Cardiac Autonomic Regulation Research Articles

Cardiac repolarization evolves differently during the course of benign and disabling multiple sclerosis

BackgroundCardiac repolarization is modulated by the autonomic nervous system. Even though multiple sclerosis associates with prolonged cardiac repolarization the physiology responsible for the phenomenon remains unknown. ObjectiveTo study in longitudinal setting whether the patients with confirmed benign and disabling outcome of relapsing-remitting multiple sclerosis (RRMS) differ in regard to changes of cardiac repolarization. MethodsTotal of 43 patients, 26% with benign (EDSS ≤2 at least 10y after onset symptom) and 74% with disabling (EDSS >2 at least 10y after onset symptom) RRMS, having 12-lead electrocardiogram (ECG) recorded at the time of onset symptom (ECG1) and for follow-up (ECG2), were studied. Heart rate (HR) corrected QT intervals (QTc) reflecting cardiac repolarization were assessed. ResultsThe time interval between ECG1 and ECG2 showed no statistical difference between benign (7.8 ± 4.8y) and disabling (10.2 ± 5.6y; p = .211) RRMS. Patients with benign and disabling RRMS showed similar values of HR (66±9 bpm vs 73 ± 15 bpm; p=.146) and QTc (403 ± 13 ms vs 408 ± 19 ms; p = .450) at the time of ECG1. However, at the time of ECG2, HR was higher (79 ± 14 bpm vs 65 ± 10 bpm; p = .004) and QTc was longer (420 ± 24 ms vs 400 ± 15 ms; p = .012) in patients with disabling than benign RRMS. Correspondingly, HR increased (p = .063) and QTc prolonged (p = .014) during the disease course only in patients with disabling RRMS. ConclusionsDeterioration of cardiac autonomic regulation during the disease course associates with disabling but not with benign RRMS. Our findings suggest that assessment of cardiac autonomic regulation should be included in the evaluation of RRMS disease course. In addition, patients with disabling RRMS might be prone to unfavorable cardiovascular outcome also due to deterioration of autonomic nervous system.

Cardiac Autonomic Function and Reactivity Tests in Physically Active Subjects with Moderately Severe COPD

ABSTRACTPatients with chronic obstructive pulmonary disease (COPD) show impairments in the autonomic nervous systems (ANS) function, which is responsible for cardiac autonomic regulation. This study assessed the autonomic function and cardio-vagal reactivity in conveniently sampled subjects with COPD participating in a pulmonary rehabilitation (PR) program. Twenty-six subjects with COPD and 22 age and gender matched control subjects were evaluated. R-R intervals were collected at rest in supine position. Thereafter, resting autonomic function parameters comprising linear and nonlinear analyses of heart rate variability (HRV) and baroreceptor sensitivity (BRS) were calculated. Autonomic reactivity tests comprising deep breathing (DB), Valsalva maneuver (VM), and head up tilt (HUT) were also performed. The results of this study indicated that resting autonomic function variables were generally reduced in COPD compared to controls. However, this difference was only statistically significant for a few HRV parameters: mean RR intervals, low frequency (LF), standard deviation of dispersion of points perpendicular to the line-of-identity (SD1), and approximate entropy (ApEn) (p < 0.05). The results also indicated that all cardio-vagal indices following the autonomic reactivity tests were comparable between COPD and controls (p > 0.05). It was concluded that subtle autonomic impairments exists in physically active COPD patients, and these autonomic function deficits were mainly recognized by resting HRV indices and not autonomic reactivity tests.

