Is a heart rate of 51 cause for concern?

A normal heart rate is between 60 - 100 times per minuet.

Sinus braydicardia is a heart rate below 60 BPM. A heart rate of 52 BPM may be dangerous but it depends on the underlying causes.

Sinus braydicardia can be causes by:

1) Rest- it can occur during sleep

2) Sinus node disease- which causes sinus node pauses

sinus braydicardia can causes hypotention ( low blood pressure 100 < 60< MMHG)

It can causes fainting and lack of blood supply to the brain. However Sinus braydicardia more often than not be harmless and a good heart rate for plenty of coronary blood flow

Treatment

Usally a heart rate below 60 does not need treatment if it is asymptomatic. However if it is symptomatic it may be treated by a pacemaker.

A heart rate of 52 may also be normal in athletes. For example Lance Armstrong's resting heart rate is 32-34 beats per minute. This is an extreme case however. So depending on your physical activity, age, weight and diet your rate could be lower then 60 with no negative effects.