H. Duff, D. Roden, A. K. Dawson
Aug 1, 1982
Citations
0
Influential Citations
25
Citations
Quality indicators
Journal
The American journal of cardiology
Abstract
Abstract Encainide is an investigational antiarrhythmic agent that is very effective in the treatment of nonlife-threatening ventricular arrhythmias. Because of its marked efficacy and short half-life it has been possible to manipulate the dose and dosing interval to produce repeatedly and predictably episodes of arrhythmia abolition followed by arrhythmia recurrence. This study examined the results of programmed electrical stimulation during periods of arrhythmia suppression and recurrence induced by encainide. Eight patients with chronic ventricular arrhythmias who had suppression of ventricular arrhythmia as assessed by ambulatory monitoring during 6 months of outpatient treatment with encainide underwent programmed electrical stimulation testing in a drug-free state. Patients were then randomly assigned to receive placebo or encainide. Thereafter, electrophysiologic testing was performed twice daily immediately before and 1 hour after administration of either placebo or encainide. In patients receiving encainide, the repetitive ventricular response was neither consistently absent during periods of arrhythmia suppression nor consistently present during periods of arrhythmia recurrence. Furthermore, four patients showed increased ease of inducibility of the repetitive ventricular response during periods when encainide had suppressed the spontaneous ventricular arrhythmias. Indeed, in one of these patients programmed electrical stimulation (single extrastimulus) in the presence of encainide elicited ventricular fibrillation. Three of four patients randomly assigned to placebo therapy initially manifested a repetitive ventricular response: However, over a period of time the zone in diastole in which the repetitive ventricular response was observed progressively diminished and became absent for at least 1 day in all patients. Indistinguishable changes over a period of time were seen in the patients treated with encainide. Time-dependent variations in cardiac electrophysiologic measurements must be taken into account when programmed electrical stimulation at a single electrode site is used to evaluate drug therapy. In this study the presence or absence of the repetitive ventricular response bore no relation to arrhythmia frequency as encainide was administered or withdrawn. Programmed electrical stimulation in the presence of encainide may elicit potentially lethal ventricular arrhythmias.