Autonomic control of cardiovascular reflexes in narcolepsy

Six male patients with narcolepsy for several years, were studied without and with amphetamine in order to evaluate possible abnormalities in autonomic control of the cardiovascular system. Studies were made of (1) heart rate and blood flow in the resting forearm during contralateral isometric handgrip, (2) respiratory sinus arrhythmia and (3) heart rate response to the Valsalva manoeuvre. The patients had a slow heart rate, a reduced forearm blood flow increase on handgrip, and a subnormal sinus arrhythmia. Only two out of the six patients had an abnormal Valsalva ratio. Amphetamine did not alter the response to handgrip but increased the sinus arrhythmia in three patients and the Valsalva ratio in two. It is concluded that narcolepsy is accompanied by reduced vegetative reactivity in the cardiovascular system. Since this applies to functions mediated by both the sympathetic and parasympathetic systems, and since some parasympathetically-mediated functions are affected while others are not, the functional disturbance found probably is of central origin.