Fig. 1

Typical recordings of a sympathetic nerve stimulation (SNS) command, heart rate (HR), R–R interval (RRI), and arterial pressure (AP) obtained from the ivabradine protocol. The data are displayed as 200-Hz resampled signals. The white line in the AP plot indicates a 2-s moving averaged signal. The first random SNS changed HR dynamically with an increase in the mean level of HR. Intravenous (i.v.) administration of ivabradine gradually decreased HR. The second random SNS also changed HR dynamically with an increase in the mean level of HR. RRI showed changes reciprocal to HR. bpm beats/min