Recent modifications to the original Fontan procedure have placed emphasis on the nature of the connection between the cavae and the pulmonary arteries. Since there is no ventricle acting as a pump to drive blood through the pulmonary circulation, a critical determinant of outcome is the overall resistance to flow across the surgical connection and pulmonary circuit. This study addressed the hypothesis that Fontan connection geometry significantly affects resistance to flow. Methods: Connections of the following three types were performed on explanted canine hearts; (1) atriopulmonary connection (APC), (2) lateral tunnel total cavopulmonary connection (TCPC) and(3) partial cavopulmonary connection (intra-atrial baffle with posterior cavo-atriopulmonary connection) (PCPC). Anatomically correct transparent urethane flow models were constructed using injection molding and casting procedures. The models were perfused using a blood analog fluid at flow rates ranging from 2-7 L/min. A variable voltage pumping system allowed input voltage, which can be related to the rate of energy expenditure, to be recorded for each flow condition. Results: Resistances at constant flow differed for each geometry (p<.01). The TCPC had the lowest values of resistance for equivalent flows through each model followed by the PCPC and the APC. Resistance differentials increased with flow rate for each model(p<.05). Conclusions: Based on these experiments, we conclude that a lateral tunnel TCPC offers the least resistance flow among these commonly used connections. The observed increase in resistance differentials with flow may have implications regarding exercise capacity and suggests that minimizing resistance in the Fontan circuit may have significant implications for postoperative morbidity and survival. Figure

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Figure 1