Rhythms and Arrhythmia
The rate at which the heart beats is measured in beats per minute (or bpm) and is generally calculated over several RR intervals. The normal rate in an adult is between 50 and 120 bpm. However, it is natural for a healthy heart to beat at rates outside of this range when resting, exercising, or in response to other external factors and emotions.
Alterations in heart rhythm, arrhythmias, are heartbeats that are irregular, too fast, too slow, or conducted via an abnormal electrical pathway through the heart.
In common usage, the term dysrhythmia is synonymous with arrhythmia, although in the strictest sense, arrhythmia is the absence of cardiac rhythm and dysrhythmia is an abnormal cardiac rhythm.
The term bradyarrhythmia is used to define abnormally slow rhythms, either regular or irregular, or a slow ventricular response due to heart block.
Tachyarrhythmia describes arrhythmia characterised by a rapid irregular heartbeat.
Rhythms and arrhythmia are further classified by the site of the origin of the heartbeat or conduction abnormality, which generally fall into one of four areas:
Links to the more common rhythms and arrhythmias, with ECG examples, are presented below.