Look before you close: atrial septal defect with undiagnosed partial anomalous pulmonary venous return.

The growing and continued success of percutaneous closure of atrial defects is related to its high benefit-to-risk ratio in appropriately selected patients. The following case illustrates a previously undocumented danger, namely, the potential for incomplete correction. A thorough transesophageal examination performed at the time of the planned atrial defect closure suggested the presence of a partial anomalous pulmonary vein insertion, which was then appropriately documented and the incomplete closure was averted.