Abdominal aortic aneurysm – a localized dilation of the abdominal aorta – is a common disorder. If this bulge in the aorta grows and remains untreated it may lead to rupture of the vessel wall, causing internal bleeding. Maaike Koenrades of the University of Twente (who also works at Medisch Spectrum Twente) obtained her PhD with research into the behaviour of stent-grafts: vascular implants composed of synthetic fabric tube (graft) supported by a metal structure (stent) that are placed inside patients with an aortic aneurysm. This intervention is termed endovascular aneurysm repair (EVAR). Koenrades: “My research enables to develop better stent-grafts, because we can now measure what happens to a stent-graft when it is implanted in a patient.”
Various studies have shown that treating aortic aneurysm using EVAR – implanting a stent-graft via the groin – gives better short-term results than the more invasive method of open surgery. However, in the longer term 10 to 20% of these patients need another intervention following EVAR: the stent-graft did not remain in place, for instance, or a gap arose between the stent-graft and the vessel wall, allowing blood to leak through placing pressure on the aneurysm again.
The aorta is in constant movement because of the heart’s pumping action. The stent-graft−aorta combination is therefore exposed to about 40 million pulsations per year, which can present a challenge to its stability. Until now little was known about the dynamic behaviour of stent-graft implants. Improved insight into this behaviour helps physicians to select the most appropriate stent-graft for a given patient, and to improve stent-graft design.
Research into stent-graft behaviour
Maaike Koenrades studied the behaviour of stent-grafts following EVAR treatment. In her thesis she developed, validated and applied methods to examine the interaction between the stent-graft and the aortic vessel, on the basis of heartbeat-coupled CT scans. The insights provided by her thesis will contribute to improved decision-making in the selection, positioning and monitoring of stent-grafts. They could also lead to modifications in stent-graft design, which could reduce the incidence of complications in the future. This work supports the development of more realistic preclinical tests and more durable stent-grafts.
Maaike Koenrades has a degree in Technical Medicine and has worked as a researcher and doctoral student at the University of Twente (Techmed Centrum) and Medisch Spectrum Twente since 2015. On 1 November 2019 Koenrades reveived her PhD cum laude with her thesis On evaluating stent–artery interaction in abdominal aortic stent grafting. Her promotors were Professor R.H. Geelkerken (MST/UT) and Professor C.H. Slump (UT). On 4 November Koenrades began work at MST as a project leader in 3D technology innovation, to strengthen and expand the 3D Medical Lab at MST. For patient information, click here.