Clamshell percutaneous closure of secundum ASD

Transvenous catheter techniques have been devised to cross the open secundum septal defect and release a variously-shaped expandable framework to seal the opening. One of the requirements however is that the defect have sufficient tissue to act as an anchorable 'lip' so that the device remains stable and does not migrate over time. 

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Transesophageal apical 4 chamber view prominently showing the right atrial side of the clamshell device closely applied to the interatrial fossa.

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Transesophageal apical 4 chamber view with color doppler showing the right atrial bloodflow does not communicate with the left atrium by the clamshell device closely applied to the interatrial fossa.

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Another transesophageal apical 4 chamber view with color doppler showing the right atrial bloodflow does not communicate with the left atrium since it is now sealed by the clamshell device applied across the interatrial fossa.