# Entropy in Investigation of Vasovagal Syndrome in Passive Head Up Tilt Test

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## Abstract

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## 1. Introduction

## 2. Materials and Methods

#### 2.1. Approximate Entropy and Sample Entropy

**N**, the length of the basic sequence was named as m and the similarity criterion as r. The algorithm for ApEn calculation is well known and its detailed description is available in the literature [19,29,30,31,32]. Here, we only describe it briefly.

**N**:

**N**and after some modifications [30,31,32,33,34,35,36], Formula (7) can finally be expressed as:

**N**data points. This limitation is important in case of short data sets [20,37]. The recommended data sets for calculating ApEn for a given m is: ${10}^{m}-{20}^{m}$ points [39]. Another limitation is that ApEn is sensitive to parameters (m,r). In consequence, ApEn is useful as a measure for comparing data sets only for fixed parameters (m,r).

#### 2.2. Study Group

#### 2.3. Measurements

#### 2.4. Data Analysis and Statistical Methods

## 3. Results

#### 3.1. Comparisons of Parameters for Selected HUTT Stages

#### 3.2. Sample Entropy in Sliding Windows

_{max}) and the beat number for the minimum values (T

_{min}). Mean values of these parameters are presented in Table 2.

## 4. Discussion

## 5. Limitations

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

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**Figure 1.**The recorded parameters: RR-intervals (RRI), systolic blood pressure (sBP), diastolic blood pressure (dBP), stroke volume (SV) and the phases of the measurements (

**I**,

**II**,

**III**) used for calculations.

**Figure 2.**Friedmann test and multicomparison post hoc test in phase I, II and III of tilt test. (

**a**) RRI; (

**b**) sBP; (

**c**) dBP; (

**d**) SV.

**Figure 3.**Friedmann test and multicomparison post hoc test in phase I, II and III of tilt test. (

**a**) ApEn (RRI); (

**b**) ApEn; (sBP); (

**c**) ApEn; (dBP); (

**d**) ApEn (SV).

**Figure 4.**Friedmann test and multicomparison post hoc test in phase I, II and III of tilt test. (

**a**) Sample Entropy (SampEn) (RRI); (

**b**) SampEn (sBP); (

**c**) SampEn (dBP); (

**d**) SampEn (SV).

**Figure 6.**The average SampEn with standard error (SEM) in the pre-syncope phase (phase III) in sliding windows.

Parameter | I | II | III |
---|---|---|---|

RRI (ms) | 854.23 ± 111.75 | 694.72 ± 113.70 | 668.65 ± 143.26 |

sBP (mmHg) | 118.61 ± 25.4 | 121.19 ± 16.79 | 101.60 ± 10.56 |

dBP (mmHg) | 68.08 ± 19.75 | 85.94 ± 14.92 | 67.17 ± 11.21 |

SV (mL) | 89.93 ± 18.73 | 66.60 ± 10.27 | 61.79 ± 9.11 |

ApEn (RRI) | 0.98 ± 0.19 | 0.75 ± 0.26 | 0.32 ± 0.22 |

ApEn (sBP) | 0.73 ± 0.31 | 0.70 ± 0.26 | 0.46 ± 0.23 |

ApEn (dBP) | 0.75 ± 0.30 | 0.66 ± 0.24 | 0.38 ± 0.23 |

ApEn (SV) | 0.93 ± 0.19 | 0.72 ± 0.21 | 0.79 ± 0.26 |

SampEn (RRI) | 1.24 ± 0.46 | 0.86 ± 0.35 | 0.36 ± 0.26 |

SampEn (sBP) | 0.88 ± 0.45 | 0.82 ± 0.36 | 0.51 ± 0.27 |

SampEn (dBP) | 0.91 ± 0.41 | 0.76 ± 0.31 | 0.41 ± 0.27 |

SampEn (SV) | 1.16 ± 0.32 | 0.80 ± 0.29 | 0.95 ± 0.38 |

**Table 2.**The characteristics of systolic blood pressure (sBP) and diastolic blood pressure (dBP) changes in the pre-syncope phase (phase III).

Parameter | $\overline{\mathit{m}\mathit{a}\mathit{x}}$ | $\overline{\mathit{m}\mathit{i}\mathit{n}}$ | $\overline{{\mathit{T}}_{\mathit{m}\mathit{a}\mathit{x}}}$ | $\overline{{\mathit{T}}_{\mathit{m}\mathit{i}\mathit{n}}}$ | $\overline{{\mathit{T}}_{\mathit{m}\mathit{a}\mathit{x}}-{\mathit{T}}_{\mathit{m}\mathit{i}\mathit{n}}}$ |
---|---|---|---|---|---|

sBP (mmHg) | 133 ± 3.13 | 63 ± 19.72 | 69 ± 66 | 237 ± 25 | 160 ± 73 |

dBP (mmHg) | 88 ± 21 | 36 ± 21 | 63 ± 59 | 236 ± 29 | 172 ± 66 |

**Table 3.**The characteristics of SampEn changes in a 100 beats sliding window in the pre-syncope phase (phase III).

Parameter | $\overline{\mathit{S}\mathit{a}\mathit{m}\mathit{p}\mathit{E}{\mathit{n}}_{\mathit{m}\mathit{a}\mathit{x}}}$ | $\overline{\mathit{S}\mathit{a}\mathit{m}\mathit{p}\mathit{E}{\mathit{n}}_{\mathit{m}\mathit{i}\mathit{n}}}$ | $\overline{{\mathit{T}}_{\mathit{S}\mathit{a}\mathit{m}\mathit{p}\mathit{E}\mathit{n}}}$ |
---|---|---|---|

RRI | 1.20 ± 0.41 | 0.34 ± 0.30 | 96 ± 40 |

sBP | 1.29 ± 0.37 | 0.57 ± 0.34 | 82 ± 41 |

dBP | 1.19 ± 0.36 | 0.48 ± 0.34 | 83 ± 44 |

SV | 1.62 ± 0.33 | 0.91 ± 0.40 | 89 ± 45 |

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**MDPI and ACS Style**

Buszko, K.; Piątkowska, A.; Koźluk, E.; Opolski, G. Entropy in Investigation of Vasovagal Syndrome in Passive Head Up Tilt Test. *Entropy* **2017**, *19*, 236.
https://doi.org/10.3390/e19050236

**AMA Style**

Buszko K, Piątkowska A, Koźluk E, Opolski G. Entropy in Investigation of Vasovagal Syndrome in Passive Head Up Tilt Test. *Entropy*. 2017; 19(5):236.
https://doi.org/10.3390/e19050236

**Chicago/Turabian Style**

Buszko, Katarzyna, Agnieszka Piątkowska, Edward Koźluk, and Grzegorz Opolski. 2017. "Entropy in Investigation of Vasovagal Syndrome in Passive Head Up Tilt Test" *Entropy* 19, no. 5: 236.
https://doi.org/10.3390/e19050236