ICD-10-CM 2027 diagnosis code
Q21.3Tetralogy of Fallot
Q21.3 is a valid, billable ICD-10-CM code for tetralogy of fallot. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.
Looking up by condition? See ICD-10 code for Tetralogy of Fallot.
Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About Q21.3
Q21.3 is the ICD-10-CM diagnosis code for tetralogy of Fallot. It belongs to category Q21 (congenital malformations of cardiac septa), block Q20-Q28 (congenital malformations of the circulatory system) and chapter 17 (congenital malformations, deformations, chromosomal abnormalities, and genetic disorders). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.
Within Q21 (congenital malformations of cardiac septa), Q21.3 is specifically for tetralogy of Fallot. Related codes cover ventricular septal defect (Q21.0), atrial septal defect (Q21.1), atrioventricular septal defect (Q21.2), Aortopulmonary septal defect (Q21.4), other congenital malformations of cardiac septa (Q21.8) and congenital malformation of cardiac septum, unspecified (Q21.9).
As a secondary diagnosis it is an MCC (major complication or comorbidity), which can move an inpatient stay into the highest-paying "with MCC" MS-DRG of its family, unless the principal diagnosis excludes it.
In MS-DRG v44.0, it is part of the grouping logic for DRG 306 (Cardiac Congenital and Valvular Disorders with MCC, relative weight 1.546) and DRG 307 (Cardiac Congenital and Valvular Disorders without MCC, relative weight 0.9148), in MDC 05 (Diseases and Disorders of the Circulatory System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
It is exempt from present-on-admission (POA) reporting, so no POA indicator is required.
It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.
Before ICD-10, this condition was coded in ICD-9-CM as 745.2 (tetralogy of fallot).
Coding notes
- Ventricular septal defect with pulmonary stenosis or atresia, dextroposition of aorta and hypertrophy of right ventricle.
Notes that apply from higher levels
Instructions written at a parent level also apply to Q21.3.
› From Q21 Congenital malformations of cardiac septa
- acquired cardiac septal defect (I51.0)
Broader instructions also apply from Chapter 17: Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders.
Alphabetic index entries
16 entriesTerms in the official ICD-10-CM index that lead to Q21.3.
- Anomaly, anomalous (congenital) (unspecified type) › heart › septum › interventricular › with pulmonary stenosis or atresia, dextraposition of aorta and hypertrophy of right ventricle
- Anomaly, anomalous (congenital) (unspecified type) › heart › septum › ventricular › with pulmonary stenosis or atresia, dextraposition of aorta and hypertrophy of right ventricle
- Anomaly, anomalous (congenital) (unspecified type) › heart › tetralogy of Fallot
- Defect, defective › interventricular septal › with dextroposition of aorta, pulmonary stenosis and hypertrophy of right ventricle
- Defect, defective › interventricular septal › in tetralogy of Fallot
- Defect, defective › ventricular septal › in tetralogy of Fallot
- Dextraposition, aorta › in tetralogy of Fallot
- Fallot's › tetrad or tetralogy
- Hypertrophy, hypertrophic › ventricle, ventricular (heart) › in tetralogy of Fallot
- Imperfect › closure (congenital) › septum › interventricular › in tetralogy of Fallot
- Imperfect › closure (congenital) › septum › ventricular › with pulmonary stenosis or atresia, dextraposition of aorta, and hypertrophy of right ventricle
- Imperfect › closure (congenital) › septum › ventricular › in tetralogy of Fallot
- Stenosis, stenotic (cicatricial) › pulmonary (artery) (congenital) › with ventricular septal defect, transposition of aorta, and hypertrophy of right ventricle
- Stenosis, stenotic (cicatricial) › pulmonary (artery) (congenital) › in tetralogy of Fallot
- Syndrome › Fallot's
- Tetralogy of Fallot
MS-DRG v44.0 grouping
All DRGs →Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.
MDC 05 · Diseases and Disorders of the Circulatory System
ICD-9-CM equivalent
Converter →- 745.2Tetralogy of fallotexact
From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
- No changes since FY2016.
Common questions about Q21.3
Is Q21.3 billable?
- Yes. Q21.3 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can Q21.3 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict Q21.3 as a principal diagnosis.
Is Q21.3 a CC or MCC?
- Q21.3 is an MCC (major complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.
What DRG does Q21.3 group to?
- Q21.3 is used in the MS-DRG v44.0 logic for MS-DRG 306 (Cardiac Congenital and Valvular Disorders with MCC) and MS-DRG 307 (Cardiac Congenital and Valvular Disorders without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.
What is the ICD-9 code for Q21.3?
- The CMS General Equivalence Mappings map Q21.3 to ICD-9-CM 745.2.