Coding Tip: Cardiac Arrest and Cardiac Shock

Can cardiac arrest and cardiac shock be coded together beginning October 1, 2020?

In the past, there had been an Excludes1 note at I46.- Cardiac arrest that excluded R57.0, Cardiac shock. HIA had also received a letter from AHA on a case in the past that had stated that only I46.- Cardiac arrest would be coded if both were documented. In addition, the Third Quarter Coding Clinic page 26 had a similar case that asked if both could be coded, and AHA had instructed that only I46.9, cardiac arrest, cause unspecified would be coded if both were documented and that the CDC would be looking at possible revision to the Excludes1 note.   As of October 1, 2020, the Excludes1 note has been revised to an Excludes2 note. So what does this now mean? First lets look at the definitions of these two conditions.

What is Cardiac Arrest?

Cardiac arrest is when the patient’s heart stops. It is the abrupt loss of heart function due to a disruption in the heart’s electrical system.  The heart function or pumping totally stops.  Hence the name “arrested” or stopped. Death can result quickly if CPR and defibrillator is not used to restore the heart rhythm.   The most common cause of cardiac arrest is an arrythmia.  Ventricular fibrillation is the most common arrhythmia to cause cardiac arrest.  Other causes include MI, coronary artery disease, cardiomyopathy, valvular heart disease, and congenital heart disease.

What is Cardiac Shock?

Cardiac shock is when the heart pumping slows to the point where the body is not getting enough blood, but is not yet stopped like in cardiac arrest.   It can be caused by a heart attack, heart failure, myocarditis (inflammation of the heart), endocarditis (inflammation of the heart valves), drug overdoses or poisoning or other causes.  It is not fatal if treated immediately.  Symptoms include rapid breathing, severe shortness of breath, sudden, rapid heartbeat (tachycardia), loss of consciousness, weak pulse, low blood pressure (hypotension), sweating, pale skin, cold hands or feet and urinating less than normal or not at all. It can be fatal if not treated and cause damage to the liver, kidneys or other organs.  Treatment includes possible mechanical ventilation, inotropic agents such as Levophed or dopamine, aspirin, thrombolysis such as Activase or Retavase and blood thinning  and antiplatelet medications. If coronary blockage is causing an MI and cardiogenic shock, then an angioplasty with stents may be performed.   A balloon pump may also be utilized.  Cardiogenic shock can lead to cardiac arrest if not treated immediately.

So What is the Coder to Do?

On October, 1, 2020 the  CDC changes the Excludes1 note to Excludes2 note per below.

I46 Cardiac arrest
Excludes2: cardiogenic shock (R57.0)
I46.2 Cardiac arrest due to underlying cardiac condition
Code first underlying cardiac condition
I46.8 Cardiac arrest due to other underlying condition
Code first underlying condition
I46.9 Cardiac arrest, cause unspecified

AHA will most likely be addressing this in the future in an issue in Coding Clinic. Excludes2 notes are defined as “Not included here.” An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.  That being said, if cardiac shock is due to something other than what caused the cardiac arrest, both can be coded. However if cardiac shock leads to cardiac arrest, what is the coder to do? My interpretation is that there would not be a excludes2 note at all at this code if both codes were ALWAYS allowed to be reported together.  There simply would not be a need for an excludes note.   However the fact that there is now an Excludes2 note,  and cardiogenic shock is a symptom code, it is unclear if the CDC did this to allow both to be reported when they are related to the same cause.  My thought is they would not be reported together if the cardiogenic shock is documented as leading to cardiac arrest. In that case you would only report the definitive code, the cardiac arrest.  However, AHA may come out later and state you can code both. We don’t know yet. For the record, HIA is going to resubmit a case to see if both cardiogenic shock and cardiac arrest are both coded or not when documented. For the time being I think it best to follow the usual guidelines that if the cardiogenic shock leads to cardiac arrest due to the same cause, that the coder would only report the cardiac arrest code.  The cardiogenic shock code is still a “symptom” code that is not usually reported if the underlying cause is stated.  If the cardiogenic shock leads to cardiac arrest, then it makes sense that only the cardiac arrest code would be reported.  This tip will be updated when we get more information from AHA.


The information contained in this post is valid at the time of posting. Viewers are encouraged to research subsequent official guidance in the areas associated with the topic as they can change rapidly.

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