Myocardial infarction, acute (AMI), NOS

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ICD10 Diagnosis
Dx: Myocardial infarction, acute (AMI), NOS
ICD10 code: I21.9
Pre-ICD10 counterpart: Myocardial infarction
Charlson/ALERT Scale: Myocardial infarction
APACHE Como Component: none
APACHE Acute Component: 2019-0: Coronary Artery Disease
Start Date:
Stop Date:
External ICD10 Documentation

This diagnosis is a part of ICD10 collection.

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    • 2019-01-01
    • 2999-12-31
    • I21.9
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Additional Info

This code is only used for an Acute Myocardial Infarction (AMI) when the more specific type is unknown(i.e. Q-wave, non-Q-wave).

  • includes missed MI

"We are bringing it up at task, because it was 8 days old and the primary reason for admission, and treated like an acute, when I searched ICD codes for missed MI this is the code that came up. But you are right if it’s a month old it would be a comorb, so need some clarification. "

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MI - type vs mechanism

MIs are occasionally listed as "Type 2 MIs", ie no evidence of coronary artery disease (CAD). This refers to the mechanism, and the AMI codes include any/all mechanisms (including coronary artery embolism, thrombosis or thromboembolism); said another way, we don't particularly care about the mechanism. They should be coded based on their manifestation.

In ICD10, this will mean:


MI - acute vs past history

To decide whether to code an acute MI dx in the Admit Diagnosis or Acquired Diagnosis / Complication, or a Past history, myocardial infarction (old MI) in the Comorbid Diagnosis, consider the following:

  • Regarding an MI that occured prior to the current hospitalization -- might be coded as either Comorbid Diagnosis, or a Past history, myocardial infarction (old MI)
  • In ICD10 the code for Past history, myocardial infarction (old MI) reads as follows: Healed myocardial infarction -- Past myocardial infarction diagnosed by ECG or other special investigation, but currently presenting no symptoms.
  • If the prior MI is still active and we're not dealing with any current complications of it, then instead use one of the AMI codes, as a Comorbid Diagnosis.
  • If the prior MI is still active and we are dealing with any current complications of it, then instead use one of the AMI codes, as a Admit Diagnosis.
    • Examples: Papillary muscle rupture or Ongoing angina related to a recent MI prior to this unit/ward admission.
  • For a missed MI: code it as one of the "...acute..." codes if the missed MI is being treated as an acute MI

Alternate ICD10s to consider coding instead or in addition

Ischemic heart disease codes:
Myocardial Infarction codes:
Arterial thromboembolism codes:

Candidate Combined ICD10 codes

  • Also code any acute complications from Myocardial Infarction list.

Related CCI Codes

Data Integrity Checks (automatic list)

none found

Related Articles

Related articles:


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