Background: The development of time series data analysis methods in past 15 years tends to elaborate new ways of investigating Autonomic Nervous System (ANS) disorders. The evaluation of asymmetry in the natural variability of heart rate and beat-to-beat variation of the blood pressure aims to assess the ANS control in human body during various conditions. Vasovagal syndrome is an illness of specific reflex syncope in which a malfunction of ANS plays a key role. The exact causes of vasovagal syncope are unknown therefore deepened studies of ANS control assessment methods during this incidents are highly needed.
Objectives: To evaluate the potential of asymmetry in heart rate and blood pressure variability as a diagnostic tool in vasovagal syncope episodes.
Methods: The analyzed groups consisted of 19 healthy females and 16 vasovagal female patients. The participants undertook a head up tilt test. During the test an ECG signal has been recorded and extracted into normal RR intervals. Furthermore the systolic and diastolic blood pressure has been simultaneously registered with beat-to-beat method. Time variability and its asymmetry in signals has been tested with variance-based descriptors derived from Poincaré plots.
Results: We observed lack of difference in heart rate asymmetry indices (Guzik’s index and Porta’s index) between supine and tilt phases of tilt test in patients with vasovagal episodes history. The analysis of Poincaré plots revealed lack of difference in short-term variability of diastolic blood pressure between supine and tilt in group of studied patients. Moreover, the pulse pressure in vasovagal patients appeared to be significantly higher than in healthy volunteers.
Conclusions: The results show that the analysis of heart rate and blood pressure asymmetry may become a valuable tool in predicting vasovagal episode during the head up tilt test.