Post-EVAR surveillance recommendations have undergone significant updates. Original practice guidelines included a postoperative 30-day CTA study, repeated at 6 months, 1 year, and annually thereafter. There is increasing evidence of the need to decrease the imaging frequency. Specifically, elimination of the 6-month follow-up study and substitution of the CTA beyond, or even at, 1 year with CDU have been suggested [29]. The follow-up protocol remains ill-defined when a type II endoleak is diagnosed. Although current guidelines suggest CTA at 6 months upon type II endoleak detection at the postoperative CTA study, accumulating evidence suggests that omission of this follow-up visit and repeated imaging at 12 months with either CTA or CDU (combined with radiographs) or non-contrast-enhanced computed tomography to check for sac growth with subsequent annual CDU are adequate, provided the sac does not expand [29].

The following is a summary of the evolution of our surveillance policy over the years. In 2003 a new follow-up schedule for endovascular aneurysm repair surveillance was initiated for selected patients treated at the UPMC (University of Pittsburgh Medical Center). Annual duplex scanning as the sole imaging modality was offered as early as 1 year post endovascular aneurysm repair for those patients with a collapsed aneurysm sac <4 cm in diameter. This policy was expanded 1 year later to include patients with significant shrinkage of the aneurysm sac to any size or a stable aneurysm without enlargement for 2 years whether a type II endoleak was present or not. Patients with contrast allergy or significant renal insufficiency (serum creatinine >2) were switched at earlier intervals depending on aneurysm size and presence or absence of endoleaks. Diameter measurements were defined as the minor axis of the largest axial slice on CT. A significant shrinkage was considered to be a minimum of 5 mm from the baseline 1-month CT. A stable aneurysm was defined as an aneurysm with <3 mm increase in diameter from baseline. Patients with enlargement of the sac by ≥3 mm from the baseline CT were not considered for switching. Most patients underwent duplex scanning to complement the CT scan when the decision to switch the patient was made. All patients with suboptimal studies secondary to anatomy or body habitus were not switched to duplex scanning surveillance.

In our institutional series, 184 patients (159 males) were switched to duplex scanning surveillance between 2003 and 2006 [13]. All duplex scanning examinations were technically satisfactory for determination of aneurysm size and presence of an endoleak. The mean follow-up on duplex scanning was only 24 ± 13 months (range 1–4 years). Initial follow-up of these patients included X-rays and CT 1 month after endovascular aneurysm repair, 6 months (for patients on investigational protocols), 12 months, and yearly thereafter [13]. Following commercial release of each graft, the 6-month follow-up was discontinued because of the low incidence of adverse events detected [44].

After implementing duplex scanning-only surveillance, three new endoleaks were diagnosed during the duplex-only surveillance, only one presenting with sac enlargement. All prompted CT evaluation: one type II endoleak with stable sac size that could not be identified on the CT obtained 3 months later, and two distal type I endoleaks that required limb extension. No patient had a clinical adverse event during the period of observation. No ruptures or graft occlusions were noted [13]. These findings demonstrated to us the safety of using duplex scanning as a replacement modality for CT in the FU of EVAR.

Since these changes were adopted slowly over time, we evaluated how many patients would be suited for the switch and how early after endovascular aneurysm repair it could be implemented, based on our current criteria. The clinical and follow-up imaging records of 200 consecutive patients with available imaging, treated in 2004 and 2005, were reviewed, demonstrating that 97% of patients are eligible for duplex scanning-only surveillance by 3 years after endovascular aneurysm repair. This finding is quite encouraging as it suggests that the majority of patients can be followed with US-only surveillance post EVAR.

These results and others confirm the safety and efficacy of US surveillance post EVAR, which can be applied to most patients, potentially as early as 30 days post procedure after the first CT scan follow-up. Candidate patients include:

However, that patients with initial suboptimal anatomy for EVAR may be at a higher risk for future complications and be better followed by CT at least intermittently alternating CDU with CT to detect early changes in aortic neck anatomy and morphology. Other patients who may not benefit from strict US follow-up include those being concomitantly followed for a thoracic aortic aneurysm and patients with excessive bowel gas, ascites, or a challenging body habitus. A CT may still be indicated every 5 years to detect remote aneurysmal changes or other structural defects.

It should be noted that our recommendations may not be universally accepted, but are similar to the recent guidelines issued by the Society for Vascular for post-EVAR surveillance [45]. The guidelines recommend contrast-enhanced CT imaging at 1 and 12 months during the first year after EVAR and also at 6 months in patients with endoleak or other abnormality of concern. If neither an endoleak nor aneurysm enlargement is documented during the first year after EVAR, the guidelines suggest CDU as a reasonable alternative to CT imaging for postoperative surveillance, with the recommendation that these studies be performed by a skilled technician in an accredited noninvasive vascular laboratory.