Contrast Enhanced Ultrasound vs. Computed Tomographic Angiography in the Detection of Endoleaks Following AAA Repair

Background:

Abdominal aortic aneurysms (AAAs) continue to be a leading cause of death in older age
groups. In the 60-85 year-old population, AAA represents the 14th-leading cause of death.
Federal funding through Medicare has been allocated for early detection using abdominal
ultrasound screening programs. Despite these more aggressive screening programs and concerted
efforts by surgeons for timely repair, the incidence of ruptured AAA has continued to
increase.

Endovascular aneurysm repair (EVAR) has been the most common type of repair since 2006.
Multiple studies reflecting decreased perioperative morbidity and mortality over open repair
make this an attractive option for patients. EVAR requires more intensive follow-up than
standard open surgical repair, however. Secondary interventions are more common to maintain
"seal" of the endograft within the aorta and subsequent exclusion of the aneurysmal
component.

The term endoleak is specific to EVAR, and describes the primary means by which endografts
fail. Type I endoleaks occur because of inadequate graft seal proximally or distally,
resulting in perigraft flow and aneurysm sac pressurization. Type II endoleaks occur when
branch arteries arising from the aneurysmal aorta back-bleed into the aneurysm sac due to
collateral flow. Type III endoleaks occur when flow persists between segments of a modular
graft. Type IV endoleaks occur when flow persists through endograft material (graft
porosity). Type V endoleaks have also been called "endotension", and occur when
pressurization of the sac occurs in the absence of any demonstrable endoleak. Type I and Type
III endoleaks are most concerning for rupture, although persistent Type II endoleaks can also
lead to aneurysm rupture and premature death.

The most common method of EVAR follow-up is computed tomographic angiography (CTA). These
studies allow accurate measurement of aneurysm sac diameters and volumes. They also are
highly sensitive and specific for endoleaks. Type II endoleaks are treated if they remain
persistent and are present in the setting of aneurysm sac enlargement. Type I and III
endoleaks are immediately treated when identified. Type IV endoleaks are rarely seen with
current endograft technology.

Study Objectives:

The purpose of the current study is to compare routine postoperative surveillance by CTA with
color duplex ultrasound and contrast enhanced ultrasound (CEUS) for the detection of
endoleaks.

Study Design

This is a pilot study comparing the imaging techniques of CTA to CEUS in 25 patients
undergoing EVAR at their one month post endograft surveillance. The one month standard
follow-up will be used for comparing techniques as this will yield the highest number of
endoleak positive patients. Patients will complete a color duplex examination in conjunction
with CEUS using the FDA approved ultrasound contrast agent OptisonTM (Perflutren Protein Type
A Microspheres for Injection, USP). Following ultrasonographic evaluation, study patients
will undergo routine CTA.

Eligible subjects will be asked to participate in the trial following post-op day number 1
from their endovascular procedure. Study participation is ~30 days (+ 7 days).

Inclusion Criteria:

- 18 years old and greater

- Men or postmenopausal/non-pregnant women

- Abdominal aortic aneurysm successfully repaired by endograft deployment

- Creatinine < 2.0 mL

- Planned CTA follow-up

Exclusion Criteria:

- Subjects with known or suspected hypersensitivity to blood, blood products, or
albumin.

- Subjects unable/unwilling to give informed consent

- Unable to complete post-operative imaging studies

- Subjects identified to have a cardiac shunt by TTE

- Subjects with hepatic or respiratory disease

- Nursing mothers