Coding and Documentation of Myocardial Infarction

Good afternoon!

Let’s take a look at some of the guideline changes coming to ICD-10-CM and use these guidelines to code an acute MI scenario.

Review of the Circulatory Chapter for ICD-9 and ICD-10 makes clear there are many changes are on the horizon. Guideline I.C.9.e.4. states a code from Category I22, Subsequent STEMI and NSTEMI, is to be used when a patient has suffered an AMI and has a new AMI within the 4-week timeframe of the initial AMI. However, below Category 410 in ICD-9-CM, the note refers to an 8-week or less time period. Not only has the period of time for initial treatment changed from 8 weeks to 4 weeks, but also the definition of Subsequent Episode of Care has changed from care related to the initial AMI to care related to a new AMI. Another change to Coding Guidelines is I.C.9.e.1., which states: “If NSTEMI evolves to STEMI, assign the STEMI code. If STEMI converts to NSTEMI due to thrombolytic therapy, it is still coded to a STEMI.”

The guidelines will be important to coders, but there are additional documentation requirements that will be important to everyone in the agency! Currently in ICD-9-CM, we need to know the site of the MI (subendocardial, posterior wall, etc.), the episode of care (initial, subsequent), and whether any complications are present (rupture of tendon or muscle or septal defect). However, documentation in ICD-10 will need more specific information for each episode of care (initial and subsequent). In the initial episode of care, coders will need to know not only the type of MI but also the specific location of occurrence (left main coronary artery, left circumflex coronary artery, etc.), as well as more specific information regarding type of complication that occurred within the 28 day initial time period (thrombosis of atrium, post infarction angina, ventricular or atrial septal defect, etc.). Furthermore, documentation should be present to identify whether the patient has ever been exposed to tobacco smoke (environmental, personal history or current use, occupational exposure).

Taking all of this into consideration, let’s code using ICD-10-CM:

A 54-year-old female was treated for an acute non-ST anterior wall MI.  This patient also has atrial fibrillation.  After discharge home, the patient presented to the ED two weeks later and was diagnosed with an acute inferior wall MI.  She is still being monitored following her initial heart attack two weeks earlier and continues to have atrial fibrillation.  She was treated with a cardiac catheterization while in the hospital. Upon discharge, the patient is referred to home health.  What diagnosis codes will be assigned?

Work through this scenario during the week and be on the lookout for the correct responses, along with rationale soon!


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