Atrial fibrillation (AFib) and ventricular fibrillation (VFib) are arrhythmias, or when the heart beats abnormally. AFib affects the upper parts of the heart (atria). VFib affects the lower parts of the heart (ventricles).

AFib and VFib have several symptoms in common. However, VFib is more serious.

This article looks at the similarities and differences between AFib and VFib. It explains what they are and their effects on the body.

The article also examines the symptoms, diagnosis, treatment, and outlook for AFib and VFib.

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According to the American Heart Association (AHA), AFib is an irregular heartbeat.

In people with AFib, the upper chambers of the heart beat irregularly. These are the atria. When the atria beat in this way, there is not enough blood leaving this part of the heart. This can make blood pool within them, causing blood clots.

Those blood clots can leave the heart and travel to the brain. When this happens, they can cause a stroke. AFib can cause other issues with the body, like heart failure.

VFib is when a person’s lower chambers of the heart, or ventricles, quiver instead of beat. When they quiver, the heart cannot pump blood around the body. This can cause a sudden cardiac arrest, which can be fatal within minutes.

Both AFib and VFib arise due to distorted electrical activity in parts of the heart. They are forms of arrhythmia.

The main difference between them is that AFib affects the atria, while VFib affects the ventricles.

Is one more serious than the other?

According to the AHA, VFib is the most severe form of arrhythmia. Without treatment, VFib can cause sudden cardiac arrest, which can result in death within minutes of starting.

According to a 2022 review, AFib can remain asymptomatic for extended periods. However, when AFib does cause noticeable symptoms, these can sometimes be similar to specific symptoms of VFib.

AFib can cause:

Those with AFib can experience symptoms for days, weeks, or months depending on the type of AFib.

In contrast, those experiencing VFib will likely experience symptoms immediately. A person may:

  • suddenly collapse
  • stop breathing
  • lose consciousness
  • have no pulse

Treatments for AFib and VFib aim to stabilize the person and address the underlying cause.

Doctors can treat AFib by prescribing medications to regulate a person’s heart rate. These include:

They can also perform procedures to bring a person’s heart rate back to normal rhythm, such as synchronized cardioversion or ablation.

Treatments for acute VFib focus on treating a heart attack. These include:

  • CPR
  • defibrillation
  • medications, including lidocaine and amiodarone

A person with AFib can go on to develop VFib. Avoiding AFib and working to prevent heart disease may help prevent a person from developing VFib.

Research suggests that the following steps can help a person avoid AFib:

The outlook for a person with AFib depends on individual factors.

While individuals with AFib may be asymptomatic, other people may experience symptoms such as chest pain, shortness of breath, and difficulties breathing.

According to the 2022 review, people with AFib have an increased risk of stroke.

If not managed, AFib may lead to lead to severe complications, including VFib. VFib can transform into cardiac arrest.

Outlook for VFib may depend on how quickly an individual receives treatment. According to additional research from 2022, the survival rate for people with VFib is 30–50% with prompt treatment. The survival rate can drop by 5–10% for every minute of delay.

Doctors diagnose AFib and VFib by analyzing their person’s symptoms while running an electrocardiogram (EKG) test.

This test uses a particular machine to record the electrical activity of a person’s heart. The EKG test can pick up on unusual heart rhythms.

The following pictures show how EKGs can produce different patterns for AFib and VFib.

The following are frequently asked questions about AFib and VFib.

Can AFib turn into VFib?

People with AFib are roughly 4.6 times more likely to develop VFib than people without AFib. However, the reason why this is the case is unclear.

Can you have AFib and VFib at the same time?

There is evidence that people can have AFib and VFib at the same time.

Atrial fibrillation vs. flutter

AFib is when the atria beat irregularly, whereas atrial flutter is when the atria beat too quickly.

VFib vs. ventricular tachycardia

VFib is when the ventricles quiver. In ventricular tachycardia, they beat too quickly.

AFib is when the upper chambers of the heart beat with an irregular rhythm. VFib is when the lower chambers of the heart quiver instead of beating. Both conditions are forms of arrhythmia.

AFib can sometimes transform into VFib. VFib is a severe condition that can quickly cause a heart attack. However, AFib is also serious, as it can increase the likelihood of stroke.

Maintaining a healthy lifestyle can reduce the risk of both conditions.