2025 ICD-10-CM Diagnosis Code I42.1

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Obstructive hypertrophic cardiomyopathy

  • I42.1 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
  • The 2025 edition of ICD-10-CM I42.1 became effective on October 1, 2024.
  • This is the American ICD-10-CM version of I42.1 – other international versions of ICD-10 I42.1 may differ.

Applicable To

  • Hypertrophic subaortic stenosis (idiopathic)

The following code(s) above I42.1 contain annotation back-references

 that may be applicable to I42.1:

  • I00-I99  Diseases of the circulatory system
  • I42  Cardiomyopathy

Approximate Synonyms

  • Cardiomyopathy, hypertrophic obstructive
  • Hypertrophic obstructive cardiomyopathy
  • Idiopathic hypertrophic subaortic stenosis

Clinical Information

  • A condition in which the myocardium is hypertrophied without an obvious cause. The hypertrophy is generally asymmetric and may be associated with obstruction of the ventricular outflow tract.
  • A form of cardiac muscle disease, characterized by left and/or right ventricular hypertrophy (hypertrophy, left ventricular; hypertrophy, right ventricular), frequent asymmetrical involvement of the heart septum, and normal or reduced left ventricular volume. Risk factors include hypertension; aortic stenosis; and gene mutation; (familial hypertrophic cardiomyopathy).
  • Myocardial disease characterized by hypertrophy, involving mainly the interventricular septum, interfering with left ventricular emptying.

ICD-10-CM I42.1 is grouped within Diagnostic Related Group(s) (MS-DRG v42.0):

  • 314 Other circulatory system diagnoses with mcc
  • 315 Other circulatory system diagnoses with cc
  • 316 Other circulatory system diagnoses without cc/mcc

Convert I42.1 to ICD-9-CMCode History

  • 2016 (effective 10/1/2015): New code (first year of non-draft ICD-10-CM)
  • 2017 (effective 10/1/2016): No change
  • 2018 (effective 10/1/2017): No change
  • 2019 (effective 10/1/2018): No change
  • 2020 (effective 10/1/2019): No change
  • 2021 (effective 10/1/2020): No change
  • 2022 (effective 10/1/2021): No change
  • 2023 (effective 10/1/2022): No change
  • 2024 (effective 10/1/2023): No change
  • 2025 (effective 10/1/2024): No change

Code annotations containing back-references to I42.1:

  • Code Also: E74.05
  • Type 2 Excludes: I35

Diagnosis Index entries containing back-references to I42.1:

  • Cardiomyopathy (familial) (idiopathic) I42.9
    • hypertrophic (nonobstructive) I42.2
      • obstructive I42.1
  • Myocardiopathy (congestive) (constrictive) (familial) (hypertrophic nonobstructive) (idiopathic) (infiltrative) (obstructive) (primary) (restrictive) (sporadic) I42.9 – see also Cardiomyopathy
    • hypertrophic obstructive I42.1
  • Stenosis, stenotic (cicatricial) – see also Stricture
    • myocardium, myocardial – see also Degeneration, myocardial
      • hypertrophic subaortic I42.1 (idiopathic)
    • subaortic (congenital) Q24.4
      • hypertrophic I42.1 (idiopathic)
    • hypertrophic subaortic I42.1 (idiopathic)
  • Stricture – see also Stenosis
    • myocardium, myocardialI51.5
      • hypertrophic subaortic I42.1 (idiopathic)
    • subaorticQ24.4
      • hypertrophic I42.1 (acquired) (idiopathic)
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