Fluid dynamic comparison of intra-atrial and extracardiac total cavopulmonary connections

Objective: Extracardiac total cavopulmonary connection has recently been introduced as an alternative to intra-atrial procedures. The purpose of this study was to compare the hydrodynamic efficiency of extracardiac and intra- atrial lateral tunnel procedures in total cavopulmonary connections. Methods: Intra-atrial lateral tunnel, extracardiac tunnel, and extracardiac conduit with and without caval vein offset were performed on explanted sheep heart preparations and studied in an in vitro flow loop. A rate of fluid-energy dissipation analysis was performed for each model using simultaneous measurement of pressure and flow at each inlet and outlet of the right side of the heart. Preparations were perfused by using a steady flow blood pump at 4 flow indices (1-6 L/min/m²) with the inferior vena cava carrying 65% of the total venous return. Results: Fluid-power losses were consistently lower for the extracardiac conduit procedure compared with the two tunnel configurations (P <.01). A further reduction: in energy dissipation of up to 36% was noted in the extracardiac procedure, with 5 mm offset of the extracardiac conduit toward the distal right pulmonary. The intra-atrial and extracardiac tunnel procedures were least efficient, with losses 73% greater than the optimal extracardiac conduit procedure. Conclusions: The extracardiac conduit procedure provides superior hemodynamics compared with the intra-atrial lateral tunnel and extracardiac tunnel techniques. This hydrodynamic advantage is markedly enhanced by the use of conduit-superior vena cava offset, particularly at high physiologic flows that are representative of exercise. These data suggest additional rationale for the use of extracardiac conduit procedures for final-stage completion of the Fontan circulation.