Definition Ventricular tachycardia (VT) is an abnormal heart rhythm, or irregular type of heartbeat. It is defined as three or more heartbeats in a row that come from a part of the heart known as the ventricles. This is called non-sustained VT. Sustained VT is VT that lasts longer than 30 seconds. It is life-threatening.
What is going on in the body? The ventricles, or lower chambers of the heart, usually beat in a regular pattern. They beat in response to electrical impulses that start in the upper chambers of the heart, or atria. VT occurs when the electrical impulse starts in the ventricles instead of the atria. This impulse takes over the heartbeat, causing the heart to beat very rapidly. It also keeps the ventricles from filling with blood. This causes the pumping action of the heart to stop and blood pressure to drop. It can quickly lead to death if the heartbeat doesn't return to normal.
VT is usually caused by some sort of damage to the heart or by heart disease. Sometimes, though, it can happen for unknown reasons in the absence of heart disease.
What are the signs and symptoms of the disease? Non-sustained VT sometimes does not have any symptoms. Affected people may notice their heart pounding or a flutter in their chest. Lightheadedness may occur very rarely but quickly goes away.
Symptoms from sustained VT depend on:
the heart rate
how long the abnormal rhythm lasts
any underlying heart disease
If the heart rate is rapid and there is underlying heart damage, the symptoms and signs include:
low blood pressure
a fluttering in the chest or an abnormal awareness of the heartbeat
shortness of breath
If it is not treated, this can quickly lead to serious damage to the heart and even death. Heart attacks can often bring on VT, so affected people may have chest pain coming from the heart with either type of VT.
What are the causes and risks of the disease? VT can be caused by certain conditions, including:
What can be done to prevent the disease? VT usually comes on suddenly and cannot be prevented. Prevention of future episodes is geared toward finding and fixing any underlying heart problems.
How is the disease diagnosed? An ECG, which is a printout of the electrical impulses of the heart, will show a certain abnormal pattern. The printout will show ventricular beats, usually at a rate greater than 100 beats per minute.
What are the long-term effects of the disease? This is closely related to the underlying condition that led to VT. For example:
if sustained VT occurs within the first 6 weeks after a heart attack, there is a 75% chance of death due to VT within one year.
a person with non-sustained VT after a heart attack is 3 times more likely to die than someone with a heart attack who did not develop VT.
Sustained VT of any cause can lead to death if it is not treated.
Non-sustained VT will almost always go away on its own if there is no underlying heart disease.
What are the treatments for the disease? Persons with non-sustained VT, no symptoms, and no underlying heart disease do not need treatment. Treatment is needed for persons who have symptoms and underlying heart disease.
Treatments may include electrical shock to the heart and medications. Finding the right drug needs to be done in the hospital. Often, surgery is needed to insert a special type of device that can deliver shocks to the heart. This device can often correct an abnormal heartbeat as soon as it starts.
Other tests can be done to find out what is causing an abnormal heart rhythm. In these types of tests, the electrical activity of the heart is mapped. The site with the abnormal electrical activity is located. This area can then be inactivated or destroyed.
What are the side effects of the treatments? Shocks to the heart are uncomfortable. They may cause the heart to go into other irregular heartbeats or stop beating altogether in some cases. All medications have possible side effects. These include allergic reactions, stomach upset, and other types of abnormal heartbeats. Specific side effects depend on the drugs used.
Possible side effects of surgery include bleeding, infection and even a heart attack and death in rare cases.
What happens after treatment for the disease? People who have non-sustained VT may not need any treatment. This is especially true if they didn't have symptoms from their VT. Routine monitoring in the hospital often detects non-sustained VT in people without symptoms. If symptoms occur from non-sustained VT or sustained VT occurs, further monitoring is needed in many cases. Those on medications or who have special devices implanted to deliver shocks to their heart need regular doctor visits to ensure these treatments are effective.
Those who have artery blockage in their heart or who had a heart attack need aggressive treatment. This includes control of high blood pressure, diabetes, and high cholesterol if present. People are also advised to quit smoking. Any of these treatments need further monitoring.
How is the disease monitored? People with VT that causes symptoms need to be followed closely. They will need regular ECG tests, blood tests, physical examinations, and exercise testing.
Author: Susan Woods, MD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
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