Arrhythmia, or an irregular fast or slow heart rate, affects approximately 1 in 250 to 1,000 children and adolescents each year. While most arrhythmias in children are not life threatening, if left untreated, some types of arrhythmia can lead to serious consequences including dizziness, syncope (fainting), or rarely, sudden death. The Arrhythmia Clinic at Children's Hospital & Medical Center is a leader in the diagnosis and treatment of pediatric arrhythmias in fetuses, infants, children, adolescents and young adults. Specialists at Children's have more than 30 years of experience in treating young patients with a variety of arrhythmia conditions.
What is an arrhythmia?
Children with arrhythmias have an abnormal heart beat. It may beat too rapidly, too slowly or erratically. Fast rhythms are called tachycardia. Slow ones are called bradycardia. Arrhythmias are often a byproduct of an inherited heart condition and occur in as many as 33 to 50 percent of congenital heart disease patients, especially after heart surgery. In many people who have had heart surgery for their congenital heart defect, the risk of arrhythmia increases with time after surgery. There are many different types of arrhythmias. Determining the type of arrhythmia your child has is important to determine appropriate treatment. Arrhythmias are categorized into several types:
- Sinus arrhythmia is a normal variation of the heart rhythm in which the normal pacemaker of the heart or sinus node beats irregularly in relation to breathing producing a variable heart rate and rhythm.
- Premature atrial contraction (PACs) and premature ventricular contraction (PVCs) occur when single extra beats arise from either the atrium (top chamber) or ventricle (lower chamber). Most people who have these extra beats do not need treatment but may need extra tests to determine if other problems exist.
- Tachycardia is fast heart rate. When the normal pacemaker of the heart beats fast (from running, fever, fear/panic, worry), it is called sinus tachycardia. Seldom do people need treatment for sinus tachycardia. When the fast heart rate is from the top chamber of the heart atrium, it is called atrial or supraventricular tachycardia. When it originates from the bottom or pumping chamber of the heart ventricle, it is called ventricular tachycardia. Most people with either of these abnormal tachycardias require more testing and treatment.
- Bradycardia is a slow heart rate and most commonly originates from the normal pacemaker of the heart. In this case, it is called sinus bradycardia. Sinus bradycardia is a normal variant in most people.
- Supraventricular tachycardia (SVT) is an abnormal fast heart rhythm that starts in the upper chambers, or the atria, of the heart. There are several different types of SVT. The most common include arrhythmias related to Wolff-Parkinson-White (WPW) syndrome, intra-atrial reentrant tachycardia (sometimes called atrial flutter), and AV nodal reentrant tachycardia.
- Sinus node dysfunction, also called sick sinus syndrome, is most often found in people who have had heart surgery during which the normal pacemaker sinus node is damaged. This causes the heart rate to beat at a rate that is slow at rest and/or even slower during exercise.
- Complete AV block, also called heart block, can be a congenital condition that occurs both before (fetal) or after birth or after surgery. The normal electrical conduction of the heart is not allowed to travel from top chambers to lower chambers so the upper chamber beats separately from the lower chamber, which beats at a rate that is often too slow.
Signs and symptoms
Arrhythmias can occur at any age and many times they have no symptoms. Children who do have symptoms may experience fast, slow or irregular palpitations, dizziness, a feeling of tiredness or light-headedness, passing out, shortness of breath and/or chest pain. Rarely are arrhythmias life-threatening and lead to the need for cardiopulmonary resuscitation (CPR).
Diagnosis of arrhythmias
Diagnosing arrhythmias may be accomplished by one or several tests described below. Determining the type of arrhythmia your child has is necessary to provide the most appropriate and effective treatment. Diagnosis often is made by an electrophysiologist, a cardiologist with specialized training in the diagnosis and treatment of heart rhythm disorders.
Diagnostic tests include:
- Electrocardiogram (ECG or EKG) - An ECG is performed by placing stickers (electrodes) on the arms, legs and chest with wires connected to the ECG machine. The ECG machine records the heart's electrical activity providing the cardiologist important information about the size, shape, and rhythm of the heart. The test does not hurt and is commonly done for most initial and some follow-up clinic visits.
- Holter monitor - This test records the heart's rhythm for an entire 24-hour period. This allows your cardiologist to observe the rhythm during daytime, nighttime, activity, and at rest. Electrodes are placed onto the chest and attached to a small recording monitor. The patient carries the Holter monitor in a pocket or small pouch worn around the neck or waist. A technician scans and processes the Holter data in a computer that provides the maximum, minimum and average heart rates and shows any arrhythmias during the 24 hours. If symptoms occur during the Holter monitoring, the patient or parent is asked to write these in a diary so they can be compared to the rhythm at the time of the symptom.
- Exercise stress testing - Exercise stress tests are performed on a patient while riding a stationary bike or walking and running on a treadmill. The heart's electrical activity is recorded throughout the test. This test can reveal whether exercise contributes to the development of arrhythmias and also shows how well the heart and lungs work together. During exercise the patient may be asked to breathe into a mask or tube in the mouth held by biting on a mouthpiece. This allows accurate measurement of oxygen use and carbon dioxide output so that calculations can be done to measure exercise performance.
