When a heart beats too fast, too slow or with an irregular rhythm it is known as an arrhythmia. There are three classifications of arrhythmias: A heartbeat that is too fast is called tachycardia. A heartbeat that’s too slow is called bradycardia, and premature heartbeats are extra beats.
“Most arrhythmias are harmless, but some can be serious or even life threatening,” says Dr. Andrew Kaplan, a board certified cardiac electrophysiologist at Banner Heart Hospital in Mesa, Arizona. “When the heart rate is too fast, too slow, or irregular, the heart may not be able to pump enough blood to the body. Under certain circumstances, this lack of blood flow can damage the brain, heart, and other organs,” he said.
The most common type of arrhythmia is premature beats. Most of the time, they are harmless, occur naturally and seldom cause any noticeable symptoms, according to the National Heart, Lung and Blood Institute (NHLBI), part of the Institutes of Health.
Atrial Fibrillation (AF) is the most common type of serious arrhythmia, affecting about 2.2 million Americans, according to the Heart Rhythm Society. It occurs when the right atria (the upper right chamber of the heart) experiences very fast and irregular contractions caused by irregular electrical signals.
"When AF happens, the electrical signal doesn't travel through its normal pathways in the atria. Instead, it spreads throughout the atria in a rapid and disorganized manner, sometimes as fast 300 beats per minute. As a result, the atria aren't able to pump blood into the ventricles (lower chambers of the heart) the way they should,” says Dr. Kaplan. “AF is typically not life threatening, but it can be dangerous when the impulses cause the ventricles to beat at a very high rate.”
Dr. Kaplan says two of the most serious long-term complications of AF are heart failure and stroke. A stroke happens if a blood clot travels to an artery in the brain, causing a block in blood flow. Heart failure occurs when the heart can’t pump enough blood to meet the body’s needs. Heart failure causes tiredness, leg swelling, and shortness of breath, according to the American Heart Association.