Myocardial Infarction ICD-10-CM codes

Category I21 covers an acute MI for four weeks (28 days) from onset. STEMI codes are built on the artery or wall involved: I21.01 (left main), I21.02 (left anterior descending), I21.09 (other anterior wall), I21.11 (right coronary artery), I21.19 (other inferior wall), I21.21 (left circumflex), I21.29 (other sites), and I21.3 when the site is not documented. NSTEMI is I21.4 regardless of site, and a subendocardial MI is also I21.4. An MI documented only as acute with no type is I21.9.

Type 2 MI (infarction from supply and demand mismatch) is I21.A1, and the underlying cause such as anemia, hypotension, or COPD exacerbation is sequenced first. Types 3, 4, and 5 are I21.A9. Demand ischemia without an infarction is not an MI; report I24.89. If a STEMI converts to an NSTEMI after thrombolytic therapy, keep the STEMI code, and an NSTEMI that evolves into a STEMI is coded as a STEMI.

Category I22 is for a new type 1 MI that occurs within four weeks of a previous acute MI. An I22 code is always paired with an I21 code for the earlier infarction, and sequencing depends on which event occasioned the encounter. I22 is never used for type 2 MI. Complications such as postinfarction angina (I23.7) or ventricular septal defect (I23.2) are reported from I23 during the same 28-day window.

Once the four weeks have passed, a patient still receiving care for the MI is reported with the appropriate aftercare code rather than I21. A healed or old MI with no current symptoms is I25.2. Add Z92.82 when tPA was given at another facility within 24 hours of transfer, and report tobacco use or history (F17.-, Z87.891) as instructed at the category level.