ELECTRO-ACUPUNCTURE AT JIANSHI (PC5) AND NEIGUAN (PC6) ALTERS HEART RATE VARIABILITY (HRV) IN FRIGHTENED VOLUNTEERS

Background: Fear is one of the most widely studied emotions and is closely associated with the autonomic nervous system (ANS). Previous studies have proven that acupuncture directly impacts the ANS, influences the heart rate (HR) and the heart rate variability (HRV) and exerts other effects. The aim of this study was to explore the effect of Jianshi (PC5) and Neiguan (PC6) electro-acupuncture on HRV during fear-invoking auditory stimulation using an Actiheart ECG recorder.&#x0D; Materials and Methods: Two hundred healthy subjects were recruited. Using a random number table, subjects were grouped for exposure to fear-invoking auditory stimulation (n=40) or neutral auditory stimulation (n=40). After determining that our fear-invoking auditory stimulation produced the fear emotion, the other 120 subjects were similarly divided into an electro-acupuncture (EA group) and a control group that received PC5 and PC6 electro-acupuncture or no intervention. &#x0D; Results: The fear score of the fear-invoking auditory group was significantly higher than that of the neutral auditory group. The EA group showed higher SD, RMSSD, and high frequency (HF) components of HRV than those of the control group.&#x0D; Conclusion: The primary result suggests that PC5 and PC6 electro-acupuncture affects cardiac autonomic neural regulation, mainly via the parasympathetic system, in subjects exposed to fear-invoking auditory stimulation.

Changes of heart rate variability predicting patients with acute exacerbation of chronic obstructive pulmonary disease requiring hospitalization after Emergency Department treatment

BackgroundIndexes of heart rate variability (HRV) appear to reflect severity and may have prognostic value in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). We hypothesized that AECOPD without adequate treatment response would demonstrate impaired cardiac autonomic regulation and changes in HRV after emergency department (ED) treatment. MethodsA prospective study of measuring HRV in admitted and discharged patients with AECOPD shortly after ED arrival and again 24 h after treatment. ResultsTotal consecutive 33 patients (18 admitted and 15 discharged, age 77.1 ± 1.6 years) were enrolled. Among admitted patients, high frequency in normalized unit (HF%) was significantly lower (P < 0.001) while Ratio of LF to HF (LF/HF ratio) was significantly higher (P < 0.001) than discharged. 24 h after treatment, admitted patients had a significantly larger increase in HF% (P < 0.002) and larger decrease in LF/HF ratio (P < 0.05) than discharged. ROC curve analysis show the relative potential of the ΔHF% and ΔLF/HF% in the discrimination of groups. The area under the ROC curve between the 2 groups was 0.807 (P < 0.01) and 0.722 (P < 0.05), respectively. The best cut-off value for the admission between groups was ΔHF% >7.1 and ΔLF/HF% ≦−0.39. ConclusionPatients with AECOPD requiring admission after ED treatment had a greater increase in HF% and greater decrease in LF/HF ratio compared to those discharged. Our study demonstrates patient with ΔHF% was >7.1 or a ΔLF/HF% ≦−0.39 require admission despite 24 h of ED treatment.

Sphenopalatine ganglion stimulation induces changes in cardiac autonomic regulation in cluster headache.

Cluster headache is characterized by attacks of severe unilateral pain accompanied by cranial and systemic autonomic changes. Our knowledge of the latter is imperfect. This study aimed to investigate the effect of low-frequency sphenopalatine ganglion stimulation on cardiac autonomic regulation. In a double-blind, randomized, sham-controlled crossover design, patients received low-frequency and sham stimulation. RR intervals were recorded, and heart rate variability was analysed (time-domain, frequency-domain, nonlinear parameters). Headache characteristics, including cranial autonomic symptoms, were recorded at baseline and every 10min for 60min. Sixteen patients were included. Changes in heart rate variability from baseline in the analysed parameters differed significantly between low-frequency and sham stimulation. Initially, during low-frequency stimulation, there was a greater increase in heart rate compared to sham (P<0·05) and changes in the frequency, nonlinear and time domain (P<0·05) reflecting a higher sympathetic tone. These preceded the observed cranial autonomic symptoms. Ten episodes of cluster-like attacks were reported (six following low-frequency stimulation, four following sham). During these, parasympathetic tone (P<0·05) was higher compared to baseline. In cluster headache patients subjected to low-frequency and sham stimulation of the sphenopalatine ganglion, we found changes indicating higher sympathetic tone during low-frequency stimulation preceding cranial autonomic symptoms or cluster pain. During cluster pain, regardless of stimulation parameters, we saw increased parasympathetic activity, congruent with previous reports. The results indicate involvement of cardiac autonomic regulation before and during cluster headache attacks.

