Predominant cardiac sympathetic modulation during wake and sleep in patients with Rett syndrome.

BACKGROUND: Rett syndrome (RTT) is a rare neurological disorder primarily associated with mutations in the methyl-CpG-binding protein 2 (MECP2) gene. The syndrome is characterized by cognitive, social, and physical impairments, as well as sleep disorders and epilepsy. Notably, dysfunction of the autonomic nervous system is a key feature of the syndrome. Although Heart Rate Variability (HRV) has been used to investigate autonomic nervous system dysfunction in RTT during wakefulness, there is still a significant lack of information regarding the same during sleep. Therefore, our aim was to investigate cardiovascular autonomic modulation during sleep in subjects with RTT compared to an age-matched healthy control group (HC). METHOD: A complete overnight polysomnographic (PSG) recording was obtained from 11 patients with Rett syndrome (all females, 10 ± 4 years old) and 11 HC (all females, 11 ± 4 years old; p = 0.48). Electrocardiogram and breathing data were extracted from PSG and divided into wake, non-REM, and REM sleep stages. Cardiac autonomic control was assessed using symbolic non-linear heart rate variability analysis. The symbolic analysis identified three patterns: 0 V% (sympathetic), 2UV%, and 2LV% (vagal). RESULTS: The 0 V% was higher in the RTT group than in the HC group during wake, non-REM, and REM stages (p < 0.01), while the 2LV and 2UV% were lower during wake and sleep stages (p < 0.01). However, the 0 V% increased similarly from the wake to the REM stage in both RTT and HC groups. CONCLUSIONS: Therefore, the sympatho-vagal balance shifted towards sympathetic predominance and vagal withdrawal during wake and sleep in RTT, although cardiac autonomic dynamics were preserved during sleep.

Women have a greater cardiac vagal withdrawal to heat stress compared to men.

The heated environment shifts the sympatho-vagal balance toward sympathetic predominance and vagal withdrawal. Women's heart is more reliant on vagal autonomic control, while men's heart is more dependent on sympathetic control. However, sex differences in cardiovascular autonomic responses to heat stress remain unknown. We aimed to investigate the cardiovascular autonomic regulation under heat stress between sexes. Thirty-two young participants (27 ± 4 years old; 16 women) were enrolled in a single visit, resting for 30min at baseline (thermal reference condition TC; ∼24°C) and 30min under a heated environment (HOT; ∼38°C). Blood pressure (BP), skin temperature, electrocardiogram, and respiratory oscillations were continuously recorded. The heart rate variability (HRV) was assessed by spectral analysis (low-frequency [LFnu; sympathetic and vagal] and high-frequency [HFnu; vagal]), and symbolic analysis (0 V% [sympathetic] and 2UV%, and 2LV% [vagal]). The spontaneous baroreflex sensitivity (BRS) was calculated by the gain between BP and R-R within the LF band (αLF). The estimated maximal aerobic capacity and body surface area were employed as covariates in sex comparisons. The effects of HOT were the following: 1) Women have a greater cardiac vagal withdrawal to heat stress compared to men; 2) Sex differences on cardiac autonomic response to heat stress exist after controlling for the effect of estimated physical fitness and body surface area. Therefore, heat stress provokes a higher vagal withdrawal to the heart in women compared to men. It could be attributed to sex per se since significant differences between men and women were not modified after covariate analysis.

Heated environment offsets the cardiovascular responses to prolonged rowing exercise in competitive athletes.

Prolonged rowing exercise sessions are often prescribed considering competitive training schedules, and under hostile environments (e.g., heated ambient). The study aimed to investigate the effect of heat stress (HS) on physical performance, Lactate concentration ([Lac]), and cardiorespiratory responses during prolonged exercise sessions in competitive rowers. Twelve rowers performed preliminary exercise tests (2-km test and five-step incremental lactate test) to assess the target workload intensity corresponding to a 2.5 mmol.L-1 of [Lac]. On two separate days, participants were enrolled in two exercise sessions of 12 km in a rowing machine under HS (∼30 °C) and thermal comfort (TC 22 °C) conditions. Heart rate (HR), stroke volume (SV), cardiac output (CO), oxygen uptake (VO2), [Lac], and the rating of perceptual exertion (RPE) were obtained. From baseline, HS increased the maximum temperature of the face compared to TC. Workload and VO2 reduced while RPE increased at 9- and 12-km of rowing exercise under HS compared to TC. From baseline to the last stage of exercise, HS shifted SV downwards and HR upwards compared to TC. Consequently, CO did not change between thermal conditions (TC vs. HS). Therefore, HS provokes a cardiovascular drift during prolonged rowing in comparison to TC. The last stages of prolonged rowing sessions under HS seem to be critical to physical performance and relative perceptual of effort in rowers.

Transfer function analysis of dynamic cerebral autoregulation: A CARNet white paper 2022 update.

