Cardiology Coding Alert

Remember: Report I21.4 for type 1 NSTEMIs or nontransmural myocardial infarctions.

Reporting myocardial infarctions in your cardiology practice can be daunting because you must follow numerous rules in the ICD-10-CM Official Guidelines for Coding and Reporting. Not only should you read the medical documentation to find out exactly which site the myocardial infarction occurred, but you also should know if it’s a STEMI or NSTEMI and the age of the myocardial infarction, as well.

Follow these rules to hone your myocardial infarction coding smarts.

Rule 1: Rely on These Codes for STEMIs

If the cardiologist documents a type I ST elevation myocardial infarction (STEMI), you will look to the following codes, per the ICD-10 guidelines:

• I21.01 (ST elevation (STEMI) myocardial infarction involving left main coronary artery)-I21.09 (ST elevation (STEMI) myocardial infarction involving other coronary artery of anterior wall)
• I21.11 (ST elevation (STEMI) myocardial infarction involving right coronary artery) and I21.19 (ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall)
• I21.21 (ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery) and I21.29 (ST elevation (STEMI) myocardial infarction involving other sites)
• I21.3 (ST elevation (STEMI) myocardial infarction of unspecified site)

Don’t miss: You will see that the above codes specify the particular site of the acute myocardial infarction (AMI). For example, I21.01 involves a STEMI in the left main coronary artery.

Rule 2: Always Pay Attention to Included Conditions

When you report an ICD-10 code for a myocardial infarction, you should always check the ICD-10 manual to see if the code encompasses other conditions. For example, I21.29 includes the following conditions:

• Acute transmural myocardial infarction of other sites
• Apical-lateral transmural (Q wave) infarction (acute)
• Basal-lateral transmural (Q wave) infarction (acute)
• High lateral transmural (Q wave) infarction (acute)
• Lateral (wall) NOS transmural (Q wave) infarction (acute)
• Posterior (true) transmural (Q wave) infarction (acute)
• Posterobasal transmural (Q wave) infarction (acute)
• Posterolateral transmural (Q wave) infarction (acute)
• Posteroseptal transmural (Q wave) infarction (acute)
• Septal transmural (Q wave) infarction (acute) NOS

Example: The cardiologist documents a high lateral transmural (Q wave) acute infarction. You should report I21.29 for this diagnosis.

Reasoning: Although you will not find “high lateral transmural (Q wave) acute infarction” in the code descriptor for I21.29 (ST elevation (STEMI) myocardial infarction involving other sites), if you check the ICD-10 manual, you will see this condition included under I21.29.

Rule 3: Report I21.4 for NSTEMIs

If your cardiologist documents a type 1 non-ST elevation myocardial infarction (NSTEMI) or a nontransmural myocardial infarction, you should report I21.4 (Non-ST elevation (NSTEMI) myocardial infarction).

Caution: If the patient’s type I NSTEMI evolves to STEMI, you should report a STEMI code, according to the ICD-10 guidelines. And, if a patient’s type 1 STEMI coverts to NSTEMI because of thrombolytic therapy, you would report a STEMI code, as well.

Example: The patient has a type I NSTEMI myocardial infarction, but it evolves to a STEMI myocardial infarction involving the right coronary artery. You should report I21.11, a STEMI code, in this situation, according to the guidelines.

Rule 4: Know Age of MI

You must always read your cardiologist’s documentation to learn the age of the myocardial infarction because you will report different codes based upon this information.

If the myocardial infarction is equal to or less than four weeks old and it meets ICD-10’s definition of “other diagnoses,” you should report the appropriate code from category I21-. This includes “transfers to another acute setting or a postacute setting,” per the guidelines.

On the other hand, if the encounter occurs after the four-week timeline, and the patient is still receiving care related to the myocardial infarction, you should report the appropriate aftercare code, not a code from category I21-.

Old or healed MIs: If the old or healed myocardial infarction does not require further care, you should report I25.2 (Old myocardial infarction).

Example: The patient had a STEMI myocardial infarction involving the left circumflex coronary artery on June 1. The patient comes into the cardiologist’s office for a follow-up appointment to address the patient’s hypertension on July 13, and it’s mentioned that the patient had a STEMI on June 1 that was resolved. You should report I10 (Essential (primary) hypertension) and I25.2 (Old myocardial infarction) on this claim.

Rule 5: Discover Codes for Other Types of MIs

You should report type I myocardial infarctions with codes I21.0-I21.4.

On the other hand, you should report type 2 myocardial infarctions, which are due to demand ischemia or secondary to ischemic imbalance, with I21.A1 (Myocardial infarction type 2). Remember, in this case, you should always code the underlying cause first on your claim. And, you should never report I24.8 (Other forms of acute ischemic heart disease) for the demand ischemia, per the guidelines.

“If a type 2 AMI is described as NSTEMI or STEMI, only assign code I21.A1,” according to the guidelines.

Caution: “If the documentation shows the AMI as type 2, which is due to demand ischemia or secondary to ischemic imbalance, don’t be confused if it’s also referred to as NSTEMI or STEMI,” explains Robin Peterson, CPC, CPMA, Manager of Professional Coding, Pinnacle Integrated Coding Solutions, LLC. “It’s still a type 2 AMI and should be coded as I21.A1.”

If the patient has a type 3, type 4a, type 4b, type 4c, or type 5 myocardial infarction, you should report I21.A9 (Other myocardial infarction type).

Don’t miss: Make sure you pay attention to any “Code also” and “Code first” notes regarding how to handle complications involving postprocedural myocardial infarctions during or following cardiac surgery.