2026 ICD-10-CM Diagnosis Code I27.21Secondary pulmonary arterial hypertension

ICD-10-CM Codes›I00–I99›I26-I28›I27

ICD-10-CM I27.21
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I27.21 is a billable ICD-10-CM diagnosis code for secondary pulmonary arterial hypertension. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pulmonary heart disease.

For Medicare Advantage risk adjustment, I27.21 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.

This medical diagnosis code is frequently used in Cardiology medical specialties to designate conditions such hypertension.

Code Identity

ICD-10-CM Code
I27.21
Billable Status
Yes — Valid for Submission
Code Describes
Secondary pulmonary arterial hypertension
Short Description
Secondary pulmonary arterial hypertension
Same as the full description in the CMS dataset.
Parent Code
I27.2
Other secondary pulmonary hypertension

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI26-I28Pulmonary heart disease and diseases of pulmonary circulation
CategoryI27Other pulmonary heart diseases
This CodeI27.21Secondary pulmonary arterial hypertension

Medicare Risk Adjustment (HCC)Billing

I27.21 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.

CMS-HCC V28 Category (Payment Model)
HCC 226— Heart Failure, Except End Stage and Acute
Payment HCC · PY 2026 one of 34 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.360
community, non-dual, aged · ranges 0.217–0.537 across segments
Hierarchy
Superseded by HCC 221, HCC 222, HCC 223, HCC 224, and HCC 225
a more severe related category takes the payment when both are reported
Prior Model (CMS-HCC V24)
HCC 85
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 85 · ESRD (V21): HCC 85 · ESRD (V24): HCC 85
ESRD V21 weights: 0.082 dialysis, 0.186–0.336 functioning graft · ESRD V24 weights: 0.063 dialysis, 0.169–0.302 functioning graft
Part D (RxHCC)
RxHCC 183 — Pulmonary Arterial Hypertension
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.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Associated pulmonary arterial hypertension
  • Pulmonary arterial hypertension associated with chronic hemolytic anemia
  • Pulmonary arterial hypertension associated with congenital heart disease
  • Pulmonary arterial hypertension associated with congenital systemic-to-pulmonary shunt
  • Pulmonary arterial hypertension associated with connective tissue disease
  • Pulmonary arterial hypertension associated with HIV infection
  • Pulmonary arterial hypertension associated with schistosomiasis
  • Pulmonary arterial hypertension induced by drug
  • Pulmonary arterial hypertension induced by toxin
  • Pulmonary hypertension due to familial pulmonary capillary hemangiomatosis
  • Pulmonary hypertension due to pulmonary capillary hemangiomatosis
  • Pulmonary hypertension due to pulmonary veno-occlusive disease
  • Secondary pulmonary hypertension
  • Small vessel pulmonary hypertension
  • Solitary pulmonary hypertension

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • (Associated) (drug-induced) (toxin-induced) pulmonary arterial hypertension NOS
  • (Associated) (drug-induced) (toxin-induced) (secondary) group 1 pulmonary hypertension

Code Also

  • associated conditions if applicable, or adverse effects of drugs or toxins, such as:
  • adverse effect of appetite depressants T50.5X5
  • congenital heart disease Q20 Q28
  • human immunodeficiency virus [HIV] disease B20
  • polymyositis M33.2
  • portal hypertension K76.6
  • rheumatoid arthritis M05
  • schistosomiasis B65
  • Sjögren syndrome M35.0
  • systemic sclerosis M34

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 CIR014
Pulmonary heart disease
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Pulmonary Hypertension

Pulmonary hypertension, sometimes called PH, is a serious condition that affects the blood vessels in the lungs. It develops when the blood pressure in your lungs is higher than normal.

The full article covers:

  • What is pulmonary hypertension?
  • What causes pulmonary hypertension?
  • Who is more likely to develop pulmonary hypertension?
  • What are the symptoms of pulmonary hypertension?
  • What other problems can pulmonary hypertension cause?
  • How is pulmonary hypertension diagnosed?
  • What are the treatments for pulmonary hypertension?

Read the full article at MedlinePlus

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

Convert I27.21 to ICD-9-CMHistory

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

ICD-9-CM
416.8 Chr pulmon heart dis NEC
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Replacement I27.21 replaces the following previously assigned code(s):

  • I27.2 - Other secondary pulmonary hypertension
FY 2019AddedAdded to the ICD-10-CM code setEffective October 1, 2018.
FY 2020–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About I27.21Overview

What is the ICD-10 code for secondary pulmonary arterial hypertension?

The ICD-10-CM code for secondary pulmonary arterial hypertension is I27.21 (sometimes written as I2721). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is I27.21 (Other secondary pulmonary hypertension) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report secondary pulmonary arterial hypertension on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does I27.21 group to?

When secondary pulmonary arterial hypertension 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.

What is the ICD-9 equivalent of I27.21?

Under the General Equivalence Mappings, secondary pulmonary arterial hypertension converts to ICD-9-CM 416.8 (chr pulmon heart dis NEC). The mapping is approximate, so confirm the match fits the documentation.

What HCC is I27.21?

I27.21 (secondary pulmonary arterial hypertension) 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 183.

Does I27.21 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, I27.21 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.