Conventional management of cardiac arrythmias relies on oral drug therapy which minimizes recurrence of the arrhythmia, but risks unpleasant side effects and even long-term toxicity. The authors propose acute management instead, from an implanted drug pump which automatically senses the onset of arrhythmia, delivers a pharmacokinetically-based infusion to terminate the episode, and discontinues drug delivery until the next occurrence. A bedside system consisting of a personal computer and conventional intravenous pump has been developed and tested in five dogs and 24 patients during a catheter electrophysiologic study. After detection of the arrhythmia plasma levels of the antiarrhythmia drug rose immediately to the therapeutic range and were subsequently well-controlled for 30 to 60 minutes. In all five dogs and in seven of the eight patients in whom atrial fibrillation was induced during the study, conversion to normal rhythm occurred within fifteen minutes.>