The electrical system of the heart is made up of several parts that communicate with one another to signal the heart muscle fibers when to contract. The SA node starts the signal causing the atria to contract. This signal travels through the AV node and on to the bundle of His and bundle branches causing the ventricles to contract. The flow of electrical signals is what produces a normal heartbeat.

In ventricular tachycardia, abnormal firing of electrical signals in the ventricle interfere with electrical signals coming from the natural pacemaker of the heart, the SA node. The rapid heartbeat does not allow enough time for the heart to fill before it contracts so blood flow to the rest of the body is compromised which may lead to symptoms of dizziness, lightheadedness, unconsciousness, and cardiac arrest.