Proarrhythmia

Proarrhythmia is a new or more frequent occurrence of pre-existing arrhythmias, paradoxically precipitated by antiarrhythmic therapy, which means it is a side effect associated with the administration of some existing antiarrhythmic drugs, as well as drugs for other indications. In other words, it is a tendency of antiarrhythmic drugs to facilitate emergence of new arrhythmias.

Types of proarrhythmia

According to the Vaughan Williams classification (VW) of antiarrhythmic drugs, there are 3 main types of Proarrhythmia during treatment with various antiarrhythmic drugs for Atrial Fibrillation or Atrial flutter:

Ventricular proarrhythmia
  • Torsades de pointes (VW type IA and type III drugs)
  • Sustained monomorphic ventricular tachycardia (usually VW type IC drugs)
  • Sustained polymorphic ventricular tachycardia/ventricular fibrillation without long QT (VW types IA, IC, and III drugs)

Atrial proarrhythmia
  • Conversion of atrial fibrillation to flutter (usually VW type IC drugs or amiodarone). May be a desired effect.
  • Increase of defibrillation threshold (a potential problem with VW type IC drugs)
  • Provocation of recurrence (probably VW types IA, IC and III drugs). It is rare.

Abnormalities of conduction or impulse formation
  • Sinus node dysfunction, atrioventricular block (almost all drugs)
  • Accelerate conduction over accessory pathway (digoxin, intravenous verapamil, or diltiazem)
  • Acceleration of ventricular rate during atrial fibrillation (VW type IA and type IC drugs).

Increased risk
  • Presence of structural heart disease, especially LV systolic dysfunction.
  • Class IC agents.
  • Increased age.
  • Females.

Clinical pointers

Class IA drugs
  • Dose independent, occurring at normal levels.
  • Follow QT interval, keep ms.

Class IC drugs
  • May be provoked by increased heart rate.
  • Exercise stress tests after loading.

Class III drugs
  • Dose dependent.
  • Follow bradycardia, prolonged QT closely.
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References
    • Roden DM (August 1998). "Mechanisms and management of proarrhythmia". Am. J. Cardiol. 82 (4A): 49I–57I. doi:10.1016/S0002-9149(98)00472-X. PMID 9737654.
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