During the past decade enormous progress has been made in the development of new cardiovascular drugs and in our understanding of the clinical pharma­ cology and the pharmacokinetics of old drugs. In addition, newer applications of older agents have emerged. For example, vasodilators such as nitroglycerin are now being employed in the treatment of congestive heart failure, and anti­ hypertensives such as bretylium are used in the management of ventricular arrhythmias. Individual chapters in this book focus on (1) the clinical pharmacology and pharmacokinetics of the individual drugs, and (2) the clinical applications of these drugs, with attention also to serum concentrations, pathophysiology, and drug interactions where appropriate. The contributors to this text have labored to provide the reader with a meaningful, practical update on the clinical uses and usefulness of cardioactive drugs. We are deeply grateful to each of them for their generous participation in this endeavor. LEONARD S. DREIFUS, M.D. ALBERT N. BREST, M.D. 1. ANTIARRHYTHMIC AGENTS LEONARD S. DREIFUS and JOEL MORGANROTH Ideally, the management of cardiac arrhythmias must be predicated on (1) complete elucidation of the genesis of the various rhythm disturbances, and (2) a full understanding of the pharmacologic action of individual antiarrhythmic agents. Only with this precise information does it become possible to administer a particular agent or agents specifically effective against a given arrhythmia.