Entropy Measures in Analysis of Head up Tilt Test Outcome for Diagnosing Vasovagal Syncope

Abstract

The paper presents possible applications of entropy measures in analysis of biosignals recorded during head up tilt testing (HUTT) in patients with suspected vasovagal syndrome. The study group comprised 80 patients who developed syncope during HUTT (57 in the passive phase of the test (HUTT(+) group) and 23 who had negative result of passive phase and developed syncope after provocation with nitroglycerine (HUTT(−) group)). The paper focuses on assessment of monitored signals' complexity (heart rate expressed as R-R intervals (RRI), blood pressure (sBP, dBP) and stroke volume (SV)) using various types of entropy measures (Sample Entropy (SE), Fuzzy Entropy (FE), Shannon Entropy (Sh), Conditional Entropy (CE), Permutation Entropy (PE)). Assessment of the complexity of signals in supine position indicated presence of significant differences between HUTT(+) versus HUTT(−) patients only for Conditional Entropy (CE(RRI)). Values of CE(RRI) higher than 0.7 indicate likelihood of a positive result of HUTT already at the passive phase. During tilting, in the pre-syncope phase, significant differences were found for: (SE(sBP), SE(dBP), FE(RRI), FE(sBP), FE(dBP), FE(SV), Sh(sBP), Sh(SV), CE(sBP), CE(dBP)). HUTT(+) patients demonstrated significant changes in signals' complexity more frequently than HUTT(−) patients. When comparing entropy measurements done in the supine position with those during tilting, SV assessed in HUTT(+) patients was the only parameter for which all tested measures of entropy (SE(SV), FE(SV), Sh(SV), CE(SV), PE(SV)) showed significant differences.

Transfer Information Assessment in Diagnosis of Vasovagal Syncope Using Transfer Entropy

“…Therefore, we propose to include SV measurements as a standard tool for diagnosing VVS, along with ICG and blood pressure monitoring. This conclusion is in line with our previous analysis based on other entropy measures [ 17 , 39 , 40 , 41 ]. Others investigators arrived at similar conclusions based on the measurement of SV in the early tilt [ 42 ].…”

“…In our previous investigations the Conditional Entropy occurred the only entropy measure, which has a prognostic value in predicting the HUT test. The entropy measures from the ApEn family (Approximate Entropy, Sample Entropy and Fuzzy Entropy) did not turn out good candidates for VVS prediction in a passive HUT test [ 17 ]. The two mentioned reasons induced us to choose the Transfer Entropy as a measure of the relation between the measured parameters during the HUT test.…”

“…Against this background, the transfer entropy allows to investigate the relation between the parameters during the test. Moreover the algorithm of calculation of Transfer Entropy is based on assessment of Conditional Entropy, which has been calculated in the previous investigation and it turned out to be a useful tool in passive HUT test prediction [ 17 ]. The features of TE mentioned above motivated us to explore the TE in diagnosing of VVS.…”

Quantitative Complexity Theory (QCT) in Integrative Analysis of Cardiovascular Hemodynamic Response to Posture Change

“…Koźluk et al [ 3 ] reported a higher reduction in SV (−27.2 ± 21.2 mL vs. −9.7 ± 27.2 mL; p = 0.03) and CO (−1.78 ± 1.62 L/min vs. −0.34 ± 2.48 L/min; p = 0.032) five minutes after tilting in subjects with positive HUTT results compared to HUTT-negative ones. Buszko et al [ 21 ] identified the measures of entropy for stroke volume as the best discriminators between patients with positive and negative HUTT results. Schang et al [ 22 ] analyzed the pre-tilting supine rest impedance waveform using neural networks and were able to predict a positive HUTT with 64% specificity and 88% sensitivity.…”

Application of a Head-Up Tilt Table Test in Differentiation Between Epilepsy and Syncope in Children

“…Although syncope and pre-syncope are common in children, they have low mortality and complications (18,19). Convulsive movements and recurrent loss of consciousness can be considered epileptic events, especially in the presence of an abnormal EEG, while, in fact, it is a syncope or pre-syncope event.…”