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Ventricular tachycardia is a heart rhythm that originates in the ventricles and produces a heart rate of at least 120 beats per minute.
Ventricular tachycardia may be thought of as a sequence of consecutive ventricular premature beats. Sometimes only a few such beats occur together, and then the heart returns to a normal rhythm. Ventricular tachycardia that lasts more than 30 seconds is called sustained ventricular tachycardia. Sustained ventricular tachycardia usually occurs in people with a structural heart disorder such as a heart attack or a cardiomyopathy. It is more common among older people. However, rarely, ventricular tachycardia develops in young people who do not have a structural heart disorder. Such young people may have a heart disorder called long QT syndrome (see Long QT Syndrome and Torsades de Pointes Ventricular Tachycardia), which can be inherited or caused by certain drugs. It can also be due to a rare inherited disorder, the Brugada syndrome, which may require treatment with an implanted defibrillator.
People with ventricular tachycardia almost always have palpitations. They may have weakness, light-headedness, and/or chest discomfort. Sustained ventricular tachycardia can be dangerous because the ventricles cannot fill adequately or pump blood normally. Blood pressure tends to fall, and heart failure follows. Sustained ventricular tachycardia is also dangerous because it can worsen until it becomes ventricular fibrillation—a form of ventricular fibrillation. Sometimes ventricular tachycardia causes few symptoms, even at rates of up to 200 beats per minute, but it may still be extremely dangerous.
Electrocardiography (ECG—see Electrocardiography) is used to diagnose ventricular tachycardia and to help determine whether treatment is required.
Ventricular tachycardia is treated when it causes symptoms or when episodes last more than 30 seconds even without causing symptoms.
People who have symptoms, particularly if blood pressure is too low, require immediate cardioversion (an electrical shock to convert the heart to normal rhythm).
People who have no symptoms but who have had ventricular tachycardia for more than 30 seconds should be treated either with cardioversion or intravenous drugs. Cardioversion is painful, so sedation is required, but cardioversion is almost always effective and aside from the discomfort has few side effects. Drugs are not uncomfortable but are not as effective as cardioversion and are more likely to cause side effects. The most commonly used drugs are amiodarone, lidocaine, and procainamide.
The long-term goal is to prevent sudden death, rather than simply stopping the abnormal rhythm. In people with ventricular tachycardia who have an underlying heart disorder, particularly if their heart does not pump well, an implantable cardioverter-defibrillator (ICD, a small device that can detect an arrhythmia and deliver a shock to correct it—see Restoring normal rhythm) is often used. This procedure is similar to implantation of an artificial pacemaker.
Certain procedures may be used to destroy the small abnormal area in the ventricles, identified by ECG, that is usually responsible for sustained ventricular tachycardia. They include radiofrequency ablation (delivery of energy of a specific frequency through an electrode catheter inserted in the heart) and open-heart surgery.
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* This is the Consumer Version. *