PhD defence Cindy van Loo

Keywords: Arterial biomechanics, Aortic vasoreactivity, Tubular testing, Planar testing

"Limits under pressure: From passive arterial biomechanics to aortic vasoreactivity"

Large elastic arteries close to the heart are known for their buffering function of the blood, as they expand and recoil passively with every heartbeat. Thereby, they smooth out blood flow to the organs, preventing large pressure fluctuations at the organs and reducing the load on the heart. This thesis addresses the fact that these large arteries can also actively modulate their diameter which affects this buffering function. A literature review synthesized the existing knowledge on this active behavior, while a clinical study in patients undergoing cardiac surgery quantified the magnitude of these effects. The impact of changes in arterial diameter on the buffering function of large arteries should be considered when prescribing medication that influences vascular tone.

In addition, this thesis evaluates the limitations of several methods used to assess the biomechanical properties of arteries, both inside (in vivo) and outside (ex vivo) the human body. When testing arterial tissue outside of the body, tubular testing provides the most physiologically relevant results because it preserves the vessel's natural geometry. However, this approach requires specialized equipment and expertise. Planar testing, in which a section of arterial tissue is stretched as a flat specimen, is simpler and more accessible, but its results are less readily translatable to physiological conditions in the body. Overall, this thesis advances our understanding of arterial stiffness and provides insight into the strengths and limitations of the various methods available for its assessment.

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