Vaughan williams arrhythmia meaning

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Universität Leipzig, Herzzentrum Leipzig, Klinik für Herzchirurgie, Leipzig, Germany

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Definition

Antiarrhythmic drugs are substances that block cardiac ionic channels, thereby altering the cardiac action potential. This results in changes of the spread of activation or the pattern of repolarization. Thereby, these drugs suppress cardiac arrhythmia.

These drugs can be classified according to Vaughan-Williams (Table 1): (a) sodium channel blockers; slowing the spread of activation (Class I Antiarrhythmic Drugs) with prolongation of the action potential (class IA), with shortening of the action potential (class IB) or without effect on action potential duration (class IC), (b) β-adrenoceptor antagonists; slowing sinus rhythm and atrioventricular conduction (Class II Antiarrhythmic Drugs), (c) potassium kanal blockers; prolonging the action potential (Class III Antiarrhythmic Drugs), (d) calcium channel blockers; mainly

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Antiarrhythmics

Understand the pharmacology of antiarrhythmic drugs

Antiarrhythmic drugs are typically classified using the Vaughan Williams classification struktur, which divides drugs into fyra classes based on their effect on the cardiac action potential. Many drugs will act via multiple mechanisms.

Class I: Block voltage-gated Na channels
- Class Ia: Intermediate dissociation
- Class Ib: Fast dissociation
- Class Ic: Slow dissociation
Class II: β-Blockers
Class III: Prolong the action potential (Usually via K⁺ channel blockade)
Class IV: Ca²⁺ antagonists

This classification is notably incomplete, as some drugs (such as amiodarone) fit into multiple categories, and others (such as digoxin, adenosine, and magnesium) fit into none.

Class I

Na⁺-channel blockade inhibits action potential prolongation by blocking active and refractory sodium channels in a use-dependent fashion
This inhibits tachyarrhythmias whilst allowing normal conduction
Ext

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Antiarrhythmic agent

Heart rhythm medication

Antiarrhythmic agents, also known as cardiac dysrhythmia medications, are a class of drugs that are used to suppress abnormally fast rhythms (tachycardias), such as atrial fibrillation, supraventricular tachycardia and ventricular tachycardia.

Many attempts have been made to classify antiarrhythmic agents. Many of the antiarrhythmic agents have multiple modes of action, which makes any classification imprecise.

Action potential

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Main article: Cardiac action potential

The cardiac myocyte has two general types of action potentials: conduction system and working myocardium. The action potential is divided into 5 phases and shown in the diagram. The sharp rise in voltage ("0") corresponds to the influx of sodium ions, whereas the two decays ("1" and "3", respectively) correspond to the sodium-channel inactivation and the repolarizing efflux of potassium ions. The characteristic plateau ("2") results from the opening of