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Medical Coding for Myocardial InfarctionsMyocardial infarction (MI) refers to heart attack, which occurs when a portion of the heart is deprived of oxygen as a result of the blockage of a coronary artery. The most common cause for this heart attack is occlusive intracoronary thrombus, a substance called plaque made up of cholesterol and other cells that build up in the walls of coronary arteries. A tear in the plaque triggers blood platelets and other substances to form a clot that blocks the flow of blood to the heart.

The upcoming ICD-10 implementation will bring significant changes in medical coding for myocardial infarctions. The implementation will have an impact on how Medical billing and coding companies as well as Cardiology Coding in Medical offices approach their coding. The changing definition of “initial” and “subsequent” as well as “duration” is crucial among them. Let’s take a detailed look into ICD-10 coding and documentation for MI.

Before exploring the critical differences between ICD-9 and ICD-10, we will see different types of MI and their treatment. There are mainly two types of MI such as:

  • ST Elevation Myocardial Infarction (STEMI): This is also known as Transmural Acute MI and occurs as a result of atherosclerosis involving a major coronary artery. It is classified into anterior, posterior, inferior, lateral, and septal. The electrocardiogram (ECG) shows ST elevation and Q waves. The possible treatments for STEMI involves thrombolysis using tissue plasminogen activator (tPA) administered intravenously, percutaneous transluminal coronary angioplasty (PTCA) with or without stent placement and coronary artery bypass graft (CABG).
  • Non ST Elevation Myocardial Infarction (NSTEMI): This is also called Subendocardial Acute MI, or a Non Transmural MI, or a Non-Q Wave MI. NSTEMI involves a small area in the subendocardial wall of the left ventricle, ventricular septum, or papillary muscles, Unlike STEMI, this type of MI does not extend through the thickness of the heart muscles and ECG shows ST depression. The possible treatments include medications to protect the heart as well as reduce its workload, one or more anti-clotting medications to prevent blood clots and percutaneous transluminal coronary angioplasty (PTCA) with or without stent placement.

Major Difference between ICD-9 and ICD-10

In ICD-9, Acute MI is classified based on the episode of care – initial, subsequent or unspecified. When the word ‘initial’ is used to describe Acute MIs in ICD-9, it means the ongoing visit is the patient’s first episode of care regardless of the facility site for newly diagnosed AMI. At the same time, ‘subsequent’ indicates an episode of care following the initial episode, when the patient is admitted for further observation, evaluation or treatment for an AMI for which the patient received initial treatment and it is less than 8 weeks old. However, in ICD-10-CM, ‘initial’ indicates a newly diagnosed AMI and ‘subsequent’ indicates a second AMI that occurs while the initial AMI is still considered acute (4 weeks or less). AMI 8 weeks old is called acute in ICD-9, whereas it requires only 4 weeks for ICD-10-CM to consider an AMI acute.

ICD-10 Codes

Apart from the initial and subsequent episode and MI type, you should also consider the location of the infarct (anterior, inferior or other) while choosing the relevant ICD-10-CM codes. The ICD-10-CM codes for MI are as follows:

  • I21.01: STEMI involving left main coronary artery
  • I21.02: STEMI involving left anterior descending coronary artery
  • I21.09: STEMI involving other coronary artery of anterior wall
  • I21.11: STEMI involving right coronary artery
  • I21.19: STEMI involving other coronary artery of inferior wall
  • I21.21: STEMI involving left circumflex coronary artery
  • I21.29: STEMI involving other sites
  • I21.3: STEMI, unspecified site
  • I21.4: NSTEMI myocardial infarction

Here are the codes for ‘subsequent’ episode of care, which must be reported using any of the codes given above.

  • I22.0: Subsequent STEMI anterior wall
  • I22.1: Subsequent STEMI inferior wall
  • I22.2: Subsequent NSTEMI
  • I22.8: Subsequent STEMI other sites
  • I22.9: Subsequent STEMI unspecified sit

The code for old MI is:

  • I25.2: Old myocardial infarction

Documentation for MI

As you know, ICD-10-CM will increase the level of detail required for MI. Here are the details to be included in your documentation.

  • Identify and document the number of weeks since the AMI
  • Indicate subsequent MI appropriately
  • Document when a NSTEMI evolves into a STEMI and when a STEMI converts into a NSTEMI as a result of thrombolytic therapy
  • If the patient is still receiving care for the MI, then you should use the term ‘aftercare’ and if the patient no longer receives care for the MI, use the term ‘old’ or ‘healed’ MI
  • Document the exact site (for example, left main coronary)

With accurate and comprehensive documentation, your coders can determine the correct codes and the appropriate sequencing of ICD-10 codes to ensure efficient medical billing and coding.