Impaired cardiac autonomic regulation and long-term risk of atrial fibrillation in patients with coronary artery disease

The influence of autonomic cardiac regulation on long-term risk of new-onset atrial fibrillation (AF) in coronary artery disease (CAD) is not well established. The purpose of this study was to evaluate the value of heart rate variability, a marker of cardiac autonomic regulation, in predicting new-onset AF in CAD. The Innovation to Reduce Cardiovascular Complications of Diabetes at the Intersection study population consisted of 1946 patients with CAD. After exclusions, the present analysis included 1710 patients. Those patients had a 24-hour electrocardiographic recording at baseline. A total of 143 cases (8.4%) of new-onset AF were observed during a follow-up of 5.6 ± 1.5 years. The lower values of the short-term scaling exponent of the detrended fluctuation analysis (DFA1) and the ratio of the low-frequency and high-frequency components of the power spectrum (LF/HF ratio) remained the strongest heart rate variability predictors of the development of AF after relevant adjustments in Cox multivariate regression analysis (P < .001 for both). The accuracy of these parameters in prediction of AF was even better (area under the receiver operating characteristic curve 0.630 and 0.631, respectively) than that of echocardiographic left atrial diameter (area under the curve 0.618). Including DFA1 and LF/HF ratio in the AF risk model increased the C-index from 0.630 (95% confidence interval 0.569-0.692) to 0.666 (95% confidence interval 0.612-0.720). Impaired cardiac autonomic regulation measured by DFA1 and LF/HF ratio predicts the development of new-onset AF as well as or even better than left atrial diameter in patients with CAD.

Modulation of Cardiac Autonomic Function by Fingolimod Initiation and Predictors for Fingolimod Induced Bradycardia in Patients with Multiple Sclerosis.

Objective: It is well-known that initiation of fingolimod induces a transient decrease of heart rate. However, the underlying cardiac autonomic regulation is poorly understood. We aimed to investigate the changes of autonomic activity caused by the first dose of fingolimod using a long-term multiple trigonometric spectral analysis for the first time. In addition, we sought to use the continuous Holter ECG recording to find predictors for fingolimod induced bradycardia.Methods: Seventy-eight patients with relapsing-remitting multiple sclerosis (RRMS) were included. As a part of the START study (NCT01585298), continuous electrocardiogram was recorded before fingolimod initiation, and until no <6 h post medication. Time domain and frequency domain heart rate variability (HRV) parameters were computed hourly to assess cardiac autonomic regulation. A long-term multiple trigonometric regressive spectral (MTRS) analysis was applied on successive 1-h-length electrocardiogram recordings. Decision tree analysis was used to find predictors for bradycardia following fingolimod initiation.Results: Most of the HRV parameters representing parasympathetic activities began to increase since the second hour after fingolimod administration. These changes of autonomic regulations were in accordance with the decline of heart rate. Baseline heart rate was highly correlated with nadir heart rate, and was the only significant predicting factor for fingolimod induced bradycardia among various demographic, clinical and cardiovascular variables in the decision tree analysis.Conclusions: The first dose application of fingolimod enhances the cardiac parasympathetic activity during the first 6 h post medication, which might be the underlying autonomic mechanism of reduced heart rate. Baseline heart rate is a powerful predictor for bradycardia caused by fingolimod.

Early Seizure Detection Based on Cardiac Autonomic Regulation Dynamics.

