Ventricular Tachycardia

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

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

The chaotic heartbeats prevent the heart chambers from properly filling with blood. As a result, your heart may not be able to pump enough blood to your body and lungs.

Ventricular tachycardia may last for only a few seconds, or it can last for much longer. You may feel dizzy or short of breath, or have chest pain. Sometimes, ventricular tachycardia can cause your heart to stop (sudden cardiac arrest), which is a life-threatening medical emergency.

Questions to Ask Your Doctor

• What is likely causing my symptoms?
• What tests do I need?
• What treatment approach do you recommend, if any?
• What lifestyle changes can I make to reduce my symptoms?
• Do I need to eliminate alcohol and caffeine?
• Am I at risk of long-term complications?
• How will you monitor my health over time?
• Do I need to adjust the medications I'm taking for other health conditions?

Brief episodes of ventricular tachycardia may not cause any symptoms in some people. Or you may have:

• Dizziness
• Shortness of breath
• Lightheadedness
• Feeling as if your heart is racing (palpitations)
• Chest pain (angina)

Sustained and more-serious episodes of ventricular tachycardia may cause:

• Loss of consciousness or fainting
• Cardiac arrest (sudden death)

When to see a doctor

Many different conditions can cause ventricular tachycardia. It's important to get a prompt, accurate diagnosis and appropriate care. See your doctor if you or your child has any problems with the heartbeat. In some cases, urgent care is needed.

Get emergency care, or call 911 or your local emergency number for anyone experiencing these symptoms:

• Chest pain that lasts more than a few minutes
• Difficulty breathing
• Fainting

Causes

Ventricular tachycardia is caused by a disruption in the normal electrical impulses that control the rate of your heart's pumping action.

Many things can cause or contribute to problems with the heart's electrical system. These include:

• Abnormalities of the heart that result in scarring of heart tissue (sometimes called "structural heart disease"), the most common cause is a prior heart attack
• Poor blood flow to the heart muscle due to coronary artery disease
• Congenital heart conditions, including long QT syndrome
• Imbalance of electrolytes necessary for conducting electrical impulses
• Medication side effects
• Use of drugs such as cocaine or methamphetamine

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

The heart's electrical system

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To understand the causes of heart rate or rhythm problems such as tachycardia, it helps to understand how the heart's electrical system works.

Your heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles). Your heartbeat is normally controlled by a natural pacemaker called the sinus node, which is located in the right atrium. The sinus node produces electrical impulses that normally start each heartbeat.

From the sinus node, electrical impulses travel across the atria, causing the atrial muscles to contract and pump blood into the lower chambers of the heart (ventricles).

The electrical impulses then arrive at a cluster of cells called the atrioventricular (AV) node — usually the only pathway for signals to travel from the atria to the ventricles.

The AV node slows down the electrical signal before sending it to the ventricles. This slight delay allows the ventricles to fill with blood. When electrical impulses reach the muscles of the ventricles, they contract, causing them to pump blood either to the lungs or to the rest of the body.

When anything disrupts this complex system, it can cause the heart to beat too fast (tachycardia), too slow (bradycardia) or with an irregular rhythm.

Risk factors

Any condition that puts a strain on the heart or damages heart tissue can increase your risk of ventricular tachycardia. Lifestyle changes or medical treatment may decrease the risk associated with the following factors:

• Heart disease
• Medication side effects
• Severe electrolyte imbalances
• Use of stimulant drugs such as cocaine or methamphetamine

If you have a family history of ventricular tachycardia or other heart rhythm disorders, you may have an increased risk of ventricular tachycardia.

Complications

Complications of ventricular tachycardia vary in severity and depend on how fast your heart is beating, how long the rapid heartbeat lasts, how often tachycardia occurs and your overall heart health. Possible complications include:

• Frequent fainting spells or unconsciousness
• Heart failure
• Sudden death caused by cardiac arrest

Ventricular fibrillation

A dangerous condition related to ventricular tachycardia is ventricular fibrillation (V-fib). In V-fib, your lower heart chambers contract in a very rapid and uncoordinated manner.

This abnormal rhythm happens most often in people with heart disease or a prior heart attack. It may also occur due to electrolyte problems (such as high or low potassium levels) or, rarely, in otherwise normal hearts.

Ventricular fibrillation may also cause sudden cardiac arrest and lead to death if not treated immediately.

Prevention

The best way to prevent ventricular tachycardia is to treat or eliminate risk factors that may lead to heart disease. If you already have heart disease, follow your treatment plan and a heart-healthy lifestyle.

