Ventricular tachycardia (sometimes referred to as "VT" or "V-Tach") is a potentially life-threatening rhythm disturbance. It occurs when rapid, abnormal electrical impulses arise from the ventricles. It can result in heart rates of up to 300 beats per minute! When VT occurs for only a few seconds and then stops on its own, it is called "non-sustained" VT. Non-sustained VT can cause palpitations, lightheadedness, and even fainting. "Sustained" VT is ventricular tachycardia that does not stop without medical intervention. It is most often caused by reentry within the ventricular heart muscle, and is almost always associated with underlying heart disease. Most commonly, a patient with VT has had a heart attack in the past and the tachycardia is arises from the edge of the scar tissue left behind from the heart attack. The continuous rapid heart beat that results prevents the ventricles from filling properly, and so effective pumping stops (even though the ventricles are contracting rapidly). This causes the cardiac output (and the blood pressure) to bottom out, which can in some cases cause collapse and death. Sustained VT is the most common cause of sudden cardiac death. Rarely, sustained VT will be slow enough for the heart to maintain an adequate cardiac output, and will only result in weakness, lightheadedness, and palpitations. Patients with VT are generally treated by paramedics or brought to an emergency room to be treated. If a person with VT remains awake, medications can be given intravenously to stop the arrhythmia. However, most often patients with sustained VT quickly go into Cardiac Arrest (a life-threatening condition of unconsciousness associated with no detectable pulse or blood pressure). In this case, electrical cardioversion (a shock across the chest) is necessary to stop the abnormal electrical signals and rapidly restore a normal rhythm to save the person's life. Intensive medical treatment is usually necessary to prevent recurrent sustained VT. Often, medical therapy is not effective, and another approach is required. The surgical treatment of sustained ventricular tachycardia usually involves the insertion of an Implantable Cardioverter-Defibrillator or "ICD." An ICD is an electrical device that can automatically shock the heart back into a normal rhythm if ventricular tachycardia occurs. This device has been in use since 1985 and has saved the lives of many people who would otherwise have been sent home to die. Recent advances in ICD technology have made it relatively safe to insert. In addition, sustained VT can now be stopped by the ICD with the use of "anti-tachycardia pacing," a rapid, painless stimulation of the ventricles that avoids the need for an uncomfortable shock. Medical research has demonstrated that ICDs are more effective than medical therapy in nearly all cases of life-threatening ventricular arrhythmias. Invasive testing of the electrical system of the heart by a cardiac electrophysiologist (an Electrophysiologic Study) is usually performed in cases of sustained VT.
Rarely, VT can occur in the absence of underlying heart disease. This condition is often called "Idiopathic Ventricular Tachycardia." It includes several unusual electrical disturbances that, in general, are less severe than the VT that occurs in the setting of underlying heart disease. Idiopathic VT can be exercise-induced, or it may occur anytime. This arrhythmia may require medical therapy to prevent recurrent symptoms, but usually is not life-threatening. Often, idiopathic ventricular tachycardia can be cured with catheter ablation.