Physiological and pharmacological analysis of transmembrane action potentials of human atrial fibers.

Transmembrane action potentials (APs) of electrically paced right-atrial tissue obtained from 38 patients of corrective open-heart surgery were analyzed. Two types of APs could be found. The APs of 20 patients (group I) were similar to those of other laboratory mammals. The average resting potential (RP) and the amplitude and maximum rate of rise of phase 0 of APs (Vmax) were -75 mV, 86 mV, and 152 V/sec, respectively, only the repolarization phase being more prolonged than that of other mammalian APs. Epinephrine (5.8 X 10(-6) mole/liter) increased the amplitude of APs and prolonged the plateau phase, producing odd-looking, humped APs. Prostacyclin-Na (6.7 X 10(-7) and 8.7 X 10(-6) mole/liter) increased Vmax. Celluline-A (a biological Ca-complex obtained from frog skin) increased both Vmax and the amplitude of APs and, similar to epinephrine, prolonged the plateau phase. In group I, postoperative arrhythmias occurred in only 1 of the 10 patients. APs obtained from another 18 preparations (group II) were characterized by low RP (-55 mV), small amplitude of AP (59 mV), slow rate of rise of AP (less than 10 V/sec), and very prolonged repolarization. This type of APs can be referred to as slow-response APs. Neither epinephrine, prostacylin-Na, nor celluline-A modified the characteristics of these slow-response APs. In group II, postoperative arrhythmias could be observed in 8 of the 10 patients.