Atrial Fibrillation

The most common cardiac arrhythmia, atrial fibrillation, occurs when the normal electrical impulses that are generated by the SA node are overwhelmed by disorganized electrical impulses in the atria.

These disorganized impulses cause the muscles of the upper chambers of the heart to quiver (fibrillate) and this leads to the conduction of irregular impulses to the ventricles.

For ACLS, atrial fibrillation becomes a problem when the fibrillation produces a rapid heart rate which reduces cardiac output and causes symptoms or an unstable condition.

When atrial fibrillation occurs with a (RVR) rapid ventricular rate (rate > 100 beats/min), this is called a tachyarrhythmia. This tachyarrhythmia may or may not produce symptoms. Significant symptoms that occur are due to a reduction in cardiac output.

The following is a list of the most common symptoms.

• palpitations or chest discomfort
• shortness of air and possibly respiratory distress
• hypotension, light-headedness and possibly loss of consciousness
• peripheral edema, jugular vein distention, and possibly pulmonary edema

For the purpose of ACLS, it is important to be able to recognize atrial fibrillation when the patient is symptomatic. On an ECG monitor, there are two major characteristics that will help you identify atrial fibrillation.

1. No p-waves before the QRS on the ECG. This is because there are no coordinated atrial contractions.
2. The heart rate will be irregular. Irregular impulses that the ventricles are receiving cause the irregular heart rate.

When the heart rate is extremely rapid, it may be difficult to determine if the rate is irregular, and the absence of p-waves will be the best indicator of atrial fibrillation.

ACLS Treatments:

For the purposes of ACLS atrial fibrillation is treated when the arrhythmia/tachyarrhythmia produces hemodynamic instability and serious signs and symptoms.

For the patient with unstable tachycardia due to a tachyarrhythmia, immediate cardioversion is recommended. Drugs are not used to manage unstable tachycardia. The appropriate voltage for cardioverting unstable atrial fibrillation is 120-200 J.

Cardioversion of stable atrial fibrillation should be performed with caution if the arrhythmia is more than 48 hours old and no anticoagulant therapy has been initiated due to the risk of emboli that can cause MI and stroke.

Below is a short video which will help you quickly identify atrial fibrillation on a monitor.
Please allow several seconds for the video to load. (5.11 mb)

Click for next Rhythm Review: Other Tachycardias

Top Questions Asked On This Page

1. Q: To treat a patient with rapid atrial fibrillation (HR >180bpm), can calcium channel blockers be given to help control the rate?

   A: Yes, in some cases, calcium channel blockers are a good choice to help control atrial fibrillation with a rapid ventricular rate.

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2. Q: What are atrial fibrillation and atrial flutter considered in terms of narrow or wide QRS complexes?

   A: Unless there is an underlying block the QRS complex will typically be normal/narrow. There is the possibility of occasional wide QRS complexes due to abnormal ventricular depolarization via an accessory pathway.

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3. Q: What does the DC before the word cardioversion stand for?

   A: DC cardioversion simply means direct current cardioversion.

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4. Q: What are some of the beta blockers used with stable tachyarrhythmias?

   A: Metoprolol, labetalol, and Propranolol are commonly used, but there are others.

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5. Q: why the voltage difference in the Cardioversion of Fib Flutter?

   A: The reason is that atrial flutter tends to convert with a much lower dose of electricity than atrial fibrillation.

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6. Q: How do I determine if a patient is unstable?

   A: The major difference that will be associated with unstable arrhythmias will be a systolic blood pressure less than 90 mmHg with other signs of poor perfusion like LOC changes.
   A patient that is simply symptomatic may have dizziness, tachycardia, weak pulses, etc. but the systole blood pressure remains greater than 90 mmHg, and there are no LOC changes or other signs of poor perfusion.

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7. Q: Can you provide some guidance on how to recognize the difference between atrial and ventricular impulses on an ECG?

   A: The ventricular portion of the ECG is known as the QRS complex. The QRS complex is the electrical equivalent of the ventricular contraction. If there is no ventricular contraction, there is no pulse. Therefore, if your patient has a pulse, you will see a QRS complex. The QRS complex will be the tallest and most pronounced portion of the ECG reading. The atrial impulses may or may not be present depending on the rhythm. Atrial impulses are recognized on the ECG monitor as P-waves that typically precede the QRS complex. The p-waves are much smaller than the QRS complexes.

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8. Q: How can you know buy the ECG alone if the rhythm is pulseless?

   A: You cannot determine a pulseless state by only looking at the ECG monitor. A rhythm can be determined to be pulseless simply by manually palpating for a pulse.

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9. Q: What is the drug of choice for AF? Here our cardiologists use Amiodarone regularly. Do we have to treat rate & rhythm separately in AF?

   A: I would not say that there is one drug of choice for atrial fibrillation.
   In the critical care setting when atrial fibrillation is accompanied by a rapid ventricular rate amiodarone is used. Quite frequently, I have seen Cardizem or some other calcium channel blocker used to slow the heart rate.

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10. Q: Cardioversion begins at what level?

    A: For the patient who has atrial fibrillation, the indication for cardioversion would be if the patient is hemodynamically unstable. Some things to look for would be SBP< 90mmhg, altered mental status, and chest pain. Also, with atrial fibrillation, a TEE (Transesophageal Echocardiogram) should be performed before cardioversion if the pt. has not had anticoagulant therapy. This would ensure that the patient did not have any thrombus that could worsen the patient’s condition if cardioversion is performed.

