Efficacy of Biomarkers and CEUS Versus CTA in AAA Follow-up Post-EVAR

This prospective observational study evaluates the efficacy of contrast-enhanced ultrasound and biomarker determination in the follow-up of patients with abdominal aortic aneurysm (AAA) treated with Endovascular Aneurysm Repair (EVAR). Currently, computed tomography angiography (CTA) is the standard for follow-up, although it has disadvantages such as radiation exposure and the use of iodinated contrasts. Contrast-enhanced ultrasound (CEUS), free of radiation and nephrotoxicity, and biomarkers could reduce the need for CTA minimizing the associated risks. Biomarkers will be measured before and after EVAR and CEUS will be performed at various time points and compared with CTA results to validate concordance and effectiveness in detecting endoleaks and aneurysm remodeling. The objectives include determining the efficacy of these combined methods and establishing a follow-up protocol that reduces exposure to radiation and iodinated contrast agents.

Background/Rationale:

Patients with AAA who have undergone EVAR of the abdominal aortic aneurysm require indefinite follow-up since a 4-year complication rate after EVAR of up to 40% has been described in some series.

In some patients a decrease in the diameters of the residual aneurysm sac after EVAR has been described, which is known as remodeling.

CTA is the gold standard imaging technique for the follow-up of these patients, although it has the disadvantage of using ionizing radiation and iodinated contrasts that are nephrotoxic and can produce hypersensitivity reactions. Furthermore, there is no consensus on which protocol is the most suitable (one phase, two phases or three phases). Currently, in our hospital, three-phase CTA is being performed, as well as CTA with the Split Bolus technique, which allows the acquisition of images in arterial and venous phases in a single acquisition, thus reducing radiation doses; a correlation between both techniques of 85.7-100% and a decrease in radiation doses of between 30-78% has been described.

An alternative to CTA is CEUS that presents a sensitivity of 90.5% (22-100%) and a specificity of 90.65% (71-100%) for the detection of endoleaks. It is a technique that does not use ionizing radiation; furthermore, ultrasound contrasts are not nephrotoxic and hypersensitivity reactions to them are exceptional. In addition, there are publications concerning the determination of biomarkers in the follow-up of patients with AAA both before and after treatment with EVAR.

Hypothesis:

Performing CEUS together with biomarker determination in patients with AAA treated by EVAR would allow reducing the number of CTA to these patients; and, therefore, radiation doses and the use of iodinated contrasts that may cause nephrotoxicity, as well as hypersensitivity reactions.

Primary objectives:

1. - To determine whether the combination of biomarker levels together with CEUS in the follow-up of treated AAA patients is as effective as performing CTA to detect endoleaks.
2. - To validate the usefulness of CEUS together with biomarker determination in the follow-up of these patients.

Secondary Objectives:

1.- To determine the cost-effectiveness of biomarkers in the follow-up of these patients.

To establish a protocol for the follow-up of patients with AAA treated with EVAR, including biomarkers and CEUS.

3.-To reduce radiation doses in the follow-up of patients with AAA treated with EVAR.

Methodology:

Prospective observational study. Biomarker levels will be determined before (within 30 days prior to the procedure) and after stent implantation (24-48 h, 1 month, 3 months, 6 months and 1 year) together with contrast echography. In addition, a control CTA will be performed to validate concordance. These biomarkers will be analyzed comparing the values obtained in patients with endoleaks versus patients without endoleaks, as well as in those with aneurysm remodeling.

Eligibility Criteria:
Inclusion Criteria:

* patients with AAA under follow-up who are going to be treated with EVAR.
* signed informed consent to perform CTA, CEUS and for the determination of biomarkers.

Exclusion Criteria:

* patients with inflammatory abdominal aortic aneurysms or ruptured aneurysm.