Ventricular Tachycardia: Causes and Treatments

Ventricular tachycardia (v tach) is a sudden, rapid, potentially very dangerous cardiac arrhythmia originating in the heart's ventricles. While it occasionally causes only minimal symptoms, it more typically causes immediate problems. These may include 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 deteriorates during ventricular tachycardia for two reasons.

First, the heart rate during this arrhythmia tends to be very rapid (often, greater than 180 or 200 beats per minute), rapid enough to reduce the volume of blood the heart can pump.

Second, ventricular tachycardia can disrupt the normal, orderly, coordinated contraction of the heart muscle—so much of the work the heart is able to do becomes wasted.

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 heart muscle. The most common heart problems that can result in ventricular tachycardia are coronary artery disease (CAD) and heart failure. 

Cardiac disorders like these often produce weakened heart muscle with areas of scarring. Weakened and scarred cardiac tissue tends to produce tiny electrical circuits within the heart muscle—circuits that can cause reentrant tachycardias (essentially, electrical loops). Most of the time ventricular tachycardia is a type of reentrant tachycardia.

Indeed, the likelihood of developing ventricular tachycardia turns out to be proportional to the amount of damage that has been done to the ventricular muscle.

For instance, a large heart attack produces more scar tissue than a small heart attack, and is more likely to create the basis for subsequent ventricular tachycardia. The more damage, the greater the risk of the arrhythmia.

In fact, it turns out that one of the best ways to estimate a person's risk of developing ventricular tachycardia is to measure left ventricular ejection fraction. This is how much blood stays in this ventricle at the beginning of a heart beat compared to how much blood is present there after the beat is completed.

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 people—even young people—who seem completely healthy and who have no CAD or heart failure.

Most of these cases are caused by some congenital or genetic problem, such as:

• Long QT syndrome
• Repetitive monomorphic ventricular tachycardia (RMVT)
• Arrhythmogenic right ventricular cardiomyopathy (ARVC)
• Catecholamine-sensitive polymorphic ventricular tachycardia (CPVT)
• Brugada syndrome

How Is Ventricular Tachycardia Treated?

Acute episodes of sustained ventricular tachycardia are usually considered medical emergencies whether or not they produce cardiac arrest. 

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, awake, and otherwise reasonably stable, then more deliberate measures can be taken.

For instance, the arrhythmia can often be stopped by delivering intravenous medications, such as sotalol. Or a patient can be sedated and given an electrical shock to stop the arrhythmia, a procedure referred to as cardioversion.

Prevention

After the acute episode of ventricular tachycardia has been stopped and the heart rhythm has been restored to normal, attention turns to preventing future episodes.

This is an important step because if 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. 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 heart muscle changes, such as scarring, remain. This means that the risk of recurrent ventricular tachycardia usually remains high and, therefore, so does the risk of cardiac arrest and sudden death. So, additional 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. In distinct contrast to most patients with supraventricular tachycardias, however, this is often difficult to accomplish successfully.

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

Summary

Ventricular tachycardia is a sudden, rapid, potentially life-threatening cardiac arrhythmia that is usually produced either by heart disease that leaves the heart muscle scarred or weak, or by a congenital condition that alters the heart's electrical system.

Once the acute arrhythmia is treated, steps must be taken to prevent further episodes of this dangerous arrhythmia.