Duplex Ultrasound Seems Safe For Post-EVAR Surveillance

SAN DIEGO -- Postendovascular aneurysm repair surveillance, with color-flow duplex ultrasound only, is a safe alternative to the current standard practice of follow-up CT with contrast, results from a single-center study demonstrated.

"CT follow-up is associated with significant risk, including increased cost, contrast nephropathy, contrast allergy, and radiation exposure," Dr. Rabih A. Chaer said at the Vascular Annual Meeting.

He and his associates in the division of vascular surgery at the University of Pittsburgh Medical Center studied 184 patients who were switched to CDU surveillance in 2003 as an alternative to CT. Selective CT scanning was used only for new endoleaks or for those patients who presented with an enlarging abdominal aortic aneurysm (AAA) sac. Only patients with at least 1 year of follow-up were included.

Criteria for switch to CDU included patients with a residual AAA sac of 4 cm or less after the first year of follow-up, patients with a stable AAA sac size for 2 years, or patients with a stable type II endoleak for 2 years. A total of 13 patients had an active stable type II endoleak, 23 had a prior endoleak that was treated or resolved spontaneously. Mean follow-up on CDU was 24 months. Of the 184 grafts, 76 were Ancure, 58 were Zenith, 39 were Excluder, 7 were AneuRx, and 4 were Lifepath.

There were three new endoleaks detected on CDU follow-up, all in patients who received an Ancure graft. Only one patient presented with sac enlargement. "One type II endoleak was detected, but this spontaneously resolved at 3 months," Dr. Chaer said. "There were two distal type I endoleaks that were treated with limb extension."

CDU identified two patients (one with an Ancure and one with an AneruRx graft) who had an increase in their AAA sac size, yet no endoleak was detected. No endoleak was seen on CT scan, but when both patients underwent angiograms, a distal type I endoleak was detected in one.

There were no ruptures or graft occlusions observed during the follow-up period. Eight patients died. One was an aneurysm-related death following an Ancure explantation for infection that occurred 4 years post EVAR; two were related to malignancy, and five were related to acute myocardial infarctions. The cumulative freedom from secondary intervention after the switch to CDU was 98% at 4 years.

In order to determine the applicability of the switch criteria for a full cohort of EVAR patients, the researchers examined 196 consecutive EVAR patients in 2004. Of these, 86 (44%) had been switched to CDU surveillance, whereas the remaining 110 were still followed with CT scan.

At 6-month follow-up, only 1.5% of patients followed with CT scan met the current criteria for the switch to CDU-only surveillance. The proportion at 1, 2, and 3 years was 55%, 86%, and 97%, respectively.

"CDU-only surveillance is safe and can be initiated early after treatment on patients with a shrinking or a stable AAA sac," concluded Dr. Chaer. "Most patients treated with EVAR are eligible for this modality. After the 1 year follow-up, we do recommend that CT scanning should only be selectively utilized in patients treated with EVAR."

Asked to comment on this article, Dr. R. Eugene Zierler, of the University of Washington, Seattle stated: "The search for a safe and effective alternative to CT scanning is critical to more widespread EVAR application. Color-flow duplex ultrasound overcomes most of the disadvantages of CT scanning, however, like other complex applications of abdominal vascular ultrasound, a well-trained and experienced vascular sonographer is the key to success.

"I recommend a trial period where both duplex and CT scans are obtained so results can be directly compared. This is best done in the early post-EVAR period and provides feedback to the sonographer and interpreting physician. Selective use of duplex-only follow-up can then be recommended for patients based on the results of the early CT scans and the known correlation with duplex ultrasound.