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

The electrophysiologic effects of dopamine (Dop.) (3 microgram; n = 11) 6 microgram/kg/min; n = 14) were studied in 20 patients (5 females, 15 males) with and without different disturbances of rhythm utilizing His-Bundle electrography and right atrial pacing. The blood pressure increased significantly (p less than 0.01) about 10% (3 microgram Dop.) or 16% (6 microgram Dop.) respectively. Electrophysiologic parameters of the sinus node (spontaneous cycle length before and during carotid sinus pressure, max. sinus node recovery time = SKEZmax, sinoatrial conduction time = SACTc were not changed significantly. In single cases the sinus node function was improved by 3 microgram Dop., otherwise 6 microgram Dop. aggravated them partially. In 5 patients with sick-sinus syndrome the prolonged SKEZmax and SACTc were not reduced significantly. The electrophysiologic parameters of the atrium (Ah-t, effective-relative-functional refractory period) were not influenced by Dop. The AV-node conduction (AH,AH in response to right atrium stimulation, max. 1 : 1 conduction, refractory periods) was not altered by the catecholamine concentration of 6 microgram Dop. The intranodal conduction was improved by 3 microgram Dop. irrelevantly. No influence was seen in 3 patients with a delayed AV-conduction. The possible mechanism of the ineffective shortening of the AV-conduction may be the baroreceptor reflex caused by the enhanced blood pressure. The intraventricular conduction time (HV) was improved in some cases insignificantly, no differences was seen in the aberrant conduction of the His-Purkinje system provoked by paired stimulation.