Comparison of Heart Autonomic Control between Hemodynamically Stable and Unstable Patients during Hemodialysis Sessions: A Bayesian Approach.

Intradialytic hypotension is a common complication during hemodialysis sessions. The analysis of successive RR interval variability using nonlinear methods represents a promising tool for evaluating the cardiovascular response to acute volemic changes. Thus, the present study aims to compare the variability of successive RR intervals between hemodynamically stable (HS) and unstable (HU) patients during a hemodialysis session, through linear and nonlinear methods. Forty-six chronic kidney disease patients volunteered in this study. Successive RR intervals and blood pressures were recorded throughout the hemodialysis session. Hemodynamic stability was defined based on the delta of systolic blood pressure (higher SBP-lower SBP). The cutoff for hemodynamic stability was defined as 30 mm Hg, and patients were stratified as: HS ([n = 21]: ≤29.9 mm Hg) or HU ([n = 25]: ≥30 mm Hg). Linear methods (low-frequency [LFnu] and high-frequency [HFnu] spectra) and nonlinear methods (multiscale entropy [MSE] for Scales 1-20, and fuzzy entropy) were applied. The area under the MSE curve at Scales 1-5 (MSE1-5), 6-20 (MSE6-20), and 1-20 (MSE1-20) were also used as nonlinear parameters. Frequentist and Bayesian inferences were applied to compare HS and HU patients. The HS patients exhibited a significantly higher LFnu and lower HFnu. For MSE parameters, Scales 3-20 were significantly higher, as well as MSE1-5, MSE6-20, and MSE1-20 in HS, when compared to HU patients (p < 0.05). Regarding Bayesian inference, the spectral parameters demonstrated an anecdotal (65.9%) posterior probability favoring the alternative hypothesis, while MSE exhibited moderate to very strong probability (79.4 to 96.3%) at Scales 3-20, and MSE1-5, MSE6-20, and MSE1-20. HS patients exhibited a higher heart-rate complexity than HU patients. In addition, the MSE demonstrated a greater potential than spectral methods to differentiate variability patterns in successive RR intervals.

Factors influencing gait speed in community-dwelling older women: A Bayesian approach.

BACKGROUND: Human gait is a complex task resulting from the interaction of sensory perception, muscle force output, and sensory-motor integration, which declines with the aging process and impacts gait speed in older women. RESEARCH QUESTION: What are the separate and combined impacts of sensory-motor factors on gait speed of older women? METHODS: Sixty healthy older women (69.3 ±â€¯5.9 years) volunteered for this study. A previous screening using Pearson's correlation selected variables significantly correlated with gait speed: age, plantar tactile perception, lower limb explosive force, and mean velocity (MV) of the center of pressure (CoP). Simple and multivariate regression models were performed with selected variables. The magnitude of evidence was obtained using Bayesian inference, determining posterior probabilities based on our data. RESULTS: Gait speed was negatively correlated with age and positively correlated with plantar tactile perception, MV (Romberg index), and lower limb explosive force. The coefficient of determination (R2) varied between 0.06 for plantar tactile perception and 0.22 for explosive force (p < 0.05). The multivariate model, including age, MV (Romberg index), and lower limb explosive force, explained 44% (R2 = 0.44) of the variance in gait speed, with a small standard error of estimate (0.14 m/s). Bayesian inference confirmed the good posterior probability of the model. SIGNIFICANCE: Age, plantar tactile perception, MV (Romberg index), and lower limb explosive force impact gait speed, whereas the combination of the first three factors has an excellent posterior probability of predicting or affecting gait speed.

The D allele of angiotensin-converting enzyme gene is associated with a worse autonomic heart control in community-based older adults.

The relationship between the Renin-Angiotensin-Aldosterone System (RAAS) and modulation of the Autonomic Nervous System (ANS) is reported as complex and bidirectional. Thus, the present study aimed to compare autonomous heart control, through symbolic analysis parameters, in the older adults carrying different ACE I/D gene polymorphisms (rs4646994). Two hundred four older adults comprised the study population and were grouped according to the ACE I/D gene polymorphism: II + ID genotype and DD genotype. Successive RR intervals were recorded along 5 min and analyzed with Symbolic Analysis (SA) method. 0 V%, 1 V% and 2 V% patterns were quantified and compared between groups. A linear mixed model analysis was used to determine between-group differences in symbolic analysis parameters (0 V%, 1 V% and 2 V%), taken groups as fixed factor and sex, use of ACE inhibitors and Angiotensin II receptor type I blockers as random factors. The Bayesian analysis was carried out to check the magnitude of the evidence. The results of this study indicate that older adults carrying the DD genotype have statistically greater sympathetic modulation (0 V%) and poor sympathovagal balance (1 V%), but the Bayesian analysis indicate only an anecdotal effect. Sympathetic predominance is recognized a worrying condition, since may predisposes to cardiovascular risk.

