Measures Of Autonomic Function Research Articles

Cardiovascular function and ozone exposure: The Multicenter Ozone Study in oldEr Subjects (MOSES)

To date, there have been relatively few studies of acute cardiovascular responses to controlled ozone inhalation, although a number of observational studies have reported significant positive associations between both ambient ozone levels and acute cardiovascular events and long-term ozone exposure and cardiovascular mortality. We hypothesized that short-term controlled exposure to low levels of ozone in filtered air would induce autonomic imbalance, repolarization abnormalities, arrhythmia, and vascular dysfunction. This randomized crossover study of 87 healthy volunteers 55-70 years of age was conducted at three sites using a common protocol, from June 2012 to April 2015. Subjects were exposed for 3 h in random order to 0 ppb (filtered air), 70 ppb ozone, and 120 ppb ozone, alternating 15 min of moderate exercise with 15 min of rest. A suite of cardiovascular endpoints was measured the day before, the day of, and up to 22 h after each exposure. Mixed effect linear and logit models evaluated the impact of exposure to ozone on pre-specified primary and secondary outcomes. Site and time were included in the models. We found no significant effects of ozone exposure on any of the primary or secondary measures of autonomic function, repolarization, ST segment change, arrhythmia, or vascular function (systolic blood pressure and flow-mediated dilation). In this multicenter study of older healthy women and men, there was no convincing evidence for acute effects of 3-h, relatively low-level ozone exposures on cardiovascular function. However, we cannot exclude the possibility of effects with higher ozone concentrations, more prolonged exposure, or in subjects with underlying cardiovascular disease. Further, we cannot exclude the possibility that exposure to ambient ozone and other pollutants in the days before the experimental exposures obscured or blunted cardiovascular biomarker response to the controlled ozone exposures.

Heart rate variability and baroreflex sensitivity abnormalities in Guillain-Barré syndrome: a pilot study.

The current study aimed to investigate autonomic dysfunction in Guillain-Barré syndrome (GBS) patients and describe the results of computational heart rate variability (HRV)/baroreflex sensitivity (BRS) and autonomic challenge tests. GBS patients were consecutively recruited and the results were compared to age- and gender-matched healthy controls. A series of autonomic function tests including computation-dependent tests (power spectrum analysis of HRV and BRS at rest) and challenge maneuvers (deep breathing, eyeball compression, active standing, the Valsalva maneuver, sustained handgrip, and the cold pressor test) were performed. Ten GBS patients (six men; mean age = 40.1 ± 13.9years) and ten gender- and age-matched healthy controls were recruited. The mean GBS functional grading scale at disease plateau was 3.4 ± 1.0. No patients required intensive care unit admission or mechanical ventilation. Low-frequency HRV (p = 0.027), high-frequency HRV (p = 0.008), and the total power spectral density of HRV (p = 0.015) were significantly reduced in patients compared to controls. The mean up slope (p = 0.034), down slope (p = 0.011), and total slope (p = 0.024) BRS were significantly lower in GBS patients. The diastolic rise in blood pressure in the cold pressor test was significantly lower in GBS patients compared to controls (p = 0.008). Computation-dependent tests (HRV and BRS) were more useful for detecting autonomic dysfunction in GBS patients, whereas the cold pressor test was the only reliable challenge test, making it useful as a bedside measure of autonomic function in GBS patients.

Eight weeks of slow deep breathing training alters cardiorespiratory function and improves functional exercise capacity in chronic heart failure patients

