Unusual atrial septal anatomy resulting in an interatrial chamber: the true triatrial heart?

We report two patients who were found to have nearly identical, very peculiar atrial septal anatomy. The septum actually consisted of two distinct septa with discrete defects creating an interatrial chamber. The orifice from the left atrium was unrestrictive, but the orifice to the right atrium was restrictive. Overall, there was net left-to-right shunting. This finding represents a clinical dilemma: Left untreated, the interatrial chamber might be a nidus for thrombus formation, but attempting device closure might result in incomplete obliteration of the chamber, also resulting in potential locus for clot formation. Clot formation might lead to systemic embolization. Angiographic findings are correlated with echocardiographic findings. Embryology and treatment options are considered.