Proarrhythmia is a new or more frequent occurrence of pre-existing arrhythmias, paradoxically precipitated by antiarrhythmic therapy, which means it is a side effect

Adverse effect

In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...

 associated with the administration of some existing antiarrhythmic drugs

Antiarrhythmic agent

Antiarrhythmic agents are a group of pharmaceuticals that are used to suppress abnormal rhythms of the heart , such as atrial fibrillation, atrial flutter, ventricular tachycardia, and ventricular fibrillation....

, 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

Atrial fibrillation

Atrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction...

 or Atrial flutter

Atrial flutter

Atrial flutter is an abnormal heart rhythm that occurs in the atria of the heart. When it first occurs, it is usually associated with a fast heart rate or tachycardia , and falls into the category of supra-ventricular tachycardias. While this rhythm occurs most often in individuals with...

:

Ventricular proarrhythmia

• Torsade de pointes (VW type IA and type III drugs)
• Sustained monomorphic ventricular tachycardia (usually VW type IC drugs)
• Sustained polymorphic ventricular tachycardia/ventricular fibrillation
  Ventricular fibrillation
  Ventricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Ventricular fibrillation is a medical emergency and most commonly identified arrythmia in cardiac arrest...
  
   without long QT (VQ types IA, IC, and III drugs)

Atrial proarrhythmia

• Conversion of atrial fribrillation 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
  Atrioventricular block
  An atrioventricular block involves the impairment of the conduction between the atria and ventricles of the heart.The causes of pathological AV block are varied and include ischaemia, infarction, fibrosis or drugs. Certain AV blocks can also be found as normal variants, such as in athletes or...
  
   (almost all drugs)
• Accelerate conduction over accessory pathway (digoxin
  Digoxin
  Digoxin INN , also known as digitalis, is a purified cardiac glycoside and extracted from the foxglove plant, Digitalis lanata. Its corresponding aglycone is digoxigenin, and its acetyl derivative is acetyldigoxin...
  
  , intravenous verapamil
  Verapamil
  Verapamil is an L-type calcium channel blocker of the phenylalkylamine class. It has been used in the treatment of hypertension, angina pectoris, cardiac arrhythmia, and most recently, cluster headaches. It is also an effective preventive medication for migraine...
  
  , or diltiazem
  Diltiazem
  Diltiazem is a non-dihydropyridine member of the class of drugs known as calcium channel blockers, used in the treatment of hypertension, angina pectoris, and some types of arrhythmia....
  
  )
• 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.