Updates for Coding Myocardial Infarction


   •  I21.9 - Acute myocardial infarction, unspecified
  •  I21.A - Other type of myocardial infarction
  •  I21.A1 - Myocardial infarction type 2
  •  I21.A9 - Other myocardial infarction type
  •  I27.2 - Other secondary pulmonary hypertension
  •  I27.20 - Pulmonary hypertension, unspecified
  •  I27.21 - Secondary pulmonary arterial hypertension
  •  I27.22 - Pulmonary hypertension due to left heart disease
  •  I27.23 - Pulmonary hypertension due to lung diseases and hypoxia
  •  I27.24 - Chronic thromboembolic pulmonary hypertension
  •  I27.29 - Other secondary pulmonary hypertension
  •  I27.83 - Eisenmenger's syndrome
  •  I50.8 - Other heart failure
  •  I50.81 - Right heart failure
  •  I50.810 - Right heart failure, unspecified
  •  I50.811 - Acute right heart failure
  •  I50.812 - Chronic right heart failure
  •  I50.813 - Acute on chronic right heart failure
  •  I50.814 - Right heart failure due to left heart failure
  •  I50.82 - Biventricular heart failure
  •  I50.83 - High output heart failure
  •  I50.84 - End stage heart failure
  •  I50.89 - Other heart failure

Myocardial Infraction Codes Updates

1. Provider documentation will need to specify MI type to assist with choosing the most accurate code

2. The changes start with ICD-10-CM 2018 additional notes under the following subcategories and codes to clarify that they apply to type 1 MIs, which are spontaneous MIs:

  • STEMI subcategories I21.0-, I21.1-, and I21.2-
  • STEMI code I21.3
  • NSTEMI code I21.4

3. The new code I21.A1 (Myocardial infarction type 2),includes MIs due to demand ischemia or ischemic imbalance.

4. For MI types 3, 4a, 4b, 4c, and 5 , new code I21.A9 (Other myocardial infarction type) can be used

5. Type 3 involves sudden cardiac death, type 4 is PCI-related, and type 5 is CABG-related.

6. I21.9 (Acute myocardial infarction, unspecified) is to be used when documentation doesn’t support for a more specific code.

Revisions in Text

1. Subcategories I21.0-I21.2 and code I21.3 are used for type 1 ST elevation myocardial infarction (STEMI).

2. Code I21.4, Non-ST elevation (NSTEMI) myocardial infarction, is used for type 1 non ST elevation myocardial infarction (NSTEMI) and nontransmural MIs.

3. If a type 1 NSTEMI evolves to STEMI, assign the STEMI code.

4. If a type 1 STEMI converts to NSTEMI due to thrombolytic therapy, it is still coded as STEMI.

5. Code I21.9, Acute myocardial infarction, unspecified, is the default for unspecified acute myocardial infarction or unspecified type.

6. If only type 1 STEMI or transmural MI without the site is documented, assign code I21.3, ST elevation (STEMI) myocardial infarction of unspecified site.

7. Do not assign code I22 for subsequent myocardial infarctions other than type 1 or unspecified.

8. For subsequent type 2 AMI assign only code I21.A1.

9. For subsequent type 4 or type 5 AMI, assign only code I21.A9.

Types of Myocardial Infarction

The ICD-10-CM provides codes for different types of myocardial infarction.


1. Type 1 myocardial infarctions are assigned to codes I21.0-I21.4.


2. Type 2 myocardial infarction, and myocardial infarction due to demand ischemia or secondary to ischemic balance, is assigned to code I21.A1.


3. Myocardial infarction type 2 with a code for the underlying cause. Do not assign code I24.8, Other forms of acute ischemic heart disease for the demand is chemia.


4. Sequencing of type 2 AMI or the underlying cause is dependent on the circumstances of admission. When a type 2 AMI code is described as NSTEMI or STEMI, only assign code I21.A1.


5. Codes I21.01-I21.4 should only be assigned for type 1 AMIs.


6. Acute myocardial infarctions type 3, 4a, 4b, 4c and 5 are assigned to code I21.A9, Other myocardial infarction type.


7. The "Code also" and "Code first" notes should be followed related to complications, and for coding of postprocedural myocardial infarctions during or following cardiac surgery.