CARDIAC ELECTROPHYSIOLOGIC EFFECTS OF NOREPINEPHRINE IN HUMAN-BEINGS

Background The electrophysiologic effects of norepinephrine (NE) in hu man beings have not been previously described. Methods The electrophys iologic effects of NE infused at a rate of 25 ng/kg/min were determine d in 21 patients with a mean age of 41 +/- 11 years and without struct ural heart disease who underwent an electrophysiology procedure. In a subgroup of 10 patients electrophysiologic parameters were measured at baseline, after the infusion of NE, and after administration of beta- blockade while in continuous NE infusion. Results The baseline NE plas ma concentration of 298 +/- 153 pg/ml increased to 708 +/- 419 pg/ml a fter the infusion of NE. NE significantly increased the mean blood pre ssure, sinus cycle length, corrected sinus node recovery time, ventric ulo-atrial block cycle length, and the atrial and ventricular effectiv e refractory periods, in a subset of 10 patients 0.2 mg/kg propranotol administered during continued infusion of NE resulted in a further in crease in sinus cycle length, atrial-His interval, and ventricular ref ractoriness. Conclusion A physiologic elevation in the plasma NE conce ntration results in a depression of sinus node function and atrioventr icular conduction and in prolongation of atrial and ventricular refrac toriness. Some of NE's effects are partially off set by beta-adrenergi c stimulation.