Causes

For some people, a supraventricular tachycardia episode is related to an obvious trigger, such as psychological stress, lack of sleep or physical activity. For others, there may be no noticeable trigger. Things that may lead to, or cause, an episode include:

• Heart failure
• Thyroid disease
• Heart disease
• Chronic lung disease
• Smoking
• Drinking too much alcohol
• Consuming too much caffeine
• Drug use, such as cocaine and methamphetamines
• Certain medications, including asthma medications and over-the-counter cold and allergy drugs
• Surgery
• Pregnancy
• Certain health conditions, such as Wolff-Parkinson-White syndrome

What's a normal heartbeat?

Your heart is made up of four chambers � two upper chambers (atria) and two lower chambers (ventricles). The rhythm of your heart is normally controlled by a natural pacemaker (the sinus node) located in the right atrium. The sinus node produces electrical impulses that normally start each heartbeat.

From the sinus node, electrical impulses travel across the atria, causing the atria muscles to contract and pump blood into the ventricles.

The electrical impulses then arrive at a cluster of cells called the atrioventricular node (AV node) � usually the only pathway for signals to travel from the atria to the ventricles.

The AV node slows down the electrical signal before sending it to the ventricles. This slight delay allows the ventricles to fill with blood. When electrical impulses reach the muscles of the ventricles, they contract, causing them to pump blood either to the lungs or to the rest of the body.

In a healthy heart, this process usually goes smoothly, resulting in a normal resting heart rate of 60 to 100 beats a minute.

Supraventricular tachycardia occurs when faulty electrical connections in the heart or abnormal areas of electrical activity trigger and sustain an abnormal rhythm. When this happens, the heart rate accelerates too quickly and doesn't allow enough time for the heart to fill before it contracts again. These ineffective contractions of the heart may cause you to feel light-headed or dizzy because the brain isn't receiving enough blood and oxygen.

Types of supraventricular tachycardia

There are three major types of supraventricular tachycardia:

• Atrioventricular nodal reentrant tachycardia (AVNRT). This is the most common type of supraventricular tachycardia in both males and females of any age, although it tends to occur more often in young women.
• Atrioventricular reciprocating tachycardia (AVRT). AVRT is the second most-common type of supraventricular tachycardia. It's most commonly diagnosed in younger people.
• Atrial tachycardia. This type of supraventricular tachycardia is more commonly diagnosed in people with coexisting heart disease. Unlike AVNRT and AVRT, which always involve the AV node as part of the faulty connection, atrial tachycardia doesn't involve the AV node.

Other types of supraventricular tachycardia include:

• Sinus tachycardia
• Inappropriate sinus tachycardia (IST)
• Multifocal atrial tachycardia (MAT)
• Junctional ectopic tachycardia (JET)
• Nonparoxysmal junctional tachycardia (NPJT)