antiarythmiques

Antiarrhythmics, or antiarythmics, are drugs used to treat or prevent abnormal heart rhythms by modifying electrical conduction, refractoriness, or automaticity. They are commonly grouped by the Vaughan Williams classification into four main classes, with additional agents and combinations that cut across categories.

Class I comprises sodium channel blockers and is subdivided into IA (quinidine, procainamide, disopyramide), IB (lidocaine, mexiletine), and IC (flecainide, propafenone). These agents slow or alter depolarization and conduction, with IA increasing, IB shortening, and IC markedly slowing conduction. They are used for various atrial and ventricular arrhythmias but carry proarrhythmic risk and are generally avoided in ischemic heart disease or significant structural heart disease, particularly the IC subgroup.

Class II includes beta-adrenergic blockers (metoprolol, propranolol, atenolol). By reducing sympathetic tone and AV nodal conduction, they help control rate in tachyarrhythmias, especially atrial fibrillation with rapid ventricular response; caution is advised in asthma, COPD, diabetes, and other conditions.

Class III agents block potassium channels to prolong repolarization and the QT interval. Examples are amiodarone, sotalol, dofetilide, ibutilide. They are effective for a broad range of arrhythmias, including AF and ventricular tachycardia, but carry proarrhythmic risk, particularly torsades de pointes. Amiodarone is widely used even with structural heart disease but has potential long-term toxicities (thyroid, liver, lungs, eyes, skin).

Class IV consists of non-dihydropyridine calcium channel blockers (diltiazem, verapamil). They slow AV nodal conduction and are useful for certain supraventricular tachycardias but not for ventricular tachycardia; they can worsen heart failure with reduced ejection fraction in some settings.

Treatment choice depends on rhythm type, heart function, comorbidities, and drug interactions, with careful monitoring of ECG, electrolytes, and potential toxicities.