is a high heart rate, defined as above 100 bpm at rest.

Bradycardia is a low heart rate, defined as below 60 bpm at rest. When a human sleeps, a heartbeat with rates around 40-50 bpm is common and considered normal. When the heart is not beating in a regular pattern, this is referred to as a arrhythmia. Abnormalities of heart rate sometimes indicate heart disease.

Physiology

While heart rhythm

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