Seminars

Soft-tissue-derived exogenously cross-linked (EXL) biomaterials continue to play an important role in many surgical repair and medical devices, especially bioprosthetic heart valves, by having advantages in immunogenic and mechanical behaviors. Despite ongoing research, our understanding of these materials and of the mechanisms leading to their failure remains at an empirical level. The need for advancement in predicting the material behavior is further underscored by the development of percutaneously-delivered BHV devices.  While these devices offer reduced surgical risk, they also present additional challenges for the design of the valve due to limitations in thickness and folding during delivery. A significant challenge in predictive simulations of bioprosthetic heart valves are a lack of the underlying mechanisms.  Our Center has pioneered the development of constitutive models for native and engineered heart valve tissues, and their use in simulation of valvular function. In particular, microstructural-based constitutive models and their use in valve-level simulations can lead to insights into the underlying mechanisms and more accurate prediction of their long-term performance.  Our center has developed a novel model based on a constantly evolving referential configuration that occurs due to the scission-healing reaction. The model parameters were derived and validated using static and cyclic experimental data. We demonstrate how the development simplified models for computational implementation.  Next, we demonstrate our simulation framework for the complete modeling and simulation of biologically-derived soft collagenous tissues used in replacement heart valves, accounting for the effects of chemical cross-linking, permanent set, and collagen fiber-level damage. Integration into larger scale cardiac models will also be presented, as a means to integrate valvular function into the more expansive questions of the relation to cardiac functional restoration.