I21.21: ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery
I21.21 is a billable, specific ICD-10-CM code for st elevation (stemi) myocardial infarction involving left circumflex coronary artery. It is valid for submission on a claim.
Check I21.21 with the rest of the claim: free scrubberInclusion terms
Alternative wordings a physician may use in the chart for this same code.
- ST elevation (STEMI) myocardial infarction involving oblique marginal coronary artery
Other codes that can never be billed with I21.21
Their own Excludes1 notes name this code, so the conflict is not listed above.
- I5ANon-ischemic myocardial injury (non-traumatic)
Risk adjustment
I21.21 risk-adjusts. Under the CMS-HCC V28 model it maps to this category:
- HCC 228 Acute Myocardial Infarction0.252 RAF
Coefficient shown for the Community Non-dual Aged segment. A higher HCC in the same hierarchy will suppress this one, so capturing it does not always add score. Look up the whole chart to see which of its HCCs the hierarchy would zero.
Medicare coverage
I21.21 is named in 46 Medicare coverage policies: 46 listing it as supporting medical necessity. Which one applies depends on your Medicare contractor.
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Alphabetic index entries that lead here
- Infarct, infarction›myocardium, myocardial›ST elevation›involving›left circumflex coronary artery
- Infarct, infarction›myocardium, myocardial›ST elevation›involving›oblique marginal coronary artery
Code history
Unchanged in every release from FY2024 to FY2027.