Patients with chronic heart failure (CHF) display autonomic imbalance characterized by excessive sympathoexcitation and reduced vagal outflow. Respiratory sinus arrhythmia (RSA) and baroreflex sensitivity (BRS) are often used as non‐invasive indices of autonomic function. Slow deep breathing (SDB) has been shown to modulate RSA and BRS. In this preliminary study, we examined the effects of SDB in CHF patients (n=4) during a baseline condition of spontaneous breathing (5 minutes), during SDB (5 minutes) controlled at 6 breaths/minute, and during a post‐SDB condition of spontaneous breathing (5 minutes). The patients then underwent an SDB training protocol, in which SDB was practiced at least 5 days/week and with the duration of practice incrementally increasing from 10 min/day at week 0 up to 30 minutes/day by week 8. Comparisons in cardiorespiratory function were made between each of the conditions (i.e., baseline, SDB, and post‐SDB) and between each time point (i.e., week 0 and week 8). We hypothesized that acute SDB would transiently decrease blood pressure, increase BRS, and increase RSA compared to the baseline and post‐SDB conditions. We also predicted that 8 wks of SDB training would decrease baseline blood pressure, increase BRS, and increase RSA compared to week 0. SDB produced a statistically significant (p=0.01) reduction in systolic pressure after 8 wks (114 ± 5.4 mmHg) compared to week 0 (132 ± 12 mmHg). Further, 8 wks of SDB training appears to have altered acute blood pressure responses to SDB. During SDB at week 0, systolic pressure did not differ from baseline spontaneous breathing. However, after 8 wks of SDB training, patients showed a 5.4% reduction in systolic pressure to acute SDB compared to baseline spontaneous breathing (p=0.02). The decrease in systolic pressure was not correlated with the type or dose of antihypertensive drugs. Acute SDB also produced a transient increase in BRS of ~25% from the baseline condition with no differences between week 0 and week 8. RSA increased during acute SDB compared to baseline (p=0.001) but did not change after 8 weeks of SDB training. Further, a six‐minute walk test was performed to assess functional exercise capacity, and the patients with the greatest impairment at baseline showed improvements in the six‐minute walk test after 8wks of SDB. While the data are preliminary, the results suggest that SDB training improves exercise capacity and produces a stable reduction in systolic pressure and transient change in non‐invasive measures of autonomic function in CHF patients.Support or Funding InformationNIH PO1‐HL062222‐17This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Heart Rate Variability as a Predictor of Hypotension Following Spinal for Elective Caesarean Section: A Prospective Observational Study

(Anaesthesia. 2017;72(5):603–608) Hypotension after spinal anesthesia for cesarean delivery is a significant complication that can adversely affect both the mother and her unborn child. In fact, in South Africa a majority of anesthesia-related maternal deaths occur in women receiving spinal anesthesia with >50% associated with spinal-induced hypotension. Therefore, a method to predict preoperatively which patients will experience this complication would be highly desirable, with the potential to alter patient management and improve outcomes. Previous studies have found that heart rate variability (HRV) analysis, which serves as a measure of autonomic function, can predict spinal-induced hypotension in parturients. In this prospective observational study from South Africa, HRV was evaluated in comparison to other potential predictors of hypotension [baseline heart rate and body mass index (BMI)] in women undergoing elective cesarean section under spinal anesthesia.

Reproducibility of 24-h ambulatory blood pressure and measures of autonomic function: methodological and statistical issue.

Reproducibility of 24-h ambulatory blood pressure and measures of autonomic function: methodological and statistical issue.

Effects of Cognitive Behavior Therapy on Heart Rate Variability in Young Females with Constipation-predominant Irritable Bowel Syndrome: A Parallel-group Trial.

Background/AimsThe relation between heart rate variability (HRV) as non-invasive biomarkers of autonomic function and cognitive behavior therapy (CBT) as non-pharmacological treatments has rarely been examined in patients with constipation-predominant irritable bowel syndrome (IBS-C). The purpose of this study is to evaluate the efficacy of an 8-week CBT intervention on HRV and IBS symptoms, and the correlation of changes in HRV with changes in IBS symptoms among young female nursing students with IBS-C.MethodsThis study consisted of an exploratory subgroup analysis of 43 participants with IBS-C who had been randomly assigned to receive either 8 weeks of CBT (n = 23) or general medical information (control, n = 20). At baseline and 8, 16, and 24 weeks, participants completed a questionnaire assessing their gastrointestinal (GI) symptoms, anxiety, depression, and stress, and their HRV was measured via electrocardiography.ResultsAt the 8-week follow-up, the high-frequency (HF) power was significantly higher, and the low-frequency (LF)/HF ratio was lower in the CBT group than in the control group (P < 0.001 for both), and the severity of GI symptoms (P = 0.003), anxiety (P < 0.001), depression (P < 0.001), and stress (P < 0.001) was significantly lower in the CBT group than in the control group. Changes in the HF power were significantly and inversely associated with changes in GI symptoms, anxiety, depression, and stress at 16 and 24 weeks (P < 0.05 for all; range of r from −0.37 to −0.68). Changes in the LF/HF ratio were also significantly and positively associated with changes in GI symptoms, anxiety, depression, and stress at 16 and 24 weeks (P < 0.05 for all; range of r from 0.38 to 0.60).ConclusionsCBT was effective in managing symptoms in young IBS-C patients and the improvement of symptoms was sustained at 24 weeks following the completion of CBT. Furthermore, indirect measurement of autonomic function using HRV may be a useful objective parameter for assessing response to CBT in young IBS-C patients.

