Multi-Scale Modelling of Textile Reinforced Tissue Engineered Heart Valves
Transcatheter aortic valve implantation of fibrin-based tissue engineered heart valves with a tubular leaflet construct have been developed as an alternative to invasive traditional surgical heart valve implantation, but currently need reinforcement to withstand pressures found in the aortic position. To increase valve strength, a PET textile reinforcement has been introduced to the fibrin scaffold. However, care must be taken when using a textile reinforcement. Increasing reinforcement may increase the strength, but also increases stiffness which can interfere with the functionality of the valve, prohibiting full valve closure. In order to predict the behavior of the valve, improve design, and eventually optimize valve performance by tailoring the textile reinforcement, a 4-tiered hierarchical multi-scale modelling framework has been created. The model includes an individual fiber scale model, two textile-level models, and a full heart valve model. Geometry generation based on microscopic images of the composite will be discussed, along with application of boundary conditions and loading application. Fitting the various material models based on homogenization of the smaller scale will be demonstrated. Finally, experimental validation and characterization at various scales will be discussed.
On the multiscale modeling of heart valve biomechanics in health and disease
Theoretical models of the human heart valves are useful tools for understanding and characterizing the dynamics of healthy and diseased valves. Enabled by advances in numerical modeling and in a range of disciplines within experimental biomechanics, recent models of the heart valves have become increasingly comprehensive and accurate. In this paper, we first review the fundamentals of native heart valve physiology, composition and mechanics in health and disease. We will then furnish an overview of the development of theoretical and experimental methods in modeling heart valve biomechanics over the past three decades. Next, we will emphasize the necessity of using multiscale modeling approaches in order to provide a comprehensive description of heart valve biomechanics able to capture general heart valve behavior. Finally, we will offer an outlook for the future of valve multiscale modeling, the potential directions for further developments and the challenges involved.
An Essay on Modeling: The Social Model of Disability
From its first exposition almost half a century ago, the social model of disability has been aimed at altering both theory and practice, bringing about profound changes in people’s understanding of disability, and in the daily lives of disabled people as well. The social model’s foil, and on some accounts its antithesis, is the medical model of disability. Both models treat disability as a locus of difficulties. While the medical model takes disability to be a problem requiring medical intervention—and as both the prerogative and the responsibility of medical professionals to fix—the social model understands disability as a political problem calling for corrective action by citizen activists who alter other people’s attitudes and reform the practices of the state. These two conceptualizations of disability have been treated as competitors, as if one must prevail over and eradicate the other in thinking about who disabled people are and what should be said and done in regard to them.