Abstract
This paper presents an application of Approximate Entropy (ApEn) and Sample Entropy (SampEn) in the analysis of heart rhythm, blood pressure and stroke volume for the diagnosis of vasovagal syndrome. The analyzed biosignals were recorded during positive passive tilt testsâHUTT(+). Signal changes and their entropy were compared in three main phases of the test: supine position, tilt, and pre-syncope, with special focus on the latter, which was analyzed in a sliding window of each signal. In some cases, ApEn and SampEn were equally useful for the assessment of signal complexity (p < 0.05 in corresponding calculations). The complexity of the signals was found to decrease in the pre-syncope phase (SampEn (RRI): 1.20â0.34, SampEn (sBP): 1.29â0.57, SampEn (dBP): 1.19â0.48, SampEn (SV): 1.62â0.91). The pattern of the SampEn (SV) decrease differs from the pattern of the SampEn (sBP), SampEn (dBP) and SampEn (RRI) decrease. For all signals, the lowest entropy values in the pre-syncope phase were observed at the moment when loss of consciousness occurred.
Highlights
Syncope is a temporary self-regressing loss of consciousness, usually resulting in a fall.It is assumed that the direct cause of syncope is the short-term reversible global cerebral hypoperfusion.There are three types of syncope: cardiac, orthostatic and neuro-cardiogenic [1]
We extended the assessment of the system complexity to analysis of the impedance cardiography (ICG) signal, to stroke volume (SV) determined from the ICG
The results presented in the previous section, section, based based on on the the analysis analysis of of the the changes changes of of RRI, RRI, systolic blood pressure (sBP), sBP, andSV
Summary
Syncope is a temporary self-regressing loss of consciousness, usually resulting in a fall. The typical diagnostics for neuro-cardiogenic syncope are based on the patientâs medical history and the results of Head Up Tilt Test (HUTT). The observation of the signal changes (especially concerning heart rate and blood pressure) allows classification of the observed neuro-cardiogenic reaction, according to the criteria VAsovagal Syncope International Study (VASIS) [1]. I.e., comparing mean values of the parameters in each window, we focused on the assessment of the pre-syncopal changes in signal complexity. Our study demonstrates that the loss of complexity of biosignals is strictly related to the occurrence of neuro-cardiogenic reactions in HUTT. The presented analysis of changes in the complexity of joint signals of ECG, ICG and blood pressure during passive provocation of the neuro-cardiogenic reaction will add to further understanding of the course and mechanism of vasovagal syndrome
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