Abnormal Heart Rhythm

Supraventricular Tachycardia

Signs and Symptoms
Diagnosis
Treatment

Signs and Symptoms

Supraventricular tachycardia (SVT) is the most common arrhythmia in children. The condition occurs when an extra electrical pathway in the heart triggers a fast heartbeat. In a normal heart, electricity travels from the upper chambers -- the atria -- through the atrioventricular (AV) node to the lowers chambers, called the ventricle. SVT is a series of rapid heartbeats that begin in the upper chambers. It may occur when an extra pathway exists in the atria, AV node, or between the atria and the ventricles.

This normal transmission is called normal sinus rhythm, with a regular heartbeat of 60 to 100 times per minute.

There are different forms of SVT, including:

AV nodal reentrant tachycardia (AVNRT) occurs when there is an extra electrical pathway in the AV node.

The diagram above shows an example of AV nodal reentry tachycardia, where the impulse moves abnormally through the AV node.

In Wolff-Parkinson-White (WPW) Syndrome, there is an extra electrical pathway that connects the atria and ventricles. This pathway is known as an accessory pathway and may result in a very rapid heartbeat.

In atrial fibrillation (AFIB), multiple sites in the atria fire impulses in an irregular fashion. As a result, the heart can beat very quickly and ineffectively.

In atrial tachycardia, an abnormal site or focus in one of the atria fires electrical impulses at a rapid rate.

Atrial flutter is a rapid heart rhythm caused by an extra electrical pathway in the heart that begins in the upper chambers of the heart, called the atria. This causes a very fast, steady heartbeat.

The "normal" number of heartbeats per minute, called pulse rate varies with age. The heart beats about 140 times a minute in a newborn, compared to 70 times a minute in an older child at rest. Heart rate is not constant, changing in response to many factors, such as activity, fever and fear. In many situations, an increase in heart rate is normal, which is called sinus tachycardia.

In supraventricular tachycardia (SVT) the heart beats too quickly -- up to 280 beats per minute -- preventing the heart from filling completely with blood. As a result, the body doesn't receive the blood volume it needs to function properly.

SVT may cause the following symptoms:

• Palpitations, which can be skipping, fluttering or pounding in the chest
• Fatigue
• Chest pressure or pain
• Shortness of breath
• Fainting, also known as syncope, or near-syncope
• Lightheadedness or dizziness

Reviewed by health care specialists at UCSF Children's Hospital.
Last updated May 8, 2007