Investigating Blood Flow Patterns and Hydrodynamics of the Perinatal Single Ventricle Heart: An In Vivo Study*

The single ventricle (SV) describes a broad group of congenital heart defects that results in only one functional ventricle to pump blood effectively. Associated anatomical changes and varying loading conditions lead to altered diastolic blood flow patterns and hydrodynamics, which are poorly understood. Early detection of SV conditions through in-vivo echocardiography (echo) during the perinatal period is critical for treatment planning and improving outcomes. However, standard Doppler echo with Color Flow Imaging (CFI) provides a limited analysis of flow pattern changes, which is crucial for understanding SV physiology. Here we employ Doppler Vector Reconstruction (DoVeR), a novel method that resolves the underlying flow velocity vector fields from CFI by iteratively solving the vorticity-streamfunction formulation. DoVeR analysis yields advanced hydrodynamic measurements of abnormal cardiac flow, including energy loss, vortex strength and pressure fields. By comparing both prenatal and postnatal flow patterns in healthy controls and SV patients, we observe that a large free-wall vortex in the diastolic flow of SV that is asymmetric compared to the symmetric vortex in healthy hearts. The disorganized flow pattern in SV hearts results in higher flow energy loss, indicative of lower diastolic efficiency. This pioneering study establishes the significance of intraventricular flow parameters in statistically demarcating healthy versus SV heart diastolic function.