An arrhythmia of the heart is an abnormality of the rhythm or rate of the heartbeat. The arrhythmia is caused by a disturbance of the normal electrical activity within the heart.
Arrhythmias can be divided into 2 main groups: tachycardias and bradycardias. Tachycardias cause a rapid heartbeat, with over 100 beats per minute. Bradycardias cause a slow heartbeat, with less than 60 beats per minute. The rhythm of the heart may be regular during an arrhythmia. In other words, each beat of the atria, or upper chambers of the heart, is followed by one beat of the ventricles, or lower chambers of the heart. The beat may also be irregular and may begin in an abnormal area of the heart.
Most arrhythmias are caused by heart disease, including:
Arrhythmias may also be caused by:
Arrhythmias may or may not be life threatening. In general, arrhythmias that begin in the upper part of the heart are less dangerous than those that begin in the lower chambers.