Abstract
Electropharmacologists and cardiologists have proposed a number of classifications for antiarrhythmic drugs during the past 3 decades and most of them have provoked considerable controversy. The 4-part classification presented by Vaughan Williams in 1969, based on microelectrode studies in isolated cardiac cells exposed to a series of chemical compounds, has been generally accepted and is most widely used. Following this classification, antiarrhythmic drugs now clinically available are reviewed. Confusion arose when studies showed that some drugs have more than 1 mechanism of electrophysiological action. Although the classification is useful to get a quick referencec to the drug, to call a drug by the name such as “class×drug” may sometimes lead to misunderstanding. One must bear in mind that the “class” only indicates the dominant action. The division of class I into subgroups IA, IB, IC based on the frequency-dependent nature of action was introduced. Data on amiodarone, whose antiarrhythmic mechanism is uncertain despite its definite clinical efficacy, are discussed to some detail together with our experiences. In closing, it was emphasized that various therapy of underlying diseases itself might be important to treat arrhythmias through normalizing the external milieu or by eliminating arrhythmogenic conditions.
