Supraventricular tachycardia (SVT) is as an irregularly fast or erratic heartbeat (arrhythmia) that affects the heart's upper chambers. SVT is also called paroxysmal supraventricular tachycardia.
The typical heart beats about 60 to 100 times a minute. A heart rate of more than 100 beats a minute is called a tachycardia (tak-ih-KAHR-dee-uh). During an episode of SVT, the heart beats about 150 to 220 times a minute, but it can occasionally beat faster or slower.
Most people with supraventricular tachycardia don't need activity restrictions or treatment. For others, lifestyle changes, medication and heart procedures may be needed to control or eliminate the rapid heartbeats and related symptoms.
Supraventricular tachycardia (SVT) falls into three main groups:
- Atrioventricular nodal reentrant tachycardia (AVNRT). This is the most common type of supraventricular tachycardia.
- 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)
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 typical heart rates in between.
Some people with SVT have no signs or symptoms.
Signs and symptoms of supraventricular tachycardia may include:
- Very fast (rapid) heartbeat
- A fluttering or pounding in the 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 of SVT 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 care provider about SVT screening.
When to see a doctor
Supraventricular tachycardia (SVT) is generally not life-threatening unless you have heart damage or other heart conditions. However, in extreme cases, an episode of SVT may cause unconsciousness or cardiac arrest.
Call your health care provider if you have an episode of a very fast heartbeat for the first time or if an irregular heartbeat lasts longer than a few seconds.
Some signs and symptoms of SVT 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
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For some people, a supraventricular tachycardia (SVT) episode is related to an obvious cause (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 conditions, such as Wolff-Parkinson-White syndrome
- Chronic lung disease
- A lot of caffeine
- Drinking too much alcohol
- Drug misuse, including cocaine and methamphetamine
- Thyroid disease
- Certain medications, including asthma medications and cold and allergy drugs
How does the heart beat?
In a typical 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 irregularly 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).
The heart is made of four chambers — two upper chambers (atria) and two lower chambers (ventricles).
The heart's rhythm is controlled by a natural pacemaker (the sinus node) in the right upper chamber (atrium). The sinus node sends electrical signals that typically start each heartbeat. These electrical signals move across the atria, causing the heart muscles to squeeze (contract) and pump blood into the ventricles.
Next, the heart signals arrive at a cluster of cells called the AV node, where the signals slow down. This slight delay allows the ventricles to fill with blood. When the electrical signals reach the ventricles, the chambers contract and pump blood to the lungs or to the rest of the body.
In a typical heart, this heart signaling process usually goes smoothly, resulting in a 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 upper chambers of the heart (atria). When this happens, the heart rate speeds up very quickly. The heart doesn't have enough time to fill with blood before the chambers contract. As a result, you may feel lightheaded or dizzy because your brain isn't getting enough blood and oxygen.
Supraventricular tachycardia (SVT) is the most common type of arrhythmia in infants and children. It also tends to occur more often in women, particularly during pregnancy, though it may occur in anyone.
Other things that may increase the 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 disease or previous heart surgery. Narrowed heart arteries, heart failure, damage to the heart or heart valves, cardiomyopathy, and other heart disease may increase the risk of developing SVT.
- Congenital heart disease. A heart problem present at birth (congenital heart defect) may cause irregular heartbeats such as SVT.
- Thyroid disease. Having an overactive or underactive thyroid gland can increase the risk of supraventricular tachycardia.
- Diabetes. The risk of developing heart disease and high blood pressure greatly increases with uncontrolled diabetes.
- Obstructive sleep apnea. This disorder, in which breathing is interrupted during sleep, can increase the 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 (SVT) may weaken the heart and lead to heart failure, particularly if there are other medical conditions.
In extreme cases, an episode of SVT may cause unconsciousness or cardiac arrest.
To prevent an episode of supraventricular tachycardia (SVT), it's important to identify the triggers and try to avoid them. Consider keeping a diary to help identify your triggers. Track your heart rate, symptoms and activity at the time of an SVT episode.
Also, use medications with caution. Some drugs, including those bought without a prescription, may contain stimulants that trigger a rapid heartbeat.
Keeping the heart healthy is an important step in preventing SVT. Eat a heart-healthy diet, don't smoke, get regular exercise and manage stress.
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.