Circulatory Effects of Electrical Stimulation of the Carotid Sinus Nerves in Man

The effects of carotid sinus nerve (CSN) stimulation were studied at rest and during a mild level of supine bicycle exercise in seven patients in whom CSN stimulators had been implanted for the treatment of angina pectoris. At rest, CSN stimulation produced a fall in mean arterial pressure (MAP) averaging 23% and an 8% decrease in cardiac output (CO). Total peripheral resistance (TPR) fell by 14% and forearm vascular resistance (FVR) by 16%. During exercise, MAP fell 16%, but no significant change occurred in CO. Thus, the fall in MAP could be attributed to a reflexly induced decrease in peripheral vascular resistance. Only small decreases occurred in heart rate. No changes in venous tone, central venous pressure, or the maximum transverse end-diastolic diameter of the heart were produced by stimulation either at rest or during exercise. Thus, at rest, CSN stimulation reduces MAP by reflexly decreasing both vascular resistance and CO; during exercise, the diminution in CO no longer occurs. Finally, the venous system does not appear to participate in reflexes activated by CSN stimulation.