Ventricular Fibrillation (VFib)

Medically Reviewed by Poonam Sachdev on May 14, 2024
8 min read

Ventricular fibrillation also called VF or VFib, is a dangerous problem with your heart rhythm (called an arrhythmia) that keeps your heart from pumping blood the way it should. It's a medical emergency.

Your heart muscle has four main sections called chambers. The bottom two chambers are the ventricles. Ventricular fibrillation happens when the electrical signals in your heart go haywire. This causes a ventricle to quiver (fibrillate) instead of pumping blood through your body.

Without immediate medical treatment, VF stops your heart. In fact, it’s the most common cause of sudden cardiac death. It requires CPR or an automated external defibrillator (AED) machine to shock the heart rhythm back to normal.   

Coarse ventricular fibrillation

Ventricular fibrillation can be divided into two types based on the way it appears on an imaging test called an electrocardiogram (ECG or EKG). An EKG reading depicts your heart's electrical activity as high and low points (peaks and valleys). With coarse VFib, the peaks go higher and the valleys go lower. 

Fine ventricular fibrillation

With fine ventricular fibrillation, there's not as much difference between the peaks and valleys on your EKG reading. While both types are very serious, this is considered the most dangerous form.

VFib doesn’t give you much warning. The main symptom is fainting.

You may have these ventricular fibrillation symptoms just before you pass out:

  • Chest pain
  • Pounding, fluttering, or fast heartbeat  
  • Dizziness
  • Nausea
  • Shortness of breath
  • A fast or uneven pulse

When you lose consciousness because of VFib, you don't respond when someone touches or speaks to you. You also have serious problems breathing (gasping for air or not breathing at all).

Ventricular fibrillation vs. ventricular tachycardia

Both are very serous types of arrhythmia. With ventricular tachycardia or V-tach, your heart beats quickly but isn't as irregular as it is with VFib. V-tach can lead to ventricular fibrillation.  

What is ventricular flutter?

Ventricular flutter is an extreme type of ventricular tachycardia in which your heart beats 150-300 times a minute. If not treated, it usually becomes ventricular fibrillation. 

Ventricular fibrillation vs. atrial fibrillation

Atrial fibrillation, or AFib, affects the upper chambers of the heart (atria) rather than the lower ones. It causes a very fast heartbeat. Blood can pool in your atria and make them stretch out, but it can still circulate to the rest of your body. Atrial fibrillation isn't considered a medical emergency, but it raises your risk for blood clots and stroke.  


You get VFib because there's a problem with your heart's electrical properties or with the blood supply to your heart muscle.

Doctors don’t always know what causes this. But they do know some conditions and situations are linked to ventricular fibrillation. For instance, it happens most often during or right after a heart attack. That may be because your heart’s electrical signals become unstable when there's not enough blood flow.

Often, people who get ventricular fibrillation don't have heart disease. But they may have conditions that put them at risk for heart disease, like high blood pressure or diabetes. Other things that raise your chances of VFib include:

  • Weakened heart muscle (cardiomyopathy)
  • A previous heart attack
  • Certain genetic diseases
  • Certain heart medicines
  • An imbalance of electrolytes in your blood
  • Very low blood pressure (shock)
  • Electrical shock
  • Drowning
  • Problems with your main artery (aorta)
  • Drug misuse
  • Serious system-wide infection (sepsis)


When you're resuscitated after ventricular fibrillation, doctors may do several tests to diagnose it and figure out what caused it.

They include:

Ventricular fibrillation EKG. An electrocardiogram measures your heart's electrical activity. A computer displays the results of electrodes that are attached to your chest and sometimes to your limbs as well. A heartbeat of 300-400 beats a minute indicates you have VFib.

Echocardiogram. Your doctor can see the movement of your heart with this test, which uses ultrasound waves to produce an image.

Chest X-ray. This imaging test lets your doctor see the shape and size of your heart. It can also show them what your heart's blood vessels look like.

Coronary catheterization (angiogram). Dye is placed into your bloodstream through a tube (catheter) inserted into a blood vessel. The dye allows your doctor to more clearly see your heart arteries in X-rays.   

Cardiac computerized tomography (CT). A CT scan uses X-rays from several different angles to create detailed cross-section images of your heart.

Cardiac magnetic resonance imaging (MRI). This test uses radio waves and a magnetic field to create detailed images of your heart and its blood flow.

Blood tests. These are done to look for enzymes that show up in the bloodstream when your heart is damaged.

How does ventricular fibrillation rhythm look on a strip?

An EKG readout, or strip, of a VF cardiac rhythm will show irregular, squiggly lines instead of peaks and valleys at steady intervals as you'd see with a healthy heartbeat. 



VFib comes on quickly and needs treatment just as fast. Emergency ventricular fibrillation treatment involves:

Cardiopulmonary resuscitation (CPR).  These are chest compressions that imitate the heart's pumping action and keep blood moving through the body. If you're with someone who has symptoms of ventricular fibrillation, first call 911. Then start doing hard, fast pushes on their chest at a rate of 100-200 per minute. Their chest should rise between each pump. Keep doing this until help arrives.  

