Respiratory pulsations affect fontan connection power loss: using real time velocity mapping to improve the accuracy of computational simulations

Abstract

Background Total cavopulmonary connection (TCPC) hemodynamics has been hypothesized to be associated with long-term complications in single ventricle heart defect patients. Breath-holding or averaged free-breathing segmented phase contrast magnetic resonance imaging (PC-MRI) has been commonly used for the boundary conditions in numerical simulations to evaluate TCPC hemodynamics. However, the impact of ignoring respiration in the evaluation is not fully understood. Methods Nine patients with TCPC were included. Real-time PCMRI images were acquired under resting free-breathing (FB) and breath-holding (BH) conditions at superior and inferior vena cava (SVC and IVC). Patient specific 3D TCPC anatomies were reconstructed from transverse CMR images. Computational fluid dynamics (CFD) simulations were performed using caval flow waveforms derived from real-time PC-MRI as inlet boundary conditions. A Windkessel three-element model was applied at the outlets to model the downstream vasculature. Average flow rates and pulsatility indices ([maximum-minimum]/average flow rate) under these two conditions throughout the duration of one respiratory cycle were compared. TCPC power loss was quantified and qualitative flow structure within the TCPC was compared between FB and BH conditions. Lagrangian particle tracking was performed for both conditions to quantify particle washout time. Results