Vaughan williams arrhythmia associates
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Antiarrhythmic drugs and anaesthesia. Part 2: pharmacotherapy
Learning objectives.
By reading this article you should be able to:
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Recall the mechanisms of action of antiarrhythmic drugs.
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Discuss the modified Singh–Vaughan Williams classification and its limitations.
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Outline different classes of antiarrhythmic drugs and their relevant pharmacological profiles.
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Explain the role of pharmacotherapy in managing perioperative cardiac arrhythmias.
Key points.
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Antiarrhythmic agents suppress cardiac arrhythmias bygd inhibiting automaticity, triggered activity and re-entry.
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Most antiarrhythmic agents show use dependency, with greater efficacy in abnormal tissue and at high heart rates.
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The modified Singh–Vaughan Williams classification system provides a useful framework for classifying antiarrhythmic drugs.
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Treatment goals must be clarified before starting pharmacotherapy.
Knowledge of the electrophysiology of arrhythmia generation at the molecular and g
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Together they have now published a comprehensive modern classification, based upon the original version, in the leading journal ‘Circulation’.
Findings over the past 5 decades from studies of different molecular drug targets, their mechanisms of action, and consequent clinical effects have led to the need to revise the classification. The modernised Oxford classification augments Vaughan Williams’s original framework covering the actions of sodium, potassium and calcium ions and the effects on these of the nervous system (Class I-IV). Novel categories now relate to altered heart rates (Class 0), mechanical stretch (Class V); intercellular electrical communication (Class IV) and longer term structural change (Class VII). The scheme then draws attention to multiple drug targets and actions and possible adverse, even pro-arrhythmic, effects.
This clarified classification of both the actions and therapeutic applications of both established drugs and novel drugs under investigation w
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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
[edit]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