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.

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.