Defibrillators. You’ve probably seen defibrillators on TV, especially in medical dramas. They’re the paddles placed on a person’s chest to shock their heart into beating the way it should. If an automated external defibrillator (AED) is nearby, turn it on and follow the directions. The machines are programmed to recognize and treat ventricular fibrillation. If you're not sure how to use the AED, call 911 and an operator will guide you.  

Other VFib treatments that help ease arrhythmia symptoms and prevent it from happening again include:

Ventricular fibrillation medication. Antiarrhythmic drugs can be used in an emergency or as a long-term treatment. They work by slowing and stabilizing your heartbeat.  

Surgeries. Procedures used to treat VFib include:

  • Implantable cardioverter defibrillator (ICD). A surgeon places this device inside your chest or belly. When your heart is out of its regular rhythm, the ICD gives high- or low-energy electrical shocks to get your heartbeat back to normal. (If your ventricles start to quiver, it delivers a high-energy shock.) It’s like a pacemaker, but a pacemaker delivers only low-energy shocks
  • Cardiac ablation. A doctor guides a tube (catheter) into your heart through your veins or arteries or during surgery. Then, they use heat or cold energy to create small scars in your heart that block abnormal electrical signals.
  • Coronary angioplasty and stent placement. You might get this operation if a heart attack caused your VFib. Your doctor inserts a catheter through an artery and into a blocked artery in your heart. They then inflate a balloon on the end of catheter to open up the artery and restore blood flow. They may also place a mesh tube (stent) in the artery to keep it open.
  • Coronary bypass. If coronary artery disease caused your VFib, you might have this type of open-heart surgery. It uses a blood vessel taken from elsewhere in your body to redirect blood around a blocked heart artery.

Wearable cardioverter defibrillator (WCD). WCDs work much like ICDs, except they’re worn outside your body. Wires connect sensors on your skin to a unit you wear under your clothes. WCDs can be programmed to detect a certain type of arrhythmia such as VFib.

What does refractory ventricular fibrillation mean? 

Refractory VFib is when three shocks in a row from a defibrillator fail to return the heart to a normal rhythm. 

If you don't get treatment for ventricular fibrillation right away, it can be fatal in a matter of minutes. When your heart can't pump blood, a condition called cardiac arrest, your blood pressure falls very quickly. 

The longer your body is deprived of blood, the higher the chances that you'll end up with serious damage to your kidneys, liver, and nervous system. Depending on how serious this damage is, it may be reversible or permanent. You may go into a coma.

Once you recover from VFib, you may have more episodes in which you pass out or almost pass out.  One episode of ventricular fibrillation increases the risk that you'll have another one.

There's no foolproof way to prevent an episode of ventricular fibrillation. But you can treat the medical issues that can lead to it.

If you're at risk for VFib, your doctor may recommend:

  • Arrhythmia medication to control unusual heart rhythms
  • An implantable cardioverter defibrillator to correct abnormal heart rhythms
  • Cardiac ablation surgery to control unusual electrical signals

If you've had an episode of ventricular fibrillation or your doctor says you're at risk for it, talk to your loved ones and others you spend time with. Discuss when they should call 911 and the importance of learning to use an AED. It's also a good idea to wear a medical ID bracelet at all times. 

Ways to protect heart health

Damage to your heart makes it more vulnerable to ventricular fibrillation. To keep yours as healthy as possible, take these steps:

Keep cholesterol and blood pressure under control. Get checkups regularly. If your cholesterol or blood pressure is high, follow your doctor's recommended treatment plan. 

Don't smoke. Smoking makes you more likely to get heart disease. If you're a smoker, your doctor can recommend ways to help you quit.  

Avoid overusing alcohol. if you drink alcohol, stick to no more than one to two drinks per day, depending on your size. 

Follow a heart-healthy diet. Focus on veggies, fruits, whole grains, and lean proteins. Limit salt, sugar, and saturated fat. This will also help you manage your weight, which is also important for heart health.

Move on most days of the week. Do whatever exercise you enjoy, whether it's walking, swimming, or going to the gym.Shoot for 30- to 60-minute workouts at least 3 days a week. Talk to your doctor about what kind of exercise is best for you.

Get enough sleep. Most people need 7-9 hours a night for optimum health. Practice good sleep hygiene: Try to go to sleep and wake up on a regular schedule, keep your bedroom dark and quiet, and avoid screen time for at least a couple of hours before bed. 

Ventricular fibrillation is a fast, irregular heart rhythm that keeps your heart from pumping blood out to your body.  It's the most common cause of sudden cardiac death. If someone you're with has symptoms of VFib, call 911 right away, start CPR, and use a defibrillator if one is available.

How long can you live with ventricular fibrillation?

VFib is fatal within about 3-5 minutes unless someone resuscitates you. 

What happens when you have ventricular fibrillation?

When you have VFib, the electrical signals in your heart go haywire. The lower chambers of your heart  (ventricles) quiver instead of pumping like they should. This keeps blood from being pumped out to the rest of your body. 

What is the range of heart rate for ventricular fibrillation?

When you have ventricular fibrillation, the lower chambers of your heart beat over 300 times a minute.

What is the mortality rate for ventricular fibrillation?

With quick and effective treatment, up to 50% of those with ventricular fibrillation survive. If you have VFib when you're not in a hospital,  the odds that it can be reversed go down by 5% to 10% for each minute you wait for defibrillation.