Key result
Signal complexity measured by Sample Entropy decreased during the pre-syncope phase of the tilt test (e.g., RRI: 1.20 to 0.34), reaching lowest values at the moment of loss of consciousness.
Why the study?
Does entropy analysis of biosignals during head-up tilt testing identify changes in signal complexity in the pre-syncope phase of vasovagal syndrome?
Observational
Does entropy analysis of biosignals during head-up tilt testing identify changes in signal complexity in the pre-syncope phase of vasovagal syndrome?
Entropy analysis of biosignals during head-up tilt testing reveals a significant decrease in signal complexity during the pre-syncope phase, reaching its lowest point at the loss of consciousness.
Entropy analysis of tilt-test signals may aid vasovagal detection; hypothesis-generating and leaves open clinical utility pending validation.
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 tests—HUTT(+). 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): 1.20–0.34, SampEn (sBP): 1.29–0.57, SampEn (dBP): 1.19–0.48, SampEn (SV): 1.62–0.91). 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.
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Buszko et al. (2017) conducted an observational in Vasovagal syndrome. Pre-syncope phase during passive head up tilt test vs. Supine position and tilt phases was evaluated on Signal complexity (entropy) of heart rhythm, blood pressure and stroke volume (p=<0.05). Signal complexity measured by Sample Entropy decreased during the pre-syncope phase of the tilt test (e.g., RRI: 1.20 to 0.34), reaching lowest values at the moment of loss of consciousness.
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