LSPEAS

Rationale: Endovascular aortic replacement (EVAR) uses stent grafts to treat aortic aneurysms in patients at risk of aneurysm rupture. The long-term durability of these stent grafts is hindered by complications requiring reintervention. As most self-expanding stent grafts rely on oversizing in order to provide sufficient sealing, the decision for the device size is critical. Once implanted, the aorta dynamics and the device affect each other in ways that are currently not understood. Pre and post-operative imaging of aortic aneurysm is routinely performed using computerised tomographic angiography (CTA). However, these static techniques do not consider the aorta dynamics. Consequently, measurements on the vessel diameter are relatively inaccurate, and our understanding of the dynamic behaviour of the stent is limited. ECG-gated CTA is a technique that takes the patient’s heart cycle into account, enabling studies to the motion of aorta and implanted devices.



Objective: Information on the dynamics and shape of the device and how these change over time will improve our understanding about the fixation and/or sealing of the device, which may help in stent selection and in designing stent grafts that are more durable.



Study design: Patients selected for endovascular repair (EVAR) using the Anaconda or Endurant device receive multiple ECG-gated CTA’s. The resulting data is processed to measure the shape and motion of the device at surgically relevant locations.



Study population: The study population consists of 20 aortic abdominal aneurysm (AAA) patients selected for EVAR with Anaconda or Endurant endoprostheses. Only patients aged > 70 and with an eGFR > 60 ml are included.



Intervention: Present practise is that all AAA patients undergo one abdominal aorta CTA pre-operatively, and receive ultrasound duplex scanning and plain abdominal X-ray at discharge, 3 months, 6 months and yearly thereafter; CT-scans are performed on indication. Patients included in this study receive an ECG-gated CTA pre-intervention plus three ECG-gated CTAs post-operatively: at discharge, after one month, and after six months. Thereafter the routine follow up scheme will be followed.



Main study parameters/endpoints: Of primary interest are the changes in the diameter of the stent ring due to hemodynamic forces. We distinguish between changes during the heartbeat (pulsatility) and changes over a period of several months (expansion). By relating the observed motions to computational models of the stent and the biomechanics of the vessel wall, the change in vessel compliance can be estimated.



Nature and extent of the burden and risks associated with participation, benefit and group relatedness: The ECG-gated CTA protocol results in a higher dose in comparison to a routine scan. The three extra scans means an overall increase in dose applied to the patient. Further, an ECG-gated scan requires ECG electrodes to be applied before scanning.

Information on the dynamics and shape of the device and how these change over time will improve our understanding about the fixation and/or sealing of the device, which may help in stent selection and in designing stent grafts that are more durable.

The duration of this study is two years and is split in three phases:



1) Three patients are included in the study. Their pre-operative scan is performed with ECG-
gating, and one additional ECG-gated scan is performed at discharge. From this information we can determine whether the data is of sufficient quality to perform segmentation and registration;



2) Ten patients are each scanned four times (this includes the three patients from phase one, who thus only need two extra scans in this phase). From this information we should be able to estimate whether the data will lead to the insights that we are after;



3) Another 10 patients are each scanned four times.

Present practise is that all AAA patients undergo one abdominal aorta CTA pre-operatively, and receive ultrasound duplex scanning and plain abdominal X-ray at discharge, 3 months, 6 months and yearly thereafter; CT-scans are performed on indication. Patients included in this study receive an ECG-gated CTA pre-intervention plus three ECG-gated CTAs post-operatively: at discharge, after one month, and after six months. Thereafter the routine follow up scheme will be followed.