Epilepsy is a neurological disorder that causes changes in the autonomic nervous system. Heart rate variability (HRV) reflects the regulation of cardiac activity and autonomic nervous system tone. The early detection of epileptic seizures could foster the use of new treatment approaches. This study presents a new methodology for the prediction of epileptic seizures using HRV signals. Eigendecomposition of HRV parameter covariance matrices was used to create an input for a support vector machine (SVM)-based classifier. We analyzed clinical data from 12 patients (9 female; 3 male; age 34.5 ± 7.5 years), involving 34 seizures and a total of 55.2 h of interictal electrocardiogram (ECG) recordings. Data from 123.6 h of ECG recordings from healthy subjects were used to test false positive rate per hour (FP/h) in a completely independent data set. Our methodological approach allowed the detection of impending seizures from 5 min to just before the onset of a clinical/electrical seizure with a sensitivity of 94.1%. The FP rate was 0.49 h−1 in the recordings from patients with epilepsy and 0.19 h−1 in the recordings from healthy subjects. Our results suggest that it is feasible to use the dynamics of HRV parameters for the early detection and, potentially, the prediction of epileptic seizures.

Fingolimod induced reduction in cardiac autonomic regulation is fully reversible after fingolimod discontinuation

Long-term Fingolimod-therapy dampens cardiac autonomic modulation in patients with relapsing-remitting multiple sclerosis (RRMS). It is unclear whether these effects are reversible.

Last Word on Point:Counterpoint.

in these point: counterpoint articles and accompanying commentaries (see Ref. [3][1]), evidence is presented for and against exercise training-induced changes both in sinoatrial nodal intrinsic rate and cardiac autonomic neural regulation. The obvious question remains: what can explain these

Executive function and cardiac autonomic regulation in depressive disorders

Executive function impairments have been frequently observed in depressive disorders. Moreover, reduced heart rate variability (HRV) has repeatedly been described, especially in the high frequency band (i.e., respiratory sinus arrhythmia, RSA), suggesting lower vagal cardiac outflow. The study tested the hypothesis of involvement of low vagal tone in executive dysfunction in depression. In addition to RSA, HRV in the low frequency (LF) band was assessed. In 36 patients with depression and 36 healthy subjects, electrocardiography recordings were accomplished at rest and during performance of five executive function tasks (number-letter task, n-back task, continuous performance test, flanker task, and antisaccade task). Patients displayed increased error rates and longer reaction times in the task-switching condition of the number-letter task, in addition to increased error rates in the n-back task and the final of two blocks of the antisaccade task. In patients, both HRV parameters were lower during all experimental phases. RSA correlated negatively with reaction time during task-switching. This finding confirms reduced performance across different executive functions in depression and suggests that, in addition to RSA, LF HRV is also diminished. However, the hypothesis of involvement of low parasympathetic tone in executive dysfunction related to depression received only limited support.

Autonomic regulation of systemic inflammation in humans: A multi-center, blinded observational cohort study

ObjectiveExperimental animal models demonstrate that autonomic activity regulates systemic inflammation. By contrast, human studies are limited in number and exclusively use heart rate variability (HRV) as an index of cardiac autonomic regulation. HRV measures are primarily dependent on, and need to be corrected for, heart rate. Thus, independent autonomic measures are required to confirm HRV-based findings. Here, the authors sought to replicate the findings of preceding HRV-based studies by using HRV-independent, exercise-evoked sympathetic and parasympathetic measures of cardiac autonomic regulation to examine the relationship between autonomic function and systemic inflammation. MethodsSympathetic function was assessed by measuring heart rate changes during unloaded pedaling prior to onset of exercise, divided into quartiles; an anticipatory heart rate (AHRR) rise during this period is evoked by mental stress in many individuals. Parasympathetic function was assessed by heart rate recovery (HRR) 60s after finishing cardiopulmonary exercise testing, divided into quartiles. Parasympathetic dysfunction was defined by delayed heart rate recovery (HRR) ≤12.beats.min−1, a threshold value associated with higher cardiovascular morbidity/mortality in the general population. Systemic inflammation was primarily assessed by neutrophil-lymphocyte ratio (NLR), where a ratio >4 is prognostic across several inflammatory diseases and correlates strongly with elevated plasma levels of pro-inflammatory cytokines. High-sensitivity C-reactive protein (hsCRP) was also measured. ResultsIn 1624 subjects (65±14y; 67.9% male), lower HRR (impaired vagal activity) was associated with progressively higher NLR (p=0.004 for trend across quartiles). Delayed HRR, recorded in 646/1624 (39.6%) subjects, was associated with neutrophil-lymphocyte ratio >4 (relative risk: 1.43 (95%CI: 1.18–1.74); P=0.0003). Similar results were found for hsCRP (p=0.045). By contrast, AHRR was not associated with NLR (relative risk: 1.24 (95%CI: 0.94–1.65); P=0.14). ConclusionsDelayed HRR, a robust measure of parasympathetic dysfunction, is independently associated with leukocyte ratios indicative of systemic inflammation. These results further support a role for parasympathetic modulation of systemic inflammation in humans.

