Arrhythmias in Children
Basics of Arrhythmias
An arrhythmia (or “dysrhythmia”) is an abnormal heart rhythm that can cause the heart to pump less effectively.
Arrhythmias can cause problems with contractions of the heart chambers by:
- Not allowing the ventricles (lower chambers) to fill with an adequate amount of blood, due to an abnormal electrical signal causing the heart to pump too fast.
- Not allowing a sufficient amount of blood to be pumped out to the body, due to an abnormal electrical signal causing the heart to pump too slowly or too irregularly.
In either situation, the heart may not be able to pump an adequate amount of blood to the body with each beat.
Causes of Arrhythmias
To understand arrhythmias, it helps to gain a basic understanding of the heart’s internal electrical system, which controls the rate and rhythm of the heartbeat.
With each heartbeat, an electrical signal spreads from the top of the heart to the bottom, causing the heart to contract and pump blood. Each electrical signal begins in a group of cells known as the sinus node (or “sinoatrial node” or “SA node”), located in the right upper chamber of the heart (right atrium). The sinus node generates an electrical stimulus at the rate of 60 to 190 times per minute, depending on a child’s age and activity level. To visualize how the electrical stimulus travels through the heart, imagine how electricity flows through power lines from a power plant to a house.
As the electrical impulse moves through the heart, the heart contracts about 60 to 140 times a minute during a period of rest, depending on a child's age. Each contraction of the ventricles represents one heartbeat. The atria contract a fraction of a second before the ventricles, so their blood empties into the ventricles before the ventricles contract.
An arrhythmia (abnormal heartbeat) may occur when:
- The heart's natural pacemaker (the sinus node) develops an abnormal rate or rhythm
- The normal conduction pathway is interrupted
- Another part of the heart takes over the sinus node’s role as pacemaker
Symptoms of Arrhythmia
Each child may experience symptoms of arrhythmia differently, but the most common symptoms include:
- Low blood pressure
- Difficulty feeding
Because symptoms of arrhythmias may resemble other medical conditions or heart problems, it’s important to consult with a child’s physician for a diagnosis.
Health Problems Associated with Arrhythmias
Some children are born with heart defects that cause arrhythmias, while others develop arrhythmias later in childhood. Some arrhythmias are severe and require treatment, including medicines, defibrillation (electric shock), surgically implanted devices that control the heartbeat and other procedures that fix abnormal signals in the heart.
Tests, Procedures and Diagnosis of Arrhythmias
To diagnose an arrhythmia, a child’s physician will obtain a complete medical history, perform a physical examination and order diagnostic testing, which may include:
- Electrocardiogram (ECG or EKG). This diagnostic test measures the heart’s electrical activity. By placing electrodes at specific locations on the body (chest, arms and legs), a picture (or “tracing”) of the electrical activity can be obtained as the electrical activity is received and interpreted by an ECG machine. An ECG can indicate the presence of arrhythmias or other types of heart conditions. Two common variations of the ECG test are:
- Resting ECG. For this procedure, the clothing on the upper body is removed and small, sticky patches called electrodes are attached to the chest, arms and legs. These electrodes are connected to the ECG machine by wires. The ECG machine is then started and records the heart's electrical activity for a minute or so as the child lies down.
- Exercise ECG, or stress test. Electrodes are attached to the child as in a resting ECG. But rather than lying down, the child exercises by walking on a treadmill or pedaling a stationary bicycle while the ECG is recorded. This test assesses changes in the ECG during exercise.
- Holter monitor. This ECG recording is done over a period of 24 or more hours. Three electrodes are attached to the child's chest and connected to a small, portable ECG recorder by lead wires. The child goes about most of his or her usual daily activities (except showering, swimming, or exercise that breaks a heavy sweat) during this procedure. A physician may prescribe Holter monitoring when an arrhythmia is suspected but not seen on a resting ECG. Arrhythmias may be brief and not seen during a resting ECG’s shorter recording time.
- Electrophysiologic study (EPS). During this invasive test, a small, thin tube (catheter) is inserted in a large blood vessel in the leg or arm and guided into the heart. The procedure makes it possible for physicians to find the arrhythmia’s origin, a first step in determining how best to treat it. During another type of EPS called an esophageal electrophysiologic study, a soft, thin flexible plastic tube is inserted in the nostril and placed in the esophagus (close to the atria) to provide a more precise ECG recording.
- Tilt table test. This test is recommended for children who have frequent fainting (“syncope”) episodes. The test displays how the heart rate and blood pressure respond to a change in position — from lying down to standing up.
Treatment for Arrhythmias
Many arrhythmias go away on their own and require only occasional checkups or a short course of medications. Others can be persistent, requiring long-term medications or catheter-based procedures.
- Catheter Ablation. Catheter ablation is one common treatment for arrhythmia. During this procedure, a physician inserts a catheter (thin, flexible tube) into the heart. A special machine delivers heat (radiofrequency ablation) or cold (cryothermal ablation) energy through the catheter to tiny areas of the heart muscle that are causing the abnormal heart rhythm. This energy destroys (or “ablates”) the small section of heart tissue causing the abnormal rhythm.
- Pacemakers. Bradycardia, or slow heart rate, can be normal in older children and athletes. But when an abnormally slow heart rate is due to injury to the heart’s conduction system, pacemakers can be used to restore a healthy rhythm. (Though it’s important to note a pacemaker cannot repair or restore the heart’s normal conduction system.) Occasionally, special multi-lead pacemakers can assist heart function in children with congestive heart failure (CHF). This type of pacing is known as cardiac resynchronization therapy (CRT) or biventricular pacing.
- Internal Cardiac Defibrillator. In rare instances when a child has an unstable or life-threatening heart rhythm abnormality or is at high risk for developing one, a special pacemaker, called an internal cardiac defibrillator (ICD), can be implanted. The ICD can shock the heart out of a dangerous rhythm. Children requiring an ICD often suffer from congestive heart failure, ventricular tachycardia or significant impairment of heart function due to congenital heart disease. ICDs can also save the lives of children with inherited or genetic disorders that put them at risk for life-threatening arrhythmias, such as long QT syndrome, Brugada syndrome, arrhythmogenic RV dysplasia (ARVD) and hypertrophic cardiomyopathy (HCM).