Arrhythmia

A change in your heartbeat - whether it seems to skip a beat or it starts to beat faster or slower - can be very scary. But according to the National Institutes of Health, this type of change, called an arrhythmia (or dysrhythmia), is fairly common, especially as we get older.

According to the American Academy of Family Physicians (AAFP), an arrhythmia can be caused by a number of things including:

• heart disease (Read about "Coronary Heart Disease")
• stress (Read about "Stress")
• caffeine, tobacco, or alcohol use (Read about "Quit Smoking")
• diet pills
• certain cough or cold medicines

Sometimes there is no known cause for an arrhythmia. Although the occurrence of an arrhythmia does not necessarily indicate an underlying heart condition (Read about "The Heart & Cardiovascular System"), AAFP says you should see a doctor if you experience an arrhythmia often, or if you have symptoms such as a rapid heartbeat (called "tachycardia"), shortness of breath, or dizziness.

Why arrhythmias occur

The heart is a pump divided into four chambers: two atria on the top and two ventricles on the bottom.

According to the National Heart, Lung and Blood Institute (NHLBI), normally a heartbeat starts in the right atrium, where a group of cells called the sinus node, or natural pacemaker, sends an electrical signal. The signal then spreads through the atria and to the atrioventricular (AV) node. From there, the signal goes to the ventricles.

Throughout this trip, the signal causes the heart to contract. The first thing that happens is the atria contract, pumping blood into the ventricles, a fraction of a second later, the ventricles contract, sending blood throughout the body. Each full contraction is a heartbeat.

Sometimes, though, NHLBI says the heartbeat starts in a different part of the heart, or the signal from the sinus node has an abnormal rate, or there's a "heart block" in which the signal is either partially or fully blocked before it gets to the ventricle. When this happens, a person may notice a change in the normal pattern of their heartbeat, which can result in:

• bradycardia, which is a very slow heart rate
• tachycardia, which is a very fast heart rate

Types of arrhythmia

An arrhythmia is identified on the basis of where it occurs.

• Ventricular arrhythmias begin in the ventricles and are considered the most serious, according to NHLBI.
  • Ventricular tachycardia - In ventricular tachycardia, the heart beats fast due to electrical signals arising from the ventricles instead of from the atria. According to the American Heart Association (AHA), ventricular tachycardia can be a life-threatening situation.
  • Ventricular fibrillation - In ventricular fibrillation, the heartbeat is both rapid and uncoordinated. As a result, the heart can't pump any blood and immediate medical help is essential. Untreated, ventricular fibrillation can quickly result in death.
  Both ventricular tachycardia and ventricular fibrillation are very dangerous and can lead to cardiac arrest. (Read about "Cardiac Arrest") Another type of ventricular arrhythmia is premature ventricular contraction (PVC), in which the ventricles contract out of sequence with the normal heartbeat.
• Atrial or supraventricular (above the ventricles) arrhythmias originate in the atria. Examples include:
  • Atrial fibrillation - AHA says 2 million Americans experience atrial fibrillation, in which the two small upper chambers of the heart, the atria, quiver instead of beating effectively. Although atrial fibrillation is not in itself considered life threatening, people with it are at an increased risk for blood clots and stroke. (Read about "Stroke")
  • Sinus arrhythmia - This is an arrhythmia in which cyclic changes in the heart rate occur during breathing
  • Wolff-Parkinson-White syndrome - This is an arrhythmia in which abnormal pathways between the atria and ventricles cause very fast heart rates.

Testing for arrhythmias

NHLBI says one of the most common tests for detecting arrhythmia is the electrocardiogram. (Read about "EKG - Electrocardiogram") An EKG or ECG measures the electrical activity of the heart. It can be done while the patient is still, or while he or she is exercising (a stress test), or it can be used to monitor the patient over a period of time. (Read about "Stress Test") Often, patients will be fitted with a Holter monitor, which is a method to monitor a person's heartbeat constantly for 24 hours. (Read about "Cardiovascular Tests")

Treatment options

If an arrhythmia is present, and it appears to be caused by heart disease, it's important to identify the underlying causes of the heart disease. The arrhythmia itself may also require treatment. Options, according to NHLBI and AHA, include:

• drug therapy
• surgical implantation of a defibrillator or an implantable cardioverter/defibrillator which monitors the heart's rhythm and uses an electrical shock to bring it back to normal when necessary
• a pacemaker to send the proper electrical signals to make the heart beat normally. Pacemakers can be internal or external. AHA says certain medical and dental procedures can affect pacemakers, as can magnetic or power-generating equipment, so it's important that you discuss this with your doctors.
• ablation, which disconnects the pathways of the abnormal rhythm. In catheter ablation, a catheter or thin tube is inserted into a vein and guided to the heart, where it delivers energy - such as heat or cold - in order to destroy or isolate the source of the arrhythmia. There are different types of ablation treatments, depending on the cause and type of arrhythmia being treated.

Although many arrhythmias are not dangerous, they should not be ignored. Some arrhythmias for example, may cause such a slow heartbeat (or bradycardia) that an individual gets lightheaded. NHLBI says this may be normal for some people especially athletes; however it can also be caused by medications, including beta blockers, some calcium blockers such as diltiazem, aldomet and perhaps digitalis. This condition is potentially fatal, so if you have any concerns about changes in your heartbeat, see your doctor right away.

Arrhythmias that cause a rapid heartbeat may also cause an individual to feel lightheaded. Certain medications, such as antihistamines and decongestants, as well as caffeine and alcohol can result in these rapid heart rates (tachydysrhythmias). In addition, certain illicit drugs, including cocaine, amphetamines and PCP may cause a rapid heartbeat.

Related Information:

    Coronary Heart Disease

    Heart Disease and Women

    Cardiomyopathy

    Glossary of Heart Terms