If you have supraventricular tachycardia (SVT), go to the topic Supraventricular Tachycardia.

What is ventricular tachycardia?

Ventricular tachycardia is a fast heart rhythm that starts in the lower part of the heart (ventricles). If left untreated, some forms of ventricular tachycardia may worsen and lead to ventricular fibrillation, which can be life-threatening.

What causes ventricular tachycardia?

Sometimes it is not known what causes ventricular tachycardia, especially when it occurs in young people. However in most cases, ventricular tachycardia is caused by underlying heart disease, such as a previous heart attack, a congenital heart defect, hypertrophic or dilated cardiomyopathy, or myocarditis. Occasionally ventricular tachycardia occurs after heart surgery.

Some medications-including antiarrhythmic medications, used to treat other types of abnormal heart rhythms-can cause ventricular tachycardia. Less common causes include blood imbalances, such as low potassium levels and other electrolyte imbalances.

Nonprescription decongestants, herbal remedies (especially those that contain ma huang or ephedra), diet pills, and "pep" pills often contain stimulants that can trigger episodes of ventricular tachycardia. Illegal drugs (such as stimulants, like cocaine) should also be avoided. It is important to be aware of which substances have an effect on you and how to avoid them.

What are the symptoms?

In ventricular tachycardia, the heart beats too rapidly and the ventricles cannot effectively pump oxygen-rich blood to the rest of the body. This results in:

• Palpitations, an uncomfortable awareness of the heart beating rapidly or irregularly.
• Dizziness or lightheadedness.
• Shortness of breath.
• Chest pain, or angina.
• Near-fainting or fainting (syncope).

Some people who have short bouts of ventricular tachycardia do not have symptoms.

How is ventricular tachycardia diagnosed?

If an electrocardiogram (EKG, ECG) can be performed while ventricular tachycardia is occurring, it often provides the most useful information. An electrocardiogram is a tracing of the electrical activity of your heart. It is usually done along with a history and physical examination, lab tests, and a chest X-ray.

Because ventricular tachycardia can occur intermittently and may not always be captured by an EKG at the doctor's office, you may be asked to use a portable EKG to record your heart rhythm on a continuous basis, usually over a 24-hour period. This is referred to by several names, including ambulatory electrocardiography, ambulatory EKG, Holter monitoring, 24-hour EKG, or cardiac event monitoring.

Your doctor may recommend further tests, including an echocardiogram, to evaluate your heart's function, a stress test or coronary angiogram to determine whether a part of the heart is not getting enough blood, and/or an electrophysiology study. During an electrophysiology (EP) study, electrical currents are sent through a catheter into the heart to try to trigger ventricular tachycardia and record the flow of electricity through the heart. In this way, the EP study can locate specific areas of heart tissue that give rise to abnormal electrical impulses, which may be causing the ventricular tachycardia. This information is used to determine the best treatment.

How is it treated?