- Transtelephonic monitor - This monitoring technique involves the use of an event recorder device, which is like a miniature portable EKG machine that is worn by a patient daily for up to 30 days. It is designed to record the patient's heart rhythm when a symptom occurs. The device has two wires or leads that attach to stickers on the patient's skin to the device, which is about the size of a pager. When the patient feels his/her heart racing, skipping or dizziness, he/she pushes the button on the device to record the episode. The computer has memory so it is able to also save the EKG before the button was pushed. This allows your cardiologist to determine if an arrhythmia caused the symptom.
- Implantable loop recorder (ILR) - In patients who experience irregular heart beats less frequently, for instance, every few months, an implantable loop recorder may be recommended. Like an event recorder, this device is designed to record a patient's heart rhythm, but for a much longer period of time. About the size of a computer jump drive, it is placed under the skin in the left upper chest by making a small one-inch incision in a brief surgical procedure and can be worn for up to three years. The device has a detection setting that will automatically record the heart rhythm if the heart beats too slow or too fast. The patient may also activate the device to record and save a rhythm when the patient feels a symptom. When the battery has expired, the device is removed during a small surgical procedure.
- Transtelephonic pacemaker/internal cardioverter defibrillator (ICD) /ILR monitoring - This type of EKG monitoring requires the patient to call in the heart's activity over the telephone to Children's or to have a full interrogation of the device transmitted to a pacemaker company database. This information is provided to your cardiologist/electrophysiologist to determine if your device and/or heart rhythm is working properly. Pacemaker and ICD patients need to call on a regular basis to be determined by their cardiologist/electrophysiologist.
- Tilt table test - This test is reserved for those patients in whom the symptoms suggest syncope (fainting) from an atypical cause or if standard treatment for typical common faint syncope has failed. The test can only be performed after consultation with a pediatric electrophysiologist.
- Echocardiogram (echo) - This test is an ultrasound of the heart that provides an accurate illustration of the heart anatomy. It shows whether or not there are any defects, any enlargement of the heart chambers, and how strong or weak the heart pumps blood. The test does not hurt and takes 10 to 20 minutes to complete. If you have a small child, a light dose of sedative medication may be recommended to ensure a quality echo study is achieved.
- Signal Averaged Electrocardiogram (SAECG) - This is a specialized electrocardiogram performed with the same equipment as an electrocardiogram described above. However, this electrocardiogram requires the recording of about 500 beats in a quiet environment. The SAECG machine filters and computer analyzes these beats to identify signals that could indicate a possible significant risk for arrhythmias from the ventricles (lower chambers).
- Genetic testing - There are several labs in the United States that are capable of testing a patient's DNA to see if they have a detectable genetic problem (mutation) that could cause an arrhythmia. This test should be recommended only after a thorough evaluation by your electrophysiologist who will determine which type of testing may be helpful.
- CT scan - Also called CT or computerized tomography, this is a specialized X-ray technique that provides 3-D pictures of your body that show your internal structures in cross section rather than overlapping images that are typically produced by conventional X-ray exams. The CT scan uses an X-ray unit that rotates around your body and a powerful computer to create cross-sectional images, like slices, of the inside of your body with extreme clarity that can reveal detailed anatomy of your heart, major blood vessels and lungs. This is more commonly performed for diagnosis of genetic arrhythmias.
- MRI - This is an imaging technique that uses a powerful magnetic field and a computer to produce detailed 3-D images of the organs, soft tissues, bones and other internal body structures. MRI provides greater contrast between the different soft tissues of the body than computed tomography (CT) does, making it especially useful in cardiovascular imaging. This is more commonly performed for diagnosis of genetic arrhythmias.
- Epinephrine challenge - Used for diagnosis of genetic arrhythmias, this study is used for some patients with possible Long QT Syndrome. The test involves a one-time infusion of IV epinephrine (adrenaline) and then a constant infusion while being monitored by ECG. The tracings from the ECG are analyzed to look for specific changes in the heart's electrical activity.
Tests that require sedation and/or are associated with a low risk of complications include:
- Electrophysiology (EP) cardiac catheterization study - This is a study of the heart's rhythm system inside the heart to evaluate the electrical impulses traveling through the heart. The heart's rhythm is recorded from inside the heart by inserting small tubes called catheters that have tiny electrodes at the end. The electrical impulses are measured as they travel through the upper chambers or atria, through the middle (AV node and junctional conducting system), and then through the lower chambers (ventricles). Most EP studies performed on children are part of a catheter ablation procedure in which a small scar is created on the inside lining of the heart in an abnormal area where a fast heart rate is found. (See ablation for more details.) Some EP studies are done solely to see if an arrhythmia can be started so that a rhythm problem can be found.
- Esophageal EP study - This is a study of heart rhythm problems that primarily affect the upper chambers of the heart. The procedure is performed by sedating the patient and then placing a specially made electrode catheter through the nose or mouth into the food tube or esophagus. The esophagus lies behind and next to the left atrium and therefore heart signals can be recorded from inside the esophagus. In addition, the contractions of the upper heart chambers can be increased by connecting the tube to an artificial pacemaker for a short time so that the heart's rhythm system can be tested.