Heart rate variability in critical care medicine: a systematic review

BackgroundHeart rate variability (HRV) has been used to assess cardiac autonomic activity in critically ill patients, driven by translational and biomarker research agendas. Several clinical and technical factors can interfere with the measurement and/or interpretation of HRV. We systematically evaluated how HRV parameters are acquired/processed in critical care medicine.MethodsPubMed, MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials (1996–2016) were searched for cohort or case–control clinical studies of adult (>18 years) critically ill patients using heart variability analysis. Duplicate independent review and data abstraction. Study quality was assessed using two independent approaches: Newcastle–Ottowa scale and Downs and Black instrument. Conduct of studies was assessed in three categories: (1) study design and objectives, (2) procedures for measurement, processing and reporting of HRV, and (3) reporting of relevant confounding factors.ResultsOur search identified 31/271 eligible studies that enrolled 2090 critically ill patients. A minority of studies (15; 48%) reported both frequency and time domain HRV data, with non-normally distributed, wide ranges of values that were indistinguishable from other (non-critically ill) disease states. Significant heterogeneity in HRV measurement protocols was observed between studies; lack of adjustment for various confounders known to affect cardiac autonomic regulation was common. Comparator groups were often omitted (n = 12; 39%). This precluded meaningful meta-analysis.ConclusionsMarked differences in methodology prevent meaningful comparisons of HRV parameters between studies. A standardised set of consensus criteria relevant to critical care medicine are required to exploit advances in translational autonomic physiology.

Heart rate response and recovery in wheelchair tetraplegic rugby athletes: a pilot study.

Subjects with spinal cord injuries (SCI) have impaired autonomic cardiac regulation and increased risk of cardiovascular disease. In face of the insufficient research data on the autonomic control of physically active subjects with SCI, this study aimed at describing the chronotropic response, as well as the heart rate recovery behavior of a cohort of elite wheelchair rugby athletes. This is a cross-sectional study including a convenience sample of 17 elite wheelchair rugby athletes with tetraplegia. The subjects underwent a maximal arm ergometry exercise test. Heart rate (HR) was computed at five time points: at rest (before the test), peak exercise, and 1, 2, and 3 minutes after exercise. Data distribution was assessed by using the Shapiro-Wilk Test and correlations were measured by Pearson's correlation coefficient. The level of statistical significance was set at P<0.05. The subjects presented with HR at rest=69.53±8.3 bpm; HR reserve=66.9±8.3%; Chronotropic Index=47.9±11.8%; HRR at 1'=15.2±7.5 bpm; HRR at 2'=25.2±7.4 bpm; HRR at 3'=37±8.4 bpm. 82.3% of the athletes had HRR at 1'>12 bpm, and 64.7% had HRR at 2"> 22 bpm. There were associations between duration of injury and HRR at 1' (r=-0.5; P=0.0398), peak HR (HRpeak) and total weekly training time (r=-0.591; P=0.0125) and HRpeak and weekly physical training time (r=-0.519; P=0.032). Tetraplegic elite athletes present with reduced chronotropic response. Most of them exhibit an HRR within the values considered normal for the general population.

