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 speeds up to rates of 150 to 200 beats per minute and occasionally as high as 300. After some time, 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.
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. However, digoxin may be used to treat some other types of SVT (such as atrial fibrillation). 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. Additional 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.
Because supraventricular tachycardia is a problem with your heart's electrical system, the most important test is an electrocardiogram (EKG, ECG). An EKG measures the heart's electrical activity and can record supraventricular tachycardia episodes. An EKG is usually done along with a medical history and physical examination, lab tests, and a chest X-ray.
If you do not have an episode of supraventricular tachycardia while at the doctor's office, your doctor will probably ask you to wear a portable EKG to record your heart rhythm on a continuous basis. This is referred to by several names, including ambulatory electrocardiogram, ambulatory ECG, Holter monitoring, 24-hour EKG, or cardiac event monitoring. This will allow your heart rhythm to be recorded while you are having supraventricular tachycardia.
Your doctor may also recommend an electrophysiology (EP) study. In this test, flexible wires are inserted into a vein, usually in the groin, and threaded into the heart. Electrodes at the end of the wires send information about the heart's electrical activity. In this way, the EP study can map any abnormal electrical activity, identify the type of supraventricular tachycardia you have, and guide treatment.
How is it treated?
Some supraventricular tachycardias do not cause symptoms and may not need treatment. However, when symptoms occur, treatment is usually recommended.
Your doctor may teach you how to perform vagal maneuvers, such as the Valsalva maneuver or coughing, to slow your heart rate. If vagal maneuvers do not work, a fast-acting intravenous (IV) medicine such as adenosine or verapamil can be given. If the arrhythmia does not stop and symptoms are severe, electrical cardioversion, in which a brief electric shock is given to the heart to reset the heart rhythm, may be needed.
If supraventricular tachycardia recurs, you may need long-term treatment, including:
* Beta-blockers or other antiarrhythmic medicines to slow heart rate.
* Catheter ablation, which is usually done during an electrophysiology (EP) study. The most common type of catheter ablation uses radio waves (radiofrequency energy). These waves are directed through the catheter to the specific heart tissue that is generating abnormal electrical impulses. The radio waves cause the area of the heart muscle to be heated and selectively destroyed, eliminating the SVT.
What precautions should I take?
Avoid consuming large amounts of alcohol or caffeine, either of which may provoke episodes of supraventricular tachycardia. Also, nonprescription decongestants, herbal remedies, diet pills, and "pep" pills often contain stimulants and should be avoided. Illegal drugs, such as cocaine, ecstasy, or methamphetamine, also can trigger episodes. It is important to be aware of which substances have an effect on you and to avoid them.
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