What type of tachycardia starts in the ventricles?

Two main types of tachycardia start in the heart's ventricles. One is ventricular tachycardia (VT), a serious condition that can lead to ventricular fibrillation unless you get immediate medical treatment. With ventricular tachycardia there is rapid beating of the heart as a result of abnormal electrical firing from the ventricles. Usually VT happens in people who have heart conditions such as tissue damage from a previous heart attack or coronary artery disease. 

The other type of tachycardia that starts in the heart's ventricles is ventricular fibrillation, which occurs when there are fast, irregular electrical impulses that cause the ventricles to quiver and to be ineffective in pumping blood. When the heartbeat is irregular, the blood pressure drops quickly and cuts off the supply of blood to vital organs and the brain. CPR may save lives with ventricular fibrillation until the heart can be "shocked" back into regular rhythm with a defibrillator.