Version July 2025
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What is ventricular fibrillation? —
Ventricular fibrillation, or "V-fib," is a heart problem that causes death if it isn't treated within minutes.
In V-fib, the electrical signals that control the heartbeat become abnormal and fast. As a result, the bottom chambers of the heart (ventricles) twitch, but do not pump blood (figure 1).
When the heart suddenly stops beating and pumping blood, it is called "sudden cardiac arrest." This is a medical emergency that needs to be treated right away. If it isn't, it causes death. But even with treatment, most people with sudden cardiac arrest do not survive.
V-fib is the abnormal heart rhythm that most commonly causes sudden cardiac arrest.
What causes V-fib? —
V-fib can happen in people with many different conditions. But the most common cause is a heart attack. In a heart attack, 1 of the arteries that brings blood to the heart gets blocked, and heart muscle dies. V-fib usually happens within a few days of a heart attack. But sometimes, V-fib is the first sign of a heart attack.
V-fib can happen in people who have other types of heart problems. It can also happen in people who do not have a heart problem. For example, it can happen in people who have very low levels of potassium, certain lung problems, or a severe injury. It can also happen in people who use illegal drugs.
What are the symptoms of V-fib? —
V-fib causes people to collapse and pass out, and have no pulse or heartbeat.
To check for V-fib, a doctor or emergency worker will do an electrocardiogram, or "ECG." This measures the electrical activity in the heart.
How is V-fib treated? —
V-fib needs to be treated right away. The only way to stop V-fib is a treatment called "defibrillation." This involves using a device to send an electrical shock to the heart. This shock can sometimes get a normal heart rhythm started again. Defibrillation has the best chance of working when it is done right away.
V-fib is also usually treated with CPR. CPR is a way to get blood and oxygen moving through the body of someone whose heart has stopped beating. It involves "compressions," or pressing hard and fast (over and over again) on a person's chest (picture 1). This squeezes the heart and gets the blood moving again, but not as well as when the heart pumps blood on its own.
If these treatments are done within a few minutes of when V-fib starts, they sometimes work to restart the heart. After the heart is beating again and blood is flowing through the body, people have other tests and treatments.
In people who have a cardiac arrest, doctors or emergency workers sometimes start a treatment called "hypothermia" to cool the body down. This can give people a better chance of surviving in the days after cardiac arrest. For this treatment, the body is cooled down to a few degrees below normal for 1 to 2 days. This helps reduce brain injury. This is important, because brain injury is the most common cause of death after cardiac arrest.
If you had a cardiac arrest, your doctor will try to find out what caused it and treat that problem, if it can be treated. To look for the cause, your doctor will do a lot of tests. These usually include:
●ECG – This measures the electrical activity in your heart (figure 2).
●Chest X-ray
●Blood tests
●Echocardiogram, or "echo" – This uses sound waves to create pictured of your heart as it beats (figure 3).
●Other imaging tests – These create pictures of the inside of the body.
If a heart attack caused your cardiac arrest, you will have a procedure called cardiac catheterization, or "cardiac cath." The doctor puts a thin tube into a blood vessel in your leg or arm. Then, they move the tube up to your heart. When the tube is in place, the doctor can do tests or unblock a clogged artery (figure 4).
Other treatments, including long-term treatments, after an episode of V-fib can include:
●Medicines to help make the heart rhythm normal, or control the speed or rhythm of the heartbeat
●An implantable cardioverter-defibrillator, or "ICD" – This is a device that is put under the skin near the heart (figure 5). It can sense abnormal heartbeats, then treat them with an electrical shock. Most people with V-fib are treated with an ICD.
●A procedure called "ablation" – The doctor uses heat or cold to destroy the small part of the heart that is sending the abnormal electrical signals. This is usually done only if a person has many episodes of V-fib.
What will my life be like if I survive? —
It depends, in part, on what caused your V-fib and how quickly it was treated. After V-fib and sudden cardiac arrest, some people recover completely without any long-term problems. But many people have long-term brain problems. If you get an ICD, you might need to make changes to your lifestyle. Your doctor or nurse will talk to you about what to expect.
Patient education: Sudden cardiac arrest (The Basics)
Patient education: Heart attack (The Basics)
Patient education: What can go wrong after a heart attack? (The Basics)
Patient education: ECG and stress test (The Basics)
Patient education: Implantable cardioverter-defibrillators (The Basics)
Patient education: Catheter ablation for the heart (The Basics)
Patient education: Overview of heart arrhythmias (The Basics)
Patient education: Advance directives (The Basics)
Patient education: Heart attack (Beyond the Basics)
Patient education: Implantable cardioverter-defibrillators (Beyond the Basics)
Patient education: Catheter ablation for abnormal heartbeats (Beyond the Basics)
