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Atrioventricular nodal reentry tachycardia (AVNRT)

Overview

Supraventricular tachycardia (SVT), also called paroxysmal supraventricular tachycardia, is defined as an abnormally fast heartbeat. It's a broad term that includes many forms of heart rhythm problems (heart arrhythmias) that originate above the ventricles (supraventricular) in the atria or AV node.

A normal heart rate is 60 to 100 beats per minute. A heart rate of more than 100 beats per minute is called a tachycardia (tak-ih-KAHR-dee-uh). This occurs when the electrical impulses that coordinate your heartbeats don't work properly. It may feel like a fluttering or racing heart.

Most people with rare episodes of supraventricular tachycardia live healthy lives without restrictions or interventions. For others, treatment and lifestyle changes can often control or eliminate rapid heartbeats.

Symptoms

Supraventricular tachycardia may come and go suddenly, with stretches of normal heart rates in between. Symptoms may last anywhere from a few minutes to a few days, and some people have no symptoms at all.

Supraventricular tachycardia becomes a problem when it occurs frequently and is ongoing, particularly if you have heart damage or other coexisting medical problems.

Signs and symptoms of supraventricular tachycardia may include:

  • A fluttering in your chest
  • Rapid heartbeat (palpitations)
  • Shortness of breath
  • Lightheadedness or dizziness
  • Sweating
  • A pounding sensation in the neck
  • Fainting (syncope) or near fainting

In infants and very young children, signs and symptoms may be difficult to identify. Sweating, poor feeding, pale skin and infants with a pulse rate greater than 200 beats per minute may have supraventricular tachycardia.

When to see a doctor

Supraventricular tachycardia is generally not life-threatening unless you have other heart disorders, but you should talk to your doctor if you are experiencing bothersome symptoms.

Some signs and symptoms, such as shortness of breath, weakness, dizziness, lightheadedness and fainting or near fainting, may be related to a serious health condition.

Seek urgent medical care if you suddenly or frequently experience any of these signs and symptoms at a time when you wouldn't expect to feel them.

In extreme cases, an episode of SVT may cause you to pass out.

Causes

For some people, a supraventricular tachycardia episode is related to an obvious trigger, such as psychological stress, lack of sleep or physical activity. For others, there may be no noticeable trigger. Things that may lead to, or cause, an episode include:

  • Heart failure
  • Thyroid disease
  • Heart disease
  • Chronic lung disease
  • Smoking
  • Drinking too much alcohol
  • Consuming too much caffeine
  • Drug use, such as cocaine and methamphetamines
  • Certain medications, including asthma medications and over-the-counter cold and allergy drugs
  • Surgery
  • Pregnancy
  • Certain health conditions, such as Wolff-Parkinson-White syndrome

What's a normal heartbeat?

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 (the sinus node) 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 node (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.

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

Supraventricular tachycardia occurs when faulty electrical connections in the heart or abnormal areas of electrical activity trigger and sustain an abnormal rhythm. When this happens, the heart rate accelerates too quickly and doesn't allow enough time for the heart to fill before it contracts again. These ineffective contractions of the heart may cause you to feel light-headed or dizzy because the brain isn't receiving enough blood and oxygen.

Types of supraventricular tachycardia

There are three major types of supraventricular tachycardia:

  • Atrioventricular nodal reentrant tachycardia (AVNRT). This is the most common type of supraventricular tachycardia in both males and females of any age, although it tends to occur more often in young women.
  • 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 supraventricular tachycardia is more commonly diagnosed in people with coexisting heart disease. Unlike AVNRT and AVRT, which always involve the AV node as part of the faulty connection, atrial tachycardia doesn't involve the AV node.

Other types of supraventricular tachycardia include:

  • Sinus tachycardia
  • Inappropriate sinus tachycardia (IST)
  • Multifocal atrial tachycardia (MAT)
  • Junctional ectopic tachycardia (JET)
  • Nonparoxysmal junctional tachycardia (NPJT)
Normal heartbeat

In a normal heart rhythm, a tiny cluster of cells at the sinus node sends out an electrical signal. The signal then travels through the atria to the atrioventricular (AV) node and then passes into the ventricles, causing them to contract and pump out blood.

Normal heartbeat

In a normal heart rhythm, a tiny cluster of cells at the sinus node sends out an electrical signal. The signal then travels through the atria to the atrioventricular (AV) node and then passes into the ventricles, causing them to contract and pump out blood.

