Identifying Anomalies of Systemic Venous Drainage: Systemic Venous Anomalies; Atrial Morphology.

So as to produce totally anomalous systemic venous connection, all of the systemic venous tributaries, along with the coronary sinus, should be connected with the morphologically left atrium. Previous descriptions of this rare constellation of anomalous connections of the systemic venous tributaries of the heart have been compromised by the inclusion of individuals having isomeric atrial appendages. In these settings, most frequently, the totally, or almost totally, anomalous systemic venous connections are associated with a sinus venosus defect. It is the anomalous pulmonary venous connections that then create a venovenous bridge, which permits the systemic venous tributaries to drain into the morphologically left atrium, even though they may be predominantly connected to the right atrium. More rarely, it is feasible for the primary atrial septum to develop so as to leave the systemic venous sinus in direct connection with the body of the morphologically left, rather than the morphologically right, atrium. We report a series of patients potentially falling into the category of anomalous systemic venous connections. The findings show a spectrum from partially to totally anomalous connections, with some better interpreted on the basis of anomalous drainage. Included in our cases, nonetheless, is an autopsied example of totally anomalous systemic venous connection produced by an abnormal location of the primary atrial septum. We discuss the potential morphogenesis for this finding. We emphasize the distinction that needs to be made between anomalous systemic venous connections and anomalous systemic venous drainage.