An acute myocardial infarction (heart attack) results when there is an interruption of blood flow to heart muscle. The heart cells become damaged or die. Many times, heart attacks are due to coronary atherosclerotic disease (CAD). Heart attacks can also be caused by stress or physical exertion and severe infections.
Myocardial infarctions requires the coder to seek the site and type of infarction, as well as the episode of care. The site indicates the location in which the infarction occurred. The type of infarction indicates whether the infarction was ST elevated (STEMI) or non ST elevated (NSTEMI). ICD-9 currently classified MI’s to the 410 category with the 4th digit indicating the location and type, while the 5th digit indicates the episode of care.
Example: STEMI of the anterolateral wall, subsequent episode:
ICD-9-CM: 410.02
ICD-10: I21.09
Coding MIs in ICD-10 will be a bit different. The coder is no longer required to know the episode of care. MIs are classifed by site, type, and occurrence. Per the Coding Clinic, First Quarter 2013, MIs not specified as STEMI or non-STEMI should be coded as a STEMI by site.
ICD-10-CM Official Guidelines for Coding and Reporting, a myocardial infarction is considered acute for four weeks. In ICD-9-CM, a myocardial infarction is acute for eight weeks.
I21.4 is assigned for all NSTEMIs.
I22.4 is assigned for a subsequent NSTEMI, occurring within 28 days of a previous MI, regardless of the site.
Rest assured there is still a code for an old MI, I25.2.
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