Definition

Ventricular tachycardia is an abnormally fast heart rate that originates in one of the two lower chambers of the heart, known as ventricles. It is diagnosed when there are three or more beats in succession originating from a ventricle, at a rate greater than 100 beats per minute but less than 200 beats per minute.

Ventricular tachycardia is considered sustained if it lasts more than 30 seconds. When this condition is sustained, the ventricles won’t be able to fill with enough blood for the heart to keep blood flowing properly through the body. This can result in lowered blood pressure, heart failure, and death.

The rhythm of the heartbeat may be regular or irregular when a person has ventricular tachycardia. This condition is challenging to diagnose because it often happens in emergency situations and must be identified and treated very quickly.

Heart Chambers and Valves

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Causes

There are several different factors that may cause ventricular tachycardia. Scar tissue from a previous, healed heart attack]]> can make it difficult for the ventricles to function, causing increased heart rate. Certain drugs have side effects that may affect the heart rate.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

The following factors may increase your chance of ventricular tachycardia:

• Coronary artery disease]]>
• Previous heart attacks
• Heart abnormalities such as ]]>cardiomyopathy]]> , ]]>mitral valve prolapse]]> , valvular heart disease, and ion channel disorders
• Previous diagnosis of electrical instability in an otherwise healthy heart
• ]]>Sarcoidosis]]> (an inflammatory disease)
• Beginning treatment for myxedema (decreased thyroid gland activity)
• Use of medicines like digitalis, certain antipsychotics, and certain anti-arrhythmic drugs
• Extreme physical or emotional overstimulation
• Low oxygen levels in the blood
• Very high levels of acid in bodily fluids, possibly as a result of kidney disease or ]]>diabetes]]>
• Stimulants such as caffeine, ]]>cocaine]]> , or ]]>alcohol]]>

Coronary Artery Disease

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Symptoms

Symptoms include:

• A sensation of the heart beating very rapidly
• Feeling dizzy
• Feeling short of breath
• Fainting
• Chest discomfort
• Pale skin tone

Diagnosis

A physician will most likely rely on an electrocardiograph]]> (ECG), a measure of the electrical activity of the heart as it contracts, to diagnose this condition. Some patients may be asked to wear a portable ECG to record their heart rate for 24 hours. A doctor may also insert a catheter into the heart to get a better image of the organ. Other tests could include an ]]>exercise stress test]]> , to test the heart’s performance, or an ]]>electrophysiology test]]> , an in-depth study of the electrical signals of the heart.

Treatment

A doctor may recommend any of the following treatments:

• In an emergency situation, CPR]]> or a defibrillator may be required.
• Drugs to lower the heart rate, such as lidocaine, procainamide, and amiodarone, may be given.
• A doctor may prescribe beta-blockers to manage ]]>high blood pressure]]> .
• Open heart surgery or ]]>radiofrequency ablation]]> may be necessary to remove any structural abnormalities identified by the ECG. For radiofrequency ablation, a small electrode catheter is placed in the heart. It will destroy the abnormalities using specific energy frequencies.
• If other approaches fail, an automatic defibrillator will be inserted into the heart—much like a ]]>pacemaker]]> —to deliver shocks as needed to keep the heart rate steady. This has been shown to be the most effective management for patients with severe ]]>arrhythmia]]> or who had been revived after sudden cardiac death.

Prevention

Although ventricular tachycardia occasionally happens in people with no risk factors, people who are known to be at risk can take the following precautions, with a doctor’s supervision:

• Take beta-blockers to manage blood pressure.
• Take lidocaine, procainamide, or amiodarone to control heart rate.
• Treat other underlying conditions that might cause arrhythmia.
• Avoid substances, such as caffeine, cocaine, and alcohol, that can cause ventricular arrhythmia.
• Take steps to avoid heart disease, including maintaining a healthy weight and exercising appropriately.
• Take medicine to control blood pressure or cholesterol as prescribed by your physician.
• If you smoke, quit]]> .