Assessment of flow energetics using magnetic resonance phase velocity mapping

The total cavo-pulmonary connection (TCPC) is used to treat children with single-ventricle congenital heart disease. Because the procedure results in the complete bypass of the right heart, energy conservation at the connection is important for postoperative success. To evaluate the energetics of TCPC clinically, the traditional approach is to apply the mechanical energy balance, which however requires invasive pressure data. Therefore a non-invasive method is necessary. This study investigated the feasibility of the viscous dissipation method as non-invasive approach to assess the energetics of TCPC. Magnetic resonance phase velocity mapping (MRPVM) experiments in a TCPC model were performed under different imaging slice orientations and spatial resolution settings. The results showed an increase in the calculated viscous dissipation as the spatial resolution increased. Slice orientation affected the results somewhat, because of the difference in the partial volume effects between the orientations. Comparison of the experimental MRPVM results with computational fluid dynamics results on the same geometry showed agreement between them. This preliminary study provides positive evidence for the clinical potential of the viscous dissipation method as a non-invasive approach to assess the energetics of the TCPC.