Proarrhythmia
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2007-10-30T15:56:52Z
Magioladitis
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'''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) of [[antiarrhythmic]] drugs, there are 3 main types of Proarrhythmia during treatment with various antiarrhythmic drugs for [[Atrial Fibrillation]] or [[Atrial flutter]]:
===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]] 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]] (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.
==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]
[[Category:Diseases]]
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