The ICD10 code for the diagnosis "ST elevation (STEMI) myocardial infarction involving other sites" is "I21.29". I21.29 is a VALID/BILLABLE ICD10 code, i.e it is valid for submission for HIPAA-covered transactions.
The 2019 edition of ICD-10-CM I21.29 became effective on October 1, 2018.
You should report I21.11, a STEMI code, in this situation, according to the guidelines.
If your cardiologist documents a type 1 non-ST elevation myocardial infarction (NSTEMI) or a nontransmural myocardial infarction, you should report I21.4 (Non-ST elevation (NSTEMI) myocardial infarction).
Reasoning: Although you will not find “high lateral transmural (Q wave) acute infarction” in the code descriptor for I21.29 (ST elevation (STEMI) myocardial infarction involving other sites), if you check the ICD-10 manual, you will see this condition included under I21.29.
Codes. I21 Acute myocardial infarction.
A type 2 excludes note represents "not included here". A type 2 excludes note indicates that the condition excluded is not part of the condition it is excluded from but a patient may have both conditions at the same time. When a type 2 excludes note appears under a code it is acceptable to use both the code ( I21) and the excluded code together.