Cardiac autonomic changes elicited by energy-based healing modality: pilot study

Energy-based healing techniques have rarely been explored in current complementary therapies literature. This therapy is appropriate for cardiac nursing and can be implemented as part of nursing care. The authors investigated the acute effects of a standardised energy-based healing technique on cardiac autonomic regulation. Method: This study was conducted on 18 healthy students (15 female, three male), all non-smokers aged 18–35 years. Heart rate variability (HRV) was analysed 10 minutes before and 10 minutes after the energy-based healing technique was carried out. Geometric, time and frequency domain indices of HRV were examined. The subjects were blindfolded and sat at rest for 10 minutes, then received a standardised energy-based healing technique from an experienced male healer; they remained blindfolded and seated for a further 10 minutes. Results: Time and frequency domain indices of HRV were not significantly different before and after the energy-based healing technique. TINN (triangular interpolation histogram of RR intervals) (P=0.04) and RRTri (triangular index) (P=0.02) were increased after the therapy. A Poincaré plot indicated a slight increase in RR intervals dispersion after energy-based healing technique. Conclusion: A standardised energy-based healing technique marginally improved cardiac autonomic function in healthy subjects.

Acute Effects of Elevation Training Mask on Heart Rate Variability in Healthy Subjects

Elevation training mask (ETM) is purportedly designed for providing simulated altitude training, which claims that increasing respiratory resistance during exercise could provide benefits in respiratory functions and aerobic fitness. We assumed that this changed respiratory resistance may alter the autonomic cardiac regulation especially Heart Rate Variability (HRV). PURPOSE: The purpose of this study was to examine the acute effect of an elevation training mask on HRV during cycling. METHODS: This study was conducted with randomized and crossover design. Fifteen healthy male (N=9) and female (N=6) collegiate students (27.0 ± 4.42 yrs) completed two trials with mask (Mask) vs without mask (CON). The 40-minute protocol included (1) rest, (2) 50% and (3) 70% of VO2max cycling, and (4) recovery, each 10-minute phases. HRV variables including high frequency (HF), low frequency (LF), LF/HF ratio, were collected for 5 minutes at each phase with Actiwave-Cardio (CamNtech, UK). A 2x4 repeated measures (RM) MANOVA was used to analyze the data. Significant level was set at .05. RESULTS: A RM MANOVA result showed that there was no significant interaction effect on HRV. However, there were significant trial (Pillai’s F[3,12] = 4.488, p = .025) and time (Pillai’s F[9,126] = 5.383, p < .001) effects on HRV. Follow-up univariate tests revealed that HF was significantly greater in Mask than CON trial (F[1,14] = 7.484, G-G p = .016). Both HF (F[1.05,14.74] = 24.221, G-G p < .001) and LF (F[1.29,18.05] = 28.759, G-G p < .001) were decreased as cycling intensity increased. CONCLUSIONS: In summary, acute wearing of ETM does not alter the HRV during cycling. However, a greater HF response was observed in Mask than CON trial. Future studies are needed to confirm the effects of long-term training with ETM on HRV.

Four weeks of exposure to environmentally relevant levels of second hand smoke decreases heart rate variability—but not baroreflex sensitivity—in mice

