Computationeel ontwerp en experimentele ontwikkeling van een mechanocompatibele externe ondersteuning voor de Ross procedure

The Ross procedure is the only aortic valve replacement technique capable of restoring long-term survival while preserving quality-of-life. In the Ross procedure, the patient's own pulmonary valve is transplanted into aortic position, forming a so-called pulmonary autograft. Despite its clinical advantages over mechanical or bioprosthetic valve substitutes, the long-term durability of the Ross procedure is limited by progressive autograft dilatation under systemic blood pressure. Current textile reinforcements can reduce autograft dilatation and prevent valve leakage. However, their stiffness does not adequately match the biomechanical behavior of native vascular tissue. By restricting physiological wall motion, these support materials disturb hemodynamics and can induce stress-shielding effects, such as thinning of the vessel wall and smooth muscle cell loss. The central objective of this thesis is therefore to computationally design and experimentally develop a mechanocompatible external support for the Ross procedure. The dissertation first establishes a novel experimental and computational framework to comprehensively characterize arterial biomechanics. New testing procedures and constitutive descriptions are introduced to translate planar biaxial stress-stretch data into tubular extension-inflation behavior. The sensitivity of arterial pressure-diameter predictions is systematically evaluated through direct comparison of computational results with experimental measurements. Building on this foundation, constitutive artificial neural networks are used to describe the hyperelastic and anisotropic mechanical behavior of main pulmonary arteries. Data-driven automated model discovery revealed a novel constitutive model specifically tailored to pulmonary artery tissue. The thesis further investigates the long-term surgical outcomes after the Ross procedure using growth and remodeling simulations. Different mechanobiological drivers of arterial adaptation are analyzed, with particular emphasis on the role of pulsatile loading. Cyclic stresses are identified as key drivers of benign arterial adaptation following pulmonary autograft implantation. The developed computational framework is further extended through image-based finite element simulations that enable predictions of pulmonary autograft remodeling and its impact on valve leaflet coaptation over time. These simulations demonstrate the ability to predict longitudinal changes in valve leaflet coaptation, solely based on preoperative imaging. Finally, the pre-clinical evaluation of a mechanocompatible external support is presented. Electrospinning is introduced as a biomimetic fabrication strategy for implantable external scaffolds, and its efficacy is evaluated in an experimental animal study of the Ross procedure. Electrospun biodegradable polycaprolactone-elastin external supports are shown to provide compliant reinforcement while preserving physiological wall motion. A computational optimization framework is then introduced to determine optimal mechanical properties for external support materials. The simulations demonstrate that arterial distensibility is a critical metric for mechanocompatible reinforcement design. Together, this dissertation bridges engineering, medicine, and material science by integrating biomechanical modeling, clinical cardiac surgery, and polymer-based medical textiles. By combining computational biomechanics with experimental material development for cardiovascular applications, the work establishes a translational framework for mechanocompatible reinforcement strategies of pulmonary autografts. This approach has the potential to improve the long-term durability and clinical outcomes of the Ross procedure, thereby strengthening its role as the preferred aortic valve replacement strategy in appropriately selected patients worldwide.