There are many different kinds of abnormal heart rhythms. If an abnormal rhythm occurs, it's important to find out what kind it is. Treatment recommendations depend on its type. Arrhythmias can cause the heart rate to be irregular, fast or slow. Fast rhythms are called tachycardia. Slow ones are called bradycardia.

Premature atrial contraction (PAC) and premature ventricular contraction (PVC)
Tachycardia
Supraventricular tachycardia (SVT)
Wolff-Parkinson-White syndrome
Ventricular tachycardia (VT)
Bradycardia
Sick sinus syndrome
Complete heart block

Premature atrial contraction (PAC) and premature ventricular contraction (PVC)
Premature beats or extra beats most often cause irregular heart rhythms. Those that start in the upper chambers (atria) are called premature atrial contractions or PACs.  Premature ventricular contractions or PVCs start in the ventricles. If you've ever had the feeling that your heart "skipped a beat," it was probably from this type of arrhythmia. The heart really doesn't skip a beat. Instead, an extra beat comes sooner than normal. Then there's usually a pause that causes the next beat to be more forceful. You felt this more-forceful beat.

Watch an animation of premature ventricular contractions

Premature beats are very common in normal children and teenagers — most people have them at some time. Usually no cause can be found and no special treatment is needed. The premature beats may disappear later. Even if they continue, your child will stay well and won't need any restrictions. Occasionally premature beats may be caused by disease or injury to the heart. Your child's doctor may recommend more tests to make sure your child's heart is OK.

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Tachycardia
A fast heart rate is called tachycardia. The definition of "too fast" usually depends on the person's age and physical activity. A newborn has tachycardia if the resting rate is more than 160 beats per minute.   A teenager is considered to have tachycardia if the resting heart rate is more than 90 beats per minute. An exercising teenager may have a normal heart rate of up to 200 beats per minute.

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Sinus tachycardia is a normal increase in the heart rate. It occurs with fever, excitement and exercise. No treatment is needed. Rarely, disease, such as anemia (low blood counts) or increased thyroid activity can cause this fast heart rate. In these cases, when the disease is treated, the tachycardia goes away.

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Supraventricular tachycardia (SVT)
The most common abnormal tachycardia in children is supraventricular tachycardia (SVT). It's also called paroxysmal atrial tachycardia (PAT) or paroxysmal supraventricular tachycardia (PSVT). The fast heart rate involves both the heart's upper and lower chambers. This isn't a life-threatening problem for most children and adolescents. Treatment is only considered if episodes are prolonged or frequent. For many infants, SVT is a time-limited problem. Treatment with medications often stops after six to 12 months.

SVT may occur in very young infants with otherwise-normal hearts. The heart rate is usually more than 220 beats a minute. Infants with an SVT episode may breathe faster than normal and seem fussy or sleepier than usual. This situation must be diagnosed and treated to return the heart rate to normal. Once the rhythm is normal, medication usually can prevent future episodes.

Sometimes SVT can be detected while a baby is still in the womb. Then the mother may take medications to slow her baby's heart rate. If an older infant or child has SVT, the child may be aware of the rapid heart rate. This may be associated with palpitations, dizziness, lightheadedness, chest discomfort, upset stomach or weakness. Some children can learn ways to slow down their heart rate. Straining — such as closing the nose and mouth and trying to breathe out — may be successful. This is called a Valsalva maneuver.

Older children are more likely to have more episodes of tachycardia. They're more likely to need prolonged treatment. They also may need more diagnostic tests. It's unusual for episodes of SVT to keep a child from enjoying normal activities. Most children who have episodes of tachycardia stay well even though they may need to keep taking medicine. Your child will probably need periodic check-ups but will be able to enjoy unrestricted normal activities.

Treating SVT usually has two parts. The first is stopping a current episode; the second is preventing recurrences. The approach to preventing recurrences depends on the child's age. In some cases — especially those of infants — the child may need to enter the hospital for treatment and special studies.

Sometimes simple procedures can stop a fast heart rhythm. Gagging or putting ice on the face are examples. Your child's doctor can explain this to you in more detail. At other times intravenous medications may be needed to control or stop the tachycardia. Another way to stop SVT is to place a small catheter (a thin, flexible tube) through the nostril into the esophagus. A small amount of electricity is sent through this catheter to stop the SVT. On rare occasions doctors stop SVT by giving a small electrical shock to the chest wall. This is called electrical countershock or cardioversion. A sedative or anesthetic is given before this procedure.

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Wolff-Parkinson-White syndrome
If an abnormal conduction pathway runs between the atria and ventricles, the electrical signal may arrive at the ventricles sooner than normal. This condition is called Wolff-Parkinson-White syndrome (WPW syndrome). It's named after the three people who first described it. WPW syndrome is recognized by certain changes on the ECG. Many people with WPW syndrome don't have symptoms but are at risk of sudden cardiac arrest.

Often medication can improve this condition. Sometimes, though, such treatment doesn't work. Then your child will need more tests. Eliminating the abnormal pathway by passing energy through a catheter may be needed. Surgery is another option.

See an illustration of Wolff-Parkinson-White syndrome

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Ventricular tachycardia (VT)
Ventricular tachycardia (VT) is a fast heart rate that starts in the lower chambers (ventricles). This uncommon but potentially serious condition can threaten a child's life. VT may result from serious heart disease; it usually requires prompt treatment. VT occasionally occurs in children with otherwise normal hearts. Often specialized tests, including an intracardiac electrophysiologic procedure, may be needed to evaluate the tachycardia and the effect of drug treatment. Some forms of VT may not need treatment.

If treatment is required, it includes medicines and addressing the cause, if possible. The type and length of treatment depends on what's causing the problem. In some people radiofrequency ablation or surgery may be needed to control the tachycardia.

Watch an animation of ventricular tachycardia
Watch an animation of electrophysiology studies
See an illustration of radiofrequency ablation

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Bradycardia
A heart rate that's too slow is called bradycardia. What's "too slow" depends on a person's age and activity. A newborn usually won't have a heart rate of less than 80 beats a minute. An athletically trained teenager may have a normal resting heart rate of 50 beats a minute.

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Sick sinus syndrome
Sometimes the sinus node doesn't work properly. Some children who've had open-heart surgery have this problem. When the sinus node's work is seriously disturbed, it's called sick sinus syndrome. A child with this syndrome may not have any symptoms or may be tired, dizzy or faint. Children with sick sinus syndrome have episodes of tachycardia and bradycardia. Fortunately, sick sinus syndrome is unusual in children. If it does occur, an artificial pacemaker, medications or both may be needed.

Watch an animation of an artificial pacemaker

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Heart block may be present at — or even before — birth. (This is congenital heart block.) Disease or an injury to the electrical conduction system during heart surgery can also cause it. When the natural pacemaker in the lower chambers isn't fast enough or reliable enough, an artificial pacemaker is put in.

See an illustration of heart block
Watch an animation of an artificial pacemaker

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This content is reviewed regularly. Last updated 01/15/09.