top of page

What are arrhythmias?

Arrhythmias are abnormal heartbeats that are usually caused by an electrical short circuit in the heart. Normally, the heart beats in a regular, even pattern, but an arrhythmia can cause it to beat too slowly, too fast or irregularly. This can cause the heart to pump unevenly, leading to symptoms such as fatigue, dizziness and chest pain.

What causes it?

The heart has its own electrical system that sends electrical signals around itself, telling it when to contract and when to pump blood to the rest of the body. The electrical signals start in a group of cells, called the sinus node, also known as the “sinoatrial node,” located within the right atrium. The sinus node acts as the heart’s natural pacemaker and ensures that the heart beats at a normal, even rhythm. The sinus node normally speeds up the heart in response to factors such as physical exercise, emotions and stress and slows the heart rate during sleep. But sometimes the electrical signals do not “communicate” properly with the heart muscle, and the heart may start beating in an abnormal rhythm; this is an arrhythmia (also called dysrhythmia). Arrhythmias may be congenital (meaning the person is born with them) or occur later in life, and may be temporary or permanent. Arrhythmias may also be due to chemical imbalances in the blood; infections; diseases that irritate the heart; medications (prescription and over-the-counter, and some herbal medicines); injuries to the heart caused by trauma or heart surgery; use of illegal drugs, alcohol, or tobacco; caffeine; and stress. Arrhythmias can also occur for no apparent reason.

Signs and symptoms

Arrhythmias cause the heart to beat less efficiently, interrupting the blood supply to the brain and the rest of the body. When the heart beats too fast, its chambers cannot fill with enough blood. When the heart beats too slowly or irregularly, it cannot pump enough blood to the rest of the body. If a person’s body does not get the blood supply it needs to function properly, the person may have: dizziness fatigue feeling faint weakness palpitations (a fluttering or throbbing sensation in the chest) shortness of breath chest pain fainting

Arrhythmias may be constant, but most come and go randomly. Sometimes, arrhythmias may not cause any symptoms at all; in these cases, arrhythmias are only found on an ordinary physical examination or cardiac function test, such as an electrocardiogram (ECG).

What is a normal heart rate?

Heart rate is measured by counting the number of heartbeats per minute. A person’s normal heart rate depends on factors such as 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 by age are as follows: infant (birth to 3 months of age): 100-150 beats per minute. children 1 to 3 years of age: 70-110 beats per minute children up to 12 years of age: 55-85 beats per minute A doctor can determine if a heartbeat is too fast or too slow, because the significance of an abnormal heartbeat depends on the situation. For example, a teenager or adult with a slow heart rate may begin to show symptoms when it drops below 50 beats per minute. But athletes who have trained hard have even lower heart rates, which are not considered abnormal because they do not cause symptoms.

Types of arrhythmias

There are several types of arrhythmias: Premature atrial contraction (PAC) and premature ventricular contraction (PVC). Premature contractions are usually considered minor arrhythmias. The person may notice a fluttering or throbbing in the chest caused by an early beat or an extra beat. PACs and PVCs are very common, and are what happens when you feel that your heart has “skipped” a beat. In reality, the heart does not actually skip a beat, but rather beats one beat too many or too early. Occasional premature beats are common and are considered normal, but, in some cases, they may be a sign of an underlying medical problem or heart condition.


Tachycardias are arrhythmias involving an abnormally fast heartbeat. There are two different types of tachycardias: supraventricular and ventricular: Supraventricular tachycardia (SVT) is characterized by episodes of rapid heartbeats that begin in the upper chambers of the heart. They can occur suddenly and last from a few seconds to several days in a row. Treatment is usually recommended when they are of long duration or occur often. Ventricular tachycardia is a serious and rare condition that begins in the lower chambers of the heart and can be dangerous.


Bradycardias, arrhythmias characterized by an abnormally slow heartbeat, may be due to: A sinus node dysfunction, when the sinus node is not functioning properly, usually after an operation to correct a congenital heart abnormality. A heart block, when electrical impulses cannot move from the upper to the lower heart chambers. It is usually due to a congenital heart defect, but may also be due to disease or injury.

How are they diagnosed?

Arrhythmias can be diagnosed in several different ways. The physician will rely on the patient’s medical history and physical examination to begin the evaluation. If the physician suspects an arrhythmia, he or she will most likely order an electrocardiogram (ECG) to measure the electrical activity of the heart. There is nothing painful about an ECG, it is just a procedure where a series of electrodes (small metal pads) are attached to the skin by adhesive papers. The electrodes are attached to wires connected to the ECG machine. The heart’s electrical signals are recorded for a short period of time, usually only 10 seconds. This information is sent to a computer, where it is interpreted and plotted as a graph. A doctor may recommend these types of ECGs: Resting ECG. It measures heart rate and heart rhythm at rest and lasts about one minute. Stress test (also called exercise ECG). Measures heart rate and heart rhythm while a person is exercising (such as riding a stationary bike or walking on a treadmill). Signal-averaged ECG. This is like a resting ECG, but records the heart rate for 15-20 minutes. Holter. This is an ECG that is recorded over a long period of time, usually 24 hours or more. Electrodes are attached to the person’s chest and lead run to a portable ECG recorder. The person is encouraged to carry out normal day-to-day activities, instructing them to be careful not to get the electrodes wet (e.g., no swimming, bathing, showering, or activities that cause heavy sweating). Hay dos tipos de Holter, el Holter de registro continuo, en el que el ECG se hace durante todo el período de registro; y el Holter de monitorización de síntomas, donde solo se registran datos cuando la persona experimenta síntomas y entonces conecta el Holter.

How are arrhythmias treated?

Many arrhythmias do not need treatment. For those that do, the following options are available: Medications. There are many types of antiarrhythmic medications available to treat arrhythmia. Sometimes these medications can increase symptoms and have adverse side effects, so the doctor should watch the patient closely. Pacemaker. A pacemaker is a small, battery-operated device that is implanted in the body (near the collarbone) through a surgical procedure. Connected to the heart through a wire, the pacemaker can detect if the heart rate is too slow and send electrical signals to speed it up. Defibrillators. A small, battery-operated implantable cardioverter defibrillator (ICD) can be surgically implanted near the left collarbone. Leads run from the defibrillator to the heart. The ICD detects times when the heart has a dangerously fast or irregular heart rhythm and sends an electrical signal to restore a normal heart rate. Catheter ablation. A catheter (a long, thin wire) is inserted into a vein in the leg and guided to the heart. Many arrhythmias are caused by microscopic abnormalities in the heart muscle. As soon as the area of the heart causing the arrhythmia is located, the catheter heats or freezes the defective muscle cells and destroys them. Surgery. Operations are usually only recommended when all other options have failed. In these cases, the person undergoes anesthesia and the surgeon removes the tissue causing the arrhythmia.

When to call your doctor

Many arrhythmias are unimportant. But there are others that may indicate a more serious problem. If you have been having symptoms, talk to a parent or call your doctor.

4 views0 comments

Recent Posts

See All


bottom of page