Supraventricular Tachycardia (SVT, PSVT)

Picture of the Heart's Normal Electrical Activity

Supraventricular tachycardia is a rapid heart rate (tachycardia, or a heart rate above 100 beats per minute) that is caused by electrical impulses that originate above the heart's ventricles. Many doctors and other healthcare professionals include all of the many tachycardias that involve the atrioventricular node (AV node) under this classification, but others do not.

Supraventricular tachycardia does not include those tachycardia rhythms that originate from the ventricles (ventricular tachycardias) such as ventricular tachycardia or ventricular fibrillation.

Supraventricular tachycardia is also called paroxysmal supraventricular tachycardia and is abbreviated either SVT or PSVT.

How does the heart's normal electrical activity work?

Picture of the interior of the heart and chambers of the heart.

• The heart consists of four chambers; two upper chambers called atria and two lower chambers called ventricles.
• The atria receive blood from blood vessels and, with coordinated electrical impulses from the sinoatrial (SA) node, contract to push blood into the ventricles.
• The ventricles then contract to push the blood out of the heart into the blood vessels of the lungs and the rest of the body.
• The heart usually beats 60-90 times a minute. A heart rate faster than 100 beats per minute is considered tachycardia.
• Specialized heart cells coordinate the contractions using electrical signals.
• These specialized cells consist of the SA or sinus node in the right atrium, the AV node, and the bundle of His (atrioventricular bundle) in the wall between the right and left ventricles.
• The SA node, the heart's natural pacemaker, starts the electrical signals and transmits them to the AV node.
• The AV node then activates the bundle of His and its branches, resulting in the contraction of the ventricles.
• The atria contract to fill the ventricles with blood; then the ventricles contract in quick sequence to move the blood into the lungs and the rest of the body. Each sequence of atrial then ventricular contraction is one normal heartbeat.
• SA node and AV node and the path of the electrical impulse into the ventricles through the bundle and to the right and left ventricle nerve bundles (RB and LB) to complete a heartbeat.
• Nerve impulses, oxygen demand, the level of hormones in the blood, and other factors influence the rate of heart contraction at any given time. A problem in any of these areas can cause abnormal heart rhythm (arrhythmia or dysrhythmia).

Supraventricular tachycardia can be found in healthy young children, in adolescents, and in some people with underlying heart disease. Most people who experience it live a normal life without restrictions.

In supraventricular tachycardia, the heart rate is sped up by an abnormal electrical impulse starting in the atria.

• The heart beats so fast that the heart muscle cannot relax between contractions.
• When the chambers don't relax, they may not contract strongly or fill with enough blood to satisfy the body's needs at rest or especially during times of increased oxygen demand (for example stress, body movements, and walking).
• Because of the ineffective contractions of the heart, the brain does not receive enough blood and oxygen. People can become light-headed, dizzy, or feel like fainting (syncope).

Supraventricular tachycardia often occurs in episodes with stretches of normal rhythm in between. When tachycardia occurs, it is usually referred to as paroxysmal supraventricular tachycardia (often abbreviated PSVT). Supraventricular tachycardia also may be chronic (ongoing, long-term).

The most common rhythms are:

• Sinus tachycardia (normal, exercise-, or work-induced)
• Atrial fibrillation
• Atrial flutter
• Paroxysmal supraventricular tachycardia (PSVT)

The other supraventricular tachycardias are infrequently or rarely diagnosed.

The following is a list of conditions that fit under the broad definition of SVT:

• Sinus tachycardia
• Inappropriate sinus tachycardia (IST)
• Sinus nodal reentrant tachycardia (SNRT)
• Atrial tachycardia
• Multifocal atrial tachycardia (MAT)
• Atrial flutter (AF)
• Atrial fibrillation (Afib)
• Paroxysmal supraventricular tachycardia (PSVT; also termed AV nodal reentrant tachycardia or AVNRT and AV reentrant tachycardia or AVRT, a subset of PSVT)
• Junctional ectopic tachycardia (JET)
• Nonparoxysmal junctional tachycardia (NPJT)

There are two semantic problems in the literature with supraventricular tachycardias (SVTs). From the strict but extremely broad definition, an SVT can be due to any supraventricular cause. Consequently, atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia, and even normal exercise-induced tachycardia could fall under this designation. However, many clinicians consider SVT to be only paroxysmal supraventricular tachycardia (PSVT). The terminology may be somewhat confusing, but the large majority of SVTs are usually discussed separately in articles under their specific name (for example, atrial fibrillation). Because the principal SVTs listed above have separate articles devoted to them in eMedicineHealth, this article will be devoted only to paroxysmal supraventricular tachycardia (PSVT).

