How 2018 Impacts ICD-10-CM Cardiology Diagnosis Coding

There are now five types of myocardial infarction (MI) code categories, and the author describes these new options and how they will impact reimbursement.

For cardiology, the focus of ICD-10 is generally on increased specificity and documenting the downstream effects of the patient’s condition. Acute myocardial infarction, or what is more commonly known as AMI, had a definition change when the nation’s healthcare system switched from ICD-9-CM to ICD-10-CM in 2015. So when documenting AMI in ICD-10-CM, here’s a reminder to keep the following in mind before we look at 2018 changes:

  • Time frame: AMI will now be considered “acute” for four weeks from the time of the incident (remember that this is a revised time frame from ICD-9, which was a period of eight weeks).
  • Episode of care: ICD-10 does not capture episode of care (e.g. initial, subsequent, sequelae).
  • Subsequent AMI: ICD-10 allows coding of a new MI that occurs during the four-week “acute period” of the original AMI.

ICD-10 Code Examples for AMI:


 ST elevation (STEMI) myocardial infarction involving left anterior descending coronary artery


 Non-ST elevation (NSTEMI) myocardial infarction


 Subsequent ST elevation (STEMI) myocardial infarction of inferior wall


Myocardial Infarction (MI) Codes Added for 2018

New codes for myocardial infarction offer physicians and coders more then enough options when considering an MI encounter for a patient. For example, myocardial infarction (MI) type 2 (I21.A1) and other myocardial infarction type (I21.A9) means coders will need to take into consideration the type of MI the patient is experiencing. A type 2 MI describes a myocardial infarction due to demand ischemia. In addition, notes added under ST-elevation MI codes (I21.0-I21.4) clarify that the condition is a type 1 MI. ICD-10-CM further lists additional “types” of MIs, rated 1-5, for clarification of the patient’s status.

When a patient is diagnosed with type 2 myocardial infarction, myocardial infarction due to demand ischemia, or secondary to ischemic balance, you should report new code I21.A1 (myocardial infarction type 2) and include a code for the underlying cause, the guidelines state. Do not assign code I24.8 (other forms of acute ischemic heart disease) for the demand ischemia, in accordance with the instructions.

For diagnoses of myocardial infarction types 3, 4a, 4b, 4c, and 5, the guidelines instruct coders to report code I21.A9 (other myocardial infarction type). In addition, make sure to follow the “code also” and “code first” notes “related to complications, and for coding of post-procedural myocardial infarctions during or following cardiac surgery.”

Will these new classifications of MIs have any effect on reimbursement? We will not be able to fully answer that question until the payers give us feedback in the form of local coverage determinations (LCDs) and policy addendums.

I would recommend that when a Type 4 or 5 MI diagnosis is reported, meaning the patient’s myocardial infarction is related to a therapeutic procedure such as a percutaneous stent or a cardiac surgery, such as a coronary artery bypass graft, the coder and biller monitor their explanation of benefits (EOBs) and insurance company transmittals for any denials or requests for additional information to support the more specific code. Many payers have specific reimbursement guidelines when a scheduled or planned procedure has a causal relationship to an acute diagnosis.


New Codes for Heart Failure

It’s been a long time coming, but ICD-10 finally realized the need to catch up to new technology when it comes to assisting physicians in coding the most specific code for the procedure performed. The new heart failure code sets have new codes for various types of right heart failure, including acute (I50.811), chronic (I50.812), acute on chronic (I50.813), and unspecified (I50.810). You’ll also have new codes to report right heart failure due to left heart failure (I50.814), biventricular heart failure (I50.82), high-output heart failure (I50.83), and end-stage heart failure (I50.84) for patients with an advanced form of the disease who no longer respond to medication.

This was a welcome change when more and more biventricular procedures are being performed, and having a specific diagnosis to link to those services will make more sense to payors then defaulting to unspecified chronic heart failure (CHF).


Program Note: Listen to Terry Fletcher report on this story this morning on Talk-Ten-Tuesdays, at 10 a.m. EST.



Terry Fletcher, BS, CPC, CCC, CEMC, CCS, CCS-P, CMC, CMSCS, CMCS, ACS-CA, SCP-CA, QMGC, QMCRC, is a healthcare coding consultant, educator, and auditor with more than 30 years of experience. Terry is a past member of the national advisory board for AAPC, past chair of the AAPCCA, and an AAPC national and regional conference educator. Terry is the author of several coding and reimbursement publications, as well as a practice auditor for multiple specialty practices around the country. Her coding and reimbursement specialties include cardiology, peripheral cardiology, gastroenterology, E&M auditing, orthopedics, general surgery, neurology, interventional radiology, and telehealth/telemedicine. Terry is a member of the ICD10monitor editorial board and a popular panelist on Talk Ten Tuesdays.

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