Q&A: MI coding FAQs, part 1

Q: I’m having trouble determining how I would code an acute myocardial infarction (MI) for subsequent admissions occurring within four weeks of the initial MI. Can you walk me through the process?

A: To begin, let’s look at the 2021 Official Guidelines for Coding and Reporting, p. 55, for subsequent MIs (emphasis added):

A code from category I22, Subsequent ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction, is to be used when a patient who has suffered a type 1 or unspecified AMI has a new AMI within the 4-week time frame of the initial AMI.

A code from category I22 must be used in conjunction with a code from category I21. The sequencing of the I22 and I21 codes depends on the circumstances of the encounter.

Codes from category I22 should only be assigned if both the initial and subsequent myocardial infarctions are type 1 or unspecified.

There are a few takeaways from this guidance.

First, in order to have a subsequent MI, there must first be an acute MI that has occurred in the preceding 28 days (not 30 days).

Second, codes from category I22 should ONLY be applied if both the initial and subsequent MIs are type 1 MIs (coronary involvement, NSTEMI/STEMI) or unspecified.

And finally, category I22 must be used in conjunction with a code from the I21 code series. There should not be a coding session with only I22 coded.

Editor’s Note: Dawn Valdez, RN, LNC, CDIP, CCDS, CDI education specialist and CDI Boot Camp instructor for HCPro in Middleton, Massachusetts, answered this question. For information, contact her at dvaldez@hcpro.com. For information regarding CDI Boot Camps, click here.