Section 3. Heart and Blood Vessel Disorders

Chapter 27. Abnormal Heart Rhythms

Topics: Introduction | Atrial Premature Beats | Atrial Fibrillation and Atrial Flutter | Paroxysmal Supraventricular Tachycardia | Wolff-Parkinson-White Syndrome | Ventricular Premature Beats | Ventricular Tachycardia | Ventricular Fibrillation | Pacemaker Dysfunction | Heart Block | Bundle Branch Block

Ventricular Tachycardia

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 structural heart disease that damages the ventricles. Most commonly, it occurs weeks or months after a heart attack. It is more common among older people. However, rarely, ventricular tachycardia develops in young people who do not have structural heart disease.

Symptoms and Diagnosis

People with ventricular tachycardia almost always have palpitations. 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 cardiac arrest. 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 Section 3, Chapter 21) is used to diagnose ventricular tachycardia and to help determine whether treatment is required. A portable ECG (Holter) monitor may be used to record heart rhythm over a 24-hour period.

Treatment

Ventricular tachycardia is treated when it causes symptoms or when episodes last more than 30 seconds even without causing symptoms. Sustained ventricular tachycardia often requires emergency treatment. If episodes cause blood pressure to fall to a low level, cardioversion is needed immediately. Drugs may be given intravenously to end or suppress ventricular tachycardia. The most commonly used drugs are lidocaine, procainamide, and amiodarone.

Certain procedures may be performed 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.

If other therapy is ineffective, an automatic defibrillator (a small device that can detect an arrhythmia and deliver a shock to correct it) may be implanted. This procedure is similar to implantation of an artificial pacemaker.