Supraventricular tachycardia

Supraventricular tachycardia (SVT) is as an irregularly fast or erratic heartbeat (arrhythmia) that affects the heart's upper chambers. SVT is also called paroxysmal supraventricular tachycardia.

The typical heart beats about 60 to 100 times a minute. A heart rate of more than 100 beats a minute is called a tachycardia (tak-ih-KAHR-dee-uh). During an episode of SVT, the heart beats about 150 to 220 times a minute, but it can occasionally beat faster or slower.

Most people with supraventricular tachycardia don't need activity restrictions or treatment. For others, lifestyle changes, medication and heart procedures may be needed to control or eliminate the rapid heartbeats and related symptoms.

Types

Supraventricular tachycardia (SVT) falls into three main groups:

• Atrioventricular nodal reentrant tachycardia (AVNRT). This is the most common type of supraventricular tachycardia.
• Atrioventricular reciprocating tachycardia (AVRT). AVRT is the second most common type of supraventricular tachycardia. It's most commonly diagnosed in younger people.
• Atrial tachycardia. This type of SVT is more commonly diagnosed in people who have heart disease. Atrial tachycardia doesn't involve the AV node.

Other types of supraventricular tachycardia include:

• Sinus tachycardia
• Sinus nodal reentrant tachycardia (SNRT)
• Inappropriate sinus tachycardia (IST)
• Multifocal atrial tachycardia (MAT)
• Junctional ectopic tachycardia (JET)
• Nonparoxysmal junctional tachycardia (NPJT)

Symptoms

The main symptom of supraventricular tachycardia (SVT) is a very fast heartbeat (100 beats a minute or more) that may last for a few minutes to a few days. The fast heartbeat may come and go suddenly, with stretches of typical heart rates in between.

Some people with SVT have no signs or symptoms.

Signs and symptoms of supraventricular tachycardia may include:

• Very fast (rapid) heartbeat
• A fluttering or pounding in the chest (palpitations)
• A pounding sensation in the neck
• Weakness or feeling very tired (fatigue)
• Chest pain
• Shortness of breath
• Lightheadedness or dizziness
• Sweating
• Fainting (syncope) or near fainting

In infants and very young children, signs and symptoms of SVT may be difficult to identify. They include sweating, poor feeding, pale skin and a rapid pulse. If your infant or young child has any of these symptoms, ask your child's care provider about SVT screening.

When to see a doctor

Supraventricular tachycardia (SVT) is generally not life-threatening unless you have heart damage or other heart conditions. However, in extreme cases, an episode of SVT may cause unconsciousness or cardiac arrest.

Call your health care provider if you have an episode of a very fast heartbeat for the first time or if an irregular heartbeat lasts longer than a few seconds.

Some signs and symptoms of SVT may be related to a serious health condition. Call 911 or your local emergency number if you have an episode of SVT that lasts for more than a few minutes or if you have an episode with any of the following symptoms:

• Chest pain
• Shortness of breath
• Weakness
• Dizziness

Causes

For some people, a supraventricular tachycardia (SVT) episode is related to an obvious cause (trigger), such as exercise, stress or lack of sleep. Some people may not have a noticeable trigger.

Things that may cause an SVT episode include:

• Heart disease
• Heart failure
• Other heart conditions, such as Wolff-Parkinson-White syndrome
• Chronic lung disease
• A lot of caffeine
• Drinking too much alcohol
• Drug misuse, including cocaine and methamphetamine
• Pregnancy
• Smoking
• Thyroid disease
• Certain medications, including asthma medications and cold and allergy drugs

How does the heart beat?

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 heart signals arrive at a cluster of cells called the AV node, where the signals 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.

SVT occurs when faulty electrical connections in the heart set off a series of early beats in the upper chambers of the heart (atria). When this happens, the heart rate speeds up very quickly. The heart doesn't have enough time to fill with blood before the chambers contract. As a result, you may feel lightheaded or dizzy because your brain isn't getting enough blood and oxygen.

Risk factors

Supraventricular tachycardia (SVT) is the most common type of arrhythmia in infants and children. It also tends to occur more often in women, particularly during pregnancy, though it may occur in anyone.

