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Coding Myocardial Infarction
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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.