I27.21 Secondary pulmonary arterial hypertension

The ICD-10-CM code for Secondary pulmonary arterial hypertension is I27.21 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

9: Diseases of the circulatory system (I00-I99)

Section

I26-I28: Pulmonary heart disease and diseases of pulmonary circulation (I26-I28)

Category I27

21 codes (17 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to I27.21:

• Hypertension, hypertensive (accelerated) (benign) (essential) (idiopathic) (malignant) (systemic) › pulmonary › group 1 (associated) (drug-induced) (toxin-induced)
• Hypertension, hypertensive (accelerated) (benign) (essential) (idiopathic) (malignant) (systemic) › pulmonary › arterial (associated) (drug-induced) (toxin-induced)
• Hypertension, hypertensive (accelerated) (benign) (essential) (idiopathic) (malignant) (systemic) › pulmonary › secondary › arterial

Inclusion Terms

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

U.S. Hospital Utilization

• An estimated 65,415 U.S. inpatient stays in 2023 included I27.21 among the documented diagnoses.
• 3,070 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Pulmonary Hypertension

11) Pulmonary Hypertension Pulmonary hypertension is classified to category I27, Other pulmonary heart diseases. For secondary pulmonary hypertension (I27.1, I27.2-), code also any associated conditions or adverse effects of drugs or toxins. The sequencing is based on the reason for the encounter, except for adverse effects of drugs (See Section I.C.19.e.).

Presumed relationship due to Index term “with”

The classification presumes a causal relationship between hypertension and heart involvement and between hypertension and kidney involvement, as the two conditions are linked by the term “with” in the Alphabetic Index. These conditions should be coded as related even in the absence of provider documentation explicitly linking them, unless the documentation clearly states the conditions are unrelated.

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)