PSVT can cause a number of symptoms, depending on a person's overall health and how fast their heart is beating. People with heart damage or other coexisting medical problems experience a greater degree of discomfort and complications than those who are healthy. Some people have no symptoms at all.

Symptoms can come on suddenly and may go away by themselves; they can last a few minutes or as long as 1-2 days. The rapid beating of the heart during PSVT can make the heart a less effective pump so that the body's organs do not receive enough blood to work normally. The following symptoms are typical with a rapid pulse of 140-250 beats per minute:

• Palpitations (the sensation of the heart pounding in the chest)
• Dizziness, light-headedness (near-faint), or fainting
• Shortness of breath
• Anxiety
• Chest pain or tightness

In infants and very young children, symptoms are sometimes difficult to discern. However, those infants with irritability, poor feeding, sweating, poor coloration of skin, and who exhibit a pulse rate of 200-250 beats per minute may have PSVT.

Paroxysmal (also termed sporadic) supraventricular tachycardia usually occurs without other symptoms. However, it may be associated with a number of medical conditions, such as the following:

• Hardening of the arteries (atherosclerosis)
• Heart failure
• Thyroid disease
• Chronic lung disease
• Pneumonia
• Pulmonary emboli, or blood clots migrating into the lung arteries from elsewhere in the body
• Pericarditis
• Certain drugs and social habits
• Cocaine abuse
• Alcohol abuse
• Smoking
• Drinking too much caffeine in coffee, tea, or soft drinks
• Emotional stress
• Pregnancy
• Structural abnormalities, such as Wolff-Parkinson-White (WPW) syndrome, in which extra electrical tissue sets up abnormal electrical circuits that predispose the heart to arrhythmias which include PSVT, Afib, AF, and ventricular fibrillation

PSVT may also occur as a side effect of medications such as digitalis, asthma medications, or cold remedies.

In some cases, the cause of PSVT is unknown. PSVT is the most common arrhythmia in infants, children, and women who are pregnant.

PSVT is generally not life-threatening unless individuals have other heart disorders. Call a doctor or other health care professional if any of the following conditions occur:

• The episode of rapid heartbeat or palpitations is the first, and the symptoms last longer than a few seconds to a few minutes.
• The person has had previous episodes of PSVT, and the current episode does not go away with vagal maneuvers (coughing, deep breathing, or muscle tensing described below).

The person with the symptoms should not drive to the hospital. Call 911 for emergency help if needed. The following conditions or symptoms warrant a visit to the nearest hospital emergency department:

• Rapid heartbeat and feeling dizzy or faint
• Rapid heartbeat with chest pain
• Feel short of breath with a rapid heartbeat

A health care professional will ask questions about the patient's symptoms, medical and surgical history, lifestyle, and medications. The physical examination will focus on the heart and other organs, such as the lungs, that might explain the reason for the symptoms.

Other tests are likely to be done to confirm the diagnosis of PSVT and to assist the health care professional in tailoring the most appropriate treatment. Most commonly, an electrocardiogram (ECG) is done and testing includes the following:

