Systolic Blood Pressure Series Research Articles

Age induced interactions between heart rate variability and systolic blood pressure variability using approximate entropy and recurrence quantification analysis: a multiscale cross correlation analysis.

The purpose of this study is to study the effect of age on the correlation between heart rate variability (HRV) and blood pressure variability (BPV). To meetthis end, multi-scale cross correlation (CC) analysis of HRV and systolic blood pressure variability (SBPV) was performed. The Approximate Entropy (ApEn) and Recurrence Quantification Analysis (RQA) derived indices, calculated from RR interval series (RRi) and systolic blood pressure (SBP) series at multiple temporal scales, are the basis of this CC analysis. For the computation of ApEn and RQA indices, the tolerance threshold (r) is chosen by either: (i) selecting any arbitrary value (0.2) within the recommended range (0.1-0.25) times standard deviation (SD) of time series, and (ii) taking the 'r' (ropt) corresponding to maximum ApEn (ApEnmax) as tolerance threshold. It is found that (i) at each time scale (τ), a lower SD is observed when indices are computed using ropt than [Formula: see text] (r0.2), for RRi as well as SBP series, (ii) descriptive indices of RRi are found significant (p < 0.05) at all scales (τ), however for SBP, these are found insignificant (p > 0.05) at most of the scales, (iii) CC values of descriptive statistics viz., mean and SD are not significant (p > 0.05) irrespective of τ, barring τ = 1, (iv) CC values of ApEn and RQA indices, found using ropt, are found significant (p < 0.05) and provide enhanced stratification at τ = 1, 2 and 3, whereas this significant correlation and strong classification is missing for indices calculated using r0.2, and (v) Lastly as τ increases, ApEn and RQA indices, computed with ropt, reverse their trend but manage to provide significant difference in elder and younger subjects. It is concluded that HRV and SBPV interactions gets altered with age. Descriptive indicators however are not enough to capture these changes. These complex interactions can only be deciphered using complexity-based methods such as approximate entropy and that too at the multiple scale level.

Multiscale Joint Symbolic Transfer Entropy for Quantification of Causal Interactions Between Heart Rate and Blood Pressure Variability Under Postural Stress

In this paper, joint symbolic transfer entropy (JSTE) is explored to quantify causal interactions between systolic blood pressure (SBP) and RR intervals (peak-to-peak distance between consecutive R-peaks) at multiple time scales. SBP→RR coupling (C s-r ) and RR→SBP coupling (C r-s ) coupling is analyzed at multiple time scales and delays. The ability of the approach based on JSTE to detect SBP–RR causal coupling is tested on 42 healthy subjects in supine and upright position along with 21 subjects of EUROBAVAR dataset. In addition, lack of causal coupling from SBP to RR was assessed on 20 post-acute myocardial infarction (AMI) patients. Results demonstrate that (i) standard deviation (SD) of RR interval series and SBP series decreases with time scale τ = 1 to 10 for all types of subjects. (ii) SD in supine is more than that of upright position at each time scale irrespective of types of subjects. (iii) JSTE decreases with time delay for healthy and AMI patients but does not follow decreasing trend for baroflex sensitivity BRS failure patients. (iv) JSTE in supine position is more than that of upright position irrespective of time delay. (v) JSTE decreases with time scale for healthy and AMI patients but does not follow decreasing trend for BRS failure patients. (vi) JSTE in supine position is more than that of upright position only at finer scales. (vii) Enhanced feed-forward (FF) coupling and suppressed feedback (FB) coupling found at supine position within low frequency band (0.04–0.15 Hz) as well as high frequency band (0.151–0.4 Hz) indicated prevalence on non-baroreflex mechanisms. (viii) FB coupling recovered in the upright position which was stronger than FF coupling. Upon comparison with cross conditional entropy (CCE), it is found that JSTE provides more significant differences between supine and upright position.

