There are two basic types of supraventricular tachycardias: tachycardias involving the AV node and atrial tachycardias.

• Tachycardias involving the AV node:
  
  
• AV nodal reentrant tachycardia. An arrhythmia due to an extra conducting pathway within the AV node. This allows the heart’s electrical activity to “short circuit” itself (“reentry”). Episodes of this arrhythmia may be triggered by physical or emotional stress, caffeine, cocaine or certain medications (including so-called natural or herbal remedies, which may contain stimulants). AV nodal reentry can often be managed by medical therapy with beta blocker or calcium channel blocker medications, but can also be cured by catheter ablation of the extra pathway.
  
  
• AV reentrant tachycardia using an accessory bypass connection. Similar to AV node reentry, this occurs when an extra conducting pathway allows the electrical impulse to “short circuit.” In contrast to AV node reentry, however, the extra pathway in this condition bypasses the AV node, directly linking the atria and ventricles. In most cases, this pathway can only conduct “backwards” – from ventricles to atria. This is called a “concealed accessory pathway” since it cannot be diagnosed from a regular electrocardiogram (EKG). These arrhythmias may be treated medically, but can also be cured by catheter ablation. Less often, the extra pathway is evident on the EKG, in which case the condition is called the Wolff-Parkinson-White syndrome (WPW). WPW syndrome may result in extremely rapid heartbeats and could potentially result in death. Symptomatic WPW syndrome generally requires catheter ablation.
  
  
• Atrial tachycardias may be focal (arising from only one place in one of the atria) or multifocal (arising from many different places in the atria).
  
  
• Inappropriate sinus tachycardia. A relatively rare condition in which the heart is normal but the heart rate is unusually fast, both at rest and in response to physical activity. Treatment is available, but the cause is unknown.
  
  
• Premature atrial contraction (PACs). Also known as premature supraventricular contractions, PACs are irregular heart rhythms that generally do not need to be treated. They are often due to stress or use of substances such as caffeine and alcohol. They occur when one of the heart’s upper chambers contracts prematurely in the heartbeat cycle. However, in some patients, catheter ablation may be advisable to treat PACs before they can trigger atrial fibrillation.
  
  
• Paroxysmal atrial tachycardia. A condition originating in the atria, in which the heartbeat increases for several minutes to a number of hours. Treatment may be necessary for short, sudden episodes that begin and end rapidly. Most people with this condition are young with normal hearts. The condition may be exacerbated by the use of even small amounts of caffeine or alcohol. This condition has also been associated with overly high levels of digitalis (an inotropic drug) in the bloodstream.
  
  
• Atrial flutter. A specific type of atrial tachycardia in which atria contract regularly, but extremely rapidly. Patients with atrial flutter may have as great a risk of stroke as patients with atrial fibrillation (the risk is certainly greater than that of the general population). Therefore, treatment (e.g., ablation) is often recommended.
  
  
• Atrial fibrillation (AF). The result of rapid, disorganized signals in the atria that prompt the ventricles to contract irregularly. Although this condition is not directly life-threatening, when the atria fibrillate (or quiver) instead of beating, blood is not effectively passed through the heart’s chambers and may pool in the atria. A blood clot may form and may travel throughout the body, which could lead to a stroke or heart attack. AF is the most common type of sustained arrhythmia, affecting two million people each year in the United States alone. Approximately  15 percent of strokes are a direct result of atrial fibrillation. In people over age 65, AF is associated with both greater complications and greater risk of death from heart attacks.
  
  
• Multifocal atrial tachycardia is a condition in which there are multiple foci of activation of the atria, leading to different morphologies of the atrial activities in the EKG. The condition is mainly observed in patients with advanced lung disease such as chronic obstructive airway disease.