2027 ICD-10-CM Diagnosis Code Q26.8Other congenital malformations of great veins

ICD-10-CM Codes›Q00-Q99›Q20-Q28›Q26

ICD-10-CM Q26.8
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

Q26.8 is a billable ICD-10-CM diagnosis code for other congenital malformations of great veins. 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 complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 9 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.

Q26.8 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
Q26.8
Billable Status
Yes — Valid for Submission
Code Describes
Other congenital malformations of great veins
Short Description
Other congenital malformations of great veins
Same as the full description in the CMS dataset.
Parent Code
Q26
Congenital malformations of great veins

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ20-Q28Congenital malformations of the circulatory system
CategoryQ26Congenital malformations of great veins
This CodeQ26.8Other congenital malformations of great veins

Present on Admission (POA)Billing

Q26.8 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

Q26.8 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.

  • Abnormal inferior vena caval connection
  • Abnormality of right inferior caval vein
  • Abnormality of right superior vena cava
  • Absence of inferior vena cava
  • Absence of superior vena cava
  • Absent bridging vein
  • Absent right superior vena cava
  • Anomalous insertion of right superior vena cava to left atrium
  • Atresia of left superior caval vein
  • Atresia of systemic vein
  • Atretic right superior vena cava
  • Azygos continuation of inferior caval vein to right superior caval vein
  • Bilateral superior vena cava
  • Congenital abnormality of great veins and coronary sinus
  • Congenital abnormality of hepatic vein
  • Congenital absence of inferior vena cava
  • Congenital absence of superior vena cava
  • Congenital absence of vena cava
  • Congenital atresia of inferior vena cava
  • Congenital atresia of inferior vena cava without azygos continuation
  • Congenital atresia of superior vena cava
  • Congenital azygos continuation of inferior vena cava
  • Congenital dilatation of inferior vena cava
  • Congenital dilatation of superior vena cava
  • Congenital hypoplasia of cardiac vein
  • Congenital hypoplasia of pulmonary artery
  • Congenital hypoplasia of right side of chest
  • Congenital malposition of inferior vena cava
  • Congenital malposition of superior vena cava
  • Congenital pulmonary venous atrium
  • Congenital stenosis of pulmonary veins
  • Congenital systemic venous atrium
  • Hypoplasia of cardiac vein
  • Inferior cava to left of spine with right descending aorta
  • Inferior caval vein anterior and same side as descending aorta
  • Inferior caval vein connecting to right atrium and left atrium
  • Inferior vena cava connecting to coronary sinus
  • Inferior vena cava connecting to morphological left atrium
  • Inferior vena cava interruption with bilateral azygos continuation
  • Inferior vena cava interruption with left sided hemiazygos continuation
  • Inferior vena cava interruption with right sided azygos continuation
  • Inferior vena cava to left of spine
  • Interrupted left inferior caval vein
  • Interrupted right inferior caval vein
  • Left inferior caval vein connecting to left atrium and right atrium
  • Left sided azygos continuation of inferior caval vein to left superior caval vein
  • Obstructed anomalous pulmonary venous pathway
  • Obstructive eustachian valve
  • Persistent common pulmonary vein
  • Persistent eustachian valve
  • Persistent left posterior cardinal vein
  • Primary congenital aneurysm of inferior vena cava
  • Primary congenital aneurysm of superior vena cava
  • Prolapse of eustachian valve
  • Prominent valve of inferior vena cava
  • Pulmonary hypertension due to developmental abnormality
  • Pulmonary vein stenosis
  • Pulmonary venous hypertension due to congenital stenosis of pulmonary vein
  • Pulmonary venous hypoplasia
  • Right inferior caval vein connecting to left atrium and right atrium
  • Right inferior caval vein connecting to left sided atrium
  • Right superior caval vein connecting to coronary sinus
  • Right superior caval vein connecting to coronary sinus and then to left sided atrium
  • Right superior caval vein connecting to left atrium and right atrium
  • Right superior caval vein persisting to coronary sinus and then to right sided atrium
  • Right ventricular outflow tract obstruction due to prolapse of eustachian valve
  • Scimitar syndrome
  • Scimitar syndrome with additional anomalous pulmonary venous connection
  • Separate hepatic venous and inferior caval venous connections to heart
  • Sinus venosus atrial septal defect
  • Sinus venosus defect with overriding inferior vena cava
  • Sinus venosus defect with overriding superior vena cava
  • Transposition of inferior vena cava
  • Venous remnant
  • Venous valvular anomaly

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to Q26.8: its own notes plus those printed at 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.

  • Absence of vena cava (inferior) (superior)
  • Azygos continuation of inferior vena cava
  • Persistent left posterior cardinal vein
  • Scimitar syndrome

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.

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

  • Scimitar Syndrome

    an anomalous pulmonary venous return in which the right pulmonary vein is not connected to the left atrium but to the inferior vena cava. scimitar syndrome is named for the crescent- or turkish sword-like shadow in the chest radiography and is often associated with hypoplasia of the right lung and right pulmonary artery, and dextroposition of the heart.

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 Q26.8 to ICD-9-CMHistory

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

ICD-9-CM
747.49 Great vein anomaly NEC
Approximate The match is approximate rather than exact.

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 Q26.8Overview

What is the ICD-10 code for other congenital malformations of great veins?

The ICD-10-CM code for other congenital malformations of great veins is Q26.8 (sometimes written as Q268). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is Q26.8 (Congenital malformations of great veins) a billable code?

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

What MS-DRG does Q26.8 group to?

When other congenital malformations of great veins 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 Q26.8 a CC or MCC?

CMS lists Q26.8 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 9 closely related codes in its exclusion list.

Is Q26.8 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 other congenital malformations of great veins on inpatient claims. The code appears in the Congenital malformations of the circulatory system (Q20-Q28) range of the CMS exempt list.

Does Q26.8 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage: Q26.8 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).