Electrohysterogram: study of the electromechanical activity of the uterus in humans

The electromechanical activity of the uterus was studied in 18 healthy women (mean age 38.3+/-14.2 SD years; 8 were nulliparous, 10 multiparous) aiming at characterizing a normal electrohysterogram. Two monopolar silver-silver chloride electrodes were applied to the uterine and one to the cervical mucosa. The uterine pressure was measured by a water-perfused tube connected to a pressure transducer. Monophasic, negatively deflected slow waves or pacesetter potentials (PPs) were recorded from the 2 uterine electrodes. They had regular rhythm and exhibited the same frequency, amplitude and velocity of conduction by the 2 electrodes. The PPs were followed randomly by bursts of action potentials (APs). The APs and not the PPs were associated with uterine pressure rise. PPs from the cervix were registered only occasionally. The occurrence of the electric activity is believed to depend on the smooth muscle fibers content which is high in the uterine body and meagre in the cervix. The APs seem to have contractile activity which might act to sweep away the uterine secretions. According to the uterocervical reflex, the cervix dilates upon uterine contractions. A normal electrohysterogram could be characterized. It might show a different pattern in the various uterine pathologic conditions and may thus represent an investigative tool in the diagnosis of such disorders.