Tachycardia is a general term for a variety of different conditions that cause the heart to beat more than 100 times per minute. There are two general forms of tachycardia.

The first type is supraventricular tachycardia – a condition in which electrical impulses traveling through the heart are abnormal because of a cardiac problem somewhere above the lower chambers of the heart (ventricles). Common examples of supraventricular tachycardia include atrial fibrillation, atrial flutter, AV node reentry and Wolff-Parkinson-White syndrome (WPW).

The second type is ventricular tachycardia, a condition in which the electrical impulse originates somewhere in the ventricles. It may degenerate into fatal arrhythmias such as ventricular flutter and ventricular fibrillation.

The symptoms of these different tachycardias vary widely. In emergency situations, treatment of tachycardia may be necessary with defibrillation or antiarrhythmic medications delivered through an IV. Long-term management often relies on medication. Some conditions may require a medical procedure such as catheter ablation or the insertion of an implantable cardioverter defibrillator (ICD).

Tachycardia is a general term that describes a number of conditions in which the heart beats at an abnormally fast rate at rest (more than 100 beats per minute). It is a type of arrhythmia, which is an abnormal heart rhythm caused by an abnormality in the heart’s electrical system.

There are two main types of tachycardias:

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.

The different types of ventricular tachycardias include:

• Premature ventricular contractions (PVCs). Occur when an early signal from the lower chambers of the heart (ventricles) prompts an early heartbeat. Following this beat, a brief pause may occur until a properly timed ventricular contraction takes place. This is often perceived as a “skipped” beat, which can lead to ventricular tachycardia, as described below.
  
  
• Ventricular tachycardia (VT). A potentially fatal type of heartbeat (more than 100 beats per minute) that arises from the ventricles. Left untreated, ventricular tachycardia could lead to cardiac arrest or ventricular fibrillation.
  
  
• Ventricular fibrillation (VF). A result of very fast and uncontrolled electrical signals that cause the heart to quiver rather than beat in any efficient or effective manner. Ventricular fibrillation often leads to sudden cardiac death if not treated immediately. Often, the first sign of VF is sudden fainting (syncope).

The electrical system of the heart (conduction system) is a complex network of cells and fibers in the heart through which electrical impulses travel at lightning speed, triggering a heartbeat. The impulses are first sent out by the sinoatrial node (sinus node or SA node), located in the top of the upper-right chamber of the heart (the right atrium). From there, the impulses spread through the atria, causing them to contract, and then to the atrioventricular node (A-V node), where they are transmitted to the lower chambers of the heart (ventricles) via the bundle branches. Once the impulses reach the ventricles, they cause the chambers to contract and pump out blood in a routine and consistent manner.

If impulses are fired too fast – either from the heart’s normal conduction system or from other parts of the heart – the heart will beat too quickly. In many cases, a temporary rapid heartbeat is not medically significant by itself. For instance, sinus tachycardia is a normal response to increased demands on the heart during exercise. However, persistent severe tachycardia can lead to greater damage and heart malfunction.

Symptoms vary widely among the different types of tachycardias. People are encouraged to read more about a specific tachycardia of interest to learn its symptoms.

Diagnosis is made by 12-lead electrocardiogram (EKG). In cases of intermittent arrhythmias, a Holter monitor or event recorder may be required. Electrophysiology testing may be indicated in some patients to locate areas of ectopic activation, accessory pathways and to determine which patient is vulnerable for fatal arrhythmias.

Treatment of the underlying condition and control of any reversible factors is usually attempted in all patients. Examples include control of hyperthyroidism, correction of electrolyte imbalance and control of heart failure. Depending on the cause, tachycardia may be treated with medications (e.g., antiarrhythmics, anticoagulants) or by catheter ablation. In an emergency situation, or in the case of a sustained tachyarrhythmia, the patient may undergo cardioversion, or the use of electricity to establish a more normal heart rate.  

Treatment options are largely influenced by the severity of structural heart abnormalities, symptoms, type of arrhythmias and in some case the results of EP testing. Patients with atrial fibrillation or atrial flutter require administration of anticoagulants to prevent embolism.

Ventricular tachycardia may be treated by the surgical insertion of an implantable cardioverter defibrillator (ICD) in the patient’s chest. The ICD monitors and, if necessary, corrects an abnormally fast heartbeat. There has been interest in whether drug therapy alone benefits individuals with ventricular tachycardia. To date, studies have been mixed regarding the benefits of drug therapy alone, without implantation of an ICD. It appears that some antiarrhythmics are associated with increased mortality, while other medications such as beta blockers and amiodarone may be helpful in some patients. Research is still ongoing into alternatives to immediate ICD implantation.

Even with ICD implantation, about 50 percent of patients will need to continue using antiarrhythmic medications for the rest of their lives. However, the ICD allows most patients to reduce the number and/or dosage of medications.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to tachycardia:

1. What type of tachycardia do I have, supraventricular or ventricular? What is the difference?
   
   
2. How serious is my condition?
   
   
3. What treatment options are available to me for tachycardia?
   
   
4. Are there any activities I should not engage in with this condition?
   
   
5. Are there any lifestyle changes I can make to improve my condition?
   
   
6. Can my condition be controlled with medication, or do I require more serious treatment?
   
   
7. How urgently do I need to begin treatment for this condition?
   
   
8. Is my tachycardia a symptom of an underlying cardiac condition?
   
   
9. Does my arrhythmia put me at risk for any other heart-related conditions?
   
   
10. Can tachycardia affect my pregnancy in any way?