• Electrocardiogram (ECG): The ECG is a painless, quick, noninvasive test that detects the electrical activity of the heart. Through 12 electrodes, or leads, attached to the chest, arms, and legs, tracings or waves are detected and represent the electrical activity of the heart from 12 different views. This allows detection of a number of different kinds of problems in the heart. The ECG can help identify many different arrhythmias including PSVT and in some cases its underlying cause. However, further tests or even therapy may depend on the findings of the ECG.
• Ambulatory ECG: By the time a person reaches a medical facility, the symptoms will sometimes have stopped and the ECG will be normal. This is frustrating to the patient and the doctor because an accurate diagnosis depends on capturing the rapid heartbeat on an ECG. Ambulatory monitoring often solves this problem by monitoring the heart over a period of time, usually 1-2 days. The ambulatory ECG is more likely to document any abnormal heart rhythms that a person may experience. The patient wears the monitor device, called a Holter monitor, while they go about their daily activities. Patients also keep a diary while wearing the device to allow the health care professional to detect any abnormalities on the ECG recording during times when the patient has symptoms.
• Echocardiogram (ECHO): This is a noninvasive ultrasound examination of the heart. A small handheld device is passed over the chest. It transmits pictures (sonograms) of the heart walls and valves to a television screen. It also measures how well the left ventricle is pumping. The echo is used to screen for any problems in the heart structure, valves, or muscles. The echocardiogram is used frequently in patients with SVT's that are irregular, but infrequently in PSTVs.
• Stress test: The stress test is an ECG done both at rest and while the heart is under stress, usually with exercise on a treadmill or an exercise bicycle. If a patient cannot exercise, they can be given a drug that will temporarily "stress" the heart. This test helps in the diagnosis of coronary heart disease, that is, blockage of the coronary arteries by fatty plaques (atherosclerosis). Coronary heart disease prevents the heart from getting enough blood, and this can cause abnormal heart rhythms. This test is used in some patients who may have stress-induced PSVT and for other heart-related problems, such as poor blood supply to the heart (ischemia).
• Cardiac catheterization and coronary angiography: If the stress test result is abnormal or if the patient has chest pain, shortness of breath, or loss of consciousness, he or she may undergo cardiac catheterization under local anesthesia to assess disease in the heart and heart valves. Angiography is a type of imaging study that uses a dye in the arteries to highlight blockages and damage. Usually, this test is not done in patients with PSVT unless they have significant risk factors for coronary artery disease and severe symptoms.
• Electrophysiologic study: Patients may need this test if they have rapid heartbeats, but their body does not tolerate treatment, or if the heart has created new electrical pathways that contribute to the abnormal rhythm. This test involves placement of several pacemaker electrodes into the heart chambers to record electrical activity. The electrodes are placed via a catheter that is threaded through the veins to the heart, under local anesthesia in the cardiac catheterization lab. This test is rarely used in patients with PSVT.

Lab Tests

• Blood tests may be performed to rule out thyroid disease and evidence of heart muscle damage due to coronary artery disease (heart attack).
• Urine tests and additional blood tests may be performed to rule out abnormal levels of drugs or illegal drugs that can cause rapid heartbeat.

Treatment for PSVT focuses on decreasing the heart rate and breaking up the electrical circuits made by the abnormal conducting pathways. Treatment can be divided into two broad categories: halting the acute episode and preventing any new episodes. One of the most important considerations in treating an acute episode of PSVT is how severely the heart function has been affected.

The doctor may monitor the patient's progress, depending on the severity of the symptoms or the cause and treatment used for the PSVT. The doctor may choose to monitor the patient for a few weeks or months for the following reasons:

• To assess the frequency of the recurrence of arrhythmias and heart rate
• To adjust or change medications based on clinical, repeat ECG, or Holter evaluations
• To plan further therapy if the PSVT condition worsens

In most people, PSVT is not dangerous. Mild arrhythmias, such as isolated premature beats, may require no treatment. A few people, however, may have arrhythmias that become dangerous and require immediate and, perhaps, prolonged treatment.

When a person first develops symptoms of PSVT, they can attempt the following simple maneuvers, called vagal maneuvers (stimulates a vagal nerve to slow the heart rate), to assist the body in slowing the heart rate:

• Hold your breath for about 20-60 seconds
• Quickly dip the entire face in cold water (sink or large open container)
• Cough multiple times
• Tense the stomach muscles as if the patient was bearing down to have a bowel movement

If these vagal maneuvers do not work, lie down and relax. Take some slow, deep breaths. Often, the heart will slow by itself.

If the symptoms continue, get immediate transport to a hospital. If a person has frequent episodes of rapid heartbeat, they should be evaluated by a medical professional even if the episodes spontaneously resolve.

The following lifestyle choices may help many people prevent PSVT from occurring and to monitor their body responses.

