The normal heart rate for an adult at rest is 60 to 80 beats a minute. An abnormal heart rate can be too fast (tachycardia) or too slow (bradycardia). Or the rate can be normal and the rhythm not. Rhythm problems can occur in the atriums (the two upper chambers of the heart) or in the ventricles (the two lower chambers of the heart).
Disturbances in the rhythm of the heart (arrhythmias) result from a disruption in the electrical activity of the heart. This means that the electrical impulses which normally pass from the atriums to the ventricles are not generated or not conducted properly. Arrhythmias can come and go or be continuous. Some arrhythmias are harmless and can occur in anyone.
Rhythm disturbances can be caused by coronary heart disease, hypertension (high blood pressure), faults present at birth, inflammation of the heart and diseases of the heart valves. Less common causes include certain drugs, too much thyroid hormone, nicotine, caffeine, alcohol, exercise and fear or anger. In some cases the cause of the rhythm disturbance is not known.
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