Cerebral autoregulation (CA) refers to the control of cerebral tissue blood flow (CBF) in response to changes in perfusion pressure. Due to the challenges of measuring intracranial pressure, CA is often described as the relationship between mean arterial pressure (MAP) and CBF. Dynamic CA (dCA) can be assessed using multiple techniques, with transfer function analysis (TFA) being the most common. A 2016 white paper by members of an international Cerebrovascular Research Network (CARNet) that is focused on CA strove to improve TFA standardization by way of introducing data acquisition, analysis, and reporting guidelines. Since then, additional evidence has allowed for the improvement and refinement of the original recommendations, as well as for the inclusion of new guidelines to reflect recent advances in the field. This second edition of the white paper contains more robust, evidence-based recommendations, which have been expanded to address current streams of inquiry, including optimizing MAP variability, acquiring CBF estimates from alternative methods, estimating alternative dCA metrics, and incorporating dCA quantification into clinical trials. Implementation of these new and revised recommendations is important to improve the reliability and reproducibility of dCA studies, and to facilitate inter-institutional collaboration and the comparison of results between studies.

The Systolic Pulmonary Arterial Pressure Liaises Impaired Cardiac Autonomic Control to Pro-inflammatory Status in Systemic Sclerosis Patients.

The current study was undertaken to test the hypothesis that systemic sclerosis (SSc) patients with higher systolic pulmonary arterial pressures (PAPs) present a blunted cardiac autonomic modulation and a pro-inflammatory profile. Thirty-nine SSc patients were enrolled (mean age 57 ± 11 years). ECG and respiration were recorded in the supine (SUP) position and during the active standing (ORT). Heart rate variability (HRV) analysis was performed on samples of 300 beats. The symbolic analysis identified three patterns, 0V%, (sympathetic) and 2UV% and 2LV%, (vagal). The %ΔORT was calculated from the differences between HRV in ORT and SUP, normalized (%) by the HRV values at rest. The PAPs was obtained non-invasively through echocardiography. For the inter-group analysis, participants were allocated in groups with higher (+PAPs ≥ median) and lower PAPs (-PAPs < median) values. At rest, the cardiac sympathetic modulation (represented by 0V%) was positively correlated with PAPs, while parasympathetic modulation (represented by 2LV%) was negatively correlated with PAPs. The dynamic response to ORT (represented by Δ0V% and Δ2LV%), sympathetic and parasympathetic were negatively and positively correlated with PAPs, respectively. The +PAPs group presented a higher inflammatory status and a blunted cardiac autonomic response to ORT (↓Δ0V% and ↑Δ2LV%) compared to the -PAPs group. These findings suggest an interplay among cardiac autonomic control, inflammatory status, and cardiopulmonary mechanics that should be considered for the assessment, monitoring, and treatment of SSc patients.

Sex differences in blood pressure regulation during the isometric exercise under heated environment.

In the absence of heat stress, females increase blood pressure (BP) during isometric handgrip exercise due to cardiac output more than total peripheral resistance (TPR) compared to men. Although heat stress seems to blunt BP responses at rest and during handgrip, possible sex differences remained unknown. We hypothesized that BP responses during handgrip under a heated environment (HOT) will be different between men and women. Eight healthy men (29 ± 6 years) and eight women (26 ± 4 years) participated in this study. The experimental protocol was separated into two environmental conditions: HOT (~ 36 °C) and thermoneutral (TC; ~ 24 °C). In both conditions, participants rested for 30 min and performed the handgrip for 3 min. BP, heart rate (HR) stroke volume and cardiac output were continuously recorded, and TPR was calculated (TPR = mean blood pressure (MBP)/cardiac output). HOT reduced BP and TPR at baseline and during handgrip in females as compared to TC, while males showed similar responses in both thermal conditions. HR was higher under HOT in both groups. Cardiac output and stroke volume were not different under HOT compared to TC for females. In males, cardiac output increased at the last minute of handgrip under HOT through augmented HR, because stroke volume was unchanged. In conclusion, the main effect of HOT was to shift downwards BP and total peripheral resistance at rest and during isometric exercise in females. In males, the combination of handgrip and HOT increased cardiac output by augmented HR, whereas BP presented similar responses between thermal conditions during handgrip.

The Physical Capacity of Rowing Athletes Cannot Reverse the Influence of Age on Heart Rate Variability during Orthostatic Stress.

The current study was undertaken to test the hypothesis that the high physical capacity of rowing athletes may not reverse the influence of age on cardiac autonomic control decline estimated by heart rate variability (HRV). Forty-four male subjects divided in four groups: 11 young athletes (YA; 18 ±1 year), 11 young non-athletes (YNA; 20 ±1 year), 11 middle age athletes (MAA; 43 ±6 years) and 11 middle age non-athletes (MNA; 44 ±8 years) participated in the study. Heart rate (HR) was recorded beat-by-beat for 10 minutes in supine (SUP) and 10 min in orthostatic (ORT) positions. HRV was analyzed in the frequency domain to obtain the spectral power in the high (HF) and low frequency (LF) bands, and the changes to ORT (%∆HRV) were calculated (ORT - SUP / SUP). During SUP, HF was lower in MNA and MA compared to YA and YNA, while LF was lower in MNA than YA. For %ΔHRV, %ΔHF was higher in YA than YNA, MA and MNA. The %ΔLF was not different among groups. In conclusion, aging seems to overcome the influence of physical fitness on neural regulation of the heart, as highlighted by the HRV response to active standing.