Other things that may increase the risk of supraventricular tachycardia are:

• Age. Some types of SVT are more common in people who are middle-aged or older.
• Coronary artery disease, other heart disease or previous heart surgery. Narrowed heart arteries, heart failure, damage to the heart or heart valves, cardiomyopathy, and other heart disease may increase the risk of developing SVT.
• Congenital heart disease. A heart problem present at birth (congenital heart defect) may cause irregular heartbeats such as SVT.
• Thyroid disease. Having an overactive or underactive thyroid gland can increase the risk of supraventricular tachycardia.
• Diabetes. The risk of developing heart disease and high blood pressure greatly increases with uncontrolled diabetes.
• Obstructive sleep apnea. This disorder, in which breathing is interrupted during sleep, can increase the risk of supraventricular tachycardia.
• Nicotine and illegal drug use. Nicotine and illegal drugs, such as amphetamines and cocaine, may trigger an episode of supraventricular tachycardia.

Complications

Over time, untreated and frequent episodes of supraventricular tachycardia (SVT) may weaken the heart and lead to heart failure, particularly if there are other medical conditions.

In extreme cases, an episode of SVT may cause unconsciousness or cardiac arrest.

Prevention

To prevent an episode of supraventricular tachycardia (SVT), it's important to identify the triggers and try to avoid them. Consider keeping a diary to help identify your triggers. Track your heart rate, symptoms and activity at the time of an SVT episode.

Also, use medications with caution. Some drugs, including those bought without a prescription, may contain stimulants that trigger a rapid heartbeat.

Keeping the heart healthy is an important step in preventing SVT. Eat a heart-healthy diet, don't smoke, get regular exercise and manage stress.

For most people with supraventricular tachycardia, moderate amounts of caffeine do not trigger an episode of SVT. Large amounts of caffeine should be avoided, however.

Diagnosis

To diagnose supraventricular tachycardia (SVT), your health care provider will examine you and ask questions about your symptoms and medical history. Blood tests are usually done to check for conditions that can cause similar symptoms, such as thyroid disease.

Tests

Tests that may be done to evaluate the heart and diagnose supraventricular tachycardia (SVT) include:

• Electrocardiogram (ECG or EKG). An ECG records the electrical activity of the heart. An ECG measures the timing and duration of each electrical phase in the heartbeat. It can show how fast or slow the heart is beating.
• Holter monitor. This portable ECG device can be worn for a day or more to record the heart's activity during daily activities.
• Event recorder. This wearable ECG device is used to detect infrequent arrhythmias. You press a button when symptoms occur. An event recorder is typically worn for up to 30 days or until you have an arrhythmia or symptoms.
• Echocardiogram. Sound waves are used to create images of the heart in motion. An echocardiogram can provide details about the heart and heart valves.
• Implantable loop recorder. This device detects irregular heart rhythms and is implanted under the skin in the chest area.

Other tests that may be done include:

• Exercise stress test. Supraventricular tachycardia may be triggered or worsened by stress or exercise. During a stress test, you typically exercise on a treadmill or stationary bicycle while your heart activity is monitored. If you can't exercise and your provider thinks heart disease may be causing your arrhythmia, you may receive a drug during the test to stimulate the heart in a way that's similar to exercise.
• Tilt table test. Your health care provider may recommend this test if you've had fainting spells. Your heart rate and blood pressure are monitored as you lie flat on a table. The table is then tilted as if you were standing up. Your provider observes how your heart and the nervous system that controls it respond to the change in angle.
• Electrophysiological (EP) study. One or more thin, flexible tubes (catheters) are guided through a blood vessel, usually in the groin, to various spots in the heart. Sensors on the tips of the catheters record the heart's electrical patterns. An EP study allows a health care provider to see how electrical signals spread through the heart during each heartbeat.

