Electrophysiologic properties of coffee in man.

There is no information on the effects of coffee on the human conduction system. His bundle electrograms were obtained in 12 patients before and 20 minutes after the ingestion of coffee containing 150 mg caffeine. Antegrade and retrograde refractory periods were obtained with the extrastimulus method. The effective and functional refractory period of the atrioventricular node decreased after coffee ingestion. This improvement in conduction is probably mediated by a release of catecholamines.