Supraventricular tachycardia (SVT) is as an abnormally fast or erratic heartbeat that affects the heart's upper chambers. An abnormal heartbeat is called an arrhythmia. SVT is also called paroxysmal supraventricular tachycardia.
A normal heart rate is 60 to 100 beats per minute. A heart rate of more than 100 beats per minute is called a tachycardia (tak-ih-KAHR-dee-uh). During an episode of SVT, your heart beats about 150 to 220 times per minute, but it can occasionally beat faster or slower.
Most people with supraventricular tachycardia live healthy lives without restrictions or treatment. For others, lifestyle changes, medication and heart procedures may be needed to control or eliminate the rapid heartbeats and related symptoms.
The main symptom of supraventricular tachycardia (SVT) is a very fast heartbeat (100 beats a minute or more) that may last for a few minutes to a few days. The fast heartbeat may come and go suddenly, with stretches of normal heart rates in between.
Some people with SVT have no signs or symptoms at all.
Signs and symptoms of supraventricular tachycardia may include:
- Very fast (rapid) heartbeat
- A fluttering or pounding in your chest (palpitations)
- A pounding sensation in the neck
- Weakness or feeling very tired (fatigue)
- Chest pain
- Shortness of breath
- Lightheadedness or dizziness
- Fainting (syncope) or near fainting
In infants and very young children, signs and symptoms may be difficult to identify. They include sweating, poor feeding, pale skin and a rapid pulse. If your infant or young child has any of these symptoms, ask your child's doctor about SVT screening.
When to see a doctor
Supraventricular tachycardia is generally not life-threatening unless you have heart damage or other heart problems. However, in extreme cases, an episode of SVT may cause unconsciousness or cardiac arrest.
Call your doctor if you have an episode of a very fast heartbeat for the first time, and if the abnormal heartbeat lasts longer than a few seconds.
Some signs and symptoms may be related to a serious health condition. Call 911 or your local emergency number if you have an episode of SVT that lasts for more than a few minutes, or if you have an episode with any of the following symptoms:
- Chest pain
- Shortness of breath
SVT occurs when the electrical signals that coordinate your heartbeats don't work properly.
For some people, a supraventricular tachycardia episode is related to an obvious trigger, such as exercise, stress or lack of sleep. Some people may not have a noticeable trigger.
Things that may cause an SVT episode include:
- Heart disease
- Heart failure
- Other heart problems, such as Wolff-Parkinson-White syndrome
- Chronic lung disease
- Consuming too much caffeine
- Drinking too much alcohol
- Drug use, particularly stimulants such as cocaine and methamphetamines
- Thyroid disease
- Certain medications, including asthma medications and over-the-counter cold and allergy drugs
What's a normal heartbeat?
In a normal heart rhythm, a tiny cluster of cells at the sinus node sends out an electrical signal. The signal then travels through the atria to the atrioventricular (AV) node and then passes into the ventricles, causing them to contract and pump out blood.
Supraventricular tachycardia is an abnormally fast heartbeat. It occurs when faulty electrical connections in the heart set off a series of early beats in the upper chambers of the heart (atria).
SVT starts above the heart's ventricles (supraventricular) in the two upper chambers or a cluster of cells called the atrioventricular (AV) node. To understand how this occurs, it can be helpful to understand how the heart beats.
Your heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles).
The rhythm of your heart is normally controlled by a natural pacemaker (the sinus node) in the right upper chamber (atrium). The sinus node sends out electrical signals that normally start each heartbeat. These electrical signals move across the atria, causing the heart muscles to squeeze and pump blood into the ventricles.
Next, the signals arrive at the AV node. The AV node slows down the electrical signals. This slight delay allows the lower heart chambers to fill with blood. When the electrical signals finally get to the muscles of the ventricles, the lower heart chambers squeeze (contract), which pumps blood to the lungs or to the rest of the body.
In a healthy heart, this heart signaling process usually goes smoothly, resulting in a normal resting heart rate of 60 to 100 beats a minute.
SVT occurs when faulty electrical connections in the heart set off a series of early beats in the atria. When this happens, the heart rate becomes so fast so quickly, the heart doesn't have enough time to fill with blood before the chambers contract. As a result, you may feel light-headed or dizzy because your brain isn't getting enough blood and oxygen.
Supraventricular tachycardia falls into three main groups:
- Atrioventricular nodal reentrant tachycardia (AVNRT). This is the most common type of supraventricular tachycardia in both males and females of any age, although it tends to occur more often in young women.
- Atrioventricular reciprocating tachycardia (AVRT). AVRT is the second most-common type of supraventricular tachycardia. It's most commonly diagnosed in younger people.
- Atrial tachycardia. This type of SVT is more commonly diagnosed in people who have heart disease. Atrial tachycardia doesn't involve the AV node.
Other types of supraventricular tachycardia include:
- Sinus tachycardia
- Sinus nodal reentrant tachycardia (SNRT)
- Inappropriate sinus tachycardia (IST)
- Multifocal atrial tachycardia (MAT)
- Junctional ectopic tachycardia (JET)
- Nonparoxysmal junctional tachycardia (NPJT)
Supraventricular tachycardia is the most common type of arrhythmia in infants and children. It also tends to occur more often in women, particularly pregnant women, though it may occur in anyone.
Other things that may increase your risk of supraventricular tachycardia are:
- Age. Some types of SVT are more common in people who are middle-aged or older.
- Coronary artery disease, other heart problems and previous heart surgery. Narrowed heart arteries, a heart attack, abnormal heart valves, prior heart surgery, heart failure, cardiomyopathy and other heart damage increase your risk of developing SVT.
- Congenital heart disease. Being born with a heart defect or heart disease may affect your heart's rhythm.
- Thyroid problems. Having an overactive or underactive thyroid gland can increase your risk of supraventricular tachycardia.
- Drugs and supplements. Certain over-the-counter cough and cold medicines and certain prescription drugs may trigger an episode of supraventricular tachycardia.
- Anxiety or emotional stress
- Physical fatigue
- Diabetes. Your risk of developing heart disease and high blood pressure greatly increases with uncontrolled diabetes.
- Obstructive sleep apnea. This disorder, in which your breathing is interrupted during sleep, can increase your risk of supraventricular tachycardia.
- Nicotine and illegal drug use. Nicotine and illegal drugs, such as amphetamines and cocaine, may trigger an episode of supraventricular tachycardia.
Over time, untreated and frequent episodes of supraventricular tachycardia may weaken the heart and lead to heart failure, particularly if there are other coexisting medical conditions.
In extreme cases, an episode of supraventricular tachycardia may cause unconsciousness or cardiac arrest.
To prevent an episode of supraventricular tachycardia, it's important to know what triggers the episodes to occur and try to avoid them. Healthy lifestyle changes can help protect your heart. You might want to try:
- Eating a heart-healthy diet
- Increasing your physical activity
- Avoiding smoking
- Keeping a healthy weight
- Limiting or avoiding alcohol
- Reducing stress
- Getting plenty of rest
- Using over-the-counter medications with caution, as some cold and cough medications contain stimulants that may trigger a rapid heartbeat
- Avoiding illegal drug use, such as cocaine, ecstasy or methamphetamines
For most people with supraventricular tachycardia, moderate amounts of caffeine do not trigger an episode of SVT. Large amounts of caffeine should be avoided, however.
Consider keeping a diary to help identify your triggers. Track your heart rate, symptoms and activity at the time of an SVT episode.