Addition of a small curvature reduces power losses across total cavopulmonary connections

Background. In the Fontan circulation the vis a tergo for lung perfusion is limited. The hypothesis of this in vitro study was that energy dissipation at the common cavopulmonary connection can be reduced by the addition of caval curvature. Methods. Two Perspex models were analyzed, the commonly used crosslike cavopulmonary connection (model 1) and a modified curved configuration (model 2). Pressures and flows across the connections were measured simultaneously at various caval and pulmonary artery now splits and resistances. Mixing of inferior and superior caval fluid was evaluated. Results. Caval pressure oscillations occurred in model 1 only. Curvature reduced power losses in all settings significantly (alpha = 0.05), most successfully at adult caval now ratios and at high flow rates. At equal pulmonary resistances pulmonary flow was balanced in both models. The inferior caval fluid is preferably directed to the right lung in model 2 predominantly for caval flow conditions in younger patients. Conclusions. Our data show that the modified curved cavopulmonary connection is hydrodynamically advantageous but might impair caval fluid mixing in younger children. (C) 1999 by The Society of Thoracic Surgeons.