Treatment

Most people with supraventricular tachycardia (SVT) don't need treatment. However, if you have long or frequent episodes, your health care provider may recommend the following:

• Carotid sinus massage. A health care provider applies gentle pressure on the neck where the carotid artery splits into two branches. During this type of massage, the body releases chemicals that slow the heart rate. Don't attempt to do carotid sinus massage on your own.
• Vagal maneuvers. Simple but specific actions such as coughing, bearing down as if having a bowel movement or putting an ice pack on the face can help slow down the heart rate. Your health care provider may ask you to do these actions during an episode of SVT. These actions affect the vagus nerve, which helps control the heartbeat.
• Medications. If you have frequent episodes of SVT, your health care provider may prescribe medication to control your heart rate or restore a typical heart rhythm. It's very important to take the medication exactly as directed in order to reduce complications.
• Cardioversion. Paddles or patches on the chest are used to electrically shock the heart and help reset the heart rhythm. Cardioversion is typically used when vagal maneuvers and medications don't work.
• Catheter ablation. In this procedure, the doctor inserts thin, flexible tubes called catheters through the veins or arteries, usually in the groin. Sensors 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 a typical heartbeat.
• Pacemaker. Rarely, a small, implantable device called a pacemaker is needed to stimulate the heart to beat. The pacemaker is implanted under the skin near the collarbone in a minor surgical procedure. A wire connects the device to the heart.

Lifestyle and home remedies

If you have supraventricular tachycardia, a heart-healthy lifestyle is an important part of your treatment plan.

Heart-healthy lifestyle changes include:

• Eating heart-healthy foods. Eat a healthy diet rich in fruits, vegetables and whole grains. Limit salt and saturated fats.
• Exercising regularly. Exercise daily and increase your physical activity.
• Quitting smoking. If you smoke and can't quit on your own, talk to your health care provider about strategies or programs that can help.
• Maintaining weight. Being overweight increases the risk of developing heart disease. Ask your health care provider what weight is best for you.
• Controlling blood pressure and cholesterol. Make lifestyle changes and take medications as prescribed to correct high blood pressure (hypertension) or high cholesterol.
• Avoiding or limiting 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.
• Maintaining follow-up care. Take your medications as prescribed. Get regular health checkups. Tell your provider if SVT symptoms worsen.

Alternative medicine

Some types of complementary and alternative therapies may help reduce stress. Stress can trigger supraventricular tachycardia in some people. Stress-relieving techniques include:

• Yoga
• Meditation
• Relaxation techniques

Preparing for an appointment

If you think you may have supraventricular tachycardia, make an appointment with your health care provider. If the condition is found early, treatment may be easier and more effective. You may be referred to a doctor trained in heart conditions (cardiologist).

Appointments can be brief. Because there's often a lot to discuss, it's a good idea to be prepared for your appointment. Here's some information to help you get ready for your appointment, and what to expect from your health care provider.

What you can do

• Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as restrict your diet. You may need to do this if your health care provider orders any blood tests.
• Write down any symptoms you're having, including any that may seem unrelated to irregular heartbeats.
• Write down key personal information, including any family history of heart rhythm disorders (arrhythmias), heart disease, stroke, high blood pressure or diabetes, and any major stresses or recent life changes.
• Make a list of all medications, vitamins or supplements that you're taking. Include those bought without a prescription.
• Take a family member or friend along, if possible. Sometimes it can be difficult to remember all the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your health care provider.

For supraventricular tachycardia, some basic questions to ask your health care provider include:

• What's the most likely cause of my symptoms?
• Are there other possible causes for my symptoms?
• What kinds of tests will I need? Do I need to do anything to prepare for these tests?
• What's the most appropriate treatment?
• Are there any foods or drinks that you recommend I avoid? Is there anything you suggest that I add to my diet?
• What's an appropriate level of physical activity?
• How often should I be screened for heart disease or other complications of supraventricular tachycardia?
• I have other health conditions. How can I best manage these conditions together?
• Is there a generic alternative to the medicine you're prescribing?
• Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?

What to expect from your doctor

Your health care provider is likely to ask you many questions. Being ready to answer them may save time to go over anything you want to spend more time on. Your health care provider may ask:

• When did you first begin having symptoms?
• Do you always have symptoms, or do they come and go?
• How severe are your symptoms?
• Does anything seem to improve your symptoms?
• What, if anything, appears to worsen your symptoms?
• Do you have a family history of irregular heart rhythms?

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