Ventricular tachycardia

Overview

Ventricular tachycardia is a heart rhythm problem (arrhythmia) caused by irregular electrical signals in the lower chambers of the heart (ventricles). This condition may also be called V-tach or VT.

A healthy heart typically beats about 60 to 100 times a minute at rest. In ventricular tachycardia, the heart beats faster, usually 100 or more beats a minute.

Sometimes the rapid heartbeat prevents the heart chambers from properly filling with blood. As a result, the heart may not be able to pump enough blood to the body. If this happens, you may feel short of breath or lightheaded, or you may lose consciousness.

Ventricular tachycardia episodes may be brief and last only a couple of seconds without causing harm. But episodes lasting more than a few seconds (sustained V-tach) can be life-threatening. Sometimes ventricular tachycardia can cause the heart to stop (sudden cardiac arrest).

Treatment for ventricular tachycardia may include medication, a shock to the heart (cardioversion), catheter procedures or surgery to slow the fast heart rate and reset the heart rhythm.

Ventricular tachycardia is caused by faulty heart signaling that triggers a fast heart rate in the lower heart chambers (ventricles). The fast heart rate doesn't allow the ventricles to fill and squeeze (contract) to pump enough blood to the body.

Many things can cause or contribute to problems with heart signaling and lead to ventricular tachycardia. These include:

• Prior heart attack or other heart condition that caused scarring of heart tissue (structural heart disease)
• Poor blood flow to the heart muscle due to coronary artery disease
• Congenital heart diseases, including long QT syndrome
• Imbalance of substances in the blood called electrolytes — such as potassium, sodium, calcium and magnesium
• Medication side effects
• Use of stimulants such as cocaine or methamphetamine

Sometimes, the exact cause of ventricular tachycardia can't be determined (idiopathic ventricular tachycardia).

How does the heart beat?

To better understand the cause of ventricular tachycardia, it may be helpful to know how the heart typically works.

The heart is made of four chambers — two upper chambers (atria) and two lower chambers (ventricles).

The heart's rhythm is controlled by a natural pacemaker (the sinus node) in the right upper chamber (atrium). The sinus node sends electrical signals that typically start each heartbeat. These electrical signals move across the atria, causing the heart muscles to squeeze (contract) and pump blood into the ventricles.

Next, the signals arrive at a cluster of cells called the AV node, where they slow down. This slight delay allows the ventricles to fill with blood. When the electrical signals reach the ventricles, the chambers contract and pump blood to the lungs or to the rest of the body.

In a typical heart, this heart signaling process usually goes smoothly, resulting in a resting heart rate of 60 to 100 beats a minute.

In ventricular tachycardia, faulty electrical signaling in the heart's lower chambers causes the heart rate to increase to 100 or more beats a minute.

To diagnose ventricular tachycardia, the health care provider will usually do a physical exam and ask questions about your symptoms, habits and medical history. Sometimes, ventricular tachycardia is a medical emergency that requires urgent diagnosis and treatment.

Tests

If you have signs or symptoms of tachycardia, tests can be done to evaluate the heart and help confirm the diagnosis. Tests can also help determine if another health problem is contributing to ventricular tachycardia.

Electrocardiogram (ECG or EKG)

An electrocardiogram is the most common tool used to diagnose tachycardia. This painless test detects and records the heart's electrical activity using small sensors (electrodes) attached to the chest and arms.

An ECG records the timing and strength of electrical signals as they travel through the heart. A health care provider can look for patterns among the signals to determine the type of tachycardia and how problems in the heart may be causing a fast heart rate.

Your health care provider may also ask you to use a portable ECG device at home to obtain more information about your heart rate. These devices include:

• Holter monitor. This portable ECG device can be worn for a day or more to record the heart's activity during daily activities. It may be recommended if a traditional ECG doesn't give your care provider enough information about your heart's condition. Some personal devices, such as smartwatches, offer portable ECG monitoring. Ask your health care provider if this is an option for you.
• Event monitor. This portable ECG device is intended to be worn for up to 30 days or until you have an irregular heart rhythm (arrhythmia) or symptoms. You typically press a button when symptoms occur. However, some monitors automatically sense arrhythmias and then start recording.
• Implantable loop recorder. This implantable device has no wires and can sit underneath the skin for up to three years to continuously monitor the heart rhythm.

