Abstract
Summary
The combination of quinidine and propranolol has been reported to be effective in conversion of atrial tachyarrhythmias resistant to standard conversion techniques. The electrophysiology of the quinidine-propranolol combination was studied in pentobarbital anesthetized dogs which had undergone bilateral vagotomy and stellate ganglionectomy. The purpose of these studies was to determine a possible mechanism for the enhanced antiarrhythmic activity of the combination. Coadministration of quinidine and propranolol was shown to potentiate the slowing of atrial conduction time produced by the individual drugs. The quinidine-propranolol combination did not potentiate the individual drug actions to depress atrial excitability or to increase the atrial effective refractory period, atrioventricular functional refractory period and atrioventricular transmission time. Thus, these studies demonstrate that the combination of quinidine and propranolol is especially effective in slowing atrial conduction, which could account in part for the enhanced antiarrhythmic activity of the combination against resistant atrial tachyarrhythmias.
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