Ultrasound Velocimetry in the Abdominal Aorta Before and After Endovascular Aneurysm Repair

Feasibility of Ultrasound Particle Image Velocimetry to Quantify Flow in the Abdominal Aorta Before and After Endovascular Aneurysm Repair

Rationale: An abdominal aortic aneurysm (AAA) is a common vascular disease with a high mortality in case of rupture. The underlying processes initiating aneurysmal degeneration and driving aneurysmal growth remain poorly understood. Local hemodynamics might play a key role in the pathogenesis of AAA, as it is associated with aneurysmal growth, intraluminal thrombus formation and rupture risk. Visualizing and quantifying local blood flow profiles could eventually provide more insight in the underlying mechanisms of aneurysm progression as well as identify smaller AAA with increased vulnerability or larger AAA with low risk of rupture. Consequently, this may improve risk assessment and provide patient-specific therapy guidance. Nowadays, endovascular aneurysm repair (EVAR) is the preferred treatment modality in most patients with an infrarenal AAA. However, EVAR is associated with a relatively high reintervention rate. It is hypothesized that the placement of a stent graft may alter local hemodynamics and subsequent recirculations or flow stagnations promote the onset of thrombosis or micro-emboli. These unfavourable flow conditions might be related to various complications after EVAR, such as limb occlusion, renal dysfunction, and the persistence of type II endoleaks. Visualizing local blood flow profiles after EVAR might provide insight in these (un)favourable conditions. In vivo blood flow quantification is a great challenge, particularly in the abdomen. Advanced ultrasound based techniques, incorporating ultrasound contrast agents and plane wave imaging, proved to be feasible in quantifying aortoiliac blood flow patterns in healthy volunteers.

Objective: The aim of this study is to determine the feasibility of ultrafast contrast-enhanced ultrasound particle image velocimetry (echoPIV) measurements to quantify spatiotemporal blood flow velocity profiles in the abdominal aorta of AAA patients before and after endovascular repair.

Secondary objectives are to determine the correlation between echoPIV and phase-contrast MRI (PC MRI) based measurements to ultimately validate the spatiotemporal velocity profiles obtained with echoPIV. Furthermore, changes in blood flow velocity profiles after placement of a stent graft will be evaluated.

Inclusion Criteria:

• Male or female > 18 years of age
• BMI ≤ 30 kg/m2
• Infrarenal AAA
• Scheduled for elective EVAR with the Endurant II stent graft
• Informed consent form understood and signed, and agrees to all visits

Exclusion Criteria:

• Hypersensitivity to the active substance(s) or any of the excipients in Sonovue
• Right-to-left cardiac shunt
• Severe pulmonary hypertension (pulmonary artery pressure > 90mmHg)
• Uncontrolled systemic hypertension
• Severe pulmonary disease (e.g. COPD GOLD 3 or 4, adult respiratory distress syndrome)
• Clinically unstable cardiac disease (recent, < 3 months, or ongoing myocardial infarction, unstable angina at rest, recent percutaneous coronary intervention, clinically worsening cardiac symptoms, severe cardiac arrhythmia's, endocarditis, etc.)
• Prosthetic valves
• Loss of renal function (GFR < 31 ml/min), end-stage renal disease
• End-stage liver disease
• Sepsis
• Hypercoagulable status, recent (< 3 months) thrombosis
• Congestive heart failure (class III or IV)
• Pregnancy
• MRI exclusion criteria (pacemakers, cerebral vascular clips, claustrophobia)