Q21.12 Patent foramen ovale - ICD-10-CM Diagnosis Codes. Q21.10, Atrial septal defect, unspecified.Q21.11, Secundum atrial septal defect. The following diagnostic codes are found in the International Classification of. Patent foramen ovale. Persistent foramen ovale. A condition in which the foramen ovale in the atrial septum fails to close shortly after birth. Large congenital atrial septal defect (ASD) and patent foramen ovale (PFO). ICD10 Diagnosis Code(s). 1897. ICD10 Diagnosis Code(s). 1897.