Hemodynamically efficient artificial right atrium design for univentricular heart patients

Infants born with single-ventricle physiologies pose significant challenges for mechanical circulatory support devices. Their corresponding Fontan circulations consist of passive blood flow that returns to the lungs via direct connections to the pulmonary arteries without a pumping chamber. When Fontan patients reach adolescence or young adulthood, they tend to develop heart failure and may require heart transplants and/or mechanical assist devices. Mechanical supports often require a reservoir to attach, but no such blood reservoir exists in a closed Fontan circulation. This study was aimed to investigate the existence of a hemodynamically optimized geometry for an artificial right atrium (ARA) that can act as a reservoir for circulatory support in Fontan patients. Our hemodynamics-based criteria for an ARA were defined as minimum particle residence time (PRT) (to reduce the probability of blood clot formation) and maximum volume compliance (to prevent pressurization of cerebral and hepatic veins). A computational approach was used to complete this study. We utilized non-Newtonian fluid-solid interaction simulations constructed by lattice Boltzmann and immersed boundary methods. Our results show that a hemodynamically optimum shape for an ARA with minimum PRT (relative to the cases considered in this study) is convex at the outlet (towards the lungs) and concave at the opposite side of the outlet. Additionally, the optimal ARA geometry well preserves the volume compliance that is needed to prevent pressurization of cerebral and/or hepatic veins. Interestingly, this shape resembles that of the healthy anatomical right atrium. Future implantation of our proposed ARA configuration may potentially lessen the risk of implementing biventricular supports in Fontan patients.