Incremental shuttle walk test distance and autonomic dysfunction predict survival in pulmonary arterial hypertension

To ensure effective monitoring of pulmonary arterial hypertension (PAH), a simple, reliable assessment of exercise capacity applicable over a range of disease severity is needed. The aim of this study was to assess the ability of the incremental shuttle walk test (ISWT) to correlate with disease severity, measure sensitivity to change, and predict survival in PAH. We enrolled 418 treatment-naïve patients with PAH with baseline ISWT within 3 months of cardiac catheterization. Clinical validity and prognostic value of ISWT distance were assessed at baseline and 1 year. ISWT distance was found to correlate at baseline with World Health Organization functional class, Borg score, and hemodynamics without a ceiling effect (all p < 0.001). Walking distance at baseline and after treatment predicted survival; the area under the receiver operating characteristic curve for ability of ISWT distance to predict mortality was 0.655 (95% confidence interval 0.553-0.757; p = 0.004) at baseline and 0.737 (95% confidence interval 0.643-0.827; p < 0.001) at 1 year after initiation of treatment. Change in ISWT distance also predicted survival (p = 0.04). Heart rate (HR) and systolic blood pressure (SBP) parameters reflecting autonomic response to exercise (highest HR, change in HR, HR recovery at 1 minute >18 beats/min, highest SBP, change in SBP, and 3-minute SBP ratio) were significant predictors of survival (all p < 0.05). In patients with PAH, the ISWT is simple to perform, allows assessment of maximal exercise capacity, is sensitive to treatment effect, predicts outcome, and has no ceiling effect. Also, measures of autonomic function made post-exercise predict survival in PAH.

The Role of Autonomic Function in Exerciseinduced Endogenous Analgesia: A Case-control Study in Myalgic Encephalomyelitis⁄Chronic Fatigue Syndrome and Healthy People

Background: Patients with myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) are unable to activate brain-orchestrated endogenous analgesia (or descending inhibition) in response to exercise. This physiological impairment is currently regarded as one factor explaining postexertional malaise in these patients. Autonomic dysfunction is also a feature of ME/CFS. Objectives: This study aims to examine the role of the autonomic nervous system in exerciseinduced analgesia in healthy people and those with ME/CFS, by studying the recovery of autonomic parameters following aerobic exercise and the relation to changes in self-reported pain intensity. Study Design: A controlled experimental study. Setting: The study was conducted at the Human Physiology lab of the Vrije Universiteit Brussel. Methods: Twenty women with ME/CFS- and 20 healthy, sedentary controls performed a submaximal bicycle exercise test known as the Aerobic Power Index with continuous cardiorespiratory monitoring. Before and after the exercise, measures of autonomic function (i.e., heart rate variability, blood pressure, and respiration rate) were performed continuously for 10 minutes and self-reported pain levels were registered. The relation between autonomous parameters and self-reported pain parameters was examined using correlation analysis. Results: Some relationships of moderate strength between autonomic and pain measures were found. The change (post-exercise minus pre-exercise score) in pain severity was correlated (r = .580, P = .007) with the change in diastolic blood pressure in the healthy group. In the ME/CFS group, positive correlations between the changes in pain severity and low frequency (r = .552, P = .014), and between the changes in bodily pain and diastolic blood pressure (r = .472, P = .036), were seen. In addition, in ME/CHFS the change in headache severity was inversely correlated (r = -.480, P = .038) with the change in high frequency heart rate variability. Limitations: Based on the cross-sectional design of the study, no firm conclusions can be drawn on the causality of the relations. Conclusions: Reduced parasympathetic reactivation during recovery from exercise is associated with the dysfunctional exercise-induced analgesia in ME/CFS. Poor recovery of diastolic blood pressure in response to exercise, with blood pressure remaining elevated, is associated with reductions of pain following exercise in ME/CFS, suggesting a role for the arterial baroreceptors in explaining dysfunctional exercise-induced analgesia in ME/CFS patients. Key words: Aerobic exercise, aerobic power index, autonomic nervous system, exercise-induced analgesia, exercise-induced hypoalgesia, fibromyalgia, heart rate variability, stress-induced analgesia, pain Pain

