The hole in the heart is a cardiac disorder called patent Foramen ovale (FOP). It is a congenital defect in the septum (wall) between the two upper chambers (atria) of the heart that occurs due to an incomplete closure of the atrial septum. The defect creates a flap or valve-like opening in the atrial septum wall. In simple terms, it is a hole in the heart that does not close as it should after birth. The hole in the heart is a congenital anomaly. In the anomaly, the septum between the two atria of the heart normally developed before birth, but the flap was not completely sealed after birth. The exact reason behind the defect is unknown. Sometimes, it can be a viral infection that can cause heart defects. There may be genetic factors, some medical conditions (such as Down's syndrome), medical prescriptions and over-the-counter drugs.