BACKGROUNDSecond hand smoke (SHS), a source of environmental air pollution exposure, is a significant risk factor for cardiovascular morbidity and mortality. Impaired autonomic function, as indexed by decreased heart rate variability (HRV), has been implicated as one of the underlying mechanisms of increased arrhythmia susceptibility that often precedes sudden cardiac death. We previously showed, in mice, that short term (3 days) exposure to a high level of SHS (30 mg/m3, 6 hr/d) reduced HRV that persisted after this acute window of SHS exposure. However, we have limited information on the time course of SHS‐induced cardiovascular dysfunction at more environmentally relevant concentrations. Here, we sought to test the hypothesis that an environmentally relevant level of SHS decreases HRV and baroreflex sensitivity (BRS), while increasing blood pressure (BP) and BP variability (BPV).METHODSAdult male C57BL/6J mice were implanted with BP/ECG telemetry devices. Two weeks after recovering from surgery, mice were randomly assigned to either filtered air (FA, n=10 for HRV, n=5 for BPV and BRS) or SHS (n=6) groups. SHS exposure level was similar to that of a “smoky bar” (3 mg/m3) for 6hr/d, 5d/wk for 4wk. Weekly, 36 hours of continuous BP and ECG recordings were performed after five days of exposure. Data were divided into three 12‐hour periods: the dark cycle immediate after the 5th day of exposure and the following light and dark cycles. Standard time domain HRV parameters were determined from normal‐to‐normal R wave intervals (SDNN, CV% and rMSSD). BRS was determined with the sequence method using systolic BP.RESULTSSHS exposure for four weeks did not change BP and HR in either dark or light cycle. SHS significantly decreased short term HRV (rMSSD) during the light cycle in as few as two weeks of exposure (28% lower than FA group, p&lt;0.05). However, there was no significant change in overall HRV (SDNN and CV%) after four weeks of SHS exposure. These data suggest that the initial change in cardiac autonomic regulation is likely mediated by reduced vagal regulation. There was a trend, but not statistically significant effect, for an increase in BPV (12% higher than FA group) after four weeks of SHS exposure; however, no change in BRS was observed after four weeks of SHS exposure. These data suggest that changes in cardiac regulation precede changes in BP regulation, and that the cardiac vagal limb of the autonomic nervous system is particularly sensitive to SHS exposure.CONCLUSIONSWe conclude that this environmentally relevant dose of SHS can impair cardiovascular regulation in a time‐dependent manner, further emphasizing the importance of regulating and limiting exposure to SHS.Support or Funding InformationR01 ES025229; T32 HL086350

Descripción de un caso de bradiarritmia en pacientes con síndrome de Down sin enfermedad cardiaca congénita

Introducción. Los pacientes con síndrome de Down sin enfermedad cardiaca estructural pueden presentar disfunción de la regulación autonómica cardiaca, lo cual se manifiesta mediante una contestación reducida de la frecuencia cardiaca (FC) frente a los estímulos. Con base en las respuestas hemodinámicas, se postuló que dichos pacientes tienen una reducción en las retirada vagales y la activación simpática. En esta revisión se explica el rol del sistema autonómico en el control de la FC y la respuesta cronotrópica atenuada observada en esta población.Objetivo. Describir, mediante la presentación de un caso clínico, la disfunción autonómica presente en los pacientes con síndrome de Down a fin de identificar las causas atribuidas por la evidencia científicaMateriales y métodos.Se describió un caso clínico y se realizó una búsqueda a través de PubMed con los términos: “Down Syndrome” AND “Bradycardia”, “VO2peak”, “Heart Rate Variability”, “Vagal Withdrawal”, “Sympathetic Activation”.Resultados. Los hallazgos sugieren que el ejercicio físico puede ser una intervención efectiva para mejorar la función cardiaca autonómica en personas con síndrome de Down. Además, las mejoras inducidas por el entrenamiento fueron alcanzadas por los participantes con niveles más bajos de modulación vagal al inicio del estudio en pacientes con y sin discapacidad, por lo que el entrenamiento puede ser eficaz para mejorar la aptitud cardiorespiratoria en quienes tienen un mayor grado de disfunción autonómica.Conclusión. Se presentó un caso clínico de síndrome de Down con disfunción sinusal, que podía estar relacionado con la disfunción de la regulación de la función cardiaca autonómica, dada por una FC reducida frente a los estímulos.

