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 c aval curvature. Methods. Two Perspex models were analyzed, the commonly used crosslike cavo pulmonary 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 re duced power losses in all settings significantly (alpha = 0.05), most succe ssfully at adult caval now ratios and at high flow rates. At equal pulmonar y resistances pulmonary flow was balanced in both models. The inferior cava l fluid is preferably directed to the right lung in model 2 predominantly f or caval flow conditions in younger patients. Conclusions. Our data show that the modified curved cavopulmonary connectio n is hydrodynamically advantageous but might impair caval fluid mixing in y ounger children. (C) 1999 by The Society of Thoracic Surgeons.