Ventricular tachycardia (VT) is a condition in which the lower chambers of the heart (ventricles) beat abnormally fast. This rapid heart rate is caused by electrical signals that arise from the ventricles themselves instead of following the normal pattern of arising in the upper chambers of the heart (atria) and spreading throughout the heart. Alternatively, ventricular tachycardias may be caused by electrical signals that do not follow the normal path through the heart's conduction system (e.g., reentrant signals).

Ventricular tachycardias may be sustained or nonsustained, and they may occur in either of the ventricles (left and right). There are several different kinds, and their severity ranges from mostly without symptoms to a life-threatening condition that must be treated immediately. The severity is often connected to the presence of underlying heart disease.

The most dangerous kinds of ventricular tachycardia may result in fainting (syncope) or even cardiac arrest. A patient who has collapsed and gone into cardiac arrest, needs to be treated with a defibrillator immediately to avoid sudden cardiac death.

Some patients with mild forms of VT do not require treatment. For example, their VT may permanently resolve after their medication has been changed. Other patients require more regular treatment. Treatment options include medications, catheter ablation, surgery and insertion of an implantable cardioverter defibrillator. The choice of therapy depends on the nature of the VT and the risk of more serious cardiac arrhythmias.