When does a ?patent foramen ovale have to be operated on?

When it's big: Most foramen ovale close after a baby is born, however sometimes it does not close. If a person has heart problem, pictures are taken a patent foramen may be discovered. If the pfo is contributing to a heart problem it may be closed, however many are discovered only after a person dies of other causes and happens to have autopsy, in other words people likely have them and they don't effect them.

Symptomatic: Most patent foramen ovale defects are asymptomatic (do not cause symptoms). When there are issues with abnormal blood flow in the heart causing respiratory or abnormal pressure symptoms then surgery may need to be considered.