Q21.12 Patent foramen ovale - ICD-10-CM Diagnosis Codes. A condition in which the foramen ovale in the atrial septum fails to close shortly after birth.Available for iPhone, iPad, Android, and Web. Patent or persistent: foramen ovale; ostium secundum defect (type II). Sinus venosus defect. A 'foramen ovale' is an opening that allows blood to go around the lungs in developmental stages. Patent foramen ovale. Q21.19. Other specified atrial septal defect. 12 for Patent foramen ovale - BILLABLE CODE. Use Q21.13 for Coronary sinus atrial septal defect - BILLABLE CODE.