Arrhythmia (Abnormal Heartbeat)

What Is an Arrhythmia?

An  is an abnormal heartbeat. The heart normally beats in a regular rhythm, but an arrhythmia (ay-RITH-mee-uh) can make it beat too slowly, too quickly, or irregularly. This erratic pumping can lead to a variety of symptoms, including tiredness, dizziness, and chest pain.

Many arrhythmias don't need medical care, but some can pose a health problem and need to be checked and treated by a doctor.

What Causes Arrhythmias?

A unique electrical conduction system in the heart causes it to beat in its regular rhythm.

The conduction system of the heart is similar to the wiring of a light switch to a light:

1. The signal for the heart to beat comes from a place in the heart called the sinus node ("the light switch"). The sinus node controls how quickly or slowly the heart beats. The sinus node normally speeds up the heart rate in response to things like exercise, emotions, and stress, and slows the heart rate during sleep.
2. The signal then travels from the sinus node down the “wires” to a resistor that helps control the signal, called the AV node. From there, the signal travels through the heart ("the light") to tell it to pump.
   

But sometimes the electrical signals are abnormal, and the heart can start beating in a different rhythm — this is an arrhythmia (also called dysrhythmia).

Arrhythmias also can be due to chemical imbalances in the blood; infections; diseases that irritate the heart; medicines (prescription, over-the-counter, and some herbal remedies); injuries to the heart from chest trauma or heart surgery; use of illegal drugs, alcohol, or tobacco; caffeine; and stress.

Arrhythmias can be temporary or permanent. An arrhythmia can be congenital (meaning a baby is born with it) or can develop throughout life.

What Are the Signs & Symptoms of an Arrhythmia?

Arrhythmias make the heart beat less effectively, interrupting blood flow to the brain and the rest of the body. When the heart beats too fast, its chambers can't fill with enough blood. When it beats too slowly or irregularly, it can't pump enough blood out to the body.

If the body doesn't get the supply of blood it needs to run smoothly, a person might feel:

• dizzy and even faint
• tired
• lightheaded
• weak
• fluttering or pounding in the chest (palpitations)
• short of breath
• chest pain

Arrhythmias can be constant, but most come and go at random. Some cause no noticeable symptoms at all. In these cases, the arrhythmia is only found during a physical exam or a heart function test.

What's a Normal Heart Rate?

Heart rate is measured by counting the number of beats per minute. Someone's normal heart rate depends on things like the person's age and whether they lead an active lifestyle. 

The resting heart rate decreases as kids get older. Typical normal resting heart rate ranges are:

• babies (birth to 3 months of age): 100–150 beats per minute
• kids 1–3 years old: 70–110 beats per minute
• kids by age 12: 55–85 beats per minute

A doctor can determine whether a heart rate is abnormally fast or slow, depending on a person's situation. An older child or adult with a slow heart rate, for example, might have symptoms when the heart rate drops below 50 beats per minute. But trained athletes have a lower resting heart rate, so a slow heart rate in them isn't considered abnormal if it causes no symptoms.

What Are the Types of Arrhythmias?

There are many types of arrhythmias, including:

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

Premature contractions are usually considered minor arrhythmias. 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. In this case, the heart doesn't skip a beat — an extra beat comes sooner than normal. Occasional premature beats are common and considered normal, but sometimes they can be a sign of an underlying medical problem or heart condition.

Tachycardias

A tachycardia is an abnormally fast heartbeat. Tachycardias fall into two main categories — supraventricular and ventricular:

• Supraventricular tachycardia (SVT) is characterized by bursts of fast heartbeats that start in the upper chambers of the heart, closer to the sinus node. These can happen suddenly and last anywhere from a few seconds to several days. Treatment is usually recommended if SVTs are long-lasting or happen often.
• Ventricular tachycardia is a serious but uncommon condition that starts in the lower chambers of the heart and can be dangerous.

Bradycardias

A bradycardia is an abnormally slow heartbeat. Bradycardias can be due to:

• Sinus node dysfunction, when the heart's sinus node isn't working correctly, usually after surgery to correct a congenital heart defect.
• Heart block, when electrical impulses can't make their way from the upper to lower chambers of the heart. It's often caused by a congenital heart defect, but also can be due to disease or injury.

How Is an Arrhythmia Diagnosed?

Doctors use several tools to diagnose arrhythmias. It's very important to know a child's medical history and give this information to the doctor. The doctor will use the medical history, along with a physical exam, to begin the evaluation.

If the doctor suspects an arrhythmia, they will order an electrocardiogram (EKG) to measure the heart's electrical activity. For this painless test, the child will lie down and have small metal tabs (called electrodes) fixed to the skin with stickers. The electrodes have wires attached to them that connect to the EKG machine. The electrical signals from the heart are then briefly recorded, usually for just 10 seconds. This information is sent to a computer, where it's interpreted and drawn as a graph.

These types of EKG tests might be recommended:

• Resting EKG. This measures resting heart rate and rhythm and lasts about a minute.
• Exercise EKG (also called a stress test). This measures heart rate and rhythm during exercising, like riding a stationary bicycle or walking on a treadmill.
• Signal-average EKG. This is much like a resting EKG but monitors the heartbeat for about 15–20 minutes.
• Holter monitor. This EKG is done over a long period of time, usually 24 hours or more. The electrodes are fixed to the chest, and the wires are attached to a portable EKG recorder. The child 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).
  
  The two kinds of Holter monitoring are: continuous recording, which means the EKG is on during the entire monitoring period; and event monitoring, which means data is recorded only when the child feels symptoms and then turns the monitor on.

How Are Arrhythmias Treated?

Many arrhythmias don't need treatment. For those that do, these options might be used:

• Medicine. Doctors may prescribe anti-arrhythmic medicines depending on the type of arrhythmia and other considerations. Sometimes these can increase symptoms and cause side effects, so the doctor will closely monitor the patient.
• 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, a pacemaker can detect if the heart rate is too slow and send electrical signals to speed up the heartbeat.
• Defibrillators. A small battery-operated implantable cardioverter defibrillator (ICD) is surgically placed near the left collarbone. Wires run from the defibrillator to the heart. The ICD senses if the heart has a dangerously fast or irregular rhythm and sends an electrical signal to restore a normal heartbeat.
• Catheter ablation. A doctor guides catheter (a long, thin wire) through a vein in the leg to the heart. Arrhythmias often are caused by microscopic defects in the heart muscle. When the problem area of the heart is found, the doctor uses the catheter to heat or freeze the defective muscle cells and destroys them.
• Surgery. Surgery is usually done only if all other options fail. The child will get anesthesia to sleep through the procedure and not feel pain, then a surgeon will remove the tissue causing the arrhythmia.

When Should I Call the Doctor?

Many arrhythmias are minor and aren't a serious health threat. But because some can indicate a more serious problem, call your doctor if your child has symptoms of an arrhythmia.