The Effect of Antiarrhythmic Agents on Impulse Formation and Impulse Conduction

Since the dawn of modern electrophysiology in the 1950’s, many pertinent and useful observations have aided the physiologist and clinical cardiologist in the diagnosis and management of disturbances of impulse formation and conduction (91). While it is generally acknowledged that the precise action of antiarrhythmic agents remains unclear, some important strides have been made in an attempt to understand the electropharmacology of antiarrhythmic agents. Admittedly there is still an incomplete understanding of the mechanisms engendering various cardiac arrhythmias despite the recent contributions by investigators using ultramicroelectrode and His bundle techniques. Too often the clinician, surprised by the actions of a specific agent, may be unable to predict whether the drug will be beneficial or precipitate more hazardous problems. This is particularly true when one antiarrhythmic agent is used in the wake of another since the interactions of various antiarrhythmic drugs still remain unclear (210). Recent reviews have brought into sharp focus both the electrophysiology and pharmacology of anti-arrhythmic agents (210,302, 675,681,877,935). It is the purpose of this discussion to relate some of the presently available antiarrhythmic agents to their possible modes of action on impulse formation and conduction. Previously documented data will be summarized and newer information presented to define the present state of our knowledge with the hope that this will serve as a basis for future investigation.