FLUCTUATIONS OF THE SYMPATHETIC-NERVE DISCHARGES IN ANIMALS WITHOUT NATURAL HEARTBEAT

To assess the effect of artificial circulation on the circulatory regu latory system, rhythmical fluctuations in the cardiovascular system an d autonomic nerve discharges were analyzed in animal experiments using adult mongrel dogs. Two pneumatically actuated ventricular assist dev ices were implanted as total biventricular bypass (BVB) under general anesthesia; then, the natural heart was electrically fibrillated to co nstitute the BVB part of the complete prosthetic circulation model. Al l hemodynamic data and sympathetic nerve discharges were recorded and calculated in the computer system by the use of spectral analyzing met hods. In the power spectrum of the arterial blood pressure waveform du ring prosthetic circulation, the Mayer wave peak was significantly dec reased though the respiratory wave peak was not significantly changed. However, the Mayer wave peak in sympathetic nerve discharges was sign ificantly increased though the respiratory wave peak was not significa ntly changed. These results suggest that rhythmical fluctuations are a necessary response of the circulatory regulatory system including the autonomic nervous system. However, sympathetic nerve discharges respo nd to the artificial heart without rhythmical fluctuations.