Documenting Type 2 MI: Start with the Cause for a Good Effect

The Causes of Type 2 MI

To diagnose a Type 2 MI, there needs to be:

• Myocardial injury as evidenced by cTn > 99th percentile upper reference limit (URL)

AND

• Evidence of imbalance between myocardial oxygen supply and demand causing acute myocardial ischemia (one of the criteria below):
  • Symptoms of myocardial ischemia (chest pain, etc.)
  • New ischemic ECG changes
  • Development of pathological Q waves
  • Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality in a pattern consistent with an ischemic etiology

What’s Causing the Confusion?

When considering a Type 2 MI diagnosis, a common mistake is to forget about the requirement of acute myocardial ischemia. If the patient does not meet one of the criteria for myocardial ischemia, the patient should not be diagnosed with a Type 2 MI.

MI due to demand ischemia or MI secondary to ischemic imbalance are equivalent to Type 2 MI from a coding perspective. These terms map to ICD 10 code, I21.A1, MI Type 2.

Type 2 NSTEMI is a problematic term. According to coding guidelines, when Type 2 NSTEMI is documented, the code for Type 2 MI should be assigned and the code for NSTEMI should be withheld. If a coder incorrectly assigns the code for a NSTEMI – I21.4 – the case will be inappropriately pulled into the National Cardiovascular Data Registry and included in the CMS cohort for 30-day readmission rate and 30-day mortality rate.

2020 Coding Guidelines

The updated 2020 coding guidelines are creating further confusion in the accurate coding of Type 2 MI. For easy reference, here are the deletions and additions to the guidelines.

The ICD-10-CM provides codes for different types of myocardial infarction. Type 1 myocardial infarctions are assigned to codes I21.0-I21.4 and I21.9.

Type 2 myocardial infarction (myocardial infarction due to demand ischemia or secondary to ischemic imbalance) is assigned to code I21.A1, Myocardial infarction type 2 with a code for the underlying cause coded first. Do not assign code I24.8, Other forms of acute ischemic heart disease, for the demand ischemia. Sequencing of type 2 AMI or the underlying cause is dependent on the circumstances of admission. When If a type 2 AMI code is described as NSTEMI or STEMI, only assign code I21.A1. Codes I21.01-I21.4 should only be assigned for type 1 AMIs.

Acute myocardial infarctions type 3, 4a, 4b, 4c and 5 are assigned to code I21.A9, Other myocardial infarction type.

The Effect of Proper Documentation

The most significant change to note is when a Type 2 MI is diagnosed, the etiology will need to be linked. The cause of the MI will be coded first. This makes sense from a clinical perspective but will require education for clinicians who don’t always document or link the etiology. And, occasionally, there are patients where the etiology of the Type 2 MI is unclear.

Education for clinical providers is critical. When a Type 2 MI is diagnosed, the clinical provider should make it a habit to document the etiology of the MI. If the provider does not document the etiology, a query will need to be issued. Overtime, linking the etiology will become a habit for clinicians, but in the meantime, expect more queries.

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