Bradycardia

DDx

Medications (e.g., calcium channel blockers, beta blockers, digitalis, clonidine, other sympatholytics, amiodarone, other antiarrhythmics)
Normal (especially athletes)
Sick sinus syndrome
Vasovagal response
Atrioventricular block
Hypothermia
Hypothyroidism
Myocardial ischemia involving right coronary artery
Increased intracranial pressure (Cushing's reflex)
Cardiac infiltrative disease (e.g., amyloid, sarcoidosis, hemochromatosis)

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