Myocardial infarction (MI) documentation and ICD-10 coding guidance
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Provides documentation best practices and ICD-10-CM coding guidance for myocardial infarction (MI), including classification by type, acute vs old MI, and rules for subsequent MIs; intended for clinicians and coding staff working with Independence Administrators/Independence Blue Cross products.
No material clinical or coverage changes in this revision.
Documentation & Coding Criteria for Myocardial Infarction
MI documentation and coding criteria
Documentation and coding criteria to apply when coding myocardial infarction encounters:
ALL of the following
- Define a subsequent MI as a new MI occurring within four weeks of the initial MI.
- Assign I22 (subsequent MI) only when both the initial and subsequent MIs are type 1 or unspecified.
Subsequent MI — type-specific coding
- If the subsequent MI is type 2, assign I21.A1 (subsequent type 2 acute MI).
- If the subsequent MI is type 4 or type 5, assign I21.A9 (subsequent type 4 or type 5 acute MI).
- If a subsequent MI of one type occurs within four weeks of an MI of a different type, assign the appropriate I21 codes for each type and do not use I22.
ICD-10-CM Codes and Timeframe
| I21 | Acute myocardial infarction (use for initial MI by type) |
| I22 | Subsequent myocardial infarction (assign only when both initial and subsequent are type 1 or unspecified) |
| I21.A1 | Subsequent type 2 acute MI |
| I21.A9 | Subsequent type 4 or type 5 acute MI |
| I25.2 | Old myocardial infarction (healed MI with no continued symptoms or treatment) |
| Z48.812 | Surgical aftercare of the circulatory system (example aftercare Z-code) |
Documentation Best Practices and Coding Rules
Document onset, location, and use highest-specificity ICD-10 codes
Document the date of onset (to the best of your knowledge) and the specific location of the myocardial infarction. Provide the highest level of ICD-10 specificity and severity, using precise terminology for diagnoses, symptoms, or reasons for the encounter. Assign codes from category I22 only if both the initial and subsequent MIs are type 1 or unspecified; for subsequent type 2, type 4, or type 5 MIs, use the appropriate code from category I21.
- Document date of onset and specific MI location.
- Provide highest level of ICD-10 specificity and severity.
- Use precise clinical terminology in the record.
- Assign I22 only when both initial and subsequent MIs are type 1 or unspecified.
- For subsequent type 2, 4, or 5 MIs, use the appropriate I21 code.
Key Definitions
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