Restorative effect of epinephrine on the electrophysiologic properties of depressed human atrial tissue

The effects of epinephrine on the electrophysiologic properties of human right atrail tissue, obtained at cardiac surgery, were evaluated utilizing standard microelectrode techniques. In studies of electrophysiology, epinephrine had little effect on the resting membrane potential and transmembrane action potentials of normal atrial fibers. Epinephrine enhanced phase-4 depolarization and increased automaticity in normal fibers but hyperpolarized partially depolarized atrial fibers and decreased automaticity. The hyperpolarizing action of epinephrine resulted in an increase in action potential amplitude and dV/dt and enhanced conduction. Active force increased 40-230% in depressed tissues when exposed to epinephrine. Epinephrine-induced hyperpolarization of depressed atrail fibers may have a beneficial effect on atrial arrhythmias and depressed contractility encountered clinically.