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Supraventricular Tachycardia

Supraventricular Tachycardia Overview

Supraventricular tachycardia is one type of heart rhythm disorder.

  • Tachycardias are rhythm disorders in which the heart beats faster than normal.

  • Supraventricular means "above the ventricles," in other words, originating from the atria, the upper chambers of the heart.

  • Supraventricular tachycardia, then, is a rapid heartbeat originating in the atria.

  • These are sometimes referred to as atrial tachycardias. However, the atrioventricular (AV) node may be involved directly or indirectly, so AV nodal tachycardias are also included in this category.

The heart consists of 4 chambers: 2 upper chambers called atria and 2 lower chambers called ventricles.

  • The atria receive blood from blood vessels and contract to push blood into the ventricles.

  • The ventricles then contract to push the blood out of the heart into the blood vessels of your lungs and the rest of your body.

  • The heart usually beats 60-90 times a minute. A heart rate faster than 100 beats per minute is considered tachycardia.

Specialized heart cells coordinate the contractions by means of electrical signals.

  • These specialized cells consist of the sinoatrial (SA) or sinus node in the right atrium and the AV node and the bundle of His in the wall between the right and left ventricles.

  • The SA node, the natural pacemaker of the heart, starts the electrical signals and transmits them to the AV node.

  • The AV node then activates the bundle of His and its branches, resulting in contraction of the ventricles.

  • The atria and ventricles contract in quick sequence. Each sequence is 1 heartbeat.
Nerve impulses and the level of hormones in your blood influence the rate of heart contraction. A problem in any of these areas can cause abnormal heart rhythm (arrhythmia or dysrhythmia).

In supraventricular tachycardia, the heart rate is sped up by an abnormal electrical impulse starting in the atria.

  • The heart beats so fast that the heart muscle cannot relax between contractions.

  • When the chambers don't relax, they cannot contract strongly or fill with enough blood to satisfy the body's needs.

  • Because of the ineffective contractions of the heart, the brain does not receive enough blood and oxygen. You can become light-headed, dizzy, or feel like fainting (syncope).

Supraventricular tachycardia can be found in healthy young children, in adolescents, and in people with underlying heart disease. Most people who experience it live a normal life without restrictions.

Supraventricular tachycardia often occurs in episodes with stretches of normal rhythm in between. This is usually referred to as paroxysmal supraventricular tachycardia (often abbreviated PSVT). Supraventricular tachycardia also may be chronic (ongoing, long term).



Next: Supraventricular Tachycardia Causes »

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Supraventricular Tachycardia

Heart Rhythm Disorders Overview

The primary function of the heart is to supply blood and nutrients to the body. The regular beating, or contraction, of the heart moves the blood throughout the body. Each heartbeat is controlled by electrical impulses traveling through the heart. In the normal heart these electrical impulses occur in regular intervals. When something goes wrong with the heart’s electrical system, the heart does not beat regularly. The irregular beating results in a rhythm disorder, or arrhythmia.

The electrical system regulating heartbeat consists of 2 main areas of control and a series of conducting pathways, similar to the electrical wiring in a house (See Multimedia File 1).

  • The sinoatrial, or SA, node is located in the right atrium. It provides the main control and is the source of each beat. The SA node also keeps up with the body's overall need for blood and increases the he...

Read the Heart Rhythm Disorders article »



Read What Your Physician is Reading on eMedicine

Paroxysmal Supraventricular Tachycardia »

Supraventricular tachycardia (SVT), a common clinical condition, is any tachyarrhythmia that requires only atrial and/or atrioventricular (AV) nodal tissue for its initiation and maintenance.

Read More on eMedicine »

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