Bidirectional superior cavopulmonary anastomosis improves mechanical efficiency in dilated atriopulmonary connections

Objective: Few therapeutic options exist for patients with failing dilated atriopulmonary connections. We addressed the hypothesis that a bidirectional superior cavopulmonary anastomosis will improve the hemodynamic efficiency of dilated atriopulmonary connections while maintaining physiologic pulmonary flow distributions, Methods: Dilated atriopulmonary connections with and without a bidirectional superior cavopulmonary anastomosis were created in explanted sheep heart preparations and transparent glass models. ii mechanical energy balance and flow visualization were performed for 6 flow rates (1-6 L/min), both,vith and without the bidirectional superior cavopulmonary anastomosis? and were then compared. A novel contrast echocardiographic technique was used to quantify inferior vena cava flow (hepatic venous return) distributions into the pulmonary arteries, Results: The rate of fluid-energy dissipation was 52% +/- 14% greater in the dilated atriopulmonary anastomosis than in the bidirectional superior cavopulmonary anastomosis model over the range of flow rates studied (P = 6.3E(-3)). Total venous return passing to the right pulmonary artery increased from 41% +/- 2% to 47% +/- 3% (P = 9.7E(-3)) and that for inferior vena cava flow decreased from and 42% +/- 3% to 12% +/- 4% (P = 3.3E(-4)) after addition of the bidirectional superior cavopulmonary anastomosis. Flow visualization confirmed more ordered atrial flow in the bidirectional cavopulmonary anastomosis model, resulting from a reduction of caval flow stream collision and interaction. Conclusions: A bidirectional cavopulmonary anastomosis reduces fluid-energy dissipation in atriopulmonary connections, provides a physiologic distribution of total flow and maintains some hepatic venous flow to each lung. This approach may be a technically simple alternative to atriopulmonary takedown procedures and conversions to total cavopulmonary connections in selected patients.