2026 ICD-10-CM Diagnosis Code I28.1Aneurysm of pulmonary artery
ICD-10-CM Codes›I00–I99›I26-I28›I28
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 226
- Chronic Condition
I28.1 is a billable ICD-10-CM diagnosis code for aneurysm of pulmonary artery. 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. 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 4 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pulmonary heart disease.
For Medicare Advantage risk adjustment, I28.1 maps to CMS-HCC Category 226 (Heart Failure, Except End Stage and Acute) under the V28 model, adding a risk factor of about 0.360 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
I28.1 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
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.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Acquired aneurysm of pulmonary artery
- Acquired dissection of pulmonary artery
- Dilatation of pulmonary artery
- Injury of pulmonary artery
- Perforation of pulmonary artery co-occurrent and due to aneurysm of pulmonary artery
- Peripheral pulmonary artery A/V aneurysm
- Pulmonary artery aneurysm
- Pulmonary artery rupture
- Pulmonary blood vessel injury
- Pulmonary trunk dilatation
- Rupture of pulmonary artery co-occurrent and due to aneurysm of pulmonary artery
- Rupture of pulmonary vessel
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
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.
Patient EducationClinical
Aneurysms
An aneurysm is a bulge or "ballooning" in the wall of an artery. Arteries are blood vessels that carry oxygen-rich blood from the heart to other parts of the body. If an aneurysm grows large, it can burst and cause dangerous bleeding or even death.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert I28.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About I28.1Overview
What is the ICD-10 code for aneurysm of pulmonary artery?
The ICD-10-CM code for aneurysm of pulmonary artery is I28.1 (sometimes written as I281). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is I28.1 (Other diseases of pulmonary vessels) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report aneurysm of pulmonary artery on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does I28.1 group to?
When aneurysm of pulmonary artery 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.
Is I28.1 a CC or MCC?
CMS lists I28.1 as a CC (complication or comorbidity) for FY 2026. 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 4 closely related codes in its exclusion list.
What is the ICD-9 equivalent of I28.1?
Under the General Equivalence Mappings, aneurysm of pulmonary artery converts to ICD-9-CM 417.1 (pulmon artery aneurysm). The mapping is a direct match.
What HCC is I28.1?
I28.1 (aneurysm of pulmonary artery) maps to CMS-HCC Category 226 (Heart Failure, Except End Stage and Acute), commonly written as HCC 226, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 85 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 184.
Does I28.1 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, I28.1 adds a risk adjustment factor of about 0.360 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.217 to 0.537 depending on the payment segment). A more severe related category (HCC 221, HCC 222, HCC 223, HCC 224, and HCC 225) supersedes it when both are reported. See the full factor table on the HCC 226 category page.
