Ventricular tachycardia (V-tach or VT) is a type of tachycardia, or a rapid heart beat that arises from improper electrical activity of the heart presenting as a rapid heart rhythm, that starts in the bottom chambers of the heart, called the ventricles. The ventricles are the main pumping chambers of the heart. This is a potentially life-threatening arrhythmia because it can cause low blood pressure and may lead to ventricular fibrillation, asystole, and sudden death.