RESUMO
Spontaneous electrical activity correlated to cardiac rhythm has been recorded with electrodes placed on the surface of the human arm or using the rabbit hindlimb. The signal-to-noise ratio has been improved using record averaging synchronized with the ECG. The recorded activity in man is a slow negative wave of sinusoid-like shape with a mean peak amplitude 0.08 +/- 0.03 microV. The sympathetic origin of this activity is suggested by the facts that its time course and conduction velocity are similar to those of integrated spontaneous electrical activity, recorded directly from postganglionic sympathetic fibers in the rabbit, and that it can be recorded from skin surface as a response to direct electrical stimulation of sympathetic nerve in the same animal.
