Variability of arterial blood pressure and heart rate evaluated by fixed rate atrial pacing

Variability of arterial blood pressure (BPV) and heart rate (HRV) were investigated in 26 patients shortly after CABG surgery under two conditions: During the first recording patients had sinus rhythm of 65 to 88 beats per minute; after that the atrium was stimulated at 91 to 115 beats per minute with an external pacemaker. HRV and BPV were determined by discrete Fourier analysis of low frequency (LF) and high frequency (HF) spectral power. While HRV decreases in LF to <0.7% and in HF to 9% compared with sinus rhythm, BPV doesn't change significantly in LF but increases significantly in HF. This supports the idea that normally parasympathetic HF HRV can compensate blood pressure fluctuations due to respiration and that sympathetic vasomotor control does not react in these short beat to beat intervals.