Cardiac Channelopathies

• Blanket term for numerous conditions affecting the cardiac conduction system
  • Conduction speed can be increased or decreased
  • Ion channel mutations
• Major cause of sudden cardiac death
  • 5-15% of patients have structurally normal hearts
• Inherited disorders that present with arrhythmia and multi-organ involvement
  • Long QT Syndrome
  • Brugada
  • Polymorphic VT
  • Short QT Syndrome
• Genes responsible include:
  • KCNQ1
  • KCNH2
  • SCN5A

Long QT Syndrome (LQTS)

• Underdiagnosed disorder
• Prolongation of cardiac action potentials
  • Predominantly Na and K channel deficiency
    • Timothy Syndrome caused by a Ca channel deficiency

• Congenital
• Heterogeneous
• Increased risk of
  • Syncope
  • Seizure
  • SCD
  • Arrhythmia
• Arrhythmia can be triggered by
  • Exertion
  • Stress/emotion

 

Pharmacological triggers:

• Anti-arrhythmics
  • Class 1a Procainamide and Quinidine
  • Class 3 Soltalol and Amiodarone
• Non cardiac
  • Cisparide
  • Terfenadine

Multi-organ involvement:

• Jervell & Lange-Nielsen Syndrome
  • LQTS with congenital deafness
• Andersen-Tawil Syndrome
  • LQTS with facial dysmorphia and hypokalaemic paralysis
• Timothy Syndrome
  • LQTS with AV block and developmental disorders

Symptoms

• Syncope
• Seizure
• Sudden death
• Chest pain/palpitations

Diagnosis

• Resting 12-Lead ECG
• Ambulatory ECG monitoring
  • QTc boundaries for male and female criteria
• Pharamacological Stress testing
  • Usually adrenaline