Etiology

• Congenital Long QT syndromes
• Acquired LQTS (e.g., drug-induced LQTS, electrolyte abnormalities, heart disease)

Pathophysiology

Clinical features

• Often asymptomatic
• Cardiovascular features
  • Palpitations
  • Tachycardia (HR ≥100/min; typically regular)
  • Chest pain/pressure
  • Dyspnea, orthopnea
  • Symptoms of reduced cardiac output
    • Dizziness
    • Hypotension
    • Syncope
    • Cardiogenic shock and loss of consciousness
• Cardiac arrest

Diagnostics

• Polymorphic VT with QRS complexes that typically appear to twist around the isoelectric line, usually in self-limiting bursts
• Often preceded by bigeminy and followed by several premature ventricular contractions
• R-on-T phenomenon may also be seen.

Treatment

• Hemodynamically unstable patients: Defibrillation plus CPR.
• Hemodynamically stable patients: Administer IV magnesium sulfate.
• Identify and treat the underlying etiology of QT prolongation.