Coding Tip of the Month – October 2017

New MI Codes:

The ICD-10-CM updates for October 1st brought three new MI codes:

Code Description CC/MCC
I21.9 Acute myocardial infarction, unspecified MCC
I21.A1 Myocardial infarction type 2 MCC
I21.A9 Other myocardial infarction type MCC
New guidelines have been published to provide guidance on how to apply the new MI codes and existing guidelines revised for the pre-existing MI codes in category I.21. The following instructions summarize the new and revised guidelines.

I21.9 Acute Myocardial Infarction, Unspecified
This code should be assigned when both the type and site of an acute MI is unspecified. Code I21.3 is now applied when you have STEMI (transmural) MI but the site is not specified.

I21.A1 Myocardial Infarction Type 2
This code should be used for myocardial infarction secondary to an ischemic imbalance as in coronary vasospasm, anemia or hypotension. This code is used for both initial and subsequent type 2 acute myocardial infarctions. Code also the underlying cause, if known and applicable.

I21.A9 Other Myocardial Infarction Type
This code should be used for initial MIs specified as type 3, 4a, 4b, 4c or 5. This code is also used for subsequent type 4 or type 5 acute myocardial infarctions. There is no subsequent type 3 myocardial infarction, as type 3 refers to myocardial infarction resulting in death when biomarker values are unavailable. Code first, if applicable, postprocedural myocardial infarction during/following cardiac surgery. Code also complication, if known and applicable.

Category I22 Subsequent ST Elevation (STEMI) and non-ST Elevation (NSTEMI) MIs
Codes from category I22, Subsequent ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction, should not be assigned for subsequent myocardial infarctions other than type 1 or unspecified. Subsequent type 2, 4 or 5 myocardial infarctions are coded by type rather than using codes from category I22.

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