Recording Vagal Nerve Activity for the Control of an Artificial Heart System

Monitoring cardiovascular control system information is important in considering the quality of life (QOL) of patients with artificial hearts. Natural heart circulation is controlled by an autonomic nervous system. Therefore, it is desirable to record autonomic nerve activity for the control of artificial heart systems. We directly recorded vagal nerve activity in long-term animal experiments. Six healthy adult goats were anesthetized with halothane inhalation, and thoracotomy was performed with the fourth rib resection during mechanical ventilation. Arterial blood pressure and right and left atrial pressures were continuously monitored with an inserted catheter. Cardiac output was measured by an electromagnetic flow meter attached to the ascending aorta. After the chest was closed, an incision was made in the left neck, and the left vagal nerve was separated. Stainless steel electrodes were inserted into the vagal nerve and fixed by a plasticizer. After the incision was closed, the goats were transferred to a cage and extubated after waking. Vagal nerve activity was measured using hemodynamic parameters when the animals were awake. Our results show that clear observation of autonomic nerve discharge was made through this experimental system for over 1 month. The tonus of the vagal nerve was significantly altered before body motion with hemodynamic changes, suggesting the possibility of prediction. These results suggest that information from autonomic nerves may help to control implantable artificial hearts or ventricular assist devices.