Arrhythmias 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 make it beat too slowly, too quickly, or irregularly. This can cause the heart to pump inconsistently, leading 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 stress, and slows your heart rate during sleep.
But sometimes the electrical signals don't "communicate" properly with the heart muscle, and the heart starts beating in an abnormal rhythm — this is an arrhythmia (also called dysrhythmia).
Arrhythmias can be congenital (meaning a person is born with one) or happen later, and they can be temporary or permanent.
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 also can happen for no apparent reason.
Signs and Symptoms
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 have:
palpitations (a feeling of fluttering or pounding in the chest)
shortness of breath
Arrhythmias can be constant, but usually come and go at random. Sometimes arrhythmias can cause no symptoms at all — in these cases, the arrhythmia is only found 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. Someone's normal heart rate depends on things like the person's age and whether he or she leads an active lifestyle.
The resting heart rate decreases as people 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 too fast or slow, since the significance of an abnormal heart rate depends on the situation. For example, a teen or adult with a slow heart rate might begin to show 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.
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. 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. Actually, the heart doesn't skip a beat — an extra beat comes sooner than normal. Occasional premature beats are common and considered normal, but in some cases they can be a sign of an underlying medical problem or heart condition.
Tachycardias are arrhythmias that involve an abnormally rapid heartbeat. They fall into two major categories — supraventricular and ventricular:
Supraventricular tachycardia (SVT) is characterized by bursts of fast heartbeats that start in the upper chambers of the heart. 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 — arrhythmias characterized by an abnormally slow heartbeat — 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 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 ECG/EKG to measure 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. The electrodes have wires attached to them, which 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.
A doctor might recommend these 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 is much like a resting EKG, but monitors the heartbeat for about 15–20 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?
Many arrhythmias don't need treatment. For those that do, these options might be used:
Medicines. Many types of prescription anti-arrhythmic medicines are available to treat arrhythmia. Sometimes, these can increase symptoms and cause side effects, so the patient will be closely watched by the doctor.
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 catheter (a long, thin wire) is guided through a vein in the leg to the heart. Arrhythmias often are caused by microscopic defects in the heart muscle. Once the problem area of the heart is pinpointed, the catheter heats or freezes the defective 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 and a surgeon removes the tissue causing the arrhythmia.
When to Call the Doctor
Many arrhythmias are minor and aren't a significant health threat. But some can indicate a more serious problem. If you've been having any symptoms, talk to your parent or call your doctor.