Anti-Arrhythmics for Tachycardias

Anti Arrhythmic Medications

Vaughan Willaims Classification

	Mechanism of Action	Examples	Effect	Use
Class IA	Na channel blockade, some K channel block	Quinidine Procainamide Disopyramide	Slows conduction and prolongs repolarization	Preexcited AF, SVT, Ventricular arrhythmias
Class IB	Na channel blockade	Lidocaine Mexiletine Phenytoin	Slows conduction in diseased tissues, shortens repolarization	Ventricular arrhythmias
Class IC	Na channel blockade	Flecainide Propafenone	Markedly slows conduction. Slightly prolongs repolarization	AF, A flutter,
Class II	Beta blockade	Metoprolol Propranolol Atenolol	Suppresses automaticity and slows AV nodal conduction	Rate control of AF, SVT, ventricular arrhythmias
Class III	K channel blockade	Sotalol Amiodarone Dofetilide Dronedarone	Prolongs action potential duration	AF, ventricular arrhythmias
Class IV	Ca channel Blockade	Verapamil Diltiazem	Slows SA node automaticity and AV nodal conduction	SVT, rate control of atrial arrhythmias, triggered arrhythmias

USAGE:
- Avoid Class II and Class III in patients with decompensated heart failure and Wolff-Parkinson White syndrome
- Class I and III causes ventricular arrhythmias and Toxic
- Class IC (used for AF) should be avoided in those with CAD, IHD as increased risk of polymorphic VT. May also predispose to rapid 1:1 AV nodal conduction. therefore given with AV nodal blocker.
- Class III usually prolong QT interval, therefore increases risk of Torsades de pointes
- Amiodarone used in HF and LVH, but has several side effects: thyroid dysfunction, liver toxicity, pulmonary fibrosis and skin hypersensitivity
- Digoxin (MOA: Na-K exchange blocker and also increases vagal activity to heart) and Adenosine (MOA: Blocks A1 receptors in AV node) also included as anti-arrhythmics