Supraventricular tachycardia (SVT) is an abnormal rapid heart rate that starts in the upper chambers, or the atria, of the heart. Typically, during SVT episodes, the heart beats faster than 100 beats per minute; sometimes as fast as 300 beats per minute. Usually, the heart returns to a normal rate of 60 to 100 beats per minute on its own or after treatment.
Supraventricular tachycardia (SVT) is also called paroxysmal supraventricular tachycardia (PSVT) or paroxysmal atrial tachycardia (PAT).
Sometimes it is normal to have an increased heart rate - for example, during exercise, with a high fever, or when under stress. This fast heart rate, called sinus tachycardia, is a normal response to these stressors and is not considered a medical problem. This topic addresses the types of SVT that are considered abnormal. These include:
- Atrial fibrillation (most common)
- Atrioventricular nodal reentrant tachycardia (AVNRT)
- Atrioventricular reciprocating tachycardia (AVRT), including Wolff-Parkinson-White syndrome
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What causes SVT? Normally, the heart's electrical system controls the rhythm and rate at which the heart beats. The contractions of a heart beat are signaled by an electrical signal that begins in an area of the heart called the sinoatrial node (also called the sinus node or SA node). The signal moves through the upper heart chambers (the atria) and tells the atria to contract.
In SVT, abnormal firing of the heart's electrical system causes the heart to beat too fast. SVT starts with events taking place above the lower heart chambers (ventricles). SVT can be initiated in the SA node, in the upper heart chambers (atria), in the atrial conduction pathways, or other areas.
Some medicines can cause SVT. Overly high levels of the heart medicine digoxin (such as Lanoxicaps or Lanoxin) can cause some types of SVT (such as Wolff-Parkinson-White syndrome) to get worse. But digoxin may be used to treat some other types of SVT (such as
atrial fibrillation). The bronchodilator theophylline may also cause tachycardia.
In rare cases, conditions that affect the lungs - such as chronic obstructive pulmonary disease (COPD) or pneumonia - can also cause a type of SVT called multifocal atrial tachycardia (MAT).
The following increase your risk for SVT:
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Alcohol use
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Caffeine use
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Illicit drug use
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Smoking
What are the symptoms of SVT? With SVT, you may have palpitations, an uncomfortable feeling that your heart is racing or pounding. You may also notice that your pulse is rapid or see or feel your pulse pounding, especially at your neck, where large arteries are close to the skin. Other symptoms include feeling anxious, feeling dizzy or lightheaded, near-fainting or fainting, shortness of breath, chest pain or tightness, throat tightness and sweating.
Note: Symptoms may start and stop suddenly, and can last for a few minutes or several hours. A SVT lasting more than half of the day is considered an incessant SVT
How is SVT diagnosed? A description of your symptoms during a physician examination with your doctor is one of the most important clues in diagnosing SVT. Your doctor will ask what may trigger the episodes, how long they last, if they start and stop suddenly, whether anything stops them, and whether the beats are regular or irregular.
SVT can be detected through an
electrocardiogram (EKG or ECG) which records electrical signals generated by the heart. A
monitor may also be worn for one or more days to detect AF. An EKG is usually done along with a medical history and physical examination, lab tests and a chest X-ray.
If symptoms occur or if you have another heart disorders, treatment may be necessary.
If SVT recurs, you may need long-term treatment, including:
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Daily medications such as beta-blockers or other anti-arrhythmic medicines to prevent an episode or to slow the heart rate
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Pacemakers to override the fast heartbeat; very occasionally used in children with SVT who have not responded to any other treatment
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Surgery to change the pathways in the heart that send electrical signals; this may be recommended in some cases for people who need other heart surgery.
Emergency treatment of SVT may include:
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Electrical cardioversion, the use of electric shock to restore a rapid heartbeat back to normal
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Medicines through a vein, including adenosine and verapamil. Other medications may be used, such as procainamide, beta-blockers and propafenone
