Today I would like to call your attention to Type 2 myocardial infarction (MI), A21.A1, versus demand ischemia, I24.89. I frequently see denials associated with these two diagnosis codes due to conflicting documentation.
There is an Index entry under “Ischemia, demand, with myocardial infarction,” which is assigned to A21.A1. If the documentation is conflicting, you will need to query the provider regarding the establishment of the myocardial infarction.
The confirmation of the MI changes the code from I24.89 to I21.A1. Another reason to establish Type 2 MI is that demand ischemia is classified as a complication or comorbidity (CC) and Type 2 MI is a major CC (MCC). If you assign a single MCC to a case, then there is an increased likelihood that the case will be reviewed by a payer. This increased scrutiny is another reason to take the time and effort to clarify the presence of the MI.
The Coding Clinic for the fourth quarter of 2023, pgs. 78-79, reviews Chapter 9: Diseases of the Circulatory System updates to the guidelines. Type 2 myocardial infarction due to demand ischemia is assigned A21.A1. If a Type 2 myocardial infarction is described as NSTEMI or STEMI, only assign
A21.A1. Codes A21.01 through A21.4 are only to be assigned to Type 1 acute myocardial infarctions.
Do not confuse demand ischemia with non-ischemic myocardial injury, which is assigned I5A. This diagnosis is a myocardial injury in the absence of ischemia. Physicians utilize high-sensitivity troponin tests to distinguish whether the patient has suffered a non-ischemic myocardial injury versus one of the other myocardial infarction subtypes, according to the Coding Clinic for the fourth quarter of 2021, pgs. 14-15.
A good reference for the acute myocardial infarction subtypes is the Coding Clinic for the fourth quarter of 2017, pgs. 12-14. The acute myocardial infarction codes are found in category I21, with subsequent myocardial infarction codes in category I22.
When in doubt, query! It is much better to establish the diagnosis than to receive a clinical validation denial.