2026 ICD-10-CM Diagnosis Code I27.849Fontan related circulation, unspecified

ICD-10-CM Codes›I00–I99›I26-I28›I27

ICD-10-CM I27.849
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I27.849 is a billable ICD-10-CM diagnosis code for fontan related circulation, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 314 through 316.

I27.849 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 2026.

Code Identity

ICD-10-CM Code
I27.849
Billable Status
Yes — Valid for Submission
Code Describes
Fontan related circulation, unspecified
Short Description
Fontan related circulation, unspecified
Same as the full description in the CMS dataset.
Parent Code
I27.84
Fontan related circulation

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI26-I28Pulmonary heart disease and diseases of pulmonary circulation
CategoryI27Other pulmonary heart diseases
This CodeI27.849Fontan related circulation, unspecified

Medicare Risk Adjustment (HCC)Billing

I27.849 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 2026 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.

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Code History & ChangesHistory

New Code I27.849 was added to the ICD-10-CM code set for FY 2026, effective October 1, 2025.

Replacement I27.849 replaces the following previously assigned code(s):

  • I27.89 - Other specified pulmonary heart diseases
FY 2026AddedAdded to the ICD-10-CM code setEffective October 1, 2025.
FY 2026CurrentRevised in the current code setEffective October 1, 2025 through September 30, 2026.

Questions About I27.849Overview

What is the ICD-10 code for fontan related circulation, unspecified?

The ICD-10-CM code for fontan related circulation, unspecified is I27.849 (sometimes written as I27849). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is I27.849 (Fontan related circulation) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report fontan related circulation, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does I27.849 group to?

When fontan related circulation, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 314, 315, 316, with relative weights from 0.6821 to 2.0852 depending on complications. Higher weights mean higher Medicare reimbursement.

Does I27.849 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage: I27.849 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).