ICD10BillableValid for clinical use
ICD-10 Code I21.A9: Other myocardial infarction type
Reviewed by HealthAssure Clinical TeamUpdated 26 May 2026
What is this code?
ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Diseases of the circulatory system (I00-I99).
đź“‹Clinical overview
This ICD-10 code is commonly used when documentation describes an acute myocardial infarction. The most accurate code depends on STEMI versus NSTEMI pattern, infarct site or culprit coronary artery, and whether the record documents another acute-MI mechanism such as type 2 or microvascular dysfunction.
When is it used?
- May be used when a clinician documents other myocardial infarction type in a patient's medical record.
- May appear in hospital records, claims, referrals, and clinical documentation.
- This code can be used as a clinically usable diagnosis entry in standardized coding workflows.
What it does not mean
- A code alone does not explain severity, treatment plan, or outcome.
- A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
đź©şClinical context
When commonly used
- Emergency, inpatient, cardiology, and utilization-review workflows where an acute myocardial infarction is part of the documented encounter.
- Coding workflows where the chart identifies STEMI versus NSTEMI pattern, infarct territory, culprit artery, or another acute-MI mechanism that changes final code specificity.
Common management context
- Evaluation often includes chest-pain or equivalent symptom review, ECG interpretation, troponin testing, coronary-imaging or catheterization context, and acute cardiology management planning.
- Documentation usually becomes more specific when the chart identifies anterior versus inferior versus other territory, a named culprit coronary artery, STEMI versus NSTEMI, or another acute-MI mechanism such as type 2 or microvascular dysfunction.
- Specialist context already linked on this page includes Cardiologist, General Physician.
🔍Key distinctions
Important notes
- This ICD-10 family captures active acute myocardial infarction rather than chronic ischemic heart disease or a remote prior infarction.
- STEMI versus NSTEMI pattern, infarct territory, culprit-vessel detail, and alternative acute-MI mechanisms all affect final code specificity inside this family.
- Documentation that describes acute myocardial infarction is coded differently from unstable angina, chronic ischemic heart disease, or prior healed myocardial infarction.
Related codes to consider
I21.A1Myocardial infarction type 2
Related acute-myocardial-infarction ICD-10 code; documentation often becomes more specific when the chart identifies STEMI versus NSTEMI, infarct territory, culprit coronary artery, type-2 versus other mechanism, or another acute coronary context.
Code hierarchy
chapter
9Diseases of the circulatory system (I00-I99)
block
I20-I25Ischemic heart diseases
category
I21Acute myocardial infarction
category
I21.AOther type of myocardial infarction
currentI21.A
Official coding notes
Inclusion terms
- 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
Applicable to
- , if applicable, postprocedural myocardial infarction following cardiac surgery (I97.190), or postprocedural myocardial infarction during cardiac surgery (I97.790)
Code first
- , if applicable, postprocedural myocardial infarction following cardiac surgery (I97.190), or postprocedural myocardial infarction during cardiac surgery (I97.790)
Code also
- 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-)
Where you may see this code
You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records.
Related specialists
CardiologistGeneral Physician
Related codes
Sibling codes
Coverage-related procedures and services
CPT 93350high
ECHOCARDIOGRAPHY, TRANSTHORACIC, REAL-TIME WITH IMAGE DOCUMENTATION (2D), INCLUDES M-MODE RECORDING, WHEN PERFORMED, DURING REST AND CARDIOVASCULAR STRESS TEST USING TREADMILL, BICYCLE EXERCISE AND/OR PHARMACOLOGICALLY INDUCED STRESS, WITH INTERPRETATION AND REPORT;
Source: CMS coverage guidance
CPT 93351high
ECHOCARDIOGRAPHY, TRANSTHORACIC, REAL-TIME WITH IMAGE DOCUMENTATION (2D), INCLUDES M-MODE RECORDING, WHEN PERFORMED, DURING REST AND CARDIOVASCULAR STRESS TEST USING TREADMILL, BICYCLE EXERCISE AND/OR PHARMACOLOGICALLY INDUCED STRESS, WITH INTERPRETATION AND REPORT; INCLUDING PERFORMANCE OF CONTINUOUS ELECTROCARDIOGRAPHIC MONITORING, WITH SUPERVISION BY A PHYSICIAN OR OTHER QUALIFIED HEALTH CARE PROFESSIONAL
Source: CMS coverage guidance
CPT 93241high
EXTERNAL ELECTROCARDIOGRAPHIC RECORDING FOR MORE THAN 48 HOURS UP TO 7 DAYS BY CONTINUOUS RHYTHM RECORDING AND STORAGE; INCLUDES RECORDING, SCANNING ANALYSIS WITH REPORT, REVIEW AND INTERPRETATION
Source: CMS coverage guidance
CPT 93242high
EXTERNAL ELECTROCARDIOGRAPHIC RECORDING FOR MORE THAN 48 HOURS UP TO 7 DAYS BY CONTINUOUS RHYTHM RECORDING AND STORAGE; RECORDING (INCLUDES CONNECTION AND INITIAL RECORDING)
Source: CMS coverage guidance
CPT 93244high
EXTERNAL ELECTROCARDIOGRAPHIC RECORDING FOR MORE THAN 48 HOURS UP TO 7 DAYS BY CONTINUOUS RHYTHM RECORDING AND STORAGE; REVIEW AND INTERPRETATION
Source: CMS coverage guidance
CPT 93243high
EXTERNAL ELECTROCARDIOGRAPHIC RECORDING FOR MORE THAN 48 HOURS UP TO 7 DAYS BY CONTINUOUS RHYTHM RECORDING AND STORAGE; SCANNING ANALYSIS WITH REPORT
Source: CMS coverage guidance
Coding guidelines
Common synonyms
Other myocardial infarction type
Frequently asked questions
About this content
This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.