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Understanding Correct Coding for Atrial Fibrillation in 2020

Aimee WIlcox, CPMA,CCS-P, CST, MA, MT

This auditing and compliance “Tip of the Week” was originally published by the National Alliance for Medical Auditing Specialists (NAMAS), a division of DoctorsManagement.

Atrial fibrillation (AF) is the most common type of abnormal heart rhythm (arrhythmia). It is caused by a disorder in the heart’s electrical system. AF is the result of abnormal contractions of the atria (upper two chambers of the heart) causing them to quiver and beat out of sync with the ventricles (lower two chambers of the heart). These abnormal heart contractions change how blood flows through the heart and can even allow it to pool within the atria. Any time blood remains still, it begins to coagulate (thicken) and form clots. A clot (embolus) will float through the circulatory system until it reaches a vessel that is too small for it to pass through, thus blocking it. When this occurs in a vessel in the brain, it results in a stroke. As you can see, AF is a serious diagnosis with potentially serious consequences. Patients with AF may experience either no symptoms or any of the following: chest pain, rapid or irregular heartbeats (palpitations), shortness of breath, dizziness or fainting, fatigue, confusion, or weakness.

Because there are various types of arrhythmias, testing using an electrocardiogram (ECG/EKG), Holter monitor, event recorder, or echocardiogram may be ordered to determine the exact type of atrial fibrillation to facilitate proper treatment planning. Atrial fibrillation is commonly found in patients suffering from an underlying condition such as hypertension, diabetes mellitus, heart failure, chronic kidney disease, ischemic heart disease, obesity, and hyperthyroidism. As of 2019, only four ICD-10-CM codes are available to report AF:

  • I48.0    Paroxysmal AF (lasts less than a week and resolves on own)
  • I48.1    Persistent (mixed definitions)
  • I48.2    Chronic (mixed definitions)
  • I48.91  Unspecified (provider didn’t document the type)

This category has been expanded effective October 1, 2020, and will include more specific options for persistent and chronic atrial fibrillation, as follows:

  • I48  Atrial fibrillation and flutter
  • I48.0     Paroxysmal atrial fibrillation
  • I48.1     Persistent atrial fibrillation
    • I48.11   Longstanding persistent atrial fibrillation
    • I48.19   Other persistent atrial fibrillation                Chronic persistent atrial fibrillation
      Persistent atrial fibrillation, NOS
  • I48.2 Chronic atrial fibrillation
    • I48.20   Chronic atrial fibrillation, unspecified
    • I48.21  Permanent atrial fibrillation
    • I48.91   Unspecified atrial fibrillation

Definitions for New Codes

Paroxysmal atrial fibrillation: This is intermittent atrial fibrillation that comes and goes, but never lasts longer than a week and resolves on its own without treatment.

Persistent atrial fibrillation: This type lasts longer than a week and less than a year but does not resolve on its own. It requires pharmacologic treatment or cardioversion in order to return the heart to a normal rhythm and when/if it returns, repeat treatment is necessary.

Longstanding, persistent atrial fibrillation: This is persistent atrial fibrillation which lasts longer than a year and always requires repeat pharmacologic or electrical cardioversion.

Other persistent atrial fibrillation: These other types of persistent atrial fibrillation, often documented as “chronic persistent” or “persistent NOS,” last longer than a week, but less than a year. They too require pharmacological treatment or electrical cardioversion.

Chronic atrial fibrillation, unspecified: This type of atrial fibrillation lasts more than a year and is non-refractory, meaning it won’t respond to treatment and has not yet been identified in the medical record as permanent.

Permanent atrial fibrillation: This type of atrial fibrillation does not go away, as it has lasted longer than a year and has been unresponsive to cardioversion. For this reason, cardioversion for these patients is no longer recommended (indicated), cannot be performed, or will not be performed. The record must identify the condition as permanent, or the code for chronic, unspecified (I48.20) should be reported.

Unspecified atrial fibrillation: Unspecified is reported when the documentation fails to identify a specific type of atrial fibrillation.

Essential Coding Information

In the office or other outpatient setting, an assessment that states, “Rule out persistent atrial fibrillation in this patient with chronic shortness of breath and palpitations,” would report the symptoms rather than the diagnosis codes listed above, since the diagnosis has not yet been confirmed. However, in an inpatient setting, it would be appropriate to report persistent atrial fibrillation as a confirmed diagnosis because there are different rules for reporting probable diagnoses for inpatients.

Assigning the correct code to support medical necessity is also important. For example, permanent atrial fibrillation wouldn’t support medical necessity for a cardioversion procedure, since, by definition, cardioversion has not and will not resolve the atrial fibrillation, so the procedure would be useless for this patient. Querying the provider for clarification is probably necessary in this case.

Often the report from an outside testing facility will provide details about a diagnosis that is not included in the assessment portion of the E/M encounter note by the ordering provider. While it may be tempting to use those details from the external report in the code selection for higher specificity, that would go against the rules of coding. There is, however, a circumstance that would allow the coder to code directly from the test report. If the ordering provider reviewed the results of the test and stated that he/she agreed with the findings, it would then be appropriate to include those details to report a higher-specificity code. If, however, the provider’s assessment of the patient’s diagnosis differs from that of the report, the coder should only code the provider’s diagnosis.

This Week’s Audit Tip Written By:

Aimee WIlcox, CPMA,CCS-P, CST, MA, MT


Aimee is Director of Content for Find-A-Code.

What to do next…

  1. Contact us to discuss your audit needs by calling (800) 635-4040 or email
  2. Read more: What can you expect from a coding and compliance review?
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