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Bradyarrhythmias
 
 

Sinus Bradycardia

 
 
 
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Overview

Sinus bradycardia is initiated by the sinus node, and occurs in the setting of reduced automaticity due to either intrinsic or extrinsic causes.
  • Look For

  • Decreased heart rate - <60bpm (or 50bpm when asleep)
  • Regular rhythm - normal PR interval with P waves preceding each QRS complex
  • Normal axis - positive P waves in leads I and II
  •  
  • Causes of Sinus Bradycardia

  • Intrinsic

  • Idiopathic degeneration
  • Myocardial infarction
  • Infiltrative disease - sarcoidosis, amyloidosis, haemochromatosis
  • Connective tissue disease - SLE, scleroderma, RA
  • Cardiac surgery - valvular surgery, correction of congenital heart disease
  • Infections - Lyme disease, endocarditis
  • Extrinsic

  • Physiologic - sleep, athletes
  • Autonomic - neurocardiogenic syncope, carotid sinus hypersensitivity
  • Drugs - beta blockers, calcium channel blockers, digoxin, adenosine, flecainide, ivabradine, clonidine, acetylcholinesterase inhibitors
  • Hypothyroidism
  • Hypothermia
  • Hyperkalaemia
  • Obstructive sleep apnoea
  • Raised intracranial pressure
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