Observations on carotid sinus hypersensitivity from direct intraneural recordings of sympathetic nerve traffic

In summary, we studied 4 patients with mixed-type CS hypersensitivity. We demonstrated that CS massage rapidly inhibits sympathetic nerve activity and decreases heart rate. Arterial pressure starts to decline abruptly with complete sympathetic withdrawal, but the nadir is delayed, suggesting that arterial dilation is not instantaneous. Arterial pressure rebounds slowly, suggesting a latency between the neural reflex and vascular compliance. Pacing had little effect on preventing hypotension in these patients. Our data support the concept that sympathetic withdrawal is responsible for the vasodilatory component seen with CS syncope.