S1-5.8 Jan. 6 To make a valve you have to put your heart into it MILLER, L. A.; University of North Carolina, Chapel Hill email@example.com
The embryonic vertebrate hearts develops from a simple heart tube that moves blood with a wave of contraction to a valve and chambered pump through a series of complicated morphological changes. During this transformation, the flow patterns within the heart are constantly changing due to variations in the viscosity of the fetal blood, chamber and valve morphology, and the kinematics of contraction. Cardiac endothelial cells can sense and respond to local variations in shear stress caused by such changes in the larger scale fluid dynamics. A number of recent studies suggest that these fluid dynamic signals are responsible for triggering biochemical cascades within the cell, leading to the transcription of genes necessary for cardiac morphogenesis. One aspect of heart development that is particularly sensitive to alterations in cardiac flow patterns is the development of the heart valves. The broad focus of this study is to understand how the cardiac cushions, which later become the valves, are formed through a complex interaction of flow, mechanosensing, biochemical cascades within the cell, and changes in morphology. In this paper, we will focus on larger scale fluid dynamic transitions in the growing heart. Cardiac flow patterns change as the chambers form, the heart loops, and the cardiac cushions begin to expand. Such changes in flow cause temporal and spatial variations in shear stress along the endothelial lining of the heart tube. Computational fluid dynamics and physical models were used to describe how variations in shear depend upon scale and morphology. The immersed boundary method was used to determine the flow patterns and shear stresses in a model heart over a range of Reynolds numbers and morphologies. These results were validated using a physical model of the developing heart.