Disease: Ventricular tachycardia

Overview

Ventricular tachycardia is a heart rhythm disorder (arrhythmia) caused by abnormal electrical signals in the lower chambers of the heart (ventricles).

Your heart rate is regulated by electrical signals sent across heart tissues. A healthy heart normally beats about 60 to 100 times a minute when at rest and is defined by signals that originate in the upper chambers of the heart (atria).

In ventricular tachycardia (V-tach or VT), abnormal electrical signals in the ventricles cause the heart to beat faster than normal, usually 100 or more beats a minute, out of sync with the upper chambers.

When that happens, your heart may not be able to pump enough blood to your body and lungs because the chambers are beating so fast or out of sync with each other that they don't have time to fill properly.

Ventricular tachycardia may be brief, lasting for only a few seconds, and perhaps not cause any symptoms. Or it can last for much longer and cause symptoms such as dizziness, lightheadedness, palpitations or even loss of consciousness.

In some cases, ventricular tachycardia can cause your heart to stop (sudden cardiac arrest), which is a life-threatening medical emergency. This condition usually occurs in people with other heart conditions, such as those who have had a previous heart attack or other structural heart disease (cardiomyopathy).

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.

Sometimes this rhythm may occur as a result of ventricular tachycardia degenerating into ventricular fibrillation, or it may originate from single ventricular beats. This abnormal rhythm happens most often in people with established heart disease or a prior heart attack. It may also occur due to electrolyte abnormalities (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.

Source: http://www.mayoclinic.com

Symptoms

Brief episodes of ventricular tachycardia may not cause any symptoms in some people. Others may experience:

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

Sustained or more serious episodes of ventricular tachycardia may cause:

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

When to see a doctor

A number of 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 experiences any V-tach symptoms.

If you faint, have difficulty breathing or have chest pain lasting more than a few minutes, get emergency care, or call 911 or your local emergency number. Seek emergency care for anyone experiencing these symptoms.

Source: http://www.mayoclinic.com

Causes

V-tach is caused by a disruption in the normal electrical impulses that control the rate of your ventricles' pumping action.

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

  • Lack of oxygen to the heart due to tissue damage from heart disease
  • Abnormal electrical pathways in the heart present at birth (congenital heart conditions, including long QT syndrome)
  • Structural heart disease (cardiomyopathy)
  • Medication side effects
  • An inflammatory disease affecting skin or other tissues (sarcoidosis)
  • Abuse of recreational drugs, such as cocaine
  • Imbalance of electrolytes, mineral-related substances necessary for conducting electrical impulses

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

The heart's electrical system

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

Your heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles). The rhythm of your heart 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 atria muscles to contract and pump blood into the 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.

Source: http://www.mayoclinic.com

Diagnosis

To diagnose ventricular tachycardia, your doctor may review your symptoms and your family and medical history and conduct a physical examination.

Your doctor may order several tests to diagnose your condition, determine the cause and severity of your condition, and determine the most appropriate treatment.

In some cases, ventricular tachycardia may be a medical emergency and require an urgent diagnosis and prompt treatment.

Several heart tests also may be necessary to diagnose ventricular tachycardia.

Electrocardiogram (ECG)

An electrocardiogram, also called an ECG or EKG, is the most common tool used to diagnose ventricular tachycardia. It's a painless test that 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 these signals to determine what kind of tachycardia you have and how abnormalities in the heart may be contributing to a fast heart rate.

Your doctor may also ask you to use portable ECG devices at home to provide more information about your heart rate. These devices include:

  • Holter monitor. This portable ECG device is carried in your pocket or worn on a belt or shoulder strap. It records your heart's activity for an entire 24-72 hour period, which provides your doctor with 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 experience and record the time they occur.

  • Event monitor. This portable ECG device is intended to monitor your heart activity over a few weeks to a few months. You wear it all day, but it records only at certain times for a few minutes at a time.

    With many event monitors, you activate them by pushing a button when you experience symptoms of a fast heart rate. Other monitors automatically sense abnormal heart rhythms and then start recording. These monitors allow your doctor to look at your heart rhythm at the time of your symptoms.

  • 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.

Cardiac imaging

Imaging of the heart may be performed to determine if structural abnormalities are affecting blood flow and contributing to ventricular tachycardia.

Types of cardiac imaging used to evaluate V-tach include:

  • Echocardiogram (echo). An echocardiogram creates a moving picture of your heart using sound waves via a transducer placed on the chest that emits and detects these waves. An echo can identify abnormalities in the heart valves and heart muscle that contribute to poor blood flow.
  • Magnetic resonance imaging (MRI). A cardiac MRI provides still or moving pictures of how the blood is flowing through the heart and detects irregularities. It is often used to evaluate potential causes of ventricular tachycardia.
  • Computerized tomography (CT). CT scans combine several X-ray images to provide a more detailed cross-sectional view of the heart.
  • Coronary angiogram. This may be used 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 painless test is used to take still pictures of your heart and lungs and can detect if your heart is enlarged.

Stress test

Your doctor may recommend a stress test to see how your heart functions while it is working hard during exercise 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 performed in conjunction with a stress test.

Electrophysiological test

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

During this test, a doctor inserts thin, flexible tubes (catheters) tipped with electrodes into an access point, usually your groin or neck, and guides them through your blood vessels to various spots in your heart.

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: http://www.mayoclinic.com

Complications

Complications of ventricular tachycardia vary in severity depending on such factors as the rate, and duration of a rapid heart rate, the frequency with which it happens, and the existence of other heart conditions. Possible complications include:

  • Inability of the heart to pump enough blood (heart failure)
  • Frequent fainting spells or unconsciousness
  • Sudden death caused by cardiac arrest

Source: http://www.mayoclinic.com

Prevention

The most effective way to prevent ventricular tachycardia is to reduce your risk of developing heart disease. If you already have heart disease, monitor it and follow your treatment plan to lower your ventricular tachycardia risk.

In some cases, ventricular tachycardia may occur in the absence of heart disease (idiopathic ventricular tachycardia).

Prevent heart disease

Treat or eliminate risk factors that may lead to heart disease. 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.
  • 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.
  • Drink in moderation. 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. If you can't control your alcohol consumption, talk to your doctor about a program to quit drinking and manage other behaviors related to alcohol abuse.

  • 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.
  • 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.
  • Limit caffeine. If you drink caffeinated beverages, do so in moderation (no more than one to two beverages daily).
  • Control stress. Avoid unnecessary stress and learn coping techniques to handle normal stress in a healthy way.
  • Go to scheduled checkups. Have regular physical exams and report any signs or symptoms to your doctor.

Monitor and treat existing heart disease

If you already have heart disease, you can take steps to lower your risk of developing ventricular tachycardia or another arrhythmia:

  • Follow the plan. Be sure you understand your treatment plan, and take all medications as prescribed.
  • Report changes immediately. If your symptoms change or get worse or you develop new symptoms, tell your doctor immediately.

Source: http://www.mayoclinic.com

Coping and support

If you have a plan in place to deal with an episode of a fast heartbeat, you may feel calmer and more in control when one occurs. Talk to your doctor about:

  • How to take your pulse and what a normal pulse rate is for you
  • When and how to use a variety of maneuvers or take additional medications if they are appropriate for you
  • When to call your doctor
  • When to seek emergency care

Source: http://www.mayoclinic.com

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 (for example, prior heart attack, hypertrophic cardiomyopathy, inflammatory diseases of the heart or genetic conditions)
  • Use of recreational drugs
  • Severe electrolyte abnormalities
  • Medication side effects

Other risk factors

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

Source: http://www.mayoclinic.com

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