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11. Q: Imagine a patient brought to ER with SBP <90, sweating and chest pain and ECG shows Atrial fibrillation. TEE is performed and Shows thrombus. What should be our line of treatment? Should we go for cardioversion or should we initiate anticoagulation before cardioversion?

    A: You would not want to use cardioversion with this patient at this time. The patient would probably be placed on some anticoagulant and given something to decrease the heart rate and possibly something to improve blood pressure.
    This patient would need to be medically managed until the patient could be seen by a cardiologist.

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12. Q: Suppose a patient has new onset a fib and unstable with SBP of 80 and they have clear sepsis with a lactate of 4. Would you cardiovert or give fluids first?

    A: I would give fluids first. It is very likely that the hypotension is related to sepsis rather than the atrial fibrillation. You can give 500-1000 ml of fluid fairly rapidly to determine if the patient will stabilize.
    Also, if the duration of being in atrial fibrillation is not known, then a TEE (Trans-esophageal Echocardiogram) would need to be performed to rule out thrombosis before any thought of cardioversion.

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13. Q: How do you treat symptomatic bradycardia with afib? Atropine and pacing?

    A: It depends if the atrial fibrillation is new onset. If it is new onset, then it should be taken care of after the patient is stabilized and the cause of the bradycardia dealt with. Treat the patient’s slow rate first. Pacing would probably be the easiest intervention that would stabilize the patient. ECG and cardiac enzymes should be checked to r/o myocardial infarction.

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14. Q: If a patient has one of the symptoms listed does this make them unstable or would there need to be a change in vital signs also?

    A: You would see a change in vital signs that would be related to poor perfusion. You would also consider serious signs and symptoms as unstable. The most common of these s/s are chest pain, signs of shock, SOA, altered mental status, weakness, fatigue, and syncope.

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15. Q: Is NGT contraindicated in rapid AF with associated angina due to preload and afterload being possibly compromised?

    A: If the angina is being caused by the rapid AF, then NTG (nitroglycerine) would not be indicated. You would want to deal with the rapid heart rate. Deal with the rapid rate and you will most likely relief angina. A drop in pressure related to the NTG could further compromise the patient’s already compromised perfusion

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16. Q: What is the 2nd line of Rx of stable AF with rapid ventricular, not responding to a beta blocker or Calcium channel blocker +/- digoxin. Can we use amiodarone for rate control even if AF persisting more than 48 hr?

    A: Management of atrial fibrillation is complex, and treatments can vary depending on the duration of atrial fibrillation, co-morbidities, underlying cause, symptoms, and age. Here is a link to an AHA PDF on the guidelines for treating atrial fibrillation.

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17. Q: What is the recommended level of electrical shock – Cardio Version – with atrial fibrillation? Same as with A-flutter?

    A: Here are the cardioversion voltage doses:
    Pg. 118: “Initial recommended doses:

    • narrow regular: 50-100 J
    • Narrow irregular: 120-200 J biphasic or 200 J monophasic
    • Wide regular: 100 J
    • Wide irregular: defibrillation dose (not synchronized)”

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18. Q: What is the best way to distinguish between P waves and a T wave on the rhythm strip?
    (For instance, the Afib with RVR video clip from 0:50 seconds – 1:11 appears to have P waves. However, I am assuming that they are T waves.) How can I best tell the difference?

    A: The first thing you need to ask is “is the rhythm irregular?” If the rhythm is irregular, then you are most likely dealing with atrial fibrillation. The second thing is “is there a P-wave before every QRS complex?”
    If you do not see a p-wave before every QRS complex and the rhythm is irregular, then you are almost guaranteed that the patient is in atrial fibrillation. Don’t worry about figuring out anything about the t-waves. Just ask yourself “is the rhythm irregular” and “is there a p-wave preceding every QRS complex.
    If the rate is too rapid to assess p-waves but the rhythm irregular, then you can assume that the patient is in atrial fibrillation.

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19. Q: What causes jugular vein distention?

    A: Jugular vein distention is caused by increased blood volume, which can occur with heart failure, or anything that interferes with the filling of the right atrium or movement of the blood into the right ventricle, can increase the central venous pressure and the amount of jugular vein distention.

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20. Q: How is the atrial rate of 300-600bpm counted if there are no P waves?

    A: You cannot count the atrial rate when a patient has atrial fibrillation because the atrial impulses produce a quivering of the heart rather than a full impulse which creates a p-wave. Regarding atrial rates that are very rapid, You may be referring to atrial flutter. With atrial flutter, the flutter waves between the QRS complexes can be very rapid, and these can count as a separate atrial rate to determine the rate at which the atria are firing compared to the ventricles.

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21. Q: If a patient has unstable atrial fibrillation do we still need to do a TEE to rule out thrombus before we perform cardioversion?

    A: In the rare case where a patient has unstable atrial fibrillation, and there is no other way to keep them stable, and cardioversion is indicated then cardioversion may be performed emergently.
    I think that this would be a rare occurrence. Usually, instability with atrial fibrillation is caused by a rapid heart rate. Typically, you can apply some type of rate control medication like Cardizem or metoprolol to bring the heart rate down. There are a lot of variables and a lot of options and cardioversion for unstable atrial fibrillation without a TEE would be the last option.