Quinidine Syncope: Paroxysmal Ventricular Fibrillation Occurring during Treatment of Chronic Atrial Arrhythmias

Abstract

QUINIDINE occupies an almost uniqueplace in the therapy of cardiac arrhyth- mias.In the 45-odd years of its clinical use only very few drugs possessing similar pharmacologic properties have been found, but none could match quinidine in its broad ther- apeutic applications.Consequently, the knowledge concerning its clinical use and tox- icity is of considerable importance, for pa- tients who tolerate this drug poorly or are hypersensitive to it may face the prospect of inability to have normal cardiac rhythm re- stored or maintained.The pharmacology and toxicology of quinidine have been the subject of several reviews,'-5 but certain aspects of it are still poorly understood.The purpose of this communication is to focus attention on syncopal attacks occurring during quinidine therapy and apparently related to paroxysms of ventricular flutter or fibrillation.Until very recently such ventricular arrhythmias have been considered a very rare manifestation of quinidine toxicity,5 yet they may well be oc- curring quite frequently, unrecognized, in the course of quinidine therapy. Material and MethodsThe report is based on eight cases wiith re- petitive ventricular arrhythmias occurring during conversion of chronic atrial arrhythmias with quinidine, or after conversion of such arrhythmias by electric atrial defibrillation.These cases were observed during a 4-year period in this unit.While the exact number of courses of quinidine administered to patients with atrial arrhyth-