Pharmacologic Basis for the Treatment of Cardiac Arrhythmias

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The treatment of many cardiac arrhythmias occurring in the pediatric population is often a perplexing therapeutic problem. An apparent increase in the incidence of these arrhythmias is occurring, probably for several reasons. Physicians have attained a greater awareness of the problem of cardiac arrhythmias in the young; diagnostic capabilities have been improved; and large numbers of patients with congenital cardiac malformations now undergo total surgical correction and experience postoperative cardiac arrhythmias. The pharmacotherapy of cardiac arrhythmias in pediatric patients is determined by multiple factors. Probably foremost among these is the clinical efficacy of a given drug in the hands of an individual pediatrician; that is, his personal experience in antiarrhythmic therapy. Information and experience here are often limited, however, and in many instances the determining factor in selection and method of administration of a drug to the pediatric patient is its use in the treatment of arrhythmias in the adult. Additional requirements for the rational choice of the proper antiarrhythmic agent are (1) an accurate diagnosis of the cardiac arrhythmia; (2) a knowledge of the mechanism for initiation and maintenance of an arrhythmia; (3) an understanding of the electrophysiologic effects, pharmacologic properties and metabolism of the drugs available; and (4) the clinical status of the patient. Any electrolyte imbalance, concomitant drug therapy or organ system dysfunction may alter the absorption and metabolism of the drug. In the past decade there has been a large increment in the literature concerning mechanisms underlying the occurrence of cardiac arrhythmias and their therapy. Our purpose in this review is to familiarize pediatricians with the electrophysiologic basis for arrhythmias, with the mechanisms of action of the commonly used antiarrhythmic drugs, and with their administration, metabolism, excretion and undesirable effects.