ICD-10-CM 2027
ICD-10 code for hypertrophic subaortic idiopathic stenosis
From the official ICD-10-CM alphabetic index entry “Stenosis, stenotic (cicatricial) › hypertrophic subaortic (idiopathic)”. Page updated September 29, 2026.
About coding hypertrophic subaortic idiopathic stenosis
The ICD-10-CM code for hypertrophic subaortic idiopathic stenosis is I42.1 (Obstructive hypertrophic cardiomyopathy).
Within I42 (cardiomyopathy), I42.1 is specifically for obstructive hypertrophic cardiomyopathy. Related codes cover dilated cardiomyopathy (I42.0), other hypertrophic cardiomyopathy (I42.2), Endomyocardial (eosinophilic) disease (I42.3), endocardial fibroelastosis (I42.4), other restrictive cardiomyopathy (I42.5), alcoholic cardiomyopathy (I42.6), due to drug and external agent (I42.7), other cardiomyopathies (I42.8) and 1 more.
Code first: pre-existing cardiomyopathy complicating pregnancy and puerperium (O99.4).
As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.
Common questions about hypertrophic subaortic idiopathic stenosis ICD-10 codes
What is the ICD-10 code for hypertrophic subaortic idiopathic stenosis?
- I42.1 — Obstructive hypertrophic cardiomyopathy.
Is I42.1 billable?
- Yes. I42.1 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can I42.1 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict I42.1 as a principal diagnosis.
Is I42.1 a CC or MCC?
- I42.1 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.