Treatment is determined after our medical team has conducted a comprehensive evaluation and diagnosis. In some cases, no treatment will be required at all. Medical treatment is usually recommended if the arrhythmia is causing the patient problems or discomfort or if it is putting your child at risk for more serious complications. Depending on the cause of your child's irregular, fast or slow heartbeat, your cardiologist may recommend one or a combination of the following treatments: medications, nonsurgical procedures, medical devices such as a pacemaker or internal cardioverter defibrillator (ICD), catheter ablation or a surgical procedure.
Many patients with arrhythmias, especially those with fast heart rates (tachycardias), can be treated with medications. While these drugs will not cure your child's arrhythmia, they can improve symptoms. Some children will need to take the medication one or more times daily, while others will only need to take the medicine when they have a higher chance of an arrhythmia or when they have an arrhythmia event. Some of these drugs can have serious side effects so it is very important to follow the medication as prescribed. In some cases, your child may be admitted to the hospital when beginning a new medication to allow your doctor to monitor any side effects.
Electrophysiologists at Children's perform several high-tech, non-surgical catheter ablation procedures to treat arrhythmias. Our success rates and low complication rates are some of the best in the world.
In this procedure, the goal is to eliminate the abnormal fast heart rate (tachycardia) by creating a very small scar about a few millimeters in diameter and thickness at the site of the abnormal area to disable the arrhythmia permanently. This can be done by either using heat (radiofrequency) or cold (cryothermal) energy.
Radiofrequency catheter ablation uses heat or radiofrequency energy to burn (cauterize) or destroy a small amount of tissue at the source of the arrhythmia. The radiofrequency current is delivered through a wire within a small plastic tube called a catheter. At the end or tip of the catheter, the radiofrequency current is applied to the inside lining of the heart muscle. Before the radiofrequency current is delivered, the catheter is guided into the heart by the cardiologist with the aid of X-ray and by a computer image. The radiofrequency current is delivered through the catheter directly onto the abnormal pathway or heart tissue in a controlled manner to limit the amount of tissue that is cauterized.
Cryoablation uses a freezing technique called cryothermy to preserve normal electrical conduction by freezing tissue or heart pathways that interfere with the normal distribution of the heart's electrical impulses.
Cryoablation offers some advantages to radiofrequency ablation. With standard radiofrequency, the energy is delivered through a catheter tip, which can move a small amount and possibly drift off of the target area. Cryoablation makes the catheter tip stick to the tissue so it will stay and deliver energy to the intended target. This allows your doctor to place lesions during the abnormal fast heartbeat. If successful, the catheter tip will not move out of position when the rhythm changes from abnormal to normal.
Another advantage of cryoablation over radiofrequency ablation is that cryothermy takes longer to become permanent. This is valuable when there is concern of possibly damaging normal areas. If this should be the case, the tissue can be rewarmed by the blood and normal function returns without permanent damage. In addition, if the technique does not appear to be affecting the arrhythmia, the process can be stopped early and another site tried without permanent effect on the heart. These advantages also allow doctors to perform ablation in more sensitive areas of the heart and on smaller patients with less risk of permanently damaging the heart's own conduction system.
Disadvantages of cryoablation include a smaller scar or lesion size compared to radiofrequency ablation, which may not be as effective in curing the arrhythmia. In addition, with radiofrequency ablation, success is usually predictable soon after starting the procedure. With cryoablation, sometimes it is difficult to predict success early on.
While almost any fast heart rhythm disorder can be treated with cryoablation, it is reserved primarily for rhythms such as atrioventricular reentry tachycardia (AVNRT) or tachycardias that have an origin or abnormal pathway close to the normal AV node or in other areas of the heart in which there is concern for possible unintended harm. Radiofrequency ablation is believed to be more effective in treating most other arrhythmia disorders.
Medical devices implanted during surgery
Some children with rhythm disorders can be managed with an artificial pacemaker implanted under the skin and/or muscle in either the upper chest or upper abdomen (near the lowest rib or breast bone). Pacemakers are most effective in treating slow heart rates such as sinus node dysfunction or AV block (heart block). New advances in pacemaker technology however, are allowing doctors to treat some fast heart rates with a pacemaker as well.
A pacemaker is a small device about 1.5 by 1.5 inches that is placed inside the body usually under the chest or abdominal skin and muscle and connected to the heart with a thin wire called a lead. The pacemaker works by sending small, painless amounts of electricity to the heart to make it beat normally.
Internal cardioverter defibrillator (ICD)
For arrhythmias in which the heart beats too rapidly (tachycardia) or quivers (fibrillates) instead of pumping strongly, an internal cardioverter defibrillator (ICD) can be surgically implanted and programmed to respond to an abnormal life-threatening arrhythmia. The ICD detects the abnormal arrhythmia and then sends electronic signals to the heart whenever the heart rate reaches a certain rate. These signals shock the heart into returning to a normal heart rhythm again.