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Arrhythmias_KH_Teen

Arrhythmias

What Are Arrhythmias?

Arrhythmias (also called disrhythmias) are abnormal heartbeats usually caused by an electrical "short circuit" in the heart. The heart normally beats in a consistent pattern, but an arrhythmia can cause it to beat too slowly, too quickly, or irregularly. This can cause the heart to pump inconsistently, which can lead to symptoms like fatigue, dizziness, and chest pain.

What Causes Them?

Your heart has its own electrical system that sends electrical signals around the heart, telling it when to contract and pump blood around the body. The electrical signals start in a group of cells, called the sinus node, located in the right atrium. The sinus node is the heart's pacemaker and makes sure the heart beats at a normal and consistent rate. The sinus node normally increases your heart rate in response to exercise, emotions, and hormones, and slows your heart rate during sleep.

But sometimes the electrical signals flowing through the heart don't "communicate" well with the heart muscle, and the heart can start beating in an abnormal pattern, or arrhythmia.

Arrhythmias can either be temporary or permanent and they can be caused by several things — but they can also happen for no apparent reason. Arrhythmias can be congenital, meaning a person is born with the condition.

Other causes of arrhythmias include chemical imbalances in the blood, infections or other diseases that cause irritation or inflammation of the heart, medications (prescription or over-the-counter), and injuries to the heart from chest trauma or heart surgery. Other factors like illegal drugs, alcohol, tobacco, caffeine, stress, and some herbal remedies can also cause arrhythmias.

Signs and Symptoms

Because arrhythmias can cause the heart to beat less effectively, blood flow to the brain and to the rest of the body can be interrupted. If the heart is beating too fast, the heart's chambers can't fill with the right amount of blood. If it's beating too slowly or irregularly, the right amount of blood can't be pumped out to the body.

Because the body isn't getting the supply of blood it needs to run smoothly, these symptoms can occur:

  • dizziness
  • fatigue
  • lightheadedness
  • weakness
  • palpitations (a feeling of fluttering or pounding in the chest)
  • shortness of breath
  • chest pain
  • fainting

Arrhythmias can be consistent, or they can come and go at random. Sometimes arrhythmias can cause no symptoms at all — in these cases, the arrhythmia can only be discovered during a physical exam or a heart function test, like an electrocardiogram (ECG/EKG).

What's a Normal Heart Rate?

Heart rate is measured by counting the number of beats per minute. Normal heart rate can be different for each person, depending on factors like age and whether the person leads an active lifestyle or not (for example, trained athletes who play competitive sports often have a low resting heart rate).

The normal range for resting heart rate decreases as a person gets older. An infant's normal resting heart rate from age 0-3 months is usually between 100 to 150 beats per minute. A child between the ages of 1-3 years normally has a resting heart rate of 70 to 110 beats per minute, and when someone reaches 12 years of age, the normal resting heart rate is between 55 to 85 beats per minute.

An abnormally fast heart rate is call tachycardia. An abnormally slow rate is called bradycardia. Your doctor can determine whether or not your heart rate is abnormally fast or slow, since the significance of an abnormal heart rate depends on the situation. For example, a teen or adult with bradycardia might begin to show symptoms when the heart rate drops below 50 beats per minute. However, keep in mind that trained athletes have a lower resting heart rate — so bradycardia in these people isn't considered abnormal if no symptoms are associated with it.

Types of Arrhythmias

There are several types of arrhythmias, including:

Premature Atrial Contraction (PAC) and Premature Ventricular Contraction (PVC)

Premature contractions are usually considered minor arrhythmias, in which the person may feel a fluttering or pounding in the chest caused by an early or extra beat. PACs and PVCs are very common, and are what happens when it feels like your heart "skips" a beat. It doesn't skip a beat — an extra beat actually comes sooner than normal. Occasional premature beats are common and considered normal, but in some cases they can indicate an underlying medical problem or heart condition.

Tachycardias

Tachycardias are arrhythmias that involve abnormally rapid heartbeat. They fall into two major categories — supraventricular and ventricular:

  • Supraventricular tachycardia (SVT). Supraventricular tachycardia (SVT) is the most common significant arrhythmia. It's characterized by bursts of fast heartbeats that originate in the atria (upper chambers of the heart) or the heart cells that carry electrical signals from the atria to the ventricles (lower chambers of the heart). The bursts can happen suddenly, and episodes can last anywhere from a few seconds to several days. Specific treatment is usually recommended if incidents of SVT are long-lasting or happen often.
  • Wolff-Parkinson-White (WPW) syndrome. Wolff-Parkinson-White (WPW) syndrome, a type of SVT, can run in families and is characterized by an extra electrical conduction path that connects the upper and lower chambers of the heart. The presence of this extra pathway can cause the heart to become flooded with electrical impulses, speeding up the heart rate.
  • Ventricular tachycardia. Ventricular tachycardia is a serious but relatively uncommon condition. It originates in the lower chambers of the heart and is usually a sign of serious underlying heart disease.

