Both AFib and VFib are cardiac arrhythmias. Afib affects the atria or the upper part of your heart. VFib affects the lower part of the ventricles. Compared to AFib, VFib is immediately life threatening.

Healthy hearts contract in a synchronized way. Electrical signals in the heart cause each of its parts to work together.

In AFib and Fib, the electrical signals in the heart muscle become chaotic, preventing the heart from contracting.

Learn more about the differences between these types of arrhythmia and how they’re treated.

AFib is the most common type of heart arrhythmia (irregular heartbeat). It develops in the heart’s upper chambers (atria), disrupting blood flow to the lower chambers (ventricles) and throughout the body. Although serious, AFib is typically not an immediately life threatening event.

On the other hand, VFib is the most serious type of arrhythmia, in which the heart’s lower chambers are unable to pump effectively. It’s considered an emergency and is often triggered by a heart attack, though there are other causes.

The most obvious sign of any arrhythmia will be heart palpitations. However, not everyone with AFib will have symptoms. If you do them, other symptoms may include:

  • chest pain
  • difficulty breathing
  • fatigue and weakness
  • dizziness
  • loss of consciousness
  • confusion
  • swelling in the feet and ankles

VFib symptoms can be similar but are more acute or sudden. You may also experience symptoms related to the underlying cause, such as a heart attack.

Is it an emergency?

If you’re experiencing VFib symptoms, have someone nearby call emergency services. If someone near you appears to be experiencing a heart attack, stay with them after you call for help.

If they lose consciousness and stop breathing, you will need to perform CPR:

  • Lay the person on their back and clear their airways.
  • Place one hand over the other on their sternum.
  • Press quickly with 2 compressions per second.

Your symptoms can indicate that you have arrhythmia and whether you have AFib or VFib. If your symptoms come on suddenly, your doctor is more likely to think you have VFib than AFib.

That said, several tests can help diagnose arrhythmia and determine the type.

These include:

If you have a pacemaker, your doctor may also use its data to help make the diagnosis.

What is the difference between AFib and VFib on an ECG?

Because AFib is an abnormal heart rhythm caused by irregular electrical activity in the upper chambers of the heart, you won’t see clear P waves on an EKG. These waves show the organized depolarization of the atria, which is the electrical change that triggers a coordinated contraction of the heart’s upper chambers.

You will, however, still see QRS complexes, which show the depolarization of the ventricles. These are the electrical changes that trigger a coordinated contraction of the lower chambers of the heart.

Since VFib is a rapid, irregular electrical activity of the heart’s lower chambers, you won’t see any clear P waves or QRS complexes.

Your AFib treatment plan will address three goals: preventing blood clots and restoring normal heart rate and rhythm. Medications can help with all three, but if they don’t work, other options include medical procedures or surgery.

Since VFIB is life threatening, an emergency health professional may need to do some or all of the following to return your heart to its healthy rhythm.

When it comes to surgical procedures, your doctor will determine what you need based on your specific case, symptoms, and cause of your condition.

A heart-healthy lifestyle can help reduce your likelihood of both AFib and VFib. Regular physical activity and a diet rich in heart-healthy fats and limited in saturated and trans fats are key to keeping your heart strong for a lifetime.

Prevention tips

  • Quit smoking.
  • Avoid alcohol and excessive caffeine.
  • Reach and maintain a healthy weight.
  • Control your cholesterol.
  • Monitor and manage your blood pressure.
  • Treat conditions leading to cardiac issues, including obesity, sleep apnea, and diabetes.

If you’ve already been diagnosed with AFib, work closely with your doctor to develop a treatment and lifestyle program that addresses your risk factors, history of arrhythmia, and health history. They will likely prescribe medications to keep you from progressing to VFib.

With treatment, you can live with chronic AFIB, though having it increases your chance of developing a stroke.

Overall, treatment has improved outlook, though people living with AFib still lose a mean of 10 years off their life spans because of the condition.

AFib can transform into VFib, but not in all cases. Once you have VFib, your condition becomes life threatening and can lead to death without immediate treatment. How long you survive once symptoms kick in depends on how fast you get treatment.

Research shows shorter treatment delays can result in a 50% survival rate. In many locations, defibrillators are available, which can help provide immediate treatment while waiting for emergency services.

However, the longer it takes to get treatment, the lower the survival odds and the higher the chance of neurological complications for those who do survive.

AFib and VFib are both types of cardiac arrhythmias. AFib disrupts the rhythm of the atria, or the heart’s upper chambers, whereas VFib affects the lower chambers or ventricles.

AFib can be managed with medical treatment, as well as some lifestyle changes. However, unlike AFib, VFib is life threatening and requires emergency treatment.