Ventricular Fibrillation (V-Fib): What to Know

Colleen Doherty, MD
·9 min read

Medically reviewed by Rafle Fernandez, MD

Ventricular fibrillation, called V-fib or VF, is an extremely dangerous arrhythmia. It causes the heart's lower chambers to twitch (fibrillate), preventing blood from being pumped out of the heart to the brain and other vital organs within the body.

V-fib results in cardiac arrest within seconds and death soon after if not treated with chest compressions and defibrillation (delivering an electric shock to restore the heart's normal rhythm).

This article explores V-fib, including how it develops and its symptoms and treatment. It will also briefly review the differences between V-fib and other arrhythmias like atrial fibrillation (A-fib) and ventricular tachycardia (V-tach).

<p>Jackyenjoyphotography / Getty Images</p>

Jackyenjoyphotography / Getty Images

What Happens During Ventricular Fibrillation (V-Fib)?

To best understand V-fib, you must first understand what happens when the heart is in normal sinus rhythm. The heart is a muscular organ with two upper chambers (right and left atria) and two lower chambers (right and left ventricles).

During a normal heartbeat:

  • A specialized group of cells at the top of the right atrium—the sinoatrial (SA) node—first generates an electrical impulse.

  • This impulse spreads across the atria before reaching the atrioventricular (AV) node within the heart's center.

  • The AV node then transmits the electrical impulse to the ventricles, causing them to contract and pump blood out of the heart.

In ventricular fibrillation, electrical impulses do not begin in the SA node or travel through the heart in a coordinated, deliberate manner.

Instead, in V-fib, multiple electrical impulses originate within different areas of the ventricles, causing the ventricles to twitch and quiver uncontrollably and chaotically.

As a result of the ventricles twitching, they cannot do their job and pump blood to the rest of the body, leading to sudden cardiac arrest within seconds and, in severe cases, death.

Learn More: The Heart's Electrical System: Anatomy and Function

V-Fib vs. A-Fib

Atrial fibrillation, or A-fib, is an arrhythmia that originates in the atria, not the ventricles, as in ventricular fibrillation.

As a result of the atria quivering in A-fib, blood is not strongly pumped into the ventricles, often causing a sensation of the heart fluttering or pounding in the chest. Also, due to blood pooling in the atria, blood clots can develop and cause a stroke if they travel to the brain.

While V-fib is dangerous, causing sudden cardiac arrest, A-fib is not generally considered life-threatening. A-fib is also more common than V-fib, affecting up to 6 million adults in the United States.

V-Tach vs. V-Fib

Ventricular tachycardia (V-tach) and ventricular fibrillation are rapid arrhythmias originating in the heart's lower chambers instead of the SA node.

However, while multiple electrical signals within the ventricles are produced and spread simultaneously in V-fib, an area within the left or right ventricle typically generates the electrical impulse in V-tach.

Also, the ventricles quiver irregularly in V-fib, whereas the ventricles usually contract regularly in V-tach.

Lastly, V-fib is always life-threatening, leading to cardiac arrest and death if not treated immediately. In contrast, V-tach is only considered life-threatening when sustained (lasting more than 30 seconds).

Learn More: V-Tach vs. V-Fib: Differences and Similarities

Ventricular Fibrillation Symptoms

The ventricles in V-fib twitch erratically and are, therefore, unable to pump blood to the rest of the body, leading to sudden cardiac arrest (SCA) within seconds.

Sudden cardiac arrest means the heart's electrical system malfunctions, causing the heart to suddenly stop beating. If not treated immediately, death will occur within minutes.

Symptoms and signs of sudden cardiac arrest include:

  • Gasping for air or not breathing

  • Sudden collapse and loss of consciousness (passing out)

  • No response to shouting or shaking

  • No pulse (heartbeat)

Causes and Risk Factors of V-Fib

Ventricular fibrillation has multiple potential causes, with a heart attack being a common one.

A heart attack—known medically as a myocardial infarction—occurs when a part of the heart is damaged or dies when its blood supply is blocked.



Symptoms of a Heart Attack

Symptoms of a heart attack vary, although common ones include:

  • Pain or discomfort in the center or left side of the chest

  • Shortness of breath

  • Dizziness

  • Sweating

  • Nausea

If you are experiencing heart attack symptoms, call 911 or seek medical care immediately.



Most heart attacks occur due to coronary artery disease, in which fatty deposits (plaque) build up within the coronary arteries, whose job is to transport oxygenated blood to the heart.

These plaques can break open, and a blood clot can form. This can entirely or partially block off a coronary artery, depriving the heart muscle of blood and causing a heart attack.

