The proarrhythmic effects of amiodarone

P ROARRHYTHMIA is a term used to describe the apparent paradoxical exacerbation or development of new arrhythmia by antiarrhythmic drugs. In its most liberal interpretation this would include drug-induced bradyarrhythmia as well as tachyarrhythmia and increases in complexity or frequency of asymptomatic atria1 or ventricular ectopic activity (VEA). Programmed electrical stimulation (PES) studies can also detect atria1 or ventricular proarrhythmic effects using various criteria. What is of most interest clinically, however, is the drug-related potentiation of symptomatic arrhythmia by the production of a hemodynamitally poorly tolerated tachycardia. Finally, antiarrhythmic drugs may increase the minimum energy required for defibrillation, thus rendering implantable cardioverter defibrillators or external DC cardioversion less effective. Amiodarone is a recently approved Class III antiarrhythmic agent which is capable of producing almost all of these proarrhythmic effects.