality they observed was only 1.6%. “While there is indeed a subset of patients at very high risk for EVAR,” says Dr. Kent, “this subset of patients was extraordinarily small compared to the number of patients treated for aneurysms. Our findings showed that many patients who are at high risk for open repair can be safely treated with endovascular repair.”

A Scoring System for Physicians

Dr. Egorova says that EVAR is a safe technique that can be used relatively freely in patients with aneurysms, with notable exceptions. “Physicians should use a simple scoring system to help them identify high risk patients preoperatively,” she adds. Dr. Egorova and her colleagues created a scoring system to identify individuals who fall into this small subset of high risk in order to determine who should not receive EVAR based on patient and institutional factors (Table). The scoring system provides physicians with criteria to quantify perioperative risk for EVAR candidates.

 “Our scoring system depicts risk scores for all statistically significant risk factors identified in our study,” says Dr. Egorova. “Risk scores can range from 1 point for chronic pulmonary disorders to 7 points for renal failure with dialysis. A score of 9 or less correlated with a mortality for patients of less than 5%. The scoring system is designed to assist interventionalists by assessing the surgical risk of patients with multiple comorbidities, a task which is often challenging. The system compares the impact of individual risk factors on mortality as well as a summation of their combined effects. The higher the score, the higher the likelihood of mortality [Figure]. A mortality of 5% is considered very high for endovascular AAA repair, corresponding with a score of 9 points. Patients who have scores of 9 and higher clearly belong to the high-risk group.”

 A limitation of the scoring system is that the Medicare database that was analyzed in the study was not able to provide patient anatomy, which is an important variable in making surgical decisions. “Along with anatomy, physicians should also take into consideration the predicted longevity of patients based on age and other comorbidities when deciding whether or not to perform a prophylactic aneurysm repair,” says Dr. Kent. “The scoring system is a simple, predictive, validated model that uses information that is readily available to providers. However, at the end of the day, the decision on repairing an aneurysm should be individualized to each patient.”