Ventricular Fibrillation

Ventricular fibrillation is a life-threatening heart rhythm problem that causes your heart’s lower chambers to quiver instead of pumping blood. Without immediate treatment, this condition can lead to sudden cardiac death within minutes.

Table of contents

• What is ventricular fibrillation?
• Symptoms and warning signs
• What causes this condition?
• Risk factors
• How doctors diagnose ventricular fibrillation
• Emergency treatment
• Long-term treatment and prevention
• Possible complications

VFib, V-fib, VF

• Heart ventricles (lower chambers)
• Heart muscle (myocardium)
• His-Purkinje system

What is ventricular fibrillation?

Ventricular fibrillation is the most common deadly arrhythmia, which means an irregular heart rhythm. Your heart is a muscle with four chambers. The two bottom chambers are called ventricles, and they are responsible for pumping blood out to your body^[2].

During ventricular fibrillation, the lower heart chambers contract in a very rapid and uncoordinated manner. Instead of expanding and squeezing normally, they quiver or twitch. This means they cannot pump blood as they should^[1].

The condition is caused by irregular electrical activity in the heart. On an electrocardiogram (a test that measures heart electrical activity), the heart rate is usually greater than 300 beats per minute, with the heart rhythm appearing very irregular^[4].

When blood stops flowing for this reason, you typically have just a few seconds before you pass out. This is called cardiac arrest, which is usually fatal in a few minutes without immediate care^[2]. Ventricular fibrillation has been identified in nearly 70% of cardiac arrest patients^[4].

Symptoms and warning signs

Collapse and loss of consciousness are the most common symptoms of ventricular fibrillation^[1]. Someone who has this condition will collapse with little or no warning and will not respond or react when you try to wake them. They will also gasp for breath or stop breathing^[2].

Before a ventricular fibrillation episode, you may experience symptoms of an irregularly fast or erratic heartbeat. These warning signs include^[1][2]:

• Chest pain
• Very fast heartbeat, also called tachycardia
• Dizziness or lightheadedness
• Nausea
• Shortness of breath
• Heart palpitations, where you become unpleasantly aware of your own heartbeat
• Racing or erratic pulse

What causes this condition?

Ventricular fibrillation is often linked to underlying structural heart disease. Three percent to 12% of people who have a myocardial infarction, which means a heart attack, develop ventricular fibrillation during the acute phase. Heart attack patients with complete coronary blockage, damage to the front wall of the heart, irregular upper heart rhythms, and pain before the heart attack are more likely to develop this condition^[4].

The causes of ventricular fibrillation include^[2][4]:

• Heart attack or ischemia (reduced blood flow to the heart)
• Heart conditions like cardiomyopathy that change the structure of your heart
• Other abnormal heart rhythms or conditions that cause them
• Congenital heart problems present at birth, like Brugada syndrome
• Heart surgery
• Certain medications
• Use of drugs including cocaine and methamphetamine
• Electrolyte imbalances, which means having too much or too little potassium or magnesium in your blood
• Acidosis, which means too much acid in your body
• Hypothermia, or low body temperature
• Hypoxia, or lack of oxygen
• Electrical shock
• Commotio cordis, which happens when you get hit in the chest with a small, fast-moving object like a baseball or hockey puck
• Alcohol use

Many common conditions associated with ventricular fibrillation include problems with electrolytes in the blood, too much acid in the body, low body temperature, lack of oxygen, diseases of the heart muscle, family history of sudden cardiac death, congenital problems with the heart’s electrical system, and alcohol use^[4].

Genetic predisposition to ventricular fibrillation is now increasingly recognized. The first large study of genetic factors reported identifying a location in the genetic code that increases susceptibility to this condition^[4].

Risk factors

In addition to existing heart conditions like coronary artery disease, the following factors raise your risk of ventricular fibrillation^[2]:

• Hypoxemia, which means low oxygen in your blood
• Abnormalities in electrolytes
• Too much acid in your body

Other risk factors include^[7]:

• A weakened heart muscle
• A previous heart attack or acute heart attack
• Genetic diseases such as long QT syndrome, short QT syndrome, Brugada disease, or hypertrophic cardiomyopathy
• Certain medicines that affect heart function

How doctors diagnose ventricular fibrillation

Ventricular fibrillation is always diagnosed in an emergency situation. If sudden cardiac death has occurred, checking for a pulse will reveal no pulse^[8].

