Characterization of Flow Efficiency, Pulsatility, and Respiratory Variability in Different Types of Fontan Circuits Using Quantitative Parameters

Purpose Details on the hemodynamic differences among Fontan operations remain unclear according to respiratory and cardiac cycles. This study was undertaken to investigate hemodynamic characteristics in different types of Fontan circulation by quantification of blood flow with the combined influence of cardiac and respiratory cycles. Materials and Methods Thirty-five patients [10 atriopulmonary connections (APC), 13 lateral tunnels (LT), and 12 extracardiac conduits (ECC)] were evaluated, and parameters were measured in the superior vena cava, inferior vena cava (IVC), hepatic vein (HV), baffles, conduits, and left and right pulmonary artery. Pulsatility index (PIx), respiratory variability index (RVI), net antegrade flow integral (NAFI), and inspiratory/expiratory blood flow (IQ/EQ) were measured by intravascular Doppler echocardiography. Results The PIx between APC and total cavopulmonary connection (TCPC; LT and ECC) showed significant differences at all interrogation points regardless of respiratory cycles. The PIxs of HVs and IVCs in APC significantly increased, compared with that in LT and ECC, and the RVI between APC and TCPC showed significant differences at all interrogation points (p<0.05). The NAFI and IQ/EQ between APC and TCPC showed significant differences at some interrogation points (p<0.05). Conclusion Patients with different types of Fontan circulation show different hemodynamic characteristics in various areas of the Fontan tract, which may lead to different risks causing long-term complications. We believe the novel parameters developed in this study may be used to determine flow characteristics and may serve as a clinical basis of management in patients after Fontan operations.