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ICD-10-CM 2027 diagnosis code

Q21.13Coronary sinus atrial septal defect

✓ Billable / specificPOA exemptCC — complication/comorbidity

Q21.13 is a valid, billable ICD-10-CM code for coronary sinus atrial septal defect. 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 Unroofed coronary sinus.

Code last changed in FY2023 (effective October 1, 2022). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About Q21.13

Q21.13 is the ICD-10-CM diagnosis code for coronary sinus atrial septal defect. 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 Q21.1 (atrial septal defect), Q21.13 is specifically for coronary sinus atrial septal defect. Related codes cover unspecified (Q21.10), secundum atrial septal defect (Q21.11), Patent foramen ovale (Q21.12), superior sinus venosus atrial septal defect (Q21.14), inferior sinus venosus atrial septal defect (Q21.15), sinus venosus atrial septal defect, unspecified (Q21.16) and other specified atrial septal defect (Q21.19).

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" 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 was added in FY2023, effective October 1, 2022.

Coding notes

Applicable toConditions and synonyms classified to this code
  • Coronary sinus defect
  • Unroofed coronary sinus

Notes that apply from higher levels

Instructions written at a parent level also apply to Q21.13.

› From Q21.1 Atrial septal defect
Excludes2
  • ostium primum atrial septal defect (type I) (Q21.20)
› From Q21 Congenital malformations of cardiac septa
Excludes1
  • acquired cardiac septal defect (I51.0)

Broader instructions also apply from Chapter 17: Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders.

Alphabetic index entries

3 entries

Terms in the official ICD-10-CM index that lead to Q21.13.

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.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2023 (effective 10/1/2022): Added
  • No changes since FY2023.

Common questions about Q21.13

Is Q21.13 billable?

Yes. Q21.13 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can Q21.13 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict Q21.13 as a principal diagnosis.

Is Q21.13 a CC or MCC?

Q21.13 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does Q21.13 group to?

Q21.13 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.