Introduction
Atrial septal defects (ASD) with more than 1.5:1 left to right shunts warrant closure by intervention or surgery. Interventional closure of ASDs is the preferred treatment modality if the rims of ASD are amenable to device closure. Deficiency of rims (< 5mm) is considered a contraindication for device closure of ASDs(1). The inferior vena cava rim and the atrioventricular valve rim are the most important borders to be assessed when considering a patient for device closure. ASD device closure has been attempted in patients with a borderline mitral rim if the other rims are adequate. Instability of the device and development of conduction disturbances and heart block have been attributed to attempted device closure in deficient atrioventricular valve rims because of the close proximity to the AV node. Eustachian valve frequently interferes with the proper deployment of device. Here, we describe a patient with borderline mitral rim where ASD device closure was successful because of the added stability provided by a prominent Eustachian valve.