Certain factors elevate a person's chances of developing coronary artery disease, such as:

  • Increasing age, especially over 45 years in men and over 55 years in women (the terms for sex from the cited source are used)

  • Family history of early heart disease

  • History of high blood pressure, diabetes, high cholesterol, or smoking

  • Being overweight or having obesity

  • Lack of physical activity

Learn More: Causes and Risk Factors of Coronary Artery Disease

In addition to heart attacks, other possible causes of or contributors to ventricular fibrillation include:

How Is V-Fib Diagnosed?

Since V-fib causes cardiac arrest within seconds, there is no time for a diagnostic evaluation.

Instead, if a person is experiencing symptoms of sudden cardiac arrest, call 911, get an automatic external defibrillator (AED) immediately, and perform cardiopulmonary resuscitation (CPR).



What Is an AED?

An AED is a sophisticated yet easy-to-operate portable device that analyzes the heart's rhythm and delivers an electrical shock if an arrhythmia like V-fib is detected.



AEDs are available in most public places and can be used by untrained bystanders in an emergency, as the device "speaks," providing simple step-by-step instructions.

Once a person has been resuscitated from cardiac arrest, an electrocardiogram (ECG or EKG), among other tests, will be performed to discern the cause of the ventricular fibrillation.

V-fib resembles chaotic, patternless waves or a thin, bumpy line on an ECG. The grossly irregular electrical activity on the ECG usually has a ventricular rate (a measure of how fast impulses move through the AV node) greater than 300 beats per minute.

Moreover, the height of the waves distinguishes the two types of ventricular fibrillation—coarse and fine V-fib.

Coarse V-fib is where the ECG waves measure 3 millimeters (mm) or more. It tends to occur early after the onset of cardiac arrest and is more likely to be shocked into a normal heart rhythm than fine V-fib.

V-Fib Treatment

The treatment of V-fib is twofold, first requiring emergency care and resuscitation followed by hospital care if the person survives the cardiac arrest.

Emergency Treatment

The first response to V-fib and cardiac arrest is calling 911, performing CPR, and using electrical defibrillation.

More specifically, take the following steps:

  • If someone is nearby, tell them to call 911 and bring you an AED. Time is of the essence, so tell that person to be fast. If you are alone, call 911 and get an AED (if available).

  • Begin CPR with compressions, pushing at least 2 inches in the middle of the person's chest. Allow the chest to return to its normal position after each push. Aim for a compression rate of 100 to 120 pushes a minute.

  • When you receive the AED, turn it on and follow the device's prompts.

  • Continue CPR while the AED monitors the heartbeat until first responders take over.

Hospital Treatment

If a person survives a cardiac arrest, they will be admitted to a critical-care facility with a comprehensive post–cardiac arrest treatment system.

One of the main goals of this system is to minimize organ damage by, for example, placing the person on a ventilator (breathing machine) to protect the lungs and cooling the body's temperature to protect the brain.

Another primary goal is promptly treating the cause of the V-fib. For example, if underlying coronary artery disease is the culprit, various procedures or surgeries may be performed, such as:

While in the hospital, an implantable cardioverter defibrillator (ICD) may also be placed.

Can V-Fib Be Prevented?

There is no surefire way to reverse or cure V-fib once it has occurred.

However, some therapies, like taking certain medications, such as a beta-blocker or antiarrhythmic, having an implantable cardioverter defibrillator (ICD) placed, or undergoing catheter ablation, may help prevent future V-fib episodes.

An ICD is a small, battery-operated device surgically placed under the skin in a person's chest or abdomen. It's connected to the heart with wires (leads) and can deliver an electric shock to the heart if a dangerous arrhythmia is detected.

Catheter ablation is a procedure that destroys parts of the heart that are generating abnormal electrical signals and may help prevent future V-fib episodes.

In addition, practicing healthy lifestyle behaviors can help prevent V-fib episodes by controlling the conditions that cause it.

These behaviors include:

  • Eating a diet rich in fruit, vegetables, and whole grains and minimizing consumption of trans fats, added sugars, red meat, salt, and saturated fats

  • Exercising regularly (under the guidance of a healthcare professional)

  • Maintaining a healthy body weight

  • Stopping smoking

  • Managing high blood pressure or cholesterol

When to Seek Emergency Care

If you see someone with a known or possible heart problem suddenly lose consciousness, call 911, get an AED, and start CPR immediately.

Also, seek emergency care if you are experiencing early symptoms of V-fib, such as those associated with ventricular tachycardia:

Summary

Ventricular fibrillation, or V-fib or VF, is a dangerous arrhythmia that causes the heart's lower chambers (ventricles) to erratically quiver instead of pumping blood as they should. V-fib results in sudden cardiac arrest and requires emergent defibrillation (electric shock) to restore the heart's normal rhythm.

Once the heart's rhythm is restored, specialized post–cardiac arrest care within a hospital is required to help prevent organ damage. This care often involves oxygen therapy and cooling devices to lower the body's temperature.

Determining the cause of the V-fib is also done, including procedures to address that cause—for example, opening up a blocked coronary artery with a stent.

Read the original article on Verywell Health.