Ventricular tachycardia is a rapid heart beat initiated within the ventricles, characterized by 3 or more consecutive premature ventricular beats. Ventricular tachycardia is a difficult clinical problem for the physician.
Causes, incidence, and risk factors
Ventricular tachycardia is a potentially lethal disruption of normal heartbeat (arrhythmia) that may cause the heart to become unable to pump adequate blood through the body. The heart rate may be 160 to 240 (normal is 60 to 100 beats per minute).
Ventricular tachycardia can occur in the absence of apparent heart disease. It can also develop as an early or a late complication of a heart attack, or during the course of cardiomyopathy, alveolar heart disease, myocarditis, and following heart surgery.
Healed heart attacks form scar tissue which can lead to ventricular tachycardia. This can occur days, months, or years after the heart attack.
Ventricular tachycardia can also result from anti-arrhythmic medications (an undesired effect) or from altered blood chemistries (such as a low potassium level), pH (acid-base) changes, or insufficient oxygenation.
A common mechanism for ventricular tachycardia is reentry (re-stimulation of the electrical conductive pathway from a single initial stimulus). Ventricular tachycardia is classified as nonsustained (often defined as lasting less than 30 seconds) or sustained.
"Torsade de pointes" is a form of ventricular tachycardia with a specific variation in the conduction of the ventricular stimulus.
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Ventricular tachycardia occurs in approximately 2 out of 10,000 people.
Note: Symptoms may start and stop suddenly. In some cases, there are no symptoms.
Signs and tests
Ventricular tachycardia can occur in episodes during which the person will have a rapid pulse or the symptoms described above. The blood pressure may be normal or low. Loss of consciousness may occur. Ventricular tachycardia is a potentially lethal arrhythmia and may result in an absent pulse.
Ventricular tachycardia may be seen on:
Blood chemistries and other tests may be performed.
Treatment varies with the symptoms, the situation, and the underlying cardiac disorder. No treatment may be required in some cases.
Ventricular tachycardia may become an emergency situation and may be require CPR, electrical defibrillation or cardioversion (electric shock), or intravenous anti-arrhythmic medications (such as lidocaine, procainamide, bretylium, or sotalol).
Long-term treatment of ventricular tachycardia may require the use of oral anti-arrhythmic medications (such as procainamide, amiodarone, or sotalol). Anti-arrhythmic medications, however, may have severe side effects, and their use is currently decreasing in favor of other treatments.
Some ventricular tachycardias may show in the electrophysiologic study to be suitable for an ablation procedure. Radiofrequency catheter ablation is a curative treatment for selected tachycardias.
In recent years, a preferred treatment for many chronic (long-term) ventricular tachycardias consists of implanting a device called implantable cardioverter defibrillator (ICD). The ICD is implanted usually in the chest, like a pacemaker, and it is connected to the heart with wires.
The ICD is programmed by the doctor to sense ventricular tachycardia when it is occurring, and to administer a shock to abort it. The ICD may also be programmed to send a rapid burst of paced beats to interrupt the ventricular tachycardia. The ventricular tachycardia may require also the use of concomitant anti-arrhythmic agents to prevent repeated firing of the ICD.
The outcome varies depending on the underlying cardiac disorder, the situation, and symptoms.
Ventricular tachycardia may not cause symptoms in some people, but may be lethal in others - it is a major cause of sudden cardiac death.
Calling your health care provider
Go to the emergency room or call the local emergency number if you feel a rapid, irregular pulse, fainting, or chest pain -- all of which may be indicative of ventricular tachycardia.
In some cases, the disorder is not preventable. In other cases, treatment of underlying cardiac disorders, correction of blood chemistries, and correction of underlying heart diseases may prevent ventricular tachycardia.