An arrhythmia is any disorder of your heart rate or heart rhythm, such as beating too fast (tachycardia), too slow (bradycardia), or irregularly.

Normally, the 4 chambers of the heart (2 atria and 2 ventricles) contract in a very specific, coordinated manner.

The electrical impulse that signals your heart to contract in a synchronized manner begins in the sinoatrial node (SA node), which is your heart's natural pacemaker.

The signal leaves the SA node and travels through the 2 upper chambers (atria). Then the signal passes through another node (the AV node), and finally, through the lower chambers (ventricles). This path enables the chambers to contract in a coordinated fashion.

Problems can occur anywhere along this conduction system, causing various arrhythmias. Examples include:

• Supraventricular tachycardia - a fast heart rate that originates in the upper chambers (atria). The most common are atrial fibrillation or flutter, and atrioventricular nodal reentry tachycardia.
• Ventricular tachycardia - a fast heart rate that originates in the lower chambers (ventricles).
• Bradycardia - a slow heart rate due to problems with the SA node's pacemaker ability, or some interruption in conduction through the natural electrical pathways of the heart.

The risks of getting a tachycardia or bradycardia varies greatly, depending on the condition of your heart, prior heart attack, blood chemistry imbalances, or endocrine abnormalities.

Arrhythmias may also be caused by some substances or drugs, including beta blockers, psychotropics, sympathomimetics, caffeine, amphetamines, and cocaine. Sometimes antiarrhythmic medications -- prescribed to treat one type of arrhythmia -- can actually cause another type of arrhythmia.

Some types of arrhythmias may be life-threatening if not promptly and properly treated.

• Fast or slow heart beat (palpitations)
• Skipping beats
• Fainting
• Light-headedness, dizziness
• Chest pain
• Shortness of breath
• Skipping beats - changes in the pattern of the pulse
• Paleness
• Sweating
• Cardiac arrest

The person may not have symptoms.

A doctor will listen to your heart with a stethoscope and feel your pulse. Your blood pressure may be low or normal.

The following tests may be performed to identify arrhythmias:

• ECG
• Ambulatory cardiac monitoring with a Holter monitor (used for 24 hours) or loop recorder (worn for 2 weeks or longer)
• Echocardiogram
• Electrophysiology study (EPS)
• Coronary angiography

If an arrhythmia is detected, various tests may be done to confirm or rule out suspected causes. EPS testing may be performed to locate the origin of the arrhythmia and determine the best treatment, especially if a pacemaker implantation or catheter ablation procedure is being considered.