Proarrhythmias

Proarrhythmias are drug-induced arrhythmias. Two recently recognized ventricular proarrhythmias seen with antiarrhythmic drugs:

• Torsades de pointes ("twisting of the points") or drug-induced long QT syndrome (DILQTS)

  • Polymorphic arrhythmia that can rapidly develop into ventricular fibrillation

  • Associated with drugs that have Class III actions (potassium channel blockers)

    • Also seen with other drugs such as terfenadine under certain circumstances

  • Usually occurs within the first week of therapy

  • Preexisting prolonged QT intervals may be indicator of susceptibility

  • Potentiated by bradycardia

  • Often associated with concurrent electrolyte disturbances (hypokalemia, hypomagnesemia)

• CAST proarrhythmia

  • Monomorphic, sustained ventricular tachycardia first recognized in CAST trials with encainide and flecainide

  • Patients with underlying sustained ventricular tachycardia, coronary artery disease, and poor left ventricular function (left ventricular ejection fraction <>

Category: Pharmacology Notes