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SUPRAVENTRICULAR TACHYCARDIA (SVT)

What is Supraventricular Tachycardia (SVT)?

The heart has two upper chambers (atria) and two lower chambers (ventricles). In normal rhythm, the heartbeat begins in the sinoatrial (SA) node, which is the heart’s natural pacemaker in the right upper chamber. The SA node sends out an electrical signal, which causes the atria to contract. This signal then moves throughout the heart’s electrical conduction system, causing the ventricles to contract. Supraventricular tachycardia is a rhythm originating in the upper chambers of the heart and leads to the heart beating exceedingly fast, sometimes upwards of 200 beats per minute. Supraventricular tachycardia is the most common type of arrhythmia in infants and children.

Types of SVT

There are three major types of supraventricular tachycardia:

  1. 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. It involves an accessory pathway that the electrical signals travel through.
  2. Atrioventricular reciprocating tachycardia (AVRT). AVRT is the second most common type of supraventricular tachycardia. It’s most commonly diagnosed in younger people and involves an accessory pathway that the electrical signals travel through.
  3. Atrial tachycardia (AT). This type of supraventricular tachycardia is more commonly diagnosed in people with coexisting heart disease and is therefore acquired. Unlike AVNRT and AVRT, which always involve the AV node as part of the faulty connection, atrial tachycardia doesn’t involve the AV node.

What Causes SVT?

For some people, the SVT is inherited. For some people, an SVT 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:

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

Other Factors That May Increase the Risk of SVT

  • Age. Some types of supraventricular tachycardia are more common in people who are middle-aged or older.
  • Anxiety or emotional stress.
  • Congenital heart disease. Being born with a heart abnormality may affect your heart’s rhythm.
  • 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.
  • Diabetes. Your risk of developing coronary artery disease and high blood pressure greatly increases with uncontrolled diabetes.
  • Drugs and supplements. Certain over-the-counter cough and cold medicines and certain prescription drugs may contribute to an episode of supraventricular tachycardia.
  • Gender. SVT occurs twice as often in women, particularly pregnant women, though it may occur in either sex.
  • Metabolic syndrome/insulin resistance.
  • Obstructive sleep apnea. This disorder, in which your breathing is interrupted during sleep, can increase your risk of supraventricular tachycardia.
  • Physical fatigue.
  • Thyroid problems. Having an overactive or underactive thyroid gland can increase your risk of supraventricular tachycardia.

Symptoms of SVT

Some people with SVT feel no symptoms and may not even know that they have SVT. Other people may have symptoms occurring on an intermittent or persistent basis and may experience any combination of any of the following symptoms:

Dizziness

In rare cases, SVT can cause sudden death.

Tiredness

Diagnostic Workup for SVT

  • Blood tests: to check thyroid function or other conditions that may trigger SVT
  • Electrocardiography (EKG): to measure the electrical activity of your heart and measure the timing and duration of each heartbeat
  • Echocardiogram: to obtain images of your heart’s size, structure, and motion
  • Heart monitoring: to record your heart’s rhythm continuously for anywhere from 24 hours to 30 days

Your provider might also try to trigger an episode with other tests, which may include:

SVT 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 because 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.

SVT Treatment

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

  • 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, blowing through a straw, 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 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. Some medications used to terminate symptomatic SVT episodes and reduce SVT occurrences include beta-blockers, calcium channel blockers, and less commonly, digoxin. These medications can be administered orally on a routine outpatient basis or via intravenous route if necessary in the emergency room. Drug response is variable and highly individualized, with some patients responding and others not. It is a trial-and-error proposition, with no possibility of knowing what would be most effective for each patient ahead of time.
  • Catheter ablation. Catheter ablation is for patients who elect to forgo medication either due to intolerable symptoms or side effects from their medications, recurrent symptoms, and episodes despite medical therapy, or lack of desire to take daily medications for an extended time.

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