Heart (cardiac) imaging

If you have an irregular heartbeat (arrhythmia), your health care provider may recommend cardiac imaging tests to evaluate the structure of your heart. Cardiac imaging tests used to diagnose ventricular tachycardia include:

• Chest X-ray. A chest X-ray can show the condition of the heart and lungs. A chest X-ray can help diagnose an enlarged heart.
• Echocardiogram. An echocardiogram uses sounds waves to create a picture of the heart in motion. It can identify areas of poor blood flow and heart valve problems.
• Magnetic resonance imaging (MRI). A cardiac MRI provides still or moving pictures of how blood flows through the heart.
• Computerized tomography (CT). A heart (cardiac) CT scan combines several X-ray images to provide a more detailed cross-sectional view of the heart.
• Coronary angiogram. A coronary angiogram is done to check for blockages in the heart's arteries. It uses a contrast dye and special X-rays to show the inside of the coronary arteries.

Stress test

Some types of tachycardia are triggered or worsened by exercise. During a stress test, the heart's activity is typically monitored while you're riding on a stationary bicycle or walking on a treadmill. Other heart tests may be done with a stress test. If you have difficulty exercising, a drug may be given to stimulate the heart in a way that's similar to exercise.

Electrophysiological (EP) test and cardiac mapping

This test, also called an EP study, may be done to confirm a diagnosis of ventricular tachycardia and to determine the precise location of the irregular heartbeat (arrhythmia).

During an EP study, a health care provider inserts thin, flexible tubes (catheters) tipped with sensors (electrodes) into a blood vessel, usually in the groin, and guides them to various areas in the heart. Once in place, the electrodes can precisely map the spread of electrical signals during each heartbeat.

Tilt table test

A tilt table test may be done to better understand how tachycardia contributes to fainting. Heart rate and blood pressure are monitored while lying flat on a table. Then, under careful supervision, the table is tilted to a position that mimics standing. The health care provider watches how the heart and the nervous system that controls it respond to the changes in position.

Ventricular fibrillation that lasts longer than 30 seconds (sustained VT) often requires urgent medical treatment, as this condition may sometimes lead to sudden cardiac death.

The goals of ventricular tachycardia treatment are to slow a rapid heartbeat when it occurs and to prevent future episodes of a fast heart rate. Treatment may include medications or procedures to control or reset the heart rhythm.

If another medical condition is causing tachycardia, treating the underlying problem may reduce or prevent episodes of a fast heartbeat.

Medications

If you have ventricular tachycardia, you may be given medications called anti-arrhythmics by mouth or IV to slow the fast heart rate. Other heart medications, such as calcium channel blockers and beta blockers, may be prescribed with anti-arrhythmic drugs.

Cardioversion

This medical procedure is generally used when emergency care is needed for a rapid heart rate, such as that seen with sustained ventricular tachycardia. Cardioversion sends electric shocks to the heart through sensors (electrodes) placed on the chest. The shock affects the heart's electrical signals and restores a regular heartbeat. It's also possible to do cardioversion with medications.

A shock can also be delivered to the heart using an automated external defibrillator (AED).

Surgery or other procedures

A catheter procedure or heart surgery may be needed to help prevent or manage episodes of ventricular tachycardia.

• Catheter ablation. In this procedure, a health care provider threads one or more thin, flexible tubes (catheters) through an artery, usually in the groin, and guides them to the heart. Sensors (electrodes) on the tip of the catheter use heat or cold energy to create tiny scars in the heart to block irregular electrical signals and restore the heart rhythm. Catheter ablation is often done when an extra signaling pathway is responsible for the fast heart rate.
• Implantable cardioverter-defibrillator (ICD). Your health care provider may recommend this device if you're at high risk of developing ventricular tachycardia or ventricular fibrillation. An ICD is a pager-sized device implanted under the skin near the collarbone. It continuously monitors the heartbeat and delivers precisely calibrated electrical shocks when an irregular rhythm (arrhythmia) is detected. The shocks help restore a regular heart rhythm.
• Pacemaker. This small device is surgically implanted under the skin in the chest area. When the pacemaker detects an irregular heartbeat, it sends an electrical pulse that helps correct the heart's rhythm.
• Maze procedure. In this procedure, a surgeon makes tiny incisions in the upper half of the heart (atria) to create a pattern (or maze) of scar tissue. The heart's signals can't pass through scar tissue. So the maze can block stray electrical heart signals that cause some types of tachycardia.
• Open-heart surgery. Sometimes open-heart surgery may be needed to destroy an extra electrical pathway causing tachycardia. Surgery is usually done only when other treatment options don't work or when surgery is needed to treat another heart disorder.