Ventricular Fibrillation

Ventricular fibrillation (sometimes called v-fib for short) is a malfunction of the heart’s normal pumping sequence. It is the most common deadly irregular heart rhythm (arrhythmia).


Ventricular fibrillation electrocardiogram
Electrocardiogram from a patient with ventricular fibrillation.

What is ventricular fibrillation?

Ventricular fibrillation (sometimes called v-fib for short) is an arrhythmia, a malfunction of the heart’s normal pumping sequence. It is the most common deadly arrhythmia.

When it happens, the lower chambers of your heart quiver or twitch instead of completely expanding and squeezing. This means they aren’t pumping blood as they should.

Why is ventricular fibrillation so dangerous?

When blood stops flowing for this reason, you normally have just a few seconds before you pass out. This is called sudden cardiac arrest, which usually results in death in just a few minutes without immediate care.

Sudden cardiac arrest is the No. 1 cause of natural death in the United States, and accounts for half of all deaths from heart disease.


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What are coarse ventricular fibrillation and fine ventricular fibrillation?

Ventricular fibrillation on an electrocardiogram is a wave of peaks and valleys. How this wave appears tends to get grouped into two categories, coarse and fine.

  • Coarse ventricular fibrillation: When the fibrillation is strong, the peaks are taller and the valleys are deeper. It’s called “coarse” because the line is anything but smooth.
  • Fine ventricular fibrillation: When the peaks and valleys are short and shallow, this is called fine ventricular fibrillation.

Overall, coarse ventricular fibrillation is preferred because it is more strongly associated with survival and good outcomes. That’s because coarse fibrillation is closer to normal heart activity than fine ventricular fibrillation.

What is refractory v-fib?

Refractory ventricular fibrillation happens when ventricular fibrillation continues even after three successive shocks from a defibrillator. Ventricular fibrillation is considered difficult to treat, but research is ongoing on how to overcome this complication.

Symptoms and Causes

What causes v-fib?

Ventricular fibrillation is most commonly caused by the following:

  • Heart disease.
  • Heart attack or chest pain (angina).
  • Diseases that change the structure of the heart by making its walls thicker or weaker.
  • Other arrhythmias or arrhythmia-causing conditions.
  • Heart surgery.
  • Certain medications.
  • Electrolyte imbalances (too much or too little potassium in your blood).
  • Electrical shock.
  • Being hit in the chest with a small, fast-moving object (this is called commotio cordis, and it happens most commonly in sports like baseball, hockey and lacrosse).


What are the symptoms of ventricular fibrillation?

The following symptoms are common just before v-fib:

Someone who has this condition will collapse with little or no warning and won’t respond or react when you try to wake them. They’ll also gasp for breath or stop breathing altogether.

Diagnosis and Tests

What tests are done for ventricular fibrillation?

Ventricular fibrillation is usually confirmed by an electrocardiogram (ECG or EKG), especially after a person has been resuscitated from cardiac arrest. This is also useful to determine the heart’s ability to function going forward.


Management and Treatment

How is v-fib treated?

The condition is a life-threatening medical emergency and every minute counts. The following actions can help save the life of someone who has gone into sudden cardiac arrest because of ventricular fibrillation:

  • Stay calm and call 911.
  • Begin CPR: Chest compressions are an essential, life-saving step, especially until an AED can be used or until first responders arrive (whichever happens first).
  • Use an automated external defibrillator (AED): Ventricular fibrillation is one of the “shockable” arrhythmias, meaning an AED can help return a person to a normal heartbeat rhythm. When an AED is used in the first three minutes after a person collapses because of ventricular fibrillation, the survival rate of ventricular fibrillation can be as high as 95%.

People who survive ventricular fibrillation have a higher risk of it happening again, so your healthcare provider will run tests to determine what caused it to happen and what follow-up options will work best to keep it from happening again.

  • Antiarrhythmic medications: These medications help keep your heart rhythm normal.
  • Implanted device: Most people who survive ventricular fibrillation will have an implantable cardioverter-defibrillator (ICD) placed. This device can detect arrhythmias and deliver an electric shock to restore your heart to a normal rhythm. These devices are almost always permanent.

Additional Common Questions

What is the difference between atrial fibrillation (a-fib) and ventricular fibrillation?

Atrial fibrillation is similar to ventricular fibrillation, but it’s happening in the upper chambers of the heart, called the atria. When the atria fibrillate, they beat very fast (sometimes several hundred times per minute). This can cause blood to collect in the atria and over time, this can cause the atria to stretch and enlarge.

When blood collects in one place like this, it increases the risk of forming a clot, which can then go from the heart to the brain. This is why atrial fibrillation is not considered dangerous on its own, but is a major risk factor for stroke.

Is v-fib the same as a heart attack?

Ventricular fibrillation is a malfunction of the normal beating rhythm of the lower chambers of the heart. A heart attack is different because it is caused by blockages in the blood vessels that supply the heart with enough oxygen to keep pumping. However, a heart attack can cause ventricular fibrillation.

What is the difference between ventricular tachycardia and ventricular fibrillation?

Ventricular tachycardia and ventricular fibrillation are closely related, very similar conditions. The difference between the two is that in ventricular tachycardia, the lower chambers of the heart are beating much faster than they should but the overall process is happening in the right order. In ventricular fibrillation, the heart’s beating process isn’t happening in the right order.

Both ventricular tachycardia and ventricular fibrillation are considered life-threatening because they can lead to collapse and sudden cardiac arrest. In emergencies, both are typically treated with defibrillation. Long-term, both are typically treated with a surgically placed implanted cardioverter defibrillator.

A note from the Cleveland Clinic

Ventricular fibrillation and sudden cardiac arrest can be difficult topics to discuss, especially for people who’ve experienced it before. Your healthcare provider can give you guidance that can help you better understand your condition. These resources can help you take care of yourself and focus on living your life.

Medically Reviewed

Last reviewed on 09/20/2021.

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