Symptoms and Signs of Atrial Fibrillation (AFib) vs. Ventricular Fibrillation (VFib)

Medical Author:
Medically Reviewed on 5/27/2022

Doctor's Notes on Atrial Fibrillation (AFib) vs. Ventricular Fibrillation (VFib)

An ECG (electrocardiograph or EKG) is a graphic display or measure of the electrical activity (heart rhythm) of the heart.

  • Atrial fibrillation (AFib) is a type of abnormal heart rhythm (arrhythmia), usually with a very fast heart rate, that is caused by irregular contractions of the upper chambers of the heart (the atria).
  • Ventricular fibrillation (VFib) also is a type of abnormal heart rhythm in which the heart rate that is irregular and usually fast due to irregular contractions of the lower chambers of the heart (ventricles).

ECG similarities are usually a rapid irregular tracing.

  • In AFib, abnormal p waves precede the QRS signal on the ECG. In VFib, there is a rapid irregular tracing but p waves and the QRS signal are unidentifiable.
  • In most ECGs, AFib results in a rapid irregular pulse (QRS signal), while VFib results in no pulse (no clear QRS signal) so the ECGs are quite different.

The ECG of AFib is caused by rapid irregular multifocal electrical signals from the atria, some of which get through to the ventricles to allow a heartbeat (evidenced by a QRS). VFib is caused by multiple erratic ventricular signals that originate in the ventricles that do not allow the ventricles to contract (evidenced by no QRS signal).

What Are the Treatments of AFib vs. VFib?

VFib is a medical emergency (call 911) where the most important initial treatments include CPR (cardiopulmonary resuscitation) and external electrical defibrillation (AED or defibrillator). Medications that treat VFib include the following:

AFib can be a medical emergency, but many patients do not require EMS activation or CPR. Treatment goals are to reset the heart rhythm and/or control the heart rate and prevent blood clot formation. Resetting the heart rhythm may be done by shocking the heart or by drugs, often done as a scheduled procedure in contrast to VFib. Medications used to treat AFib may include the following:

  • Beta blockers: rate control
  • Calcium channel blockers: rate control
  • Digoxin: heart rate control, often as an additional drug
  • Anti-arrhythmic: helps to maintain a normal rhythm
  • Blood thinners: prevention of blood clots

Both may need further treatments (for example, surgery) to stop electrical signals that cause the two different arrhythmias, but the details and methods are different. Occasionally, there may be some overlaps in AFib and VFib treatments. Your cardiologist can design a plan of action if you have either of these different cardiac problems.

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Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.