Cracking the Code
Coding Myocardial Infarction
Myocardial infarction (heart attack) occurs when blood flow to the heart is blocked. MIs are classified as acute if the duration is four weeks or less. When a provider documents Acute MI with no further specification, I21.9 is reported. Type 1 MI’s also can be classified by whether there is an ST-segment elevation. The ST refers to the S-T segment or wave on an ECG. The ICD-10-CM codes for type 1 acute myocardial infarction (AMI) identify the site, such as the anterolateral wall or true posterior wall. Subcategories I21.0-I21.2 and code I21.3 are used for type 1 ST elevation myocardial infarction (STEMI). A non-ST elevation myocardial infarction (NSTEMI) describes when the blood clot only partly occludes the artery, and only a portion of the heart muscle being supplied by the affected artery dies. Code I21.4, non-ST elevation (NSTEMI) myocardial infarction, is used for type 1 non-ST elevation myocardial infarction (NSTEMI) and non transmural MI’s.
If a type 1 NSTEMI evolves to STEMI, assign the STEMI code. If a type 1 STEMI converts to NSTEMI due to thrombolytic therapy, it is still coded as STEMI.