Atrial fibrillation (AFib) and supraventricular tachycardia (SVT) are two heart conditions caused by atypical electrical activity in your heart.

Supraventricular tachycardia (SVT) is an irregularly fast heartbeat in the lower chambers of your heart that’s caused by atypical electrical activity coming from above.

“Supra” means “above,” and “ventricular” refers to the lower chambers of your heart, which are called ventricles.

“Tachycardia” is the medical term for a rapid heart rate.

Atrial fibrillation (AFib) is an irregular beating of your upper heart chambers. Some people with AFib don’t have noticeable symptoms, while others may have a fast and pounding heartbeat.

Let’s examine the similarities and differences between these two conditions.

Here’s a look at the potential symptoms of AFib and SVT.

SVT symptoms

SVT causes your heart to beat much faster than usual. Your heart rate may exceed 100 beats per minute and then slow down abruptly within minutes to hours.

Some people also have:

AFib symptoms

AFib doesn’t always cause noticeable symptoms, but you may have an irregular heart rate that exceeds 100 beats per minute. Symptoms come and go, but each episode can last minutes to hours. You may experience:

Problems with the electrical signaling in your heart cause SVT and AFib.

Your heart’s sinoatrial (SA) node is considered its pacemaker. This node sends out an electrical signal that causes the upper chambers of your heart to contract.

The electrical signal passes through another bundle of cells called the atrioventricular (AV) node, which causes the lower chambers of your heart to contract.

SVT causes

SVT is caused by a problem with your heart’s electrical conduction that starts above or at your AV node, which is at the bottom of your heart’s right atrium. Possible triggers include:

  • stress
  • caffeine
  • alcohol
  • physical stress
  • emotional stress
  • cigarette smoking

AFib causes

AFib is the most common type of abnormal heart rhythm. It’s caused by electrical signals coming from outside your SA node that cause atypical contractions in the upper chambers of your heart.

It can be a result of any condition that leads to the death of heart tissue or causes stress or inflammation in your heart.

Risk factors include:

SVT and AFib can both be broken into subtypes.

SVT types

SVT has three main subtypes:

  • Atrioventricular nodal re-entrant tachycardia: This is the most common type of SVT.
  • Atrioventricular re-entrant tachycardia: This is the most common subtype seen in children.
  • Atrial tachycardia: This subtype is most commonly seen in people with structural heart disease.

AFib types

AFib has the following subtypes:

  • Paroxysmal AFib: This type of AFib occurs intermittently and stops within 7 days.
  • Persistent AFib: This type lasts longer than 7 days.
  • Long-standing persistent AFib: This is persistent AFib that has lasted longer than 12 months due to treatment failure.
  • Permanent AFib: AFib is considered permanent when all treatments are stopped because they’re ineffective.

It’s important to consult a doctor if you suspect that you might have a heart rhythm problem. Possible symptoms include:

  • an abnormally fast heartbeat
  • persistent heart fluttering
  • shortness of breath
  • an abnormally slow heartbeat
Medical emergency

The United Kingdom’s National Health Service recommends calling emergency medical services or going to the nearest emergency room if you’ve previously received an SVT diagnosis and your episode lasts longer than 30 minutes or if you have sudden shortness of breath with chest pain.

You should also call emergency medical services or have someone drive you to the emergency room if you have heart attack symptoms, such as sudden chest pain that:

  • spreads to your neck, jaw, arms, or back
  • makes your chest feel heavy or tight
  • last more than 15 minutes
  • occurs along with shortness of breath, sweating, or nausea

These are some of the treatment options for SVT and AFib.

SVT treatment

You might not need treatment if an SVT episode lasts a few minutes and doesn’t cause symptoms. Your doctor may teach you special methods to slow down your heart.

If treatment is necessary, you may receive:

AFib treatment

Treatment for AFib includes:

  • medications to prevent a stroke
  • medications to regulate your heart rhythm
  • cardioversion
  • catheter ablation

If you’re prone to episodes of SVT, you may be able to reduce your symptoms by:

  • getting plenty of rest
  • quitting smoking, if you smoke (This can be difficult, but a doctor can help you create a cessation plan.)
  • reducing your caffeine or alcohol consumption

To prevent AFib, the American Heart Association recommends:

SVT is rarely life threatening, although it can be frightening. The outlook is excellent for people who don’t have a structural abnormality in their heart.

AFib rarely causes death but is associated with a five times greater risk of stroke. The risk is particularly high in people who don’t receive treatment. Anticoagulant medications can help prevent an estimated 60% of these strokes.

Here are some frequently asked questions people have about SVT and AFib.

Which is worse, AFib or SVT?

AFib is generally more serious than SVT since it’s associated with an increased risk of blood clots and stroke.

Can you have SVT and AFib at the same time?

AFib is technically a type of SVT but is often separated into its own category. It is possible to have both SVT and AFib.

What does an SVT episode feel like?

SVT feels like a sudden rapid heart rate that lasts for minutes to hours and then stops suddenly.

How can you tell the difference between AFib and SVT?

Doctors can differentiate AFib and SVT by measuring the electrical activity of your heart.

Can SVT turn into AFib?

Recurrent SVT can potentially predispose you to AFib.

AFib and SVT are two conditions caused by electrical problems in your heart. They can cause episodes that last for minutes to hours.

SVT might not need treatment if you don’t have serious symptoms. Both conditions may be treated with medications or a procedure called catheter ablation.