Guidelines from the Society of Vascular Surgery recommend yearly surveillance imaging with CT scanning or ultrasonography after patients undergo endovascular aortic aneurysm repair (EVAR) for abdominal aortic aneurysms (AAA). Still, the frequent use of imaging may not be necessary in some patients, based on results of a study published online in JAMA Surgery on July 8.

Researchers from Stanford University found that Medicare patients who did not undergo annual surveillance had lower mortality rates than patients who adhered to the guidelines. The rates of aneurysm-related mortality were similar in the groups.

“I think the take-home message from this paper is that not everybody needs yearly follow up, but we don’t know which patients don’t need yearly follow up and we don’t know how often they should get follow up surveillance,” Matthew W. Mell, MD, MS, from the division of vascular surgery at Stanford and one of the study’s authors, told Cardiovascular Business. “We are not recommending that surveillance is unnecessary. We are interpreting our findings that because we couldn’t demonstrate a negative outcome from those with incomplete surveillance, it suggests that there’s an opportunity to better refine the best practice for post-EVAR surveillance.”

An estimated 80 percent of abdominal aortic aneurysms are treated with EVAR, according to Mell. He also said that 70 percent of abdominal aortic aneurysms are found in Medicare patients.

Mell and colleagues examined 9,975 Medicare patients who underwent AAA-related EVAR from Jan. 1, 2002, through Dec. 31, 2005. Mean follow up was 5.2 years and the median duration was 6.1 years.

Of the patients, only 43 percent had complete surveillance according to the guidelines. Mell said the researchers did not know why patients did not undergo post-operative surveillance because the claims data was incomplete.

The researchers were able to adjust for co-existing medical conditions at the time of the operations, but they couldn’t adjust for subsequent medical illnesses that may have occurred.

“It is possible that patients with more frequent studies actually were getting studies for other medical conditions that developed after the aneurysm was repaired,” Mell said. “To better answer this question of how frequently surveillance should be performed, I think having better information regarding the actual repair and then having better information regarding subsequent medical conditions would help answer that question.”

Mell added that future research should evaluate when an ultrasound would be adequate surveillance and when a CT scan would be more appropriate.

The Society of Vascular Surgery is in the process of revising guidelines for aneurysm care, including surveillance. Mell, who is involved in the working group that will update the guidelines, said they should be released by next year.

“We don’t believe that less frequent surveillance would result in equivalent outcomes,” Mell said. “What we believe is that less frequent surveillance may be more appropriate for some patients.”