Sinus bradycardia: aetiology

"SINUS BRADICARDIA" (sinus bradycardia):
Sleep
Infections (myocarditis)
Neap thyroid (hypothyroid)
Unconsciousness (vasovagal syncope)
Subnormal temperatures (hypothermia)
Biliary obstruction
Raised CO2 (hypercapnia)
Acidosis
Deficient blood sugar (hypoglycemia)
Imbalance of electrolytes
Cushing's reflex (raised ICP)
Aging
Rx (drugs, such as high-dose atropine)
Deep anaesthesia
Ischemic heart disease
Athletes