Stabilize ICD-10 Coding for Faulty Myocardial Infarction
Clean claims require a healthy balance of anatomy and pathophysiology knowledge as well as proper documentation.
By Jana Purrell, CPC, CPC-I, CEMC
A myocardial infarction (MI) or acute myocardial infarction (AMI), commonly referred to as a heart attack, occurs when one or more coronary arteries that carry blood to the heart are blocked. Symptoms include chest pain, pressure, or tightness, which may move into the jaw, neck, throat, or arm(s). Patients also may experience shortness of breath, excessive sweating, and/or indigestion or burning in the throat and/or chest. MI is a medical emergency. Left untreated, it can cause permanent harm to the heart muscle, brain damage, and death within a short time.
MI is part of the leading cause of death in the United States: Approximately 450,000 people die from coronary disease per year, according to the America Heart Association.
The good news is that the increase in intensive/coronary care units in communities, along with faster diagnosis of MIs resulting in early reperfusion therapy use, has improved outcomes for many patients. Early treatments now include administration of fibrinolytic agents (i.e., tissue plasminogen activator (tPA)) in the emergency setting to break up the clots that have built up in the arteries, or early percutaneous coronary interventions (PCI), such as angioplasty or coronary artery bypass grafting (CABG).
Become Familiar with Types and Classifications
There are two types of acute MI:
1. Transmural infarcts are associated with a build up of plaque in a major coronary artery. They generally extend through the whole thickness of the heart muscle.
2. Subendocardial infarcts involve the wall of the left ventricle, the ventricular septum, or the papillary muscles. They are thought to be caused by a narrowing of the coronary arteries.
Both ICD-9 and ICD-10 coding systems classify MIs as either ST elevation (STEMI) or non-ST elevation (NSTEMI). The STEMI usually results in a blockage of a coronary artery, indicated by a dramatic rise in cardiac enzymes in the blood and, eventually, Q wave changes shown on a cardiogram. The NSTEMI generally occurs with symptoms of unstable angina, which causes a smaller rise in the cardiac enzymes without a resulting shift in the Q wave of the cardiogram.
Must-knows for Coding MI
To code an MI in ICD-10, you will need to know:
- the location of the infarct (anterior, inferior, or other);
- initial or subsequent episode; and,
- STEMI or NSTEMI.
Codes for the STEMI are also based on the coronary artery involved:
- Anterior MI (I21.0 ST elevation (STEMI) myocardial infarction of anterior wall) is either left main, left anterior descending, or other coronary artery.
- Inferior MI (I21.1 ST elevation (STEMI) myocardial infarction of inferior wall) breaks down to right coronary or other coronary artery.
- STEMI of other sites involve infarct of the left circumflex artery or other sites.
The relevant ICD-10-CM codes for MI are:
I21.01 ST elevation (STEMI) myocardial infarction involving the left main coronary artery
I21.02 ST elevation (STEMI) myocardial infarction involving the left anterior descending 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
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
I21.29 ST elevation (STEMI) myocardial infarction involving other sites
I21.3 ST elevation (STEMI) myocardial infarction of unspecified site
I21.4 Non-ST elevation (NSTEMI) myocardial infarction
I22.0 Subsequent ST elevation (STEMI) myocardial infarction of anterior wall
I22.1 Subsequent ST elevation (STEMI) myocardial infarction of inferior wall
I22.2 Subsequent non-ST elevation (NSTEMI) myocardial infarction
I22.8 Subsequent ST elevation (STEMI) myocardial infarction of other sites
I22.9 Subsequent ST elevation (STEMI) myocardial infarction of unspecified site
I25.2 Old myocardial infarction
Look to Guidelines for Assistance
STEMI of an unspecified site is reported I21.3. According to ICD-10-CM Official Guidelines for Coding and Reporting, I21.3 is the default for the unspecified term “acute myocardial infarction.” As with ICD-9, you should use unspecified codes only as a last resort: If only STEMI or transmural MI is documented without mention of the site, you should ask the provider as to the site.
Note that the timeframe for the acute myocardial infarction in ICD-10 has changed from eight weeks to four weeks. This is a major change from ICD-9.
ICD-10-CM Official Guidelines for Coding and Reporting states, “For encounters after the 4 weeks time frame and the patient requires continued care related to the myocardial infarction, the appropriate aftercare code should be assigned, rather than a code from category I21. Otherwise, code I25.2 Old myocardial infarction, may be assigned for old or healed myocardial infarction not requiring further care.”
The ICD-10-CM guidelines also provide guidance on coding subsequent MI: “A code from category I22, Subsequent ST elevation (STEMI) and non ST elevation (NSTEMI) myocardial infarction, is to be used when a patient who has suffered an AMI has a new AMI within the 4 week time frame of the initial AMI. A code from category I22 must be used in conjunction with a code from category I21. The sequencing of the I22 and I21 codes depends on the circumstances of the encounter.”
For example, if a patient is in the hospital being treated for an AMI and experiences another AMI, code I21 ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction would be listed first as the reason for the admission, with code I22 Subsequent ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction listed as secondary. If a patient were discharged from the hospital after being treated for an AMI and suffers another AMI that requires admission, I22 would be listed first, followed by I21. In this case, I21 shows that the patient is still within the four-week time frame from the initial MI to support subsequent MI code use.
Also new for ICD-10 is guidance to use additional codes, if applicable, to indicate:
- Tobacco status (history of (Z87.891 Personal history of nicotine dependence), exposure to (Z77.22 Contact with and (suspected) exposure to environmental tobacco smoke (acute) (chronic)), occupational exposure (Z57.31 Occupational exposure to environmental tobacco smoke), dependence (F17.- Nicotine dependence), or use (Z72.0 Tobacco use)
- Z92.82 Status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to the current facility
- Z68 Body mass index (BMI)
Complications following an MI are now combined into one code range (I23 Certain current complications following ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction (within the 28 day period)), with guidance that a code from this category must be used with a code from either the initial (I21) or subsequent (I22) MI category. The complication code (I23) should be listed first if that is the reason for the visit, but should be listed second if the complication occurs during the encounter for the MI.
Jana Purrell, CPC, CPC-I, CEMC, has over 30 years of clinical and management experience in a variety of health care settings. She is the practice administrator for Mid Coast Medical Group in Brunswick, Maine, which is made up of 12 hospital-based physician practices with more than 60 multi-specialty providers.
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