Pediatric Arrhythmia

What are the symptoms of arrhythmia?

The following are the most common symptoms of arrhythmias. However, each child may experience symptoms differently. Symptoms may include:

• Weakness
• Fatigue
• Heart palpitations
• Low blood pressure
• Dizziness
• Fainting
• Difficulty feeding

The symptoms of arrhythmias may resemble other medical conditions or heart problems. Always consult your child's doctor for a diagnosis.

The heart's electrical system

The heart is, in the simplest terms, a pump made up of muscle tissue. The heart's pumping action is regulated by an electrical conduction system that coordinates the contraction of the various chambers of the heart.

How does the heart's electrical system work?

The electrical system in the heart consists of nodes that generate electrical signals that travel down through conduction pathways in the heart muscle similar to the way electricity flows through power lines from the power plant to your house.

• First, an electrical stimulus is generated in a specialized part of the heart muscle called the sinus node (also called the sinoatrial node, or SA node). This is a small mass of specialized tissue located in the right atrium (right upper chamber of the heart). The sinus node generates a regular electrical stimulus, 60 to190 times per minute, depending on the age of the child and his or her activity level.
• The electrical impulse travels from the sinus node to the atrioventricular node (also called AV node) located between the atria and the ventricles.
• In the AV node, the impulses are slowed down for a very short period, allowing the atria to contract a fraction of a second before the ventricles.
• The blood from the atria empties into the ventricle.
• The electrical current then continues down the conduction pathway via the bundle of His and into the ventricles.
• The bundle of His divides into right and left pathways to provide electrical stimulation to the right and left ventricles.
• The ventricles then contract and pump out blood to the body.

Under some abnormal conditions, certain heart tissue is capable of starting a heartbeat, or becoming the "pacemaker," just like the sinus node. 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 as pacemaker.

What are the different types of arrhythmias?

An atrial arrhythmia is an arrhythmia caused by abnormal function of the sinus node or the atrioventricular node, or by the development of another atrial pacemaker within the atrium that takes over the function of the sinus node.

A ventricular arrhythmia is an arrhythmia caused by an abnormal electrical focus within the ventricles, resulting in abnormal conduction of electrical signals within the ventricles. The sinus node and atrioventricular node may function normally.

Arrhythmias can also be classified as slow (bradyarrhythmia) or fast (tachyarrhythmia). "Brady-" means slow, while "tachy-" means fast.

Listed below are some of the more common arrhythmias:

The symptoms of various arrhythmias may resemble other medical conditions or heart problems. Always consult your child's doctor for a diagnosis.

How are arrhythmias diagnosed?

In addition to a complete medical history and physical examination of your child, there are several different types of procedures that may be used to diagnose arrhythmias. Some of these procedures include the following:

• Electrocardiogram (ECG or EKG). An electrocardiogram is a measurement of the electrical activity of the heart. 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. There are several variations of the ECG test, including the following:
• 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. The child is lying down during this ECG.
• Exercise ECG, or stress test. The child is attached to the ECG machine as described above. However, rather than lying down, the child exercises by walking on a treadmill or pedaling a stationary bicycle while the ECG is recorded. This test is done to assess changes in the ECG during stress such as exercise.
• Holter monitor. An ECG recording 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 his or her usual daily activities (except for activities such as taking a shower, swimming, or any activity causing an excessive amount of sweating which would cause the electrodes to become loose or fall off) during this procedure. There are two types of Holter monitoring, including the following:
  • Continuous recording
  • The ECG is recorded continuously during the entire testing period.
  • Event monitor, or loop recording
  • The ECG is recorded only when the patient starts the recording when symptoms are felt or when an abnormal rhythm is detected.
    
• Holter monitoring may be done when an arrhythmia is suspected but not seen on a resting ECG. Arrhythmias may be short-lived in nature and not seen during the shorter recording times of the resting ECG.
• Electrophysiologic study (EPS). An invasive test in which a small, thin tube (catheter) is inserted in a large blood vessel in the leg or arm and advanced to the heart. This gives the doctor the capability of finding the site of the arrhythmia's origin within the heart tissue, thus determining how to best treat it. Another procedure called an esophageal electrophysiologic study may be ordered where 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. A test 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--lying down to standing up. During this test, medication may be given intravenously to help prevent a fainting episode once the cause has been identified by the doctor.