2027 ICD-10-CM Diagnosis Code Q21.3Tetralogy of Fallot

ICD-10-CM Codes›Q00-Q99›Q20-Q28›Q21

ICD-10-CM Q21.3
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

Q21.3 is a billable ICD-10-CM diagnosis code for tetralogy of Fallot. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 306 through 307. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 91 closely related codes. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Cardiac and circulatory congenital anomalies.

Q21.3 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 191 for payment year 2027.

Code Identity

ICD-10-CM Code
Q21.3
Billable Status
Yes — Valid for Submission
Code Describes
Tetralogy of Fallot
Short Description
Tetralogy of Fallot
Same as the full description in the CMS dataset.
Parent Code
Q21
Congenital malformations of cardiac septa

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ20-Q28Congenital malformations of the circulatory system
CategoryQ21Congenital malformations of cardiac septa
This CodeQ21.3Tetralogy of Fallot

Present on Admission (POA)Billing

Q21.3 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Congenital malformations of the circulatory system (Q20-Q28).

Medicare Risk Adjustment (HCC)Billing

Q21.3 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model, but it maps to payment categories in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
no payment category in the model that pays 100% of MA risk scores
Prior Model (CMS-HCC V24)
Not mapped under V24
this diagnosis newly risk-adjusts under the V28 model
Part D (RxHCC)
RxHCC 191 — Ventricular Septal Defect and Major Congenital Heart Disorders
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Agenesis of artery
  • Anterior deviation of infundibular septum of Fallot type
  • Atrioventricular septal defect associated with tetralogy of Fallot
  • Congenital abnormality of thoracic aorta and pulmonary arteries
  • Congenital absence of ductus arteriosus
  • Congenital absence of pulmonary valve
  • Congenital atresia of pulmonary valve
  • Dextraposition of aorta in Fallot's tetralogy
  • Dextrotransposition of aorta
  • Fallot complex with intellectual disability and growth delay syndrome
  • Pulmonary atresia with ventricular septal defect
  • Pulmonary atresia with ventricular septal defect of Fallot type
  • Pulmonary valve agenesis, tetralogy of Fallot, absence of ductus arteriosus syndrome
  • Tetralogy of Fallot
  • Tetralogy of Fallot with absent pulmonary valve
  • Tetralogy of Fallot with atresia of pulmonary valve
  • Tetralogy of Fallot with pulmonary atresia and systemic-to-pulmonary collateral artery
  • Tetralogy of Fallot with pulmonary stenosis
  • Ventricular septal defect in Fallot's tetralogy

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to Q21.3: its own notes plus those printed at Q21 and Chapter 17. A note printed at a category, block or chapter applies to every code under it.

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Ventricular septal defect with pulmonary stenosis or atresia, dextroposition of aorta and hypertrophy of right ventricle.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From Q21 Congenital malformations of cardiac septa applies to 17 codes
  • acquired cardiac septal defect (I51.0)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 17 (Q00-QA1) Congenital malformations, deformations and chromosomal abnormalities applies to 900 codes
  • inborn errors of metabolism (E70-E88)

Notes

General instructions on how these codes are used.

From Chapter 17 (Q00-QA1) Congenital malformations, deformations and chromosomal abnormalities applies to 900 codes
  • Codes from this chapter are not for use on maternal records

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name Q21.3, its category, or a range that includes it.

Use Additional Code 1

These codes say to use an additional code from the note, and Q21.3 is one of the codes named.

  • Q87.88 CTNNB1 syndrome
    congenital heart malformations (Q20.0-Q24.9) names Q20.0-Q24.9, which includes this code

Code Also 1

These codes say Q21.3 may also be needed to fully describe the condition. The note gives no sequencing direction.

  • Q87.85 MED13L syndrome
    congenital malformations of cardiac septa (Q21.-) names Q21.-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MAL001
Cardiac and circulatory congenital anomalies
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Tetralogy of Fallot

    a combination of congenital heart defects consisting of four key features including ventricular septal defects; pulmonary stenosis; right ventricular hypertrophy; and a dextro-positioned aorta. in this condition, blood from both ventricles (oxygen-rich and oxygen-poor) is pumped into the body often causing cyanosis.

Patient EducationClinical

Congenital Heart Defects

Congenital heart defects (CHDs) are problems with the structure of the heart. "Congenital" means that that the problems are present at birth. These defects happen when a fetus's heart doesn't develop normally during pregnancy. Congenital heart defects are the most common type of birth defect.

The full article covers:

  • What are congenital heart defects?
  • What causes congenital heart defects?
  • Who is more likely to have a baby with a congenital heart defect?
  • What are the symptoms of congenital heart defects?
  • What other problems do congenital heart defects cause?
  • How are congenital heart defects diagnosed?
  • What are the treatments for congenital heart defects?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert Q21.3 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
745.2 Tetralogy of fallot
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About Q21.3Overview

What is the ICD-10 code for tetralogy of Fallot?

The ICD-10-CM code for tetralogy of Fallot is Q21.3 (sometimes written as Q213). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is Q21.3 (Congenital malformations of cardiac septa) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report tetralogy of Fallot on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does Q21.3 group to?

When tetralogy of Fallot is the principal diagnosis on an inpatient stay, it groups to MS-DRG 306, 307, with relative weights from 0.9146 to 1.5457 depending on complications. Higher weights mean higher Medicare reimbursement.

Is Q21.3 a CC or MCC?

CMS lists Q21.3 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 91 closely related codes in its exclusion list.

Is Q21.3 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for tetralogy of Fallot on inpatient claims. The code appears in the Congenital malformations of the circulatory system (Q20-Q28) range of the CMS exempt list.

Does Q21.3 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage: Q21.3 maps to no category in the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 191 (Ventricular Septal Defect and Major Congenital Heart Disorders).