The entropy of RR intervals is associated to gestational age in full-term newborns with adequate weight for gestational age.

INTRODUCTION: The variability of successive RR intervals has been pointed out as an indicator of systemic homeostasis. The entropy of successive RR intervals is associated with a greater adaptive capacity, which is essential after childbirth, characterized by a change from an intrauterine environment that constantly adapts to the fetal demands, to an extrauterine environment that requires constant biological adaptations by the neonate. OBJECTIVES: To analyze the association between gestational age (GA) and the entropy of RR intervals in term infants with adequate birth weight in the first hours of extrauterine life. METHODS: In a cross-sectional study design maternal, labor and neonatal characteristics were collected from the obstetric records. Successive RR intervals were recorded from neonates up to 72 hours (i.e. 3 days) of birth. SUBJECTS: Fifty term infants, healthy and with adequate birth weight. Outcome measures: the variability of RR intervals was analyzed obtaining the entropy of 1000 successive RR intervals. Pearson's correlation was used to evaluate the association between GA and the entropy of successive RR intervals, while linear regression was used to obtain the coefficient of determination (r2) as well as a prediction model. The adequacy of the prediction model was evaluated using the Komolgorov-Smirnov test to evaluate the residuals distribution. RESULTS: There was a positive and significant association between the studied variables (r = 0.437; p = .002). The coefficient of determination allowed us to infer that approximately 19.3% of the RR interval entropy from the studied sample can be explained by the GA (r2 = 0.193; p = .002). The analysis of the residuals distribution confirmed that the regression model obtained here was adequate. CONCLUSION: Our results indicate that, even within a normal range of GA (≥37 a < 42 weeks) and birth weight, a longer intrauterine life allows a greater entropy of successive RR intervals, indicating a greater maturation of biological systems and adaptive capacity.

Hyperuricemia is associated with sympathovagal imbalance in older adults.

PURPOSE: This study aimed to compare heart rate variability (HRV) parameters obtained through symbolic analysis (SA), between older adults with and without hyperuricemia. METHODS: This is a cross-sectional study including 202 community-dwelling old adults, which was clinically stratified as with or without hyperuricemia, according to the cutoff point of serum uric acid ≥ 6 mg/dL for women and ≥ 7 mg/dL for men. Successive RR intervals were recorded along 5 min and analyzed with SA method. 0 V%, 1 V% and 2 V% patterns were quantified and compared between groups. Comparisons were carried out through parametric or nonparametric tests, according to the data distribution characteristics, evaluated by Kolmogorov-Smirnov test. The significance level was set as p ≤ 0.05 for all statistical procedures. RESULTS: The prevalence of hyperuricemia was 67.8 %, and the hyperuricemic older adults exhibited significant higher values for V0% and lower values for V2% parameters when compared to normouricemic older adults. CONCLUSION: These results suggesting a sympathovagal imbalance in hyperuricemic older adults, characterized by greater sympathetic predominance (0 V%) and lower vagal modulation (2 V%) at rest conditions.

Sarcopenia is associated to an impaired autonomic heart rate modulation in community-dwelling old adults.

PURPOSE: The aims of this study were to compare the autonomic heart control parameters from sarcopenic and non-sarcopenic community-dwelling elders. METHODS: This is a cross-sectional study including 76 community-dwelling old adults, which was clinically stratified as sarcopenic or non-sarcopenic, according to the current recommendations. They were submitted to 5-min recordings of successive RR intervals. The analysis of the RR intervals variability was carried out in time (mean RR, RMSSD, pNN50, SDNN and triangular index) and frequency domains (LFnu, HFnu and LF/HF ratio), and with nonlinear methods (SD1, SD2, and D2). The parameters of autonomic heart rate modulation (AHRM) were adjusted for potential confounders: sex, diabetes, beta-blockers use, cardiovascular disease, body mass index and physical activity level, smoking habit. Normality of the data was tested by Kolmogorov-Smirnov test and, since most variables did not exhibit a normal distribution the Mann-Whitney test was used to compare the parameters of AHRM. The significance level was set as p ≤ 0.05 and all statistical procedures were performed with SPSS®. RESULTS: Adjusted parameters of AHRM obtained from time domain and nonlinear methods were significantly different between sarcopenic and non-sarcopenic elders (p < 0.05), while parameters obtained from frequency domain analysis did not were different between groups (p > 0.05). CONCLUSION: Sarcopenic old adults exhibited lower parasympathetic-associated modulation, suggesting a poor cardioprotection associated to this condition.