The human heart usually beats with a regular rhythm at a predictable rate. But sometimes the rhythm and rate will change. There are a variety of reasons that this happens. The condition is called arrhythmia (ah-RITH-me-uh).
An arrhythmia is a heartbeat that is not normal. It is also called abnormal or irregular.
Sometimes arrhythmia has no symptoms. In other cases, it causes upsetting and sometimes life-threatening conditions. To understand arrhythmia, you need to learn how the heart works.
How the heart works
Your heart is a muscular organ that is about the size of your fist. It sits in the left side of your chest. Its job is to pump oxygen-rich blood all through the body. As tissues in the body use oxygen, they return wastes in the form of carbon dioxide to the blood. These wastes are carried to the lungs and exhaled.
Your heart pumps nearly 5 quarts of oxygen-rich blood through your body every minute. The heart’s 4 chambers work together to pump the blood. The two upper chambers are called atria (AY-tree-uh), and the two lower chambers are called ventricles (VEN-truh-coals).
To do its pumping work, your heart uses a network of electrical pathways, similar to the electric wiring in your home. This electrical system passes signals from one part of the heart to another, which makes the heart beat regularly.
The heart’s electrical signals begin with a natural pacemaker called the S-A (sinoatrial) node. The S-A node is located in the heart’s upper right chamber. The specialized cells in this pacemaker send an electrical impulse from the S-A node down to the next part of the electrical system, the A-V (atrio-ventricular) node.
The A-V node serves as the bridge between the upper and lower chambers of the heart. It sends on the electrical impulse to the bundle branches, which are located inside the right and left ventricles. The electrical signal causes both the right and left ventricles to tighten or contract, then relax.
This network of signals is called the electrical conduction system. It involves passing (or conducting) the electrical current down the heart muscle to produce a strong, regular, and healthy heart contraction. The result is a single heartbeat, which occurs over and over again to pump blood all through the body.
The cardiac conduction system speeds up your heart rate as you climb stairs, for example. As a result, your heart pumps faster and your body gets more oxygen-rich blood. The conduction system also slows down the heart rate as you sleep.
Any disease or abnormality along this electrical pathway can result in an abnormal heart rate. The normal resting heart rate is between 60 and 100 beats per minute. Sometimes your heart’s natural rhythm becomes too slow, too fast, or irregular. When you have arrhythmia, your heart may not deliver enough oxygen-rich blood to your body.
Signs and symptoms
Some irregular heartbeats are common and usually harmless, such as when it happens just once in a while or without any other symptoms. It is not uncommon for a person to feel an occasional “missed beat.” It is also normal for someone to have a faster heart rate when excited or exercising.
However, when these irregularities happen over and over again, it is important to check with your doctor. Some of the signs and symptoms of arrhythmia include:
- Dizziness
- Fluttering, strong, or fast heartbeat called palpitations pronounced (pal-puh-TAY-shuns)
- Drowsiness
- Shortness of breath
- Tiredness
- Fainting
- Near-fainting
- Chest pain
- Lack of energy
- Major discomfort when exercising
- Uncomfortable awareness of your heartbeat
Types of heart rhythm problems
Heart rate that is too slow
A heart rhythm that is too slow is called bradycardia (bray-dee-CAR-dee-uh). This happens when the system that sends messages to contract the heart muscle does not work properly. Sometimes the message is not sent. In other cases, the message is sent but blocked, or takes another route. The result is a heart rate that is too slow. Your body does not get the oxygen and blood that it needs to work properly.
There are several types of bradycardia:
- Sinus bradycardia – occurs when signals from the S-A node are too slow
- Sick sinus syndrome – occurs when the heart rate switches from too fast to too slow
- Heart block – occurs when the electrical signal to contract is not passed from the A-V node to the bundle branches as it should. A blocked signal will slow your heart rate.
Heart rate that is too fast
A heart rate that is too fast is called tachycardia (tack-ee-CAR-dee-uh). Sometimes the electrical signals are sent so quickly and irregularly that they cause the heart muscle to tremble or quiver. The resulting beat is not strong enough to pump blood correctly. This leads to a condition called fibrillation (fib-ril-AY-shun).
