Bradycardia

Overview

• Bradycardia refers to heart rate <60/min in an adult
• Bradycardias are classified as regular or irregular, narrow complex or wide complex

Differential diagnosis causing bradycardia

• Cardiac disease
  • Myocardial ischaemia / infarction
  • Myocarditis
  • Cardiomyopathies
• Hypoxia
• Electrolyte disturbance – Hyperkalemia
• Medications, poisonings and toxic exposures
  • Digoxin
  • Beta blockers
  • Calcium channel blockers
  • Amiodarone
  • Clonidine
• Hypothermia
• Hypothyroidism
• Raised intracranial pressure (Cushing response)
• Infections (Lyme disease, diphtheria, typhoid fever)
• Autoimmune – Systemic lupus erythematosis
• Infiltrative disorders (e.g. sarcoidosis, amyloidosis)
• Physiological causes
  • athletes
  • vagal response

History

• Past medical history
• Cardiac history and risk
• Medical conditions – screen for
  • Hypothyroidism
  • Autoimmune/ infiltrative disease
• Medication – digoxin, beta-blocker, calcium channel blockers or other antiarythmics

Examination

• General observation
• Vitals
  • Low body temperature?
  • Cushings triad
• ECG
  • Hyperkalaemia – Tall tented T-waves
• Cardiovascular examination
• Respiratory examination

Acute Management

• ABCD
  • Oxygen
  • IV access
• Tredenleberg position if hypotensive
• ECG
• Drug: Atropine
• Transthoracic pacing
• Low dose adrenaline infusion – if transthoracic pacing unavailable
• CPR – if deteriorating

Investigations

• FBC
• EUC
  • Hyperkalaemia
• LFT
• CRP
• Cardiac biomarkers
• Cardiac ultrasound