- Proarrhythmia
Proarrhythmia is a new or more frequent occurrence of pre-existing
arrhythmia s, 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) ofantiarrhythmic drugs, there are 3 main types of Proarrhythmia during treatment with various antiarrhythmic drugs forAtrial Fibrillation orAtrial flutter :Ventricular proarrhythmia
*
Torsade de pointes (VW type IA and type III drugs)
*Sustainedmonomorphic ventricular tachycardia (usually VW type IC drugs)
*Sustainedpolymorphic ventricular tachycardia /ventricular fibrillation 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 ofdefibrillation 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 , intravenousverapamil , ordiltiazem )
*Acceleration ofventricular rate during atrial fibrillation (VW type IA and type IC drugs).Increased risk
*Presence of
structural heart disease , especiallyLV 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.External links
* [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9737654&dopt=Abstract Mechanisms and management of proarrhythmia]
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