Absence of early endoleak predicts freedom from long-term aneurysm-related morbidity after EVAR: Implications for re-defining post-operative surveillance

Background: Recommended post-operative surveillance after EVAR includes serial contrast-enhanced CT scans. The cumulative deleterious effect on renal function, radiation exposure and significant cost of this surveillance regimen are all problematic. However, there are scant supporting data available to support modulation of post-EVAR surveillance regimens.
Methods: All patients who underwent EVAR as part of the prospective multicenter phase II and III US Zenith Endovascular graft trials were studied. A core lab blinded to the patients' clinical course prospectively recorded all data. A composite aneurysm-related morbidity variable was retrospectively calculated to include AAA rupture, open conversion, any secondary intervention, limb thrombosis, migration, renal morbidity or aneurysm-related death. Kaplen-Meier analysis was employed to compare the long-term freedom from aneurysm-related morbidity as a function of the presence or cumulative absence of any endoleak at 1, 6 and 12 months. The potential additive predictive utility of aneurysm sac shrinkage (=>5 mm) was also assessed at 12 months. All patients conformed to the instructions for use (IFU) for aortic neck anatomy (=>15 mm length, 20-28 mm diameter, < 60 degree angulation). Data are expressed mean +/- S.D.
Results: 739 patients underwent EVAR with a mean follow-up of 29.9 +/- 17.1 months. Freedom from any endoleak at 1 month (table) was highly predictive (p <0.0001) of reduced aneurysm-related morbidity: freedom from aneurysm-related morbidity was 92.3%, 89.8%, 85.2%, 83.1% and 83.1 % at 1, 2, 3, 4 and 5 yrs, respectively, in patients without endoleak (n=593) compared to 75%, 67.1%, 61.5%, 55.9%, and 55.9% in patients with endoleak (n=121). Cumulative absence of endoleak at 1 yr (n=554) was associated with 94%, 91.5%, 88.1%, 85.8%, and 85.8% 1-5 yr freedom from morbidity compared with a 73.3%, 66.7%, 56.6%, 52.5% and 52.5% in patients with a history of endoleak (n=160), p <0.0001. The addition of AAA sac shrinkage (=>5 mm) at 1 yr to the absence of endoleak (n= 343) had only marginal improvement in predicting long-term morbidity: 94.2%, 92.6%, 90.1%, 88.9%, and 88.9% at 1-5 yrs vs 83.6%, 76.9%, 68.2%, 63.4%, and 63.4% in patients with endoleak and/or no shrinkage (n=232), p<0.0001.
Conclusions: Absence of endoleak at 1 month by CT scanning was highly correlated to improved long-term (5 year) freedom from aneurysm-related morbidity/mortality. Screening for cumulative absence of endoleak at 6 and 12 months improved the 5-yr predictive outcome by only 2.7%. Based on these data, modulation of the intensity and frequency of post-operative surveillance may be appropriate in selected patients.