Bradycardias

The following are examples of bradycardias — arrhythmias characterized by abnormally slow heartbeat:

  • Sick sinus syndrome. Sick sinus syndrome happens when the heart's sinus node or another part of the heart's electrical conduction system isn't working correctly. This most commonly occurs following surgery to correct a congenital heart defect. Abnormally slow heartbeat is typically seen in this condition; however, episodes of rapid heartbeat due to SVT can also occur.
  • Heart block. Heart block is often caused by a congenital heart defect, although it can also be result from disease or injury. Heart block happens when electrical impulses can't make their way from the upper to lower chambers of the heart. When this happens, another node in the lower chambers takes over and acts as the heart's pacemaker. Although it sends out electrical impulses to keep the heart beating, the transmission of the signals is much slower, leading to a slower heart rate.

How Are Arrhythmias Diagnosed?

Arrhythmias can be diagnosed in several ways. The doctor will use a person's medical history information, along with a physical examination, to begin the evaluation. If an arrhythmia is suspected, the doctor will probably recommend an electrocardiogram (ECG or EKG), which measures the heart's electrical activity.

There's nothing painful about an ECG/EKG — it's just a procedure where a series of electrodes (small metal tabs) are attached to the skin with sticky papers, and the information obtained about the electrical activity of a person's heart is transferred to a computer where it's then interpreted and drawn as a graph.

A doctor might recommend the following types of ECG/EKG tests:

  • Resting ECG/EKG. This measures resting heart rate and rhythm, and lasts about a minute.
  • Exercise ECG/EKG (also called a stress test). This measures heart rate and rhythm while a person exercises (like riding a stationary bicycle or walking on a treadmill).
  • Signal-average EKG. This measures heart rate much like a resting ECG/EKG. The only difference is the signal-average EKG monitors a heartbeat over a longer time period (around 15 to 20 minutes).
  • Holter monitor. This is an ECG/EKG done over a very long period of time, usually 24 hours or more. The electrodes are connected to a person's chest, and the wires are attached to a portable ECG/EKG recorder. The person is encouraged to continue normal daily activities, but must be careful to not get the electrodes wet (for example, no swimming, showering, or activities that cause a lot of sweating). There are two kinds of Holter monitoring — continuous recording, which means the ECG/EKG is on throughout the entire monitoring period; and event monitoring, which means data is recorded only when the person feels symptoms and then turns the Holter monitor on.

How Are Arrhythmias Treated?

Someone may have an arrhythmia but may feel no symptoms at all. Many arrhythmias don't require treatment; however, some can pose a health problem and need to be evaluated and treated by a doctor.

Depending on the type and severity of the arrhythmia, one of the following options might be recommended by a doctor:

  • Medications. Many types of prescription anti-arrhythmic medications are available to treat arrhythmia. A doctor will determine which is best by considering the type of arrhythmia, possible underlying medical causes, and any medications you are taking. Sometimes, anti-arrhythmic medications can increase symptoms and cause unwanted side effects, so their use and effectiveness should be closely monitored by a doctor, your parent, and you.
  • Pacemakers. A pacemaker is a small, battery-operated device implanted into the body (near the collarbone) through a surgical procedure. Connected to the heart by a wire, pacemakers can help treat bradycardia. Through a sensing device, a pacemaker can detect if a person's heart rate is too slow and sends electrical signals to the heart to speed up the heartbeat.
  • Defibrillators. Like a pacemaker, a defibrillator can deliver electrical impulses to the heart. A small battery-operated implantable cardioverter defibrillator (ICD) can be implanted into the body (near the left collarbone) through a surgical procedure. Wires run from the defibrillator to the heart. It can sense if the heart had developed a dangerously fast or irregular rhythm, and deliver an electrical shock to restore a normal heartbeat.
  • Catheter ablation. "Ablation" literally means removal or elimination. In the case of catheter ablation, a catheter (a long, thin tube) is guided through a vein in the arm or leg and inserted into the heart for the purpose of eliminating the heart muscle cells that are triggering the arrhythmia. Once the problem area of the heart is pinpointed, the catheter sends waves of high-frequency radio waves into the muscle cells and destroys them.
  • Surgery. Surgery is usually the treatment recommended only if all other options have failed. In this case, a person is put under anesthesia, the chest is opened, and the heart is exposed. Then, the tissue causing the arrhythmia is removed.

When to Call the Doctor

Although many arrhythmias are minor and don't represent a significant threat to a person's health, some can indicate a more serious health problem. If you've been having any symptoms, talk to your parent or call your doctor.

Reviewed by: Steven Dowshen, MD
Date reviewed: November 2009


Related Sites

National Heart, Lung, and Blood Institute (NHLBI)
American Heart Association
National Institutes of Health (NIH)

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