Arrhythmia
Signs and Symptoms
An abnormal heart rhythm is a change in the speed or pattern of the heartbeat — the heart may beat too slowly, too rapidly or irregularly. When the heart beats too slowly, too little blood is pumped out to the rest of the body. When the heart beats too quickly, it cannot fill completely with blood so the body doesn't receive the blood volume it needs to function properly. Slow heart rates are called bradycardias. Fast heart rates are called tachycardias.
The "normal" number of heartbeats varies with age. The heart beats about 140 times a minute in a newborn, compared to 70 times a minute in an older child at rest. The "normal" heart rhythm also is not constant. See more information about the heart's electrical system.
A heart that beats too fast or too slow can cause:
Children may not know how to describe what they're feeling. They may have trouble keeping up with other children or realize they are having "spells" and want to sit down and rest during a period of arrhythmia. Sometimes, there are no symptoms at all.
Left untreated, certain abnormal heart rhythms can be very dangerous and in some cases even fatal. On the other hand, some arrhythmias are common and not associated with any health problems, so-called benign arrhythmias. Many children go through life with mild arrhythmia that should be monitored but doesn't require treatment. One of the goals of evaluation is to sort out the serious from the benign forms of heart beat disturbances.
Conditions associated with a rapid heart beat or tachycardia include:
Supraventricular Tachycardia — The most common abnormal tachycardia in children, supraventricular tachycardia is when an extra electrical pathway located in the heart triggers a fast heartbeat.
Wolfe-Parkinson White Syndrome — An accessory pathway or atrial-ventricular nodal tachycardia.
Junctional Tachycardia — This is a fast heart rate that originates within or near the junction of the heart's electrical system between the upper and lower chambers.
Atrial Fibrillation — This is an irregular heartbeat that may be fast. This rhythm originates in the heart's upper chambers.
Ventricular Tachycardia — This is a fast heart rate that originates in the lower chambers of the heart.
Long QT Syndrome — This is a set of symptoms associated with a prolonged interval between certain markers on an EKG exam. QT is a measurement of the electrical recording of the heart. The symptoms are typically fainting, dizziness or even heart arrest, which may be brought on by emotional or physical stress. This condition can be fatal and appears to be genetic in origin.
Conditions associated with a slow heartbeat or bradycardia include:
Heart Block — This condition occurs when electrical signals can't pass normally between the upper and lower chambers. The heart often has a "back-up" system for pumping blood when this occurs, but it works at a slower rate that may not be adequate.
Sinus Node Dysfunction — This syndrome can occur when the sinus node — the heart's built-in pacemaker — doesn't work properly.
A child may have both tachycardia and bradycardia. In addition, there are post-operative arrhythmias that sometimes occur when surgery to repair a heart defect inadvertently damages the heart's electrical system, causing tachycardias or bradycardias.
Diagnosis
You child's pediatrician may hear an abnormal heart beat while using a stethoscope during an exam. Bradycardias — or slow heartbeats due to heart block or sinus node dysfunction — can be continuous and may be detected during such an exam. But tachycardias — or fast heartbeats — often occur spontaneously with unpredictable timing and require more specialized tests.
If your doctor suspects that your child has an arrhythmia or irregular heart rhythm, he or she will order one or more of the following tests to determine the source of the symptoms.
Electrocardiogram (ECG or EKG) — The electrocardiogram records the heart's electrical activity. Small patches called electrodes are placed on your child's chest, arms and legs and are connected by wires to the ECG machine. The electrical impulses of your child's heart are translated into a graph or chart, enabling doctors to determine the pattern of electrical current flow in the heart and to diagnose arrhythmias.
Holter Monitor — A Holter monitor is a small, portable machine that your child wears for 24 hours. It is about the size of a portable tape deck. This provides a continuous 24-hour record of your child's heartbeat. You will be asked to keep a diary of your child's activities and symptoms. This monitor may detect arrhythmias that might not show up on a resting ECG that only records for a few seconds.
Event Monitor — This is a small monitor about the size of a pager that your child can have for up to a month. Since the arrhythmia may occur at unpredictable times, this will help to record the abnormal rhythm when your child is experiencing symptoms. He or she can just push a button on the pager and record the heartbeat. The recording can than be transmitted by phone to the doctor.
Exercise Stress Test — The exercise stress or treadmill test records the electrical activity of your child's heart during exercise, which differs from the heart's electrical activity at rest.
