Ventricular Tachycardia: Causes and Treatments

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Ventricular tachycardia is a rapid cardiac arrhythmia originating in the heart's ventricles. Sometimes, people tolerate ventricular tachycardia with only minimal symptoms. But more typically this arrhythmia produces significant palpitations, severe lightheadedness, syncope (loss of consciousness), or even cardiac arrest and sudden death.

These symptoms occur because ventricular tachycardia disrupts the heart's ability to pump effectively.

The pumping action of the heart gets worse during ventricular tachycardia for two reasons. First, the heart rate during ventricular tachycardia may become rapid enough (often, greater than 180 or 200 beats per minute) to reduce the heart's efficiency. Second, ventricular tachycardia can disrupt the normal, orderly, coordinated contraction of the heart muscle. These two factors together often make ventricular tachycardia a particularly dangerous cardiac arrhythmia.

What Causes Ventricular Tachycardia?

Most of the time, ventricular tachycardia develops as a result of an underlying cardiac disorder that produces damage to the ventricular muscle - most commonly, coronary artery disease (CAD) or heart failure. Weakened and scarred cardiac muscle tends to produce tiny electrical circuits within the heart muscle, circuits that can cause "reentrant tachycardias." So most of the time ventricular tachycardia is a type of reentrant tachycardia.

In fact, the risk of developing ventricular tachycardia is proportional to the amount of damage that has been sustained by the ventricular muscle - the more damage, the greater the risk of the arrhythmia.

The best way to estimate the amount of heart muscle damage is to measure the left ventricular ejection fraction.

The lower the ejection fraction, the more extensive the muscle damage and the higher the risk of having ventricular tachycardia.

Much less commonly, ventricular tachycardia can occur in young people who seem completely healthy and who have no CAD or heart failure. Most of the time these arrhythmias are caused by some congenital or genetic problem, including:

How Is Ventricular Tachycardia Treated?

Acute episodes of sustained (that is, prolonged) ventricular tachcyardia are often medical emergencies. If a cardiac arrest has occurred, then standard cardiopulmonary resuscitation (CPR) measures must be taken immediately.

If the person having sustained ventricular tachycardia is alert and awake and otherwise stable, then more deliberate measures can be taken. For instance, the arrhythmia can often be terminated by delivering intravenous medications, such as lidocaine. Or the patient can be sedated and given an electrical shock to stop the arrhythmia, a procedure referred to as "cardioversion."

After the acute episode of ventricular tachycardia has been stopped and the heart rhythm restored to normal, the problem becomes preventing future episodes. This is an important step, since once a person has had an episode of sustained ventricular tachycardia, the odds of having another episode over the next year or two are extremely high - and any recurrent episodes can be life threatening.

The first step in preventing recurrent ventricular tachycardia is to fully assess and treat the underlying cardiac disease. In most cases, this means applying optimal therapy for CAD or heart failure (or both).

Unfortunately, even with optimal treatment of the underlying heart disease, the risk of recurrent ventricular tachycardia usually remains high and, therefore, so does the risk of cardiac arrest and sudden death - so other measures need to be taken.

Sometimes antiarrhythmic drugs can help in preventing recurrent ventricular tachycardia, but unfortunately these drugs often do not work well enough. Sometimes, the reentrant circuit that is producing the ventricular tachycardia can be electrically mapped and then ablated, but (in distinct contrast to most patients with supraventricular tachycardias) this is the exception rather than the rule.

For these reasons, implantable defibrillators should be strongly considered for most people who have survived an episode of sustained ventricular tachycardia.



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