CAN YOU IDENTIFY these Vaughan Williams classes of antiarrhythmic drugs? Match the Vaughan Williams class in Section I with its description in Section II.

Section I

_____ 1. Class I

_____ 2. Class II

_____ 3. Class III

_____ 4. Class IV

Section II

a. These drugs block calcium channels, resulting in decreased action potential generation and slowed conduction through the atrioventricular (AV) node. Examples include verapamil and diltiazem.

b. These drugs inhibit sympathetic activity, primarily by causing beta blockade. The result is decreased heart rate, cardiac excitability, and cardiac output, as well as slowed AV node conduction. Examples include propranolol, esmolol, timolol, metoprolol, and atenolol.

c. These drugs block potassium channels and prolong the action potential duration, repolarization, and the refractory period. Examples include amiodarone, sotalol, ibutilide, and dofetilide.

d. Three different subclasses of these drugs modulate or block sodium channels in the cell membrane, resulting in decreased depolarization and automaticity of ventricular cells and increased ventricular fibrillation threshold. Examples include lidocaine, quinidine, procainamide, flecainide, and propafenone.

References available upon request.

ANSWERS: 1(d), 2(b), 3(c), 4(a)