[Electrophysiologic effects of dobutamine on cardiac conduction system (author's transl)]

The electrophysiologic effects of dobutamine (D) (3 and/or 6microgram/kg/min), a new beta1 stimulator, was studied in 12 patients with different disturbances of rhythm (sinus-node dysfunction, AV-block, sinus-bradycardia, paroxysmal tachycardia) utilizing His-bundle electrography and right atrial pacing. During infusion of D sinus-rate (HR) increased significantly from 61 to 71/min. Not only in cases with enhanced sinus-node-recovery-time (SKEZ) both, the absolutely (p less than 0.05) and the corrected SKEZ(-18%,-26%) were reduced by D otherwise the calculated sino-atrial-conduction time (SACTc) was shortened only in single cases. No effect could be registered in intraventricular (HV) conduction time, whereas the AV-nodal conduction time (AH) was significantly (p less than 0.05) reduced, more effect was seen at increasing stimulation of heart rate. The intraatrial conduction time (Ah-t) was shortened not significantly. In connection with reduced AH-interval the maximum of conduction frequency of the AV-node was significantly enhanced (10%, 13%). D shortened the refractory-period (RP) of atrium and AV-node, the effect was significant (p less than 0.05) only in the functional-RP of the atrium and relative RP of the AV-node.