Myocardial infarction coding: Part 2

After my previous blog “Myocardial infarction coding is good for the heart,” one of our readers had a good question: When is a myocardial infarction considered old? I wanted to write a follow up blog to address this question.

Old MIs are best identified by physician documentation. Documentation that includes “healed,” “old” myocardial infarction (MI) or other language indicating a past MI that is not being treated or presenting any symptoms, would be coded with I25.2.

While my mind was on MI documentation I wondered, what information is needed to code acute MI appropriately? It is 2018 and by now we all are aware documentation specificity changed for MI with the implementation of ICD-10-CM. Even though we are working through year three of this coding system, are physician documents still missing elements needed to appropriately code an MI?  Probably the most common documentation errors happen with acute myocardial infarctions (AMI), so let’s look at the four main elements necessary to code:

• Location
  • Anterior wall
  • Inferior wall
• Arteries impacted
  • Left main coronary artery
  • Left anterior descending coronary artery
  • Right coronary artery
  • Left circumflex coronary artery
• Timing
  • Initial incident: up to 4 weeks (28 days)
  • Subsequent incident: AMI occurring within 4 weeks (28 days) of previous AMI
• Type of AMI
  • ST elevation (STEMI)
  • Non ST elevation (NSTEMI)
  • Non-Q wave, Nontransmural
  • Q-wave
  • Other, specified

Whenever possible, documentation for tobacco use including type of tobacco and any exposure to environmental smoke should be included. In addition, physicians should also include documentation post administration of tPA (rtPA) within the previous 24 hours, prior to admission. 

Remember, if your physician is not documenting these elements or if you’re not clear whether an MI is old, query the provider. When it comes to matters of the heart, the more specific the documentation, the better!

Karla Voneschen is a coding analyst at 3M Health Information Systems.

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