Not to worry (most of the time).

Most (87.6%) of residual atrial L-R shunts after Gore Cardioform septal occluder implant disappear by 12 months. Residual leaks at implantation were more common in larger defects with smaller retro-aortic rims, and multiple fenestrations. While most residual defects close in 12 months, we unfortunately do not yet have a clear idea why or which of the 13% do not close.