(1) The foramen ovale usually closes within the first year of life, so the foramen ovale is unclosed in newborns and infants, and if the foramen ovale remains unclosed in children older than 3 years of age, it is called unclosed foramen ovale. In about 20% to 25% of adults, the foramen ovale is not completely closed, leaving a small gap, i.e., the foramen ovale is not closed. When the fetus is in the 6th and 7th week of embryonic development, the septum of the atrium sends out 2 septa one after another. The septum that appears first is the primary septum or the first septum, and the septum that appears later is the secondary septum or the second septum, which grows in a semilunar shape from the dorsal wall of the midline of the atrium and grows toward the atrioventricular canal and fuses with the endocardial cushion, leaving a small hole before it fuses with the caudal part of the atrioventricular septum, which is called the primary foramen. When the primary foramen is not closed, the proximal part of the primary septum absorbs itself to form a second atrial foramen, called the secondary foramen. On the right side of the secondary foramen, a sickle-shaped septum grows from the atrial wall, called the secondary septum or the second septum, and the lower edge of this septum is depressed in a sickle shape, forming the edge of the fossa ovalis, and the primary and secondary septum at the fossa ovalis fail to fuse with normal natural adhesions, leaving a small gap called the fossa ovalis, which is the normal passage of blood during the fetal period. After birth, a fissure-like abnormal channel that remains at the fossa ovalis in the interatrial septum is called Patent ForamenOvale (PFO). (2) If the patent foramen ovale is not combined with paradoxical cerebral embolism or transient ischemic attack (TIA), it is unlikely to cause severe pulmonary hypertension due to its hemodynamic changes, so treatment is generally not required. However, in cases of paradoxical thrombosis or recurrent ischemic manifestations, interventional treatment should be considered. Currently, transcatheter occlusion of patent foramen ovale is safe and effective and has largely replaced surgical procedures. Patients with patent foramen ovale who have one of the following indications for intervention are better off: ① patent foramen ovale with a right-to-left shunt or a right-to-left shunt confirmed by ultrasound during contrast Valsalva maneuvers on venous sonography. (ii) Foramen ovale non-occlusion with or without atrial septal bulge tumor, often with unexplained headache. (iii) Foramen ovale unclosed with TransientIschemicAttack (TIA) manifestation of unknown origin or intracranial ischemic lesion. ④Unclosed foramen ovale with unexplained extracranial thromboembolism. (⑤) Those with unclosed foramen ovale and cerebral or pulmonary infarction caused by thrombosis of the venous system. (6) Residual unclosed foramen ovale even after surgery. (vii) The foramen ovale is not closed and has a multiforaminal septal defect.