Asymptomatic or symptomatic bradycardia
Typically appear more well than vitals/labs suggest
Multisystem organ failure (shock, pulmonary edema, renal failure, shock liver)
Altered mental status
Typically appear more well than vitals/labs suggest
Brash syndrome
Cardiac
Scleroderma
Inferior MI 
DiGeorge syndrome
Sick sinus syndrome
Sjögren syndrome
Neurocardiogenic/reflex-mediated