The foramen ovale is a hole in the wall between the left and right atria of every human fetus. This hole allows blood to bypass the fetal lungs.Introducer sheath (10, 30, 40) having a flexible kink-resistant distal tip portion (26, 32, 42). Completing the Form The I-beam pointer allows you to type text. The hand pointer allows you to select a check box or radio button. Imaging description. PFO is the persistent patency of a congenital opening or foramen ovale in the interatrial septum, which normally closes after birth. Patent foramen ovale, a possible cause of symptomatic migraine: a study of 74 patients with acute ischemic stroke. The date shown in the middle column above indicates when each form was last revised.