Tachycardia, ventricular

Ventricular tachycardia (V-tach or VT) is a tachycardia, or fast heart rhythm that originates in one of the ventricles of the heart. This is a potentially life-threatening arrhythmia because it may lead to ventricular fibrillation and sudden death.
See more at Wikipedia.org...

An abnormal heart rhythm that is rapid, regular and originates from an area of the ventricle, the lower chamber of the heart. Ventricular tachycardias are life threatening arrhythmias most commonly associated with heart attacks or scarring of the heart muscle from previous heart attack.