Ventricular Tachycardia

In ventricular tachycardia, the heart beats regularly but too rapidly. Sometimes the heart beats too rapidly for a few seconds, then returns to a normal rate. If the heart beats too rapidly for more than 30 seconds, the disorder is called sustained ventricular tachycardia.

Sustained ventricular tachycardia is more common among older people. Most commonly, it is caused by coronary artery disease (often by a heart attack), heart failure, or use of digoxin or certain other antiarrhythmic drugs in doses that are too high (causing toxicity). If sustained ventricular tachycardia is triggered by such an event and does not recur within the next few days, it is unlikely to recur.

In sustained ventricular tachycardia, the ventricles cannot fill adequately or pump blood normally. Thus, ventricular tachycardia often leads to dizziness, loss of consciousness, or heart failure. It sometimes leads to ventricular fibrillation, which causes death unless promptly corrected.

Most people with ventricular tachycardia notice palpitations. People may feel dizzy or faint because blood pressure tends to fall. Occasionally, ventricular tachycardia causes few symptoms, even at rates of up to 200 beats per minute, but it is still extremely dangerous.

Diagnosis and Treatment

Electrocardiography (ECG) is used to diagnose ventricular tachycardia and to help determine whether treatment is needed. A portable ECG (Holter) monitor may be used to record heart rhythm over a 24-hour period.

If ventricular tachycardia causes low blood pressure or fainting or is sustained (even without causing symptoms), treatment is needed immediately. Antiarrhythmic drugs (such as lidocaine, procainamide, amiodarone, or bretylium) may be given intravenously. If these drugs do not promptly restore a normal heart rhythm, cardioversion (an electrical shock applied to the chest) is used. After cardioversion, an antiarrhythmic drug (such as amiodarone or sotalol), given by mouth, is often prescribed to prevent recurrences. Such a drug may not be prescribed if sustained ventricular tachycardia was triggered by an event such as a heart attack and is unlikely to recur.

If ventricular tachycardia recurs despite treatment with antiarrhythmic drugs, electrophysiologic testing or exercise stress testing may be done while the person is given different antiarrhythmic drugs. These tests are likely to trigger the arrhythmia. Then doctors can determine which drug is most effective in preventing and treating the arrhythmia.

Alternatively, an implantable cardioverter-defibrillator (ICD) may be used. It detects ventricular tachycardia and delivers an electrical shock to correct it. Less commonly, catheter ablation or open-heart surgery is done. These procedures are used to destroy the small abnormal area in the ventricles that is usually responsible for sustained ventricular tachycardia.