Electrophysiology Study — In an electrophysiology (EP) study, doctors insert special electrode catheters — long, flexible wires — into veins and guide them into the heart. These catheters sense electrical impulses and also may be used to stimulate different areas of the heart. Doctors then can locate the sites that are causing serious arrhythmias. The EP study allows doctors to examine an arrhythmia under controlled conditions; and acquire more accurate, detailed information than with any other diagnostic test. In many cases, doctors can provide treatment, such as catheter ablation, during the same session as the EP study.
Tilt Table Test — Tilt table testing is used to diagnose fainting or black-out spells by trying to reproduce these episodes. Your child will be placed on a special table and then tilted to an angle of about 70 degrees while recording your child's heart rhythm and blood pressure.
Treatment
The treatment prescribed for your child will depend on the type and severity of your child's arrhythmia or irregular heart rhythm and the results of tests including an electrophysiology study. You and your doctor will decide which treatment is right for your child. The following are treatments that may be considered.
Medications
Certain anti-arrhythmic drugs change the electrical signals in the heart and help prevent heart abnormalities from causing irregular or rapid heart rhythms.
Follow-up Study
To make sure the medication is working properly after two or more days in the hospital, your child may return to the Electrophysiology Laboratory for a follow-up study. Our goal is to find the drug that works best for your child. On occasion, we will admit a child to the hospital and monitor the heart rhythm when administering a new medication. More frequently, patients begin taking medication without hospitalization.
Radiofrequency Catheter Ablation
Radiofrequency catheter ablation (RFA) is a technique to treat arrhythmia that was pioneered at UCSF Medical Center. It disrupts part of the electrical pathway causing irregular heart rhythms, providing relief for patients who may not respond well to medications, who prefer not to take medications or who can't take medications.
The procedure involves threading a tiny metal-tipped catheter through a vein or artery in the leg and into the heart. Using fluoroscopy or X-ray, doctors guide the catheter through a blood vessel to the heart. Additional catheters, inserted through the vein in the leg and the neck, contain electrical sensors to find the area causing the arrhythmia. This is called mapping.
The metal-tipped catheter is maneuvered to each site in the heart that causes the irregular heartbeat. Radiofrequency waves or current is sent through the tip of the catheter, cauterizing or burning cells to destroy the extra electrical pathways that cause abnormal heart rhythms. In most cases, patients leave the hospital within 24 hours or the same day.
RFA has been proven very effective in treating children with arrhythmias. Your doctor will discuss this treatment and others with you to decide the best option for you or your child. For conditions like Wolff-Parkinson-White syndrome, in which a hair-thin strand of tissue creates an extra electrical pathway between the upper and lower chambers of the heart, RFA ablation offers a cure. It has become the treatment of choice for patients with that disorder.
Cryoablation
Cryoablation, sometimes referred to as cryo, is similar to radiofrequency catheter ablation (RFA) in that it is a procedure that disrupts the abnormal electrical pathway in the heart. This newer technology has been used in the Electrophysiology Laboratory at UCSF Children's Hospital since March 2004.
Instead of burning cells, however, cryoablation destroys cells by freezing them and has been very effective in treating children with arrhythmias. Your doctor will discuss this treatment and others with you to decide which method is the best option.
Like RFA, cryoablation involves threading a tiny metal-tipped catheter through a vein or artery in the leg and into the heart. Doctors guide the catheter through the blood vessel to the heart by using fluoroscopy or X-ray.
Additional catheters, inserted through the vein in the leg and the neck, contain electrical sensors to help "map" or find the area causing the arrhythmia. The metal-tipped catheter is maneuvered to areas in the heart that cause the irregular heart rhythm. Then, cryoablation freezes the cells or extra electrical pathways that cause abnormal heart rhythms. In most cases, patients leave the hospital within 24 hours or the same day.
Pacemaker
Implantable devices or pacemakers work on "demand" to treat slow heart rhythms. These small devices are implanted beneath the skin, below the collarbone or in the abdomen. They're and connected to a pacing wire positioned inside the heart via a vein or outside the heart. The pacemaker delivers a small electrical impulse to stimulate the heart when it beats too slowly, generating a regular heart rhythm.
Implantable Cardioverter-Defibrillator
This is a device for children who are prone to life-threatening rapid heart rhythms. It is slightly larger than a pacemaker and usually implanted under the skin below the collarbone. It is connected to a pacing wire inside the heart via a vein. It can deliver an electric shock to the heart when it determines the heart rate is too fast. It also can pace or stimulate the heart when it beats too slowly.
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