Take the following steps:

• Exercise and eat a healthy diet. Live a heart-healthy lifestyle by exercising regularly and eating a healthy, low-fat diet that's rich in fruits, vegetables and whole grains.
• Maintain a healthy weight. Being overweight increases your risk of developing heart disease.
• Keep blood pressure and cholesterol levels under control. Make lifestyle changes and take medications as prescribed to correct high blood pressure (hypertension) or high cholesterol.
• Control stress. Avoid unnecessary stress and learn coping techniques to handle normal stress in a healthy way.
• Don't use recreational drugs. Don't use stimulants, such as cocaine. Talk to your doctor about an appropriate program for you if you need help ending recreational drug use.
• Go to scheduled checkups. Have regular physical exams and report any signs or symptoms to your doctor.
• Limit alcohol. If you choose to drink alcohol, do so in moderation. For healthy adults, that means up to one drink a day for women of all ages and men older than age 65, and up to two drinks a day for men age 65 and younger. For some conditions it's recommended that you completely avoid alcohol. Ask your doctor for advice specific to your condition.
• Limit caffeine. If you drink caffeinated beverages, do so in moderation (no more than one to two beverages daily).
• Stop smoking. If you smoke and can't quit on your own, talk to your doctor about strategies or programs to help you break a smoking habit.
• Use over-the-counter medications with caution. Some cold and cough medications contain stimulants that may trigger a rapid heartbeat. Ask your doctor which medications you need to avoid.

Your doctor will evaluate your symptoms, perform a physical examination, and ask you about your health habits and medical history. In some cases, ventricular tachycardia may be a medical emergency that requires urgent diagnosis and treatment.

Several tests may be done to diagnose ventricular tachycardia. 

Electrocardiogram (ECG)

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

An ECG records the timing and strength of electrical signals as they travel through your heart. Your doctor can look for patterns among the signals to determine what kind of tachycardia you have and how problems in the heart may be causing a fast heart rate.

Your doctor 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. You carry this portable ECG device in your pocket or wear it on a belt or shoulder strap. It records your heart's activity for an entire 24-hour period, which gives your doctor a prolonged look at your heart rhythms. Your doctor will likely ask you to keep a diary during the same 24 hours. You'll describe any symptoms you have and record the time they occur.
• Event monitor. This portable ECG device is intended to monitor your heart activity over a week to a few months. You wear it all day, but it records only at certain times for a few minutes at a time. You typically activate the monitor by pushing a button when you have symptoms of a fast heart rate. However, some monitors automatically sense abnormal heart rhythms and then start recording.
• Other monitors. Some personal devices, such as smart watches, offer electrocardiogram monitoring. Ask your doctor if this is an option for you.
• Transtelephonic monitor. This device provides continuous heart rhythm monitoring but must be worn continuously. It may or may not include wires.
• Implantable loop recorder. This is an implantable device that has no wires and can sit underneath your skin for up to three years to continuously monitor your heart rhythm.

Electrophysiological Test

Your doctor may recommend an electrophysiological test to confirm the diagnosis or to pinpoint the location of problems in your heart.

During this test, a doctor inserts thin, flexible tubes (catheters) tipped with electrodes into your groin, arm or neck and guides them through your blood vessels to various spots in your heart. Once in place, the electrodes can precisely map the spread of electrical impulses during each beat and identify abnormalities in your circuitry.

Cardiac Imaging

Your doctor may get images of your heart to determine if structural problems are affecting blood flow and causing your ventricular tachycardia.

Cardiac imaging tests used to diagnose ventricular tachycardia include:

• Echocardiogram. An echocardiogram creates a moving picture of your heart using sound waves. It can identify areas of poor blood flow, abnormal heart valves and heart muscle that are not working normally.
• Magnetic resonance imaging (MRI). A cardiac MRI can provide still or moving pictures of how the blood is flowing through the heart and detect irregularities.
• Computerized tomography (CT). CT scans combine several X-ray images to provide a more detailed cross-sectional view of the heart.
• Coronary angiogram. To study the flow of blood through your heart and blood vessels, your doctor may use a coronary angiogram to reveal potential blockages or abnormalities. It uses a dye and special X-rays to show the inside of your coronary arteries.
• Chest X-ray. This test is used to take still pictures of your heart and lungs and can detect if your heart is enlarged.

Stress test

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Your doctor may recommend a stress test to see how your heart works when you are active or when medication is given to make the heart beat faster.

In an exercise stress test, electrodes are placed on your chest to monitor heart function while you exercise, usually by walking on a treadmill. Other heart tests may be done along with a stress test.

Tilt table test

This test is sometimes used to help your doctor better understand how your tachycardia contributes to fainting spells. Under careful monitoring, you'll receive a medication that causes a tachycardia episode. You lie flat on a special table, and then the table is tilted as if you were standing up. Your doctor notes how your heart and nervous system respond to these changes in position.

Additional tests

Your doctor may order additional tests as needed to diagnose an underlying condition that is contributing to ventricular tachycardia and judge the condition of your heart.

Source: https://www.mayoclinic.org/diseases-conditions/ventricular-tachycardia/symptoms-causes/syc-20355138