Sex and age differences in cardiac autonomic nervous regulation in response to recumbent positions

Not much research has been conducted to determine sex and age differences in autonomic nervous activity during different positions, namely the supine, left recumbent, and right recumbent positions. Our aim was to evaluate whether the left and right recumbent positions affect heart rate variability (HRV) differently than the supine position dose in young and old adults of both sexes. Twenty‐nine young male (22.5 ± 0.5 years), 29 young female (23.1 ± 0.7 years), 18 elderly male (76.1 ± 1.1 years), and 27 elderly female (72.6 ± 1.0 years) volunteers participated in this study. After lying in the supine position, the participants maintained each recumbent position in random order for 10 min. We recorded electrocardiographic data throughout this experiment to evaluate HRV. Heart rate during the left recumbent position was the lowest among the three positions regardless of age or sex. No significant differences were observed for low‐frequency (LF) HRV, high‐frequency (HF) HRV, or their ratio (LF/HF) in young adults of both sexes and elderly women when the position was changed from supine to recumbent. However, in elderly men, the LF/HF ratio during the right recumbent position was significantly lower than that during the supine position. While in supine position, elderly men showed high LF/HF ratios when compared to the other groups. These results suggest that the right recumbent position attenuates cardiac sympathetic nerve activity, which is expressed as the LF/HF ratio, in elderly male adults. Therefore, reduction in heart rate during the left recumbent position may not be associated with autonomic nervous activity.Support or Funding InformationThis work was supported in part by a Grant‐in‐Aid for Challenging Exploratory Research from the Japan Society for the Promotion of Science.

Passive Heating Impairs Cardiac Autonomic Regulation during Exercise and Post‐Exercise Recovery

AIMThe aim of this study was to assess the effects of passive heating on exercise and post‐exercise cardiac autonomic regulation.METHODSTwelve healthy young men (25±5 yrs, 23.8±1.9 kg/m2, 47.3±7.9 ml.kg−1.min−1) randomly underwent two experimental sessions: heat stress (HEAT) and control (CON). Each session composed of: a heat stress or normothermic control intervention; 7 min of cycling at 40% HRreserve (EX1); 7 min of cycling at 60% HRreserve (EX2); and 10 min of recovery in the seated position (REC). HEAT consisted of 60 min whole‐body passive heating by perfusing hot water (48°C) in a tube‐lined suit to increase core temperature (Tc) by ~1°C. CON consisted of normothermia exposure for a similar timeframe. Heart rate (HR) and finger blood pressure were continuously assessed. HR variability (HRV) was assessed using the vagal‐related RMSSD index, baroreflex sensitivity (BRS) was assessed using the sequence technique and HR recovery (HRR) was assessed through the absolute decrease of HR at 60 (HRR60s) and 300 s (HRR300s) after exercise. Tc, skin temperature (Tsk), forearm skin blood flow (SKBF) and cutaneous vascular conductance (CVC) were also continuously measured throughout.RESULTSTc, Tsk, SKBF and CVC were significantly increased in HEAT compared with CON (Tc: 38.0±0.3 vs. 37.1±0.3 °C; Tsk: 36.8±0.6 vs. 33.2±0.8 °C; SKBF: 160±96 vs. 50±34 A.U.; CVC: 2.3±1.3 vs. 0.6±0.3 A.U/mmHg; all p&lt;0.05). During exercise, HRV and BRS were not different between trials during EX1 and EX2. However, when comparing EX1 of CON with EX2 of HS (i.e. similar absolute workloads), HRV (0.8 ± 0.4 vs. 1.9 ± 0.7 ms; p&lt;0.01) and BRS (0.6 vs. 0.3 vs. 1.5 ± 1.0 ms/mmHg; p&lt;0.01) were significantly reduced in HS. During recovery, HRV (1.7 ± 0.6 vs. 2.6 ± 0.9 ms, p&lt;0.01) and BRS (6 ± 3 vs. 4 ± 3 ms/mmHg; p&lt;0.01) were significantly reduced in HS. Furthermore, HRR60s and HRR300s were significantly reduced in HS (HRR60s = 27±9 vs. 46±10 bpm; HRR300s = 39 ± 12 vs. 61 ± 13 bpm; p&lt;0.01).CONCLUSIONPassive heating impairs cardiac autonomic regulation during exercise at the same absolute workload and during recovery.Support or Funding InformationFAPESP 2013/04997‐0; 2013/05519‐4; 2015/15466‐0