Baroreceptor reflex sensitivity in human neonates: the effect of postmenstrual age

We performed a cross-sectional study in human infants to determine if indices of R-R interval variability, systolic blood pressure (SBP) variability, and baroreceptor reflex sensitivity change with postmenstrual age (PMA: gestational age+postnatal age). The electrocardiogram, arterial SBP and respiration were recorded in clinically stable infants (PMA, 28-42 weeks) in the quiet sleep state in the first days after birth. (Cross-)spectral analyses of R-R interval series and SBP series were performed to calculate the power of low-frequency (LF, indicating baroreceptor reflex activity, 0.04-0.15 Hz) and high-frequency (HF, indicating parasympathetic activity, individualized between the p-10 and p-90 values of respiratory frequency) fluctuations, and transfer function phase and gain. The mean R-R interval, and LF and HF spectral powers of R-R interval series increased with PMA. The mean SBP increased with PMA, but not the LF and HF spectral powers of SBP series. In the LF range, cross-spectral analysis showed high coherence values (>0.5) with a consistent negative phase shift between R-R interval and SBP, indicating a approximately 3 s lag in R-R interval changes in relation to SBP. Baroreceptor reflex sensitivity, calculated from LF transfer gain, increased significantly with PMA, from 5 (preterm) to 15 ms mmHg-1 (term). Baroreceptor reflex sensitivity correlated significantly with the (LF and) HF spectral powers of R-R interval series, but not with the LF and HF spectral powers of SBP series. The principal conclusions are that baroreceptor reflex sensitivity and spectral power in R-R interval series increase in parallel with PMA, suggesting a progressive vagal maturation with PMA.

Cardiovascular Fluctuations and Transfer Function Analysis in Stable Preterm Infants

To examine the baroreceptor reflex function, a beat-to-beat analysis between systolic blood pressure (SBP) and R-R interval fluctuations was studied in 10 stable appropriate-for-gestational age preterm infants (range, 27.2–33.7 wk) in the first postnatal week during quiet sleep. Spectral power analysis, using fast Fourier transform, and transfer functions (gain and phase difference) between SBP and R-R fluctuations were estimated in a low-frequency band (LF, 0.03–0.2 Hz) and high-frequency band (HF defined as the frequency band between the 10th and 90th centiles of the individual respiratory frequency). The LF/HF ratio reflects the sympathovagal balance. The mean frequency (±SD) of LF peaks was centered at 0.07 ± 0.02 Hz. The mean frequency (±SD) of the individual HF band was 0.82 ± 0.21 Hz. The LF/HF ratio in the R-R interval series [median, 29; interquartile range (IQR), 16–40] was higher than in the SBP series (median, 8; IQR, 4–14). The gain between R-R interval and SBP fluctuations (median, 4.2 ms/mm Hg; IQR, 2.4–5.0) in the LF band was higher than in the HF band (median, 1.7 ms/mm Hg; IQR, 1.4–3.0). SBP fluctuations lead R-R interval fluctuations in the LF band with a median phase difference of +96° (IQR, 67–132). At LF the fluctuations in SBP precede changes in R-R interval with a time delay of 3.8 s. These observations indicate a dominant role of the sympathetic system in stable preterm infants in comparison with published adult values. Cross-spectral analysis allows a test for tracking the development of the sympathetic system in neonates.

Cardiovascular fluctuations and transfer function analysis in stable preterm infants.

To examine the baroreceptor reflex function, a beat-to-beat analysis between systolic blood pressure (SBP) and R-R interval fluctuations was studied in 10 stable appropriate-for-gestational age preterm infants (range, 27.2-33.7 wk) in the first postnatal week during quiet sleep. Spectral power analysis, using fast Fourier transform, and transfer functions (gain and phase difference) between SBP and R-R fluctuations were estimated in a low-frequency band (LF, 0.03-0.2 Hz) and high-frequency band (HF defined as the frequency band between the 10th and 90th centiles of the individual respiratory frequency). The LF/HF ratio reflects the sympathovagal balance. The mean frequency (+/-SD) of LF peaks was centered at 0.07 +/- 0.02 Hz. The mean frequency (+/-SD) of the individual HF band was 0.82 +/- 0.21 Hz. The LF/HF ratio in the R-R interval series [median, 29; interquartile range (IQR), 16-40] was higher than in the SBP series (median, 8; IQR, 4-14). The gain between R-R interval and SBP fluctuations (median, 4.2 ms/mm Hg; IQR, 2.4-5.0) in the LF band was higher than in the HF band (median, 1.7 ms/mm Hg; IQR, 1.4-3.0). SBP fluctuations lead R-R interval fluctuations in the LF band with a median phase difference of +96 degrees (IQR, 67-132). At LF the fluctuations in SBP precede changes in R-R interval with a time delay of 3.8 s. These observations indicate a dominant role of the sympathetic system in stable preterm infants in comparison with published adult values. Cross-spectral analysis allows a test for tracking the development of the sympathetic system in neonates.