A provider can confirm a ventricular fibrillation rhythm with an electrocardiogram (also called EKG or ECG), especially after bringing you back from cardiac arrest. They can also diagnose it during cardiac arrest if you have a cardiac monitor on or an implanted cardiac device^[2].

After emergency treatment, your provider will work to find out what caused ventricular fibrillation. They will collect your medical history and do a physical exam. They may order several other tests^[2][8]:

• Blood tests to check for proteins that leak into the bloodstream when the heart is damaged
• Echocardiogram, which uses sound waves to create images of the heart in motion
• Cardiac MRI, which stands for magnetic resonance imaging, to create detailed images of blood flow in the heart
• Coronary angiogram with cardiac catheterization to see blockages in the heart arteries
• Chest X-ray to show the size and shape of the heart and its blood vessels
• Cardiac CT scan, which stands for computed tomography, to create cross-sectional images of your body

Emergency treatment

Ventricular fibrillation is a life-threatening medical emergency. Every minute counts. If you see someone collapse, you might feel scared and not know what to do. The best way to help them is to call 911 or your local emergency number^[2].

If you see someone collapse, seek emergency medical help immediately. Follow these steps^[1]:

1. Call 911 or your local emergency number
2. If the person is unconscious, check for a pulse
3. If there is no pulse, begin cardiopulmonary resuscitation (CPR) to help keep blood flowing through the body until an automated external defibrillator (AED) is available. Push hard and fast on the person’s chest—about 100 to 120 times a minute. It is not necessary to check the person’s airway or deliver rescue breaths
4. Continue CPR until emergency medical help arrives
5. Use an automated external defibrillator as soon as one is available

Emergency treatment for ventricular fibrillation includes CPR and shocks to the heart with an AED^[1]. External electrical defibrillation remains the most successful treatment. A shock is delivered to the heart to uniformly and simultaneously cause all heart muscle cells to activate at once. The goals are to stop all abnormal heart rhythms and to allow any natural cardiac pacemakers to take over^[11].

Long-term treatment and prevention

There are two stages of treatment for ventricular fibrillation. The first tries to stop the episode immediately to restore blood pressure and pulse. The second stage focuses on reducing your chances of developing it again in the future^[7].

Medications, implanted devices, or surgery may be recommended to prevent episodes of ventricular fibrillation^[1]. Treatment options include^[7][8]:

• Medicines: Your healthcare provider may give you medicines immediately after ventricular fibrillation to help control and prevent another episode. They may prescribe additional medicines to control the abnormal rhythm and reduce your risk over time. Beta-blockers or anti-arrhythmic drugs may be used
• Implantable cardioverter defibrillator (ICD): This is a battery-powered device that is implanted near your left collarbone. A flexible wire runs from the device through the veins in your heart. If your heart rhythm becomes too slow, it sends an electrical signal to pace your heart. If it detects ventricular fibrillation, it delivers high-frequency shocks to reset your heart’s rhythm. Studies indicate that patients with ventricular fibrillation arrest who receive ICDs have better long-term survival rates than do patients who receive only medication
• Coronary bypass surgery: During this procedure, arteries or veins are sewn in place beyond the narrowed or blocked artery to restore blood flow
• Catheter ablation: This procedure uses energy to destroy small areas of your heart affected by the irregular heartbeat. This is often a treatment for ventricular tachycardia, which can trigger ventricular fibrillation. Most people who undergo this procedure already have an ICD
• Left cardiac sympathetic denervation: This is a surgical procedure that might help you if you have frequent ventricular fibrillation episodes

Prevention of ventricular fibrillation is directed at the underlying cause. Surgery may be appropriate in some cases, such as when you have operable coronary artery disease^[11].

Possible complications

It is rare for people to make a complete recovery from ventricular fibrillation. Contact your provider for help managing lingering issues after experiencing this condition^[2].

Complications of ventricular fibrillation include^[2]:

• Sudden cardiac arrest and death
• Coma
• Brain damage
• Heart muscle damage
• Kidney failure
• Liver failure

Without treatment, the condition is fatal within minutes. The rates of survival for patients outside hospitals have increased slightly, but many continue to have residual brain damage from lack of oxygen and other neurological problems^[4].