Sick sinus syndrome

Background

• Collection of bradyarrhythmias with or without tachycardia
• 50% have alternating bradycardia and tachycardia

Causes

• Intrinsic:
  • degenerative fibrosis
  • infiltrative disease process
  • ion channel dysfunction
  • SA node remodeling
• Extrinsic:
  • pharmacologic
  • metabolic/electrolyte disturbance
  • autonomic, OSA

Clinical Features

• Clinical manifestations related to end-organ hypoperfusion
  • Syncope/pre-syncope (50%)

Differential Diagnosis

Symptomatic bradycardia

• Cardiac
  • Inferior MI (involving RCA)
  • Sick sinus syndrome
• Neurocardiogenic/reflex-mediated
  • Increased ICP
  • Vasovagal reflex
  • Hypersensitive carotid sinus syndrome
  • Intra-abdominal hemorrhage (i.e. ruptured ectopic)
• Metabolic/endocrine/environmental
  • Hyperkalemia
  • Hypothermia (Osborn waves on ECG)
  • Hypothyroidism
    • Myxedema coma
  • Hypoglycemia (neonates)
• Toxicologic
  • B-blocker
  • Ca-channel blocker
  • Clonidine
  • Digoxin toxicity
  • Ethanol
  • Opioids
  • Organophosphates
  • Xylazine toxicity
• Infectious/Postinfectious
  • Chagas disease
  • Lyme disease
  • Syphilis
• Other
  • Brash syndrome

Diagnosis

• ECG identification, inpatient telemetry, outpatient Holter monitoring, event monitoring, loop monitoring
  • ECG frequently negative for findings early in disease course

Management

• remove extrinsic factors and/or pacemakers
  • Pacemakers do not reduce mortality, only decrease symptoms

Disposition

• Admit

Complications

• (50%) Tachy-brady syndrome with atrial fibrillation or atrial flutter
• (50%) AV block

See Also

• Symptomatic Bradycardia