• Learn how to count the pulse (heartbeat). Then determine if the pulse is regular or irregular. People should ask a health care professional or nurse to teach them how to count their pulse themselves and other people. In adults, the pulse should be between 50-100 per minute and regular.
• Check with a healthcare professional before taking any over-the-counter (OTC) cough, cold, or pain medicines, especially if the person has hypertension or has had episodes of PSVT.
• Exercise regularly. Exercise makes the heart stronger and more efficient and lowers blood pressure and heart rate.
• Learn to relax or control stress. Some relaxation techniques include muscle relaxation, deep breathing, meditation, and biofeedback.
• Control other illnesses by complying with the doctor's recommendations for medications and lifestyle changes.
• Quit smoking, or better, never start! Avoid second-hand smoke from others.
• Reduce or eliminate caffeine intake because it often is a stimulation source for PSVT.
• Avoid illegal drug use. Most (for example, cocaine, and amphetamines) stimulate the heart.
• Weight control and, for many, weight reduction are helpful. Obesity makes the heart work much harder.
• Work toward a lifestyle change. Eat a diet low in fat, cholesterol, and salt; eat lots of vegetables.
• Cut back on excessive alcohol use (moderate use is considered 1-2 drinks per day, depending on the weight and sex of the person).

If a person has low blood pressure, chest pain, or a failing heart with tachycardia, the condition is considered unstable. In such cases, the person may be in serious danger and need immediate treatment. They may need an electrical shock (cardioversion) to convert their heart to a normal rhythm. This is considered an emergency. Synchronized cardioversion, usually first attempted with a 50 joule shock, can be done with a defibrillator at the bedside with all emergency materials available (a resuscitation or “crash” cart) and ancillary personnel to help if the patient remains unstable or their condition deteriorates. Although this occurs infrequently with PSVT, it is best to be prepared.

If a person's condition is stable, a number of options are available to end the abnormal rhythm:

• Vagal maneuvers: Coughing, holding the breath, immersing the face in cold water, and tensing abdominal muscles as if having a bowel movement are called vagal maneuvers because they increase the tone of the vagus nerve on the heart. Increased vagal tone stimulates release of substances that decrease the heart rate, which in some people, can break the abnormal electrical circuit and stop PSVT.
• Carotid massage: Carotid massage can release chemicals to slow the heart rate. Carotid massage is generally limited to young, healthy people because older people are at risk for stroke. In the emergency department, the patient will be connected to a heart monitor because the decrease in heart rate can be dramatic. Carotid massage involves gently pressing and rubbing the carotid artery located in the neck just under the angle of the jaw.
• Medications: Patients may be given adenosine (Adenocard), a short-acting medication that decreases the heart rate by blocking the SA node conduction for a few seconds. This medication is given by IV to act quickly. Adenosine has some temporary side effects, including facial flushing, chest pain, shortness of breath, nausea, and dizziness. If a single dose does not stop supraventricular tachycardia, then the doctor may give higher doses. Adenosine successfully stops paroxysmal supraventricular tachycardia (PSVT) of all types in more than 90% of cases.
• Other medications: If adenosine is unsuccessful, other medications can be used, such as calcium channel blockers (diltiazem), digoxin (Lanoxin), or beta-blockers (esmolol). Blood pressure is monitored carefully with these drugs.

A doctor, usually a cardiologist, will devise a treatment that treats the specific cause of supraventricular tachycardias. The following treatments are infrequently used for PSVT but may be necessary depending on the severity of the patient's symptoms and their overall health condition:

• Pacemaker: A pacemaker is an electronic device that takes over the role of the SA node as pacemaker of the heart. It is often implanted inside the heart by a cardiologist or an electrophysiologist in the cardiac catheter lab, or by a surgeon.
• Other treatments: In special cases, the source of the arrhythmia or abnormal electrical pathways can be interrupted by chemicals, ablated by high frequency energy through a catheter [such as in patients with regular recurrent PSVT or the Wolff-Parkinson-White (WPW) syndrome], or by a surgeon; but this is done infrequently for PSVT.

• Reduce stress, especially emotional stress.
• Exercise regularly and maintain a healthy lifestyle.
• Eliminate caffeine and other stimulants such as alcohol or illegal drugs.
• Comply with medications and medical advice.
• Learn more about PSVT by asking the doctor to answer any questions about PSVT.

Most people with rare episodes of paroxysmal supraventricular tachycardia (PSVT) live healthy lives without restrictions, so their outlook is excellent. Those people that require medication, cardioversion, or other interventions usually have a good to a fair outcome.

• If patients are told to take medications, the person may or may not experience some side effects. Discuss those potential side effects with the doctor.
• In rare cases, if a patient has a continuous fast heart rate like PSVT that goes untreated, the heart muscle can weaken and lead to heart failure.
• If the doctor finds a specific cause related to an underlying heart or systematic condition, recovery from PSVT may depend on the prognosis for that underlying condition.