Patterns of non-linear heart rate behaviour in sinoatrial node dysfunction: effects of orthostatic test and autonomic blockade

In patients (pts) with sinoatrial node dysfunction (SAND) some types of heart rate variation (HRV) in dependence on posture alternation and autonomic regulation are presented. In 40 SAND-pts and in 40 control subjects (C-sbs) R-R interval oscillations were analysed by means of spectral analysis after FFT during spontaneous breathing in recumbent position, after up-right body movement and after autonomic blockade (AB). Only in 10% SAND-pts HRV spectra in supine were chaotic (ChF) with superimposed narrow peaks, related to regulatory mechanisms, while in 72.5% of C-sbs ChFs were present. SAND-pts characterized often suprarespiratory peaks (bifurcations, BF) or continuous spectra (random fluctuations, RF). In standing position HRV spectra became discrete (oscillatory fluctuation, OF) in 95% of C-sbs and in 50% of SAND-pts. After AB HRV almost disappeared in all C-sbs, but only in about 20% of SAND-pts. Remaining SAND-pts showed abnormal patterns, despite of tilt-up or AB