Influence of breathing patterns and orthostatic stress on postural control in older adults.

AIM: To investigate the influence of breathing patterns and blood pressure behavior postural control in older adults. METHODS: A total of 20 older adults carried out spontaneous, controlled (15 cycles/min) and deep (6 cycles/min) breathing trials, in random order. In this session, the heart rate was recorded continuously and blood pressure measured every 3 min. In addition, the challenge from sitting to an active standing position was carried out with eyes closed during 6 min on a baropodometer plate with electromyography recording. The root mean square (RMS) of electromyography was calculated. RESULTS: There were significant differences in the postural control with spontaneous breathing from the first minute (center of pressure [COP]-area 216.40 ± 116.70 mm2 ) in comparison with the third minute (COP-area 79.35 ± 68.11 mm2 ; d = 0.89; P < 0.01) and the sixth minute (COP-area 70.24 ± 41.26 mm2 ; d = 0.60; P < 0.05) of active standing. Furthermore, deep breathing significantly increases the COP-area (158.50 ± 126.2 mm2 ) at the sixth minute of active standing in comparison with spontaneous breathing (70.24 ± 41.26 mm2 ; d = 0.80; P < 0.01). There were also significant differences in systolic blood pressure during spontaneous breathing between the baseline measures (sitting position 123 ± 11 mmHg) and the first minute of active standing (117 ± 13 mmHg; d = 0.24; P < 0.05). Furthermore, electromyography activity of the tibialis anterior increased during the deep (17.52 ± 9.21 RMS) and controlled breathing (16.75 ± 5.26 RMS) compared with the spontaneous condition (14.93 ± 5.56 RMS; d = 0.17; P < 0.05). CONCLUSIONS: The present data provide important insight into the respiratory and hemodynamics effects of postural control in older adults. The current data confirm that deep breathing causes periodic perturbation in the neuromuscular compensation of the lower limbs. Geriatr Gerontol Int 2018; 18: 692-697.

Clinical determinants and prognostic significance of the electrocardiographic strain pattern in chronic kidney disease patients.

The electrocardiographic (ECG) strain pattern (Strain) is a marker of left ventricular hypertrophy (LVH) severity that provides additional prognostic information beyond echocardiography (ECHO) in the community level. We sought to evaluate its clinical determinants and prognostic usefulness in chronic kidney disease (CKD) patients. We evaluated 284 non-dialysis-dependent patients with CKD stages 3 to 5 (mean age, 61 years [interquartile range, 53-67 years]; 62% men). Patients were followed for 23 months (range, 13-32 months) for cardiovascular (CV) events and/or death. Strain patients (n = 37; 13%) were using more antihypertensive drugs, had higher prevalence of peripheral vascular disease and smoking, and higher levels of C-reactive protein, cardiac troponin, and brain natriuretic peptide (BNP). The independent predictors of Strain were: left ventricular mass index (LVMI), BNP, and smoking. During follow-up, there were 44 cardiovascular events (fatal and non-fatal) and 22 non-CV deaths; and Strain was associated with a worse prognosis independently of LVMI. Adding Strain to a prognostic model of LVMI improved in 15% the risk discrimination for the composite endpoint and in 12% for the CV events. Strain associates with CV risk factors and adds prognostic information over and above that of ECHO-assessed LVMI. Its routine screening may allow early identification of high risk CKD patients.

Clinical determinants and prognostic significance of the electrocardiographic strain pattern in chronic kidney disease patients

The electrocardiographic (ECG) strain pattern (Strain) is a marker of left ventricular hypertrophy (LVH) severity that providesadditional prognostic information beyond echocardiography (ECHO) in the community level. We sought to evaluateits clinical determinants and prognostic usefulness in chronic kidney disease (CKD) patients. We evaluated 284 nondialysis-dependent patients with CKD stages 3 to 5 (mean age, 61 years [interquartile range, 53–67 years]; 62% men).Patients were followed for 23 months (range, 13–32 months) for cardiovascular (CV) events and/or death. Strain patients(n » 37; 13%) were using more antihypertensive drugs, had higher prevalence of peripheral vascular disease and smoking,and higher levels of C-reactive protein, cardiac troponin, and brain natriuretic peptide (BNP). The independent predictors ofStrain were: left ventricular mass index (LVMI), BNP, and smoking. During follow-up, there were 44 cardiovascular events(fatal and non-fatal) and 22 non-CV deaths; and Strain was associated with a worse prognosis independently of LVMI.Adding Strain to a prognostic model of LVMI improved in 15% the risk discrimination for the composite endpoint and in12% for the CV events. Strain associates with CV risk factors and adds prognostic information over and above that ofECHO-assessed LVMI. Its routine screening may allow early identification of high risk CKD patients.