LAKE BUENA VISTA, FLA. – Serial computed tomography scans commonly used to monitor patients following endovascular aneurysm repair may be unnecessary after 6 years, according to the findings of a retrospective study of 2,965 scans in 608 EVAR patients.
Furthermore, such scans are more likely to detect a clinically significant incidental finding that warrants further workup than to find a problem with the endograft, Dr. Elizabeth L. Detschelt said at the annual meeting of the Society for Clinical Vascular Surgery.
The average annual rate of detection of EVAR-related findings was 4% (range 2%-5%), which remained constant over the first 6 years of follow-up, and the rate after 6 years was 0%. However, the annual detection rate for new clinically significant incidental findings on these scans was 25% (range 14%-32%), which remained constant for more than 10 years, said Dr. Detschelt of Allegheny General Hospital, Pittsburgh.
On multivariate analysis, predictors of detection of new clinically significant findings included age over 65 years, glomerular filtration rate less than 60 mL/min per 1.73 m2, and tobacco use. No predictors were identified for EVAR-related findings, she noted.
The patients underwent EVAR for infrarenal aneurysm at a single institution between Dec. 1, 1999, and Nov. 30, 2009, and were followed for a mean of 32 months. These results are particularly relevant, Dr. Detschelt said, because risks from repeated scans, which are commonly used for serial imaging in EVAR patients to monitor for endoleak and other problems, are currently a topic of intense debate.
"Recently, the literature has really been inundated with concerns about the cumulative effects of such radiation exposure by these CT scan protocols, and in addition there’s a fair amount of literature to cite a very high rate of incidental findings that we detect on this follow-up with CT protocol," said Dr. Detschelt. Although such findings require follow-up, the literature suggests that this often falls through the cracks, she added.
In this study, EVAR-related findings included endoleak, limb occlusion, and endograft migration. Clinically significant incidental findings were varied, with the most common occurring in the broad categories of genitourinary findings, hepatobiliary findings, hernias, pulmonary neoplasms, and other vascular and cardiac lesions.
Not only do the findings suggest that serial imaging is not needed for EVAR-related concerns after 6 years, but they also underscore the importance of carefully evaluating post-EVAR CT scans for clinically significant incidental findings.
"As the ordering physicians of these CT scans, it is our legal responsibility to ensure that they have appropriate workup, so this is going to mean that not only do we have to look at the scans to assess the status of our aneurysm repair, but we also have to read the radiologist’s report to make sure we’re not missing something," she said.
That’s particularly true for patients who are older, who smoke, and who have a degree of renal insufficiency, she added.
The findings also raise the question of whether post-EVAR patients should undergo monitoring using other imaging techniques such as ultrasound, or whether a less frequent CT scan protocol can be used to reduce patient exposure to radiation and reduce patient costs.
These questions – along with the bigger question of whether it is more prudent to not use CT scans in order to reduce radiation exposure or to continue with CT monitoring to pick up findings that potentially could save or improve lives – require better data to inform decision making, she concluded.
During a discussion period after Dr. Detschelt’s talk, one audience member cautioned against suggesting that CT monitoring be considered for the purpose of detecting incidental nonvascular issues, saying that raises the argument of whether the general population aged 65-75 years should also undergo serial CT scans to find incidental nonvascular issues. He also noted that at his institution, the concerns about serial CT monitoring post EVAR are addressed in part by using duplex ultrasound in the immediate postoperative period, with follow-up by duplex ultrasound in those patients with no problems detected on the initial ultrasound.
He said findings from his experience and others have been published, and show that this is approach is "probably safe and effective." Dr. Detschelt responded that while duplex ultrasound is not used immediately postoperatively at her institution, there has been a move toward using it for long-term follow-up there. At many institutions, however, workforce issues come into play, because the duplex studies are more time intensive and require specially trained vascular staff, she said.
Dr. Detschelt had no disclosures.