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Context: Class II agents are antisympathetic drugs, particularly the beta-adrenoceptor blockers
Class III antiarrhythmic agents include sotalol and amiodarone.
Class IV antiarrhythmic drugs are the calcium channel blockers verapamil and diltiazem.
Other agents which do not fall neatly into the Vaughan Williams classification include digoxin and perhexiline.
Antiarrhythmic drugs can be divided into four Vaughan Williams classes (I-IV) according to defined electrophysiological effects on the myocardium.
Thus, the Vaughan Williams classification also coincides with the main myocardial targets of the antiarrhythmics, i.e., myocardial sodium-, potassium-, and calcium-channels or beta-adrenergic receptors.
The sodium-channel blockade induced by class-I substances is enhanced with increasing heart rates. Thus, class-I antiarrhythmics can be subclassified as substances showing a more exponential, an approximately linear, or rather saturated block-frequency relation.
Class-III antiarrhythmics (potassium-channel blockade) can be further differentiated according to the component of the delayed rectifier potassium current (IK) which is inhibited by a drug.
Class-III substances inhibiting the slowly activating IKs component are currently under investigation and are expected to show a direct rate dependence.
Antiarrhythmic agents are traditionally classified according to Vaughan Williams into four classes of action. Class I antiarrhythmic agents include most of the drugs traditionally thought of as antiarrhythmics, and have as a common action, blockade of the fast-inward sodium channel on myocardium.
Antiarrhythmic drugs can be divided into four Vaughan Williams classes (I-IV) according to defined electrophysiological effects on the myocardium
The classification of antiarrhythmic agents according to Vaughan Williams is based on electrophysiological findings in isolated heart muscle and defines four classes of drug actions.
Antiarrhythmic agents are traditionally classified according to Vaughan Williams into four classes of action. Class I antiarrhythmic agents include most of the drugs traditionally thought of as antiarrhythmics, and have as a common action, blockade of the fast-inward sodium channel on myocardium.
Class II agents are antisympathetic drugs, particularly the b-adrenoceptor blockers.
Class III antiarrhythmic agents include sotalol and amiodarone.
Class IV antiarrhythmic drugs are the calcium channel blockers verapamil and diltiazem.
These are classified according to their electrophysiological effects observed in isolated cardiac tissues in vitro (Vaughan Williams, 1989). Fast sodium channel blockers (class I) which reduce the upstroke velocity of the action potential are usually subclassified into three groups, class I A-C, according to their effect on the action potential duration. Beta-adrenergic antagonists (class II) exert their effects by antagonizing the electrophysiological effects of beta-adrenergic catecholamines. Class III antiarrhythmic agents (eg amiodarone) prolong the action potential and slow calcium channel blockers (class IV) suppress the calcium inward current and calcium-dependent action potentials.

Question:
Which are the classes of anti-arrhythmic drugs according to Vaughan-Williams classification?
["Class I: sodium channel blockers", "ClassII: beta blockers", "Class III: potassium channel blockers", "Class IV: calcium channel blockers"]