ICD-10-CM Code I21.A9

Other myocardial infarction type

Version 2020 Billable Code

Valid for Submission

I21.A9 is a billable code used to specify a medical diagnosis of other myocardial infarction type. The code is valid for the year 2020 for the submission of HIPAA-covered transactions.

Short Description:Other myocardial infarction type
Long Description:Other myocardial infarction type

Tabular List of Diseases and Injuries

The Tabular List of Diseases and Injuries is a list of ICD-10 codes, organized "head to toe" into chapters and sections with guidance for inclusions, exclusions, descriptions and more. The following references are applicable to the code I21.A9:

Inclusion Terms

Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
  • Myocardial infarction associated with revascularization procedure
  • Myocardial infarction type 3
  • Myocardial infarction type 4a
  • Myocardial infarction type 4b
  • Myocardial infarction type 4c
  • Myocardial infarction type 5

Code First

Code First
Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first followed by the manifestation. Wherever such a combination exists, there is a "use additional code" note at the etiology code, and a "code first" note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.
  • , if applicable, postprocedural myocardial infarction following cardiac surgery I97.190 I97.790

Code Also

Code Also
A "code also" note instructs that two codes may be required to fully describe a condition, but this note does not provide sequencing direction.
  • complication, if known and applicable, such as:
  • acute stent occlusion T82.897
  • acute stent stenosis T82.855
  • acute stent thrombosis T82.867
  • cardiac arrest due to underlying cardiac condition I46.2
  • complication of percutaneous coronary intervention PCI I97.89
  • occlusion of coronary artery bypass graft T82.218

Index to Diseases and Injuries

The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10 code(s). The following references for the code I21.A9 are found in the index:

Diagnostic Related Groups

The ICD-10 code I21.A9 is grouped in the following groups for version MS-DRG V37.0 What are Diagnostic Related Groups?
The Diagnostic Related Groups (DRGs) are a patient classification scheme which provides a means of relating the type of patients a hospital treats. The DRGs divides all possible principal diagnoses into mutually exclusive principal diagnosis areas referred to as Major Diagnostic Categories (MDC).
applicable from 10/01/2020 through 09/30/2020.


Replacement Code

I21A9 replaces the following previously assigned ICD-10 code(s):

  • I21.3 - ST elevation (STEMI) myocardial infarction of unsp site

Convert I21.A9 to ICD-9

  • 410.90 - AMI NOS, unspecified (Approximate Flag)
  • 410.91 - AMI NOS, initial (Approximate Flag)
  • 410.92 - AMI NOS, subsequent (Approximate Flag)

Code Classification

  • Diseases of the circulatory system (I00–I99)
    • Ischemic heart diseases (I20-I25)
      • Acute myocardial infarction (I21)

Code History

  • FY 2018 - Code Added, effective from 10/1/2017 through 9/30/2018
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020