Summary
Background: During atrial fibrillation (AF), ventricular response is highly irregular and thus
the beat-to-beat variation of blood pressure is increased because of variations in
filling time and in contractility.
Objectives: Aim of the present study is to investigate the short-term dynamics of RR and SAP
series in patients with AF, during rest and tilt, and after restoration of sinus rhythm.
Methods: We computed symbolic sequences of the three phases, as they retain important features
of the dynamics generated by the underlying control system. Then we applied a method
based on rank order statistics of symbolic sequences to investigate the profile of
different types of dynamics. The linguistic distance (range 0–1) between sequences
represents a measure of similarity to assess whether the different physiological states
are reflected on the dynamics of RR and SAP series.
Results: The distance between rest and tilt phases is 0.06 ± 0.02 for RR series, meaning they
are very similar, while it is 0.21 ± 0.13 for SAP series, showing a difference in
the short-term dynamics. RR mean decreases during tilt (738 ± 164 vs. 692 ± 152 ms,
p < 0.05, rest vs. tilt), while mean SAP is not significantly different (101 ± 20
vs. 104 ± 14 mmHg, rest vs. tilt). Comparing AF and sinus rhythm, both RR and SAP
series result different in terms of the computed distance.
Conclusions: SAP short-term dynamics seem to significantly change when comparing rest and tilt
phases, while RR series remain unchanged. Moreover, RR mean but not SAP series significantly
decreases during tilt.
Keywords
Atrial fibrillation - blood pressure - degree of nonrandomness - heart rate variability
- linguistic analysis
