Antiarrhythmic drugs classification

Nattel S (1991) Antiarrhythmic drug classifications. A critical appraisal of their history, present status, and clinical relevance. Drugs 41(5) 672-701 Nawrath H, Wegener JW (1997) Kinetics and state-dependail effects of verapamil on cardiac L-type calcium channels. Naunyn Schmiedebergs Arch Pharmacol 355(l) 79-86 Ono K, lijima T (2010) Cardiac T-type Ca(2+) channels in the heart. J Mol Cell Cardiol 48 (l) 65-70... 

Antiarrhythmic Drugs. Table 1 Classification of antiarrhythmic drugs according to Vaughan-Williams... 

Describe the modified Vaughan-Williams classification of antiarrhythmic drugs, and compare and contrast the effects of available antiarrhythmic drugs on ventricular conduction velocity, refractory period, automaticity, and inhibition of specific myocardial ion channels. 

The Vaughan-Williams classification of antiarrhythmic drugs has been criticized for a number of reasons. The classification is based on the effects of drugs on normal, rather than diseased, myocardium. In addition, many of the drugs may be placed into more than one class. For example, the class IA drugs prolong repolarization/refractoriness, either via the parent drug8,9 or an active metabolite,10 and therefore also maybe placed in class III. Sotalol is also a 3-blocker, and therefore fits into class II. Amiodarone inhibits sodium and potassium channels, is a non-competitive inhibitor of 3-receptors, and inhibits calcium... 

Table 2. Examples of antiarrhythmic drugs (Vaughan-William s classification)...

Task Force of the Working Group on Arrhythmias of the European Society of Cardiology. The Sicilian gambit. A new approach to the classification of antiarrhythmic drugs based on their actions on arrhythmogenic mechanisms. Circulation 1991 84 1831-51. 

Nattel S and Singh BN. Evolution, mechanisms, and classification of antiarrhythmic drugs Focus on class III actions. Am J Cardiol 1999 84(9A) 11R-19R. 

The most widely used scheme for the classification of antiarrhythmic drug actions recognizes four classes ... 

The antiarrhythmic drugs can be classified according to their predominant effects on the action potential. Although this classification is convenient, it is not entirely clear-cut, because many of the drugs have... 

How should the clinician approach the patient with documented asymptomatic PVCs Clearly, attempts to suppress asymptomatic PVCs should not be made with any antiarrhythmic drug. Indeed, those at risk for arrhythmic death (recent MI, LV dysfunction, complex PVCs) should not be given any type I or III antiarrhythmic agent routinely. Of the antiarrhythmic drugs in the Vaughn Williams classification, only /3-blockers have been proven conclusively to prevent overall mortality in these patients, and therefore, chronic drug therapy should be restricted to these agents. 

Class 1, II, III, and IV drugs A method for classifying antiarrhythmic drugs, sometimes called the Vaughan-Williams classification based loosely on the channel or receptor affected... 

Antiarrhythmic drugs have been divided into four classes to facilitate comparison and discussion. Since the time the drugs were classified, however, it has become clear that drugs within each class may differ significantly and cannot be substituted for one another. The original classification scheme (bold-face print) and other generalizations include ... 

The most frequently used classification system is that proposed by Vaughan Williams (Table 6-1). Type la drugs slow conduction velocity, prolong refractoriness, and decrease the automatic properties of sodium-dependent (normal and diseased) conduction tissue. Type la drugs are broad-spectrum antiarrhythmics, being effective for both supraventricular and ventricular arrhythmias. 

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