Atrial fibrillation is the most common type of supraventricular tachycardia. For information on this condition, see the topic Atrial Fibrillation. If you have ventricular tachycardia, see the topic Ventricular Tachycardia.

What is supraventricular tachycardia?

Supraventricular tachycardia (SVT) is an abnormal fast heart rhythm that starts in the upper chambers, or the atria, of the heart. ("Supraventricular" means above the ventricles, "tachy" means fast, and "cardia" means heart.)

Normally, the heart's electrical system precisely controls the rhythm and rate at which the heart beats. In supraventricular tachycardia, abnormal electrical connections (or abnormal firing of the connections) cause the heart to beat too fast. Typically, during supraventricular tachycardia episodes, the heart beats faster than 100 beats per minute. Sometimes the heart beats as fast as 300 beats per minute. Usually, the heart returns to a normal rate (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).

What are the different types of supraventricular tachycardia?

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 supraventricular tachycardias that are considered abnormal. These include:

• Atrioventricular nodal reentrant tachycardia (AVNRT), the most common type (after atrial fibrillation).
• Atrioventricular reciprocating tachycardia (AVRT), including Wolff-Parkinson-White syndrome.

What causes supraventricular tachycardia?

Most supraventricular tachycardia results from abnormal electrical connections in the heart that short-circuit the normal electrical system. What causes these abnormal pathways is not clear. In the case of Wolff-Parkinson-White syndrome, the condition may be inherited.

Some medicines can cause supraventricular tachycardia. Overly high levels of the heart medicine digoxin (such as Lanoxicaps or Lanoxin) can cause some types of supraventricular tachycardia (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).

What are the symptoms?

With supraventricular tachycardia, 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 dizzy or lightheaded, near-fainting or fainting (syncope), shortness of breath, chest pain, throat tightness, and sweating.

How is supraventricular tachycardia diagnosed?

A description of your symptoms is one of the most important clues in diagnosing supraventricular tachycardia. Your doctor will ask what, if anything, triggers the episodes, how long they last, if they start and stop suddenly, whether anything stops them, and whether the beats are regular or irregular.