Atrial Fibrillation

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.

Atrial Fibrillation EKG Tracing

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.


  1. NCnurseAW says

    What is the best way to distinguish between a 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?


    • says

      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.

      I hope that makes sense. Please let me know if you have any other questions.

      Kind regards,

  2. walid says

    thanks for this wonderful site
    i cannot find an answer for this mcq

    -35 year old morbidly obese patient is discharged after gastric bypass surgery. She is readmitted 4 days later after she falls and twists her ankle. She is noted in the ER to be in atrial fibrillation, she is hypotensive, but only complains of leg pain. She is admitted to the hospital and temperature on admission is 38.6 c and heart rate 105.
    The next step in the management of her dysrythmia should be
    a- Ibutilide
    b- Procainamide
    c- Echocardiographic study
    d- DC cardioversion
    e- Digitalis

    • says

      The answer would be “C” the next step would be an echocardiographic study. This is because you would want to ensure that the atrial fibrillation did not cause any clots to form in the heart. Once thrombus is ruled out, you are ok to perform cardioversion if necessary.
      When a person has new onset atrial fibrillation, it can cause a thrombus to form in the heart and this can lead to a life threatening problem. This is why it is important to get an echocardiographic study completed as soon as possible.
      Kind regards,

  3. cdfrick says

    Hi Jeff –
    What is the recommendation level of electrical shock – Cardio Version – with atrial fib? Same as with A-flutter?

    • says

      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)”

      Kind regards,

  4. Md Islam says

    Hi Jeff

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

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>