Class IC antiarrhythmics treat severe ventricular tachyarrhythmias by blocking Na+ channels and slowing conduction. They have no effect on AP duration and are used as a last resort in refractory tachyarrhythmias, which may become intractable or progress to ventricular fibrillation. Drugs in this class include flecainide and propafenone, the latter of which acts as a β-adrenergic antagonist and has the side effects of bradycardia and CHF.
These drugs are contraindicated in patients immediately after myocardial infarctions and in patients with structural abnormalities due to their propensity to increase mortality in these groups.
These drugs are used as a last resort in refractory tachyarrhythmias.
Class IC antiarrhythmic drugs are used in ventricular tachycardia (especially in intractable cases), which may progress to ventricular fibrillation.
Class IC antiarrhythmics have no effect on AP duration, as opposed to other Class I antiarrhythmics.
Propafenone treats rapid heart beat arrhythmias, such as supraventricular arrhythmias. It has a similar spectrum of action to quinidine and possesses β-adrenergic antagonist activity. It may also prevent life-threatening ventricular arrhythmias, but has side effects of CHF, bradycardia and new arrhythmias.
Flecainide is a class IC antiarrhythmic drug indicated for ventricular tachyarrhythmias and for maintaining sinus rhythms in cases of paroxysmal atrial fibrillation or atrial flutter.
This class of drugs has proarrhythmic activity and are contraindicated post-MI and after structural heart disease due to increased mortality incidence with these diseases.
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