Bradyarrhythmia (Slow Heart Rate)
Arrhythmia is a medical term that refers to a heart rate that is outside the
normal range. (Normal is 60 to 100 beats per minute.) An arrhythmia that is too
slow is called a bradyarrhythmia or bradycardia.
Bradycardia means that the heart is beating too slowly (usually less than 60
beats per minute). It is important to realize that for some people with healthy
hearts, a rate below 60 beats per minute may be normal. After all, our heart
rates may dip below normal range when we sleep, and some athletes experience
heart rates below 60 beats per minute when they rest.
The two most common causes of bradycardia are diseases of the sinoatrial (SA)
node (sick sinus syndrome), which is the heart's natural pacemaker or other
problems with the heart's electrical conduction system (heart block). These
diseases can cause the heart to beat too slowly all the time or occasionally.
In either case, the heart may not pump enough blood to meet the body's needs.
As the heart rate declines, there is not sufficient blood flow to the brain,
causing feelings of light-headedness, and sometimes, fainting.
Normal Rhythm
Every normal heart has a normal rhythm. That rhythm varies from person to
person. In most healthy people, the heart at rest beats about 60 to 100 times
per minute. A small bunch of heart cells called the sinoatrial node keeps time.
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