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Arrhythmias

What is an arrhythmia?

An arrhythmia (also called dysrhythmia) is an abnormal rhythm of the heart, which can cause the heart to pump less effectively.

Arrhythmias can cause problems with contractions of the heart chambers by:

In any of these situations, the heart may not be able to pump an adequate amount of blood to the body with each beat due to the arrhythmia's effects on the heart rate. The effects on the body are often the same, whether the heartbeat is too fast, too slow, or too irregular.

What are the symptoms of arrhythmia?

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

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

Another indication of an arrhythmia is a change in the electrocardiogram (ECG or EKG) pattern. However, ECG changes are not seen unless an ECG test is performed or a child is being monitored in the hospital or other facility. Because symptoms such as those listed above may indicate the presence of an arrhythmia, an ECG is commonly done on children with one or more of the symptoms.

Anatomy of the heart, view of the electrical system

The heart's electrical system:

The heart is, in the simplest terms, a pump made up of muscle tissue. Like all pumps, the heart requires a source of energy in order to function. The heart's pumping action comes from an intrinsic electrical conduction system.

How does the heart beat?

An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node), which is a small mass of specialized tissue located in the right atrium (right upper chamber of the heart). The sinus node generates an electrical stimulus regularly (60-190 times per minute, depending on the age of the child and his/her activity level). This electrical stimulus travels down through the conduction pathways (similar to the way electricity flows through power lines from the power plant to your house) and causes the heart's lower chambers to contract and pump out blood. The right and left atria (the two upper chambers of the heart) are stimulated first and contract a short period of time before the right and left ventricles (the two lower chambers of the heart). The electrical impulses travel from the sinus node to the atrioventricular (AV) node, where impulses are slowed down briefly, then continue down the conduction pathway via the bundle of His into the ventricles. The bundle of His divides into right and left pathways to provide electrical stimulation to both ventricles.

Normally, as the electrical impulse moves through the heart, the heart contracts about 60 to 100 times a minute. 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.

Under some conditions, almost all heart tissue is capable of starting a heartbeat, or becoming the "pacemaker," just like the sinus node. An arrhythmia (abnormal heartbeat) may occur when:

What is an electrocardiogram (ECG)?

The electrical activity of the heart is measured by an electrocardiogram (ECG or EKG). By placing electrodes at specific locations on the body (chest, arms, and legs), a graphic representation, or tracing, of the electrical activity can be obtained. Changes in an ECG from the normal tracing can indicate arrhythmias, as well as other heart-related conditions.

What does an ECG mean?

Almost everyone knows what a basic ECG tracing looks like. But what does it mean?

Illustration of a basic EKG tracing

When your child's physician studies your child's ECG, he/she looks at the size and length of each part of the EKG. Variations in size and length of the different parts of the tracing may be significant.

The tracing for each lead of a 12-lead ECG will look different, but will have the same basic components as described above. Each lead of the 12-lead ECG is "looking" at a specific part of the heart from different angles. Variations in a lead may indicate a problem with the part of the heart associated with that particular lead.

What are the different types of arrhythmias?

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

A ventricular arrhythmia is an arrhythmia caused by abnormal function of the sinus node, an interruption in the electrical conduction pathways, or the development of another area within the heart tissue that takes over the function of the sinus node.

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:

Atrial Arrhythmias

Ventricular Arrhythmias

sinus arrhythmia  -  a condition in which the heart rate varies with breathing. Sinus arrhythmia is commonly found in children; adults may often have it as well. This is usually a benign condition - there may be no symptoms or problems associated with sinus arrhythmias.

premature ventricular contractions (PVCs)  -  a condition in which an electrical signal originates in the ventricles and causes the ventricles to contract before receiving the electrical signal from the atria. PVCs are not uncommon and often do not cause symptoms or problems. However, if the frequency of the PVCs increases to several per minute, symptoms such as weakness, fatigue, dizziness, fainting, or palpitations may be experienced.

sinus tachycardia  -  a condition in which the heart rate is faster than normal for the child's age because the sinus node is sending out electrical impulses at a rate faster than usual. This condition may cause symptoms such as weakness, fatigue, dizziness, or palpitations if the heart rate becomes too fast to pump an adequate supply of blood to the body. Sinus tachycardia is often temporary, occurring when the body is under stress from exercise, strong emotions, fever, or dehydration, to name a few causes. Once the stress is removed, the heart rate will usually return to its usual rate.

ventricular tachycardia (VT)  -  A condition in which an electrical signal is sent from the ventricles at a very fast but often regular rate. If the heart rate is sustained at a high rate, symptoms such as weakness, fatigue, dizziness, fainting, or palpitations may be experienced. A person in VT may require an electric shock to "convert" the rhythm to a regular one.

sick sinus syndrome  -  A condition in which the sinus node sends out electrical signals either too slowly or too fast. There may be alternation between too-fast and too-slow rates. This condition may cause symptoms if the rate becomes too slow or too fast for the body to tolerate.

ventricular fibrillation (VF)  -  A condition in which many electrical signals are sent from the ventricles at a very fast and erratic rate. As a result, the ventricles are unable to fill with blood and pump. This rhythm is life-threatening because there is no pulse and complete loss of consciousness. A person in VF requires prompt defibrillation to restore the normal rhythm and function of the heart. It may cause sudden cardiac death.

premature supraventricular contractions or premature atrial contractions (PAC)  -  A condition in which an atrial pacemaker site above the ventricles sends out an electrical signal early. The ventricles are usually able to respond to this signal, but the result is an irregular heart rhythm. PACs are common and may occur as the result of stimulants such as coffee, tea, alcohol, cigarettes, or medications.

supraventricular tachycardia (SVT), paroxysmal atrial tachycardia (PAT)  -  A condition in which the heart rate speeds up due to a series of early beats from an atrial or junctional pacemaker site above the ventricles. PAT usually begins and ends rapidly, occurring in repeated periods. This condition can cause symptoms such as weakness, fatigue, dizziness, fainting, or palpitations if the heart rate becomes too fast.

atrial flutter  -  A condition in which the electrical signals come from the atria at a fast but even rate, often causing the ventricles to contract faster and increase the heart rate. When the signals from the atria are coming at a faster rate than the ventricles can respond to, the ECG pattern develops a signature "sawtooth" pattern, showing two or more flutter waves between each QRS complex. The number of waves between each QRS complex is expressed as a ratio, i.e., a two-to-one atrial flutter means that two waves are occurring between each QRS.

atrial fibrillation  -  A condition in which the electrical signals come from the atria at a very fast and erratic rate. The ventricles contract in an irregular manner because of the erratic signals coming from the atria.

The symptoms of various arrhythmias may resemble other medical conditions or heart problems. Always consult your child's physician 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:

Treatment for arrhythmias:

Specific treatment for arrhythmias will be determined by your child's physician based on:

Arrhythmias may be present but cause few, if any, problems. In this case, your child's physician may elect not to treat the arrhythmia. However, when the arrhythmia causes symptoms, there are several different options for treatment. Your child's physician will choose an arrhythmia treatment based on the type of arrhythmia, the severity of symptoms being experienced, and the presence of other conditions (i.e., diabetes, kidney failure, heart failure) which can affect the course of the treatment.

Treatments may include:

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