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

QUINIDINE occupies an almost unique place in the therapy of cardiac arrhythmias. 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 therapeutic applications. Consequently, the knowledge concerning its clinical use and toxicity is of considerable importance, for patients who tolerate this drug poorly or are hypersensitive to it may face the prospect of inability to have normal cardiac rhythm restored 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 occurring quite frequently, unrecognized, in the course of quinidine therapy.