There are a number of conditions that result from a fast or quivering heartbeat:
- Atrial (AY-tree-al) fibrillation – occurs in the atria; can be off-and-on (intermittently) or all the time
- Ventricular (ven-TRICK-you-ler) fibrillation – occurs in the ventricles. Since the ventricles do the most work in pumping blood through the body, fibrillation in this area is very serious. It is a life-threatening arrhythmia.
- Ventricular tachycardia (VT) – occurs when abnormal electrical pathways develop in the heart. The ventricles become very "confused" and keep responding to the electrical stimulation. VT usually occurs because of heart damage from a heart attack or heart disease. Ventricular tachycardia can become life-threatening if it develops into ventricular fibrillation.
- Supraventricular tachycardia (SVT) – caused by an abnormality above the ventricles. The word supra means “above.”
- A-V node reentrant tachycardia (AVNRT) – a common SVT. It involves an extra electrical pathway that disturbs the regularity of the heartbeat.
- Wolff-Parkinson-White (WPW) syndrome – a common SVT. It involves an extra electrical pathway that disturbs the regularity of the heartbeat.
Causes of arrhythmia
There can be several reasons why arrhythmia occurs. In some cases, a medical condition such as high blood pressure or coronary artery disease can be the cause. In other cases, caffeine, smoking, or certain medicines (prescription and nonprescription) can be the cause.
Diagnostic tests
If your doctor thinks you might have arrhythmia, he or she will do a complete medical history and physical exam. The doctor also may order any of the following tests:
- Electrocardiogram (ee-leck-tro-CARD-ee-oh-gram), ECG, or EKG – a simple
record of the heart's electrical activity
- Echocardiogram – a video picture of heart activity
- Holter monitor – The patient wears a portable ECG device that records heart rate and rhythm for 24 hours. He or she keeps a record of activities performed.
- Event recorder – similar to the holter monitor. The patient wears a monitor for several days. He or she presses a button when symptoms occur. With this recording, the doctor can see the kind of arrhythmia that occurs when there are symptoms.
- Tilt table testing – may be recommended by your doctor if you have fainting spells. The test determines how changes in position affect your heart rhythm. During the test, the bed is tilted while your symptoms, heart rate, heart rhythm, and blood pressure are monitored.
- Electrophysiology (ee-LECK-tro-fizzee-ALL-oh-gee) testing – a test that looks for irregularities that might cause heart rhythm problems.
- Cardiac catheterization – a test to see if arrhythmia is caused by coronary artery disease
Treatment
There are a number of ways to treat an irregular heart beat. Treatment depends on the type and seriousness of the irregularity. It also is affected by the patient’s age, general physical condition, and medical history. Treatment may include any of the following:
- Medicines taken by mouth
- IV (intravenous) medicines
- Pacemaker placement
- Radiofrequency catheter ablation therapy, a procedure that gets rid of abnormal heart cells
- Implantable cardioverter defibrillator placement, which can help a quivering heart return to a normal beat
- Cardioversion, a noninvasive procedure that shocks the heart back to a normal rhythm
- Treatment of medical conditions that may be causing the arrhythmia, such as thyroid disease
- Lifestyle changes such as:
- Reducing stress
- Stopping smoking
- Limiting caffeine
- Eating a balanced diet
- Finding a proper mix of rest and exercise
- Avoiding stimulant drugs and excess alcohol
Prevention
If arrhythmia is caused by coronary artery disease, this condition must first be treated with medicine, surgery, or special medical procedures. These can include:
- Coronary angioplasty – uses a balloon like tool to widen a blocked blood vessel
- Stent – uses a metal mesh tube to open a blocked blood vessel and keep it from becoming blocked again
In addition, further coronary artery disease may be prevented through the following self-help approaches:
- Eat a heart healthy diet.
- Control high cholesterol and high blood pressure.
- Quit smoking.
- Control body weight.
- Get regular exercise.
- Control caffeine intake.
Many times, arrhythmia can be successfully treated with a medical or surgical treatment plan. It is very important to call your doctor if you have any symptoms of
cardiac arrhythmias.
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