Supraventricular tachycardia

Supraventricular tachycardia is an abnormally fast heartbeat. It occurs when faulty electrical connections in the heart set off a series of early beats in the atria.

Risk factors

Supraventricular tachycardia is the most common type of arrhythmia in infants and children. It also tends to occur twice as often in women, particularly pregnant women, though it may occur in either sex.

Other factors that may increase your risk of supraventricular tachycardia include:

  • Age. Some types of supraventricular tachycardia are more common in people who are middle-aged or older.
  • Coronary artery disease, other heart problems and previous heart surgery. Narrowed heart arteries, a heart attack, abnormal heart valves, prior heart surgery, heart failure, cardiomyopathy and other heart damage increase your risk of developing supraventricular tachycardia.
  • Congenital heart disease. Being born with a heart abnormality may affect your heart's rhythm.
  • Thyroid problems. Having an overactive or underactive thyroid gland can increase your risk of supraventricular tachycardia.
  • Drugs and supplements. Certain over-the-counter cough and cold medicines and certain prescription drugs may contribute to an episode of supraventricular tachycardia.
  • Anxiety or emotional stress
  • Physical fatigue
  • Diabetes. Your risk of developing coronary artery disease and high blood pressure greatly increases with uncontrolled diabetes.
  • Obstructive sleep apnea. This disorder, in which your breathing is interrupted during sleep, can increase your risk of supraventricular tachycardia.
  • Nicotine and illegal drug use. Nicotine and illegal drugs, such as amphetamines and cocaine, may profoundly affect the heart and trigger an episode of supraventricular tachycardia.

Complications

Over time, untreated and frequent episodes of supraventricular tachycardia may weaken the heart and lead to heart failure, particularly if you have other coexisting medical conditions.

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

Diagnosis

To diagnose supraventricular tachycardia, your doctor will review your symptoms and your medical history and conduct a physical examination. Your doctor may ask about — or test for — conditions that may trigger your SVT, such as heart disease or a problem with your thyroid gland. Your doctor may also perform heart-monitoring tests specific to arrhythmia. These may include:

  • Electrocardiogram (ECG). During an ECG, sensors (electrodes) that can detect the electrical activity of your heart are attached to your chest and sometimes to your limbs. An ECG measures the timing and duration of each electrical phase in your heartbeat.
  • Holter monitor. This portable ECG device can be worn for a day or more to record your heart's activity as you go about your routine.
  • Event monitor. For sporadic episodes of SVT, you keep this portable ECG device available, attaching it to your body and pressing a button when you have symptoms. This lets your doctor check your heart rhythm at the time of your symptoms.
  • Echocardiogram. In this noninvasive test, a hand-held device (transducer) placed on your chest uses sound waves to produce images of your heart's size, structure and motion.
  • Implantable loop recorder. This device detects abnormal heart rhythms and is implanted under the skin in the chest area.

If your doctor doesn't find an arrhythmia during those tests, he or she may try to trigger your arrhythmia with other tests, which may include:

  • Stress test. For some people, supraventricular tachycardia is triggered or worsened by stress or exercise. During a stress test, you'll be asked to exercise on a treadmill or stationary bicycle while your heart activity is monitored. If doctors are evaluating you to determine if coronary artery disease may be causing the arrhythmia, and you have difficulty exercising, then your doctor may use a drug to stimulate your heart in a way that's similar to exercise.
  • Tilt table test. Your doctor 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 doctor observes how your heart and the nervous system that controls it respond to the change in angle.
  • Electrophysiological testing and mapping. In this test, doctors thread thin tubes (catheters) tipped with electrodes through your blood vessels to a variety of spots within your heart. Once in place, the electrodes can map the spread of electrical impulses through your heart.

    In addition, your cardiologist can use the electrodes to stimulate your heart to beat at rates that may trigger — or halt — an arrhythmia. This allows your doctor to see the location of the arrhythmia and what may be causing it.

Treatment

Most people with supraventricular tachycardia do not require medical treatment. However, if you experience prolonged or frequent episodes, your doctor may recommend or try:

  • Carotid sinus massage. Your doctor may try this type of massage that involves applying gentle pressure on the neck — where the carotid artery splits into two branches — to release certain chemicals that slow the heart rate. Don't attempt to do this on your own as it may cause blood clots that could lead to a stroke, or heart or lung injury.
  • Vagal maneuvers. You may be able to stop an episode of SVT by using particular maneuvers that include holding your breath and straining, dunking your face in ice water, or coughing.

    These maneuvers affect the nervous system that controls your heartbeat (vagus nerves), often causing your heart rate to slow.

