Antiarrhythmic agents classification

Additionally, the electrophysiological effects are often obtained from normal myocardial preparations and the abnormalities of cellular electrophysiology which cause arrhythmias in a diseased myocardium may be uniquely related to the disease process (10). Nevertheless, antiarrhythmic agent classifications have been useful as a mnemonic device. 

Fig. 6. Influences of different types of antiarrhythmic agents (Vaughan-William s classification) on the shape of cardiac action potentials. First row Class I-agents action potentials of ventricular myocardial cells. Second row (from left to right) Action potential of SA-node cells influence of a )0-hlocker (class II). Action potential of ventricular myocardial cells influence of a class Ill-antiarrhythmic. Action potential of AV nodal cells influence of a class IV-antiarrhythmic (verapamil, diltiazem).

Classically antiarrhythmic agents are divided into four classes (Table 12.1) based upon their actions on ion channels. Although this classification is useful, some agents can be categorized into more than one group. 

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. 

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