Free Medical Coding > ICD10 CM > 2024 ICD-10-CM Codes > 2024 ICD-10-CM Codes Q00-Q99 – Congenital malformations, deformations and chromosomal abnormalities (Q00-Q99) > 2024 ICD-10-CM Codes Q20-Q28 – Congenital malformations of the circulatory system (Q20-Q28) > 2024 ICD-10-CM Codes Q21 – Congenital malformations of cardiac septa (Q21) > 2024 ICD-10-CM Codes Q21.2 – Atrioventricular septal defect (Q21.2)