Re: why does a low pulse rate cause fatigue

The pulse is a wave in an artery that is produced when the heart contracts
[beats]. The pulse rate is the number of pulsations per minute.  Under normal
conditions the heart beat is governed by the demand of oxygen, when one 
runs [more oxygen is demanded] the rate increases and at rest it slows. When a
Heartblock exists, the demand signal is not received by the heart and the
heart beats at a slow rate even when running.  This causes poor oxygenation,
accumulation of carbondioxide and wasteproduct--all making one feel tired.
Other conditions can cause a low pulse rate resulting in the above
conditions, such as under active thyroid, coma, medication, intoxication, 
brain tumors, etc.

RM