  • Cardioversion. If you're unable to stop an episode of SVT on your own using vagal maneuvers, your doctor may use cardioversion, which can be conducted as a procedure or by using medications.

    In the procedure, a shock is delivered to your heart through paddles or patches on your chest. The current affects the electrical impulses in your heart and can restore a normal rhythm.

  • Medications. If you experience frequent episodes of SVT, your doctor may prescribe medication to control your heart rate or restore a normal heart rhythm. It's very important to take any anti-arrhythmic medication exactly as directed by your doctor in order to minimize complications.
  • Catheter ablation. In this procedure, your doctor threads one or more catheters through your blood vessels to your heart. Electrodes at the catheter tips can use heat, extreme cold or radiofrequency energy to damage (ablate) a small spot of heart tissue and create an electrical block along the pathway that's causing your arrhythmia.

In rare instances, treatment for supraventricular tachycardia may involve use of a small, implantable device called a pacemaker to emit electrical impulses that stimulate your heart to beat at a normal rate. The pacemaker is placed under the skin near the collarbone in a minor surgical procedure. An insulated wire extends from the device to the heart, where it's permanently anchored.

Cardiac catheter ablation

In catheter ablation, catheters are threaded through the blood vessels to the inner heart, and electrodes at the catheter tips map the spread of electrical impulses through the heart. Electrodes at the catheter tips transmit energy to destroy a small spot of heart tissue and create an electrical block along the pathway that's causing your arrhythmia.

Alternative medicine

Research is ongoing regarding the effectiveness of several forms of complementary and alternative medical therapies for supraventricular tachycardia.

Some types of complementary and alternative therapies may be helpful to reduce stress, such as:

  • Yoga
  • Meditation
  • Relaxation techniques

Some studies have shown that acupuncture may help reduce irregular heart rates in certain arrhythmias, but further research is needed.

The role of omega-3 fatty acids, a nutrient found mostly in fish, in the prevention and treatment of arrhythmias isn't yet clear. But it appears as though this substance may be helpful in preventing and treating some arrhythmias.

Preparing for an appointment

If you think you may have supraventricular tachycardia, make an appointment with your family doctor. If it's found early, your treatment may be easier and more effective. Eventually, however, you may be referred to a doctor trained in heart conditions (cardiologist).

If you experience an episode of SVT for more than a few minutes or it's accompanied by fainting, shortness of breath or chest pain, call 911 or your local emergency number or have someone drive you to the nearest emergency room.

Because appointments can be brief, and 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 doctor.

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 doctor orders any blood tests.
  • Write down any symptoms you're experiencing, including any that may seem unrelated to heart arrhythmia.
  • Write down key personal information, including a family history of heart disease, stroke, high blood pressure or diabetes, and any major stresses or recent life changes.
  • List all of the drugs, vitamins or supplements that you're currently taking or have taken recently.
  • 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 a list of questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions will help you make the most of your time together. List your questions from most important to least important in case time runs out. For supraventricular tachycardia, some basic questions to ask your doctor 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 doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

  • When did you first begin experiencing symptoms?
  • Have your symptoms been continuous, 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?
  • Is there a family history of arrhythmia?

Lifestyle and home remedies

Your doctor may suggest that, in addition to other treatments, you make lifestyle changes that will keep your heart as healthy as possible.

These lifestyle changes may include:

  • Eat heart-healthy foods. Eat a healthy diet that's low in salt and solid fats and rich in fruits, vegetables and whole grains.
  • Exercise regularly. Exercise daily and increase your physical activity.
  • Quit 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.
  • 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.
  • Drink alcohol 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.
  • Maintain follow-up care. Take your medications as prescribed and have regular follow-up appointments with your doctor. Tell your doctor if your symptoms worsen.

Prevention

To prevent an episode of supraventricular tachycardia, it's important to know what triggers the episodes to occur and try to avoid them. You might want to try:

  • Eating a heart-healthy diet
  • Increasing your physical activity
  • Avoiding smoking
  • Keeping a healthy weight
  • Limiting or avoiding alcohol
  • Reducing stress
  • Getting plenty of rest
  • Using over-the-counter medications with caution, as some cold and cough medications contain stimulants that may trigger a rapid heartbeat
  • Avoiding stimulant drugs such as cocaine and methamphetamines

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

Consider keeping a diary to help identify your triggers. Track your heart rate, symptoms and activity at the time of an SVT episode.

Last updated: February 2nd, 2017

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