I21.A9
BillableOther myocardial infarction type
HCC Category Mapping
V28HCC 228 — Acute Myocardial Infarction
0.000V24HCC 86 — Acute Myocardial Infarction
0.274ESRDHCC 86 — Acute Myocardial Infarction
0.000RxHCCHCC 188 — Coronary Artery Disease and Angina
0.000What This Code Means
A heart attack of a type other than the standard classifications, such as those caused by coronary artery dissection or other unusual mechanisms.
Coding Tips
- •Review documentation carefully for the specific mechanism of MI (e.g., spontaneous coronary artery dissection, coronary embolism) to ensure correct subcategory selection
- •This category includes non-atherosclerotic causes; ensure the etiology is clearly documented
Clinical Significance
Other myocardial infarction type captures types 3, 4a, 4b, 4c, and 5 myocardial infarctions as defined by the universal classification. These include myocardial infarction resulting in death before biomarkers could be obtained (type 3), procedure-related myocardial infarctions (types 4a/4b/4c related to percutaneous coronary intervention, and type 5 related to coronary artery bypass graft). These are relatively uncommon but clinically important distinctions.
Documentation Requirements
- ✓Documentation of the specific myocardial infarction type (3, 4a, 4b, 4c, or 5)
- ✓For type 3: ischemic symptoms prior to death with suspected myocardial infarction but biomarkers not obtainable
- ✓For type 4: documentation of percutaneous coronary intervention with subsequent troponin elevation meeting type 4 criteria
- ✓For type 5: documentation of coronary artery bypass graft with subsequent troponin elevation meeting type 5 criteria
- ✓Cardiac biomarker results when available
- ✓Temporal relationship between the procedure and the myocardial infarction
Code First
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-)
Commonly Confused Codes
I21.A1 — Myocardial infarction type 2: supply-demand mismatch, different mechanismI21.4 — Non-ST elevation myocardial infarction (type 1): plaque rupture mechanismI21.01-I21.29 — STEMI codes (type 1): complete coronary artery occlusionI97.190 — Other postprocedural cardiac functional disturbances: procedural complications not meeting myocardial infarction criteriaI21.B — Myocardial infarction with coronary microvascular dysfunction: different mechanism
Code Hierarchy
└I21Acute myocardial infarction└I21.AOther type of myocardial infarction└I21.A9Other myocardial infarction type
└I21.A9Other myocardial infarction type