I21.9Acute myocardial infarction, unspecified
Code usage status
Primary diagnosis
May be used as the primary diagnosis
Apply only when it matches the confirmed diagnosis and the documented clinical record.
Specificity
Complete code in the classification
Use when the diagnosis matches and no exclusion applies.
- Chapter IX
- Diseases of the circulatory system
- Group I20-I25
- Ischaemic heart diseases
- Official Vietnamese name
- Nhồi máu cơ tim cấp tính, không xác định
- Additional WHO coding guidance
- Myocardial infarction (acute) NOS
Related I21 codes
I21
Acute myocardial infarction
I21.0
Primary diagnosis candidate
Acute transmural myocardial infarction of anterior wall
I21.1
Primary diagnosis candidate
Acute transmural myocardial infarction of inferior wall
I21.2
Primary diagnosis candidate
Acute transmural myocardial infarction of other sites
I21.3
Primary diagnosis candidate
Acute transmural myocardial infarction of unspecified site
I21.4
Primary diagnosis candidate
Acute subendocardial myocardial infarction
Clinical record checklist
View coding guide →- Confirm that the code matches the final documented diagnosis.
- Use one primary-diagnosis code and record only relevant additional conditions.
- Review Ministry indicators, inclusions, exclusions and notes.
- Do not infer a diagnosis beyond the clinical record.
2026 regulatory basis
Indicators are taken from columns 24–29 of the classification accompanying Circular 06/2026/TT-BYT, cross-referenced with Decision 1849/QĐ-BYT and Official Dispatch 4059/BYT-BH.
