Streamlining fluid pathways lessens flow energy dissipation: relevance to atriocavopulmonary connections

Flow energy dissipation reduces cardiac efficiency, particularly in the Fontan-modified, single-ventricle heart. To provide insight into flow energetics relevant to Fontan-type anatomy, a simple, analytical description of fluid motion was employed. Mechanical energy balance and the force-momentum relationship were used to describe theoretical pressure changes and flow energy losses. When either flow's cross-sectional area or direction changes abruptly, fluid disturbances ensue that can lead to erosion of a stream's available energy. Conversely, passages anatomically streamlined to favor gradual alterations in these flow characteristics lessen such fluid dynamic effects. We show by analogy that flow energy dissipation becomes clinically important in Fontan circuits when the magnitude and/or direction of the average velocity of flow suddenly changes as fluid enters or leaves a large chamber or negotiates a sharp bend in its connection pathway.