Sudden cardiac death: The role of imaging

Sudden cardiac death (SCD) is defined as "a non-traumatic, unexpected, fatal event occurring within one hour of the onset of symptoms in an apparently healthy subject", and it causes a fifth of all deaths worldwide. It often occurs in individuals not previously known with cardiac disease, which makes prevention challenging. The mechanism underlying SCD is thought to be a trigger (e.g. ischemia) acting upon a substrate (e.g. scar), causing a lethal arrhythmia. Primary prevention refers to patients at high risk of SCD and secondary prevention to those who have had an aborted episode of SCD. Insertion of an implantable, cardioverter-defibrillator (ICD) is the most effective approach to primary prevention; currently ICD candidate selection is based on a left ventricular ejection fraction (LVEF) ≤35%. The LVEF is neither sensitive nor specific in identifying individuals who will benefit from ICD therapy, and therefore alternative strategies are required. The present review article summarizes the evidence on various non-imaging (e.g. microvolt T-wave alternans, signal-averaged ECG, QRS fragmentation and measures of autonomic function) and imaging (echocardiography, cardiac magnetic resonance and radionuclide) modalities showing incremental value over LVEF to identify the patients who will benefit from an ICD.

Association of Heart Rate Recovery With Microalbuminuria in Non-Obstructive Coronary Artery Disease.

BackgroundNon-obstructive coronary artery disease (CAD) is associated with significantly increased risk for myocardial infarction. Heart rate recovery (HRR), a measure of autonomic function, is a strong predictor of all-cause mortality. Microalbuminuria, a marker of early arterial disease, is an independent risk factor for cardiovascular disease and mortality. We aimed to investigate HRR and determine its relationship with microalbuminuria in patients with non-obstructive CAD.MethodsWe prospectively studied 565 patients who underwent elective coronary angiography. All participants underwent urinary analysis and then an exercise test. Microalbuminuria was defined as an urinary albumin-to-creatinine ratio (UACR) of 30 - 299 mg/g. The HRR was abnormal if ≤ 12 beats/min during the first minute after exercise. First, all patients were divided into two groups, patients with microalbuminuria (n = 152) and patients without microalbuminuria (n = 413). Then, all patients were re-divided into two groups, those with lower HRR (≤ 12 beats/min, n = 126) and those with higher HRR (> 12 beats/min, n = 439).ResultsPatients with microalbuminuria had lower HRR and patients with lower HRR had higher UACR. While UACR was negatively correlated with HRR in patients with microalbuminuria (r = -0.424; P < 0.001) and in patients with lower HRR (r = -0.192; P= 0.042), there was no correlation of UACR with HRR in neither patients with normoalbuminuria nor patients with higher HRR, respectively. In the all study population, there was a significant inverse association between UACR and HRR (r = -0.445, P < 0.001), and UACR independently predicted the presence of lower HRR (P < 0.001).ConclusionsOur findings showed that there was a significant inverse association between UACR and HRR in patients especially with microalbuminuria, and that albuminuria might predict cardiac autonomic imbalance evaluated by HRR in patients with non-obstructive CAD.

PP.13.09] THE EFFECTS OF BAROREFLEX ACTIVATION THERAPY ON BLOOD PRESSURE AND SYMPATHETIC FUNCTION IN PATIENTS WITH REFRACTORY HYPERTENSION – THE RATIONALE AND DESIGN OF THE NORDIC BAT STUDY

Objective: Baroreflex activation therapy (BAT) modulates the autonomic nervous system to restore sympathovagal balance. The aim of this study is to explore the effects of BAT on hypertension in patients with refractory (true resistant) hypertension (RH). Design and method: This academic (independent of industry support) randomized, double-blind, 1:1 parallel-design clinical trial will include 100 patients with RH from six hypertension centers in the Nordic countries. A Barostim Neo® System will be implanted and after 1 month of stabilization patients will be randomized to either BAT for 16 months or continuous pharmacotherapy (BAT off) for 8 months followed by the BAT for 8 months (Figure). Blood and urine samples will be drawn and measures of arterial and cardiac function and structure, and of autonomic function will be performed at randomization, and after 8 and 16 months. Eligible patients will be 18–70 years and have a daytime systolic ambulatory blood pressure (ABMP) of 145 mmHg or more, and/or a daytime diastolic ABMP of 95 mmHg or more, after witnessed intake of antihypertensive treatment (including at least 3 antihypertensive drugs, preferably a diuretic), with no changes in medication for a minimum of 4 weeks prior to enrolment. Patients with secondary causes of hypertension, severe renal insufficiency, untreated sleep apnea, pregnancy, type 1 diabetes, alcohol/drug abuse, or psychiatric illnesses, other than sinus rhythm (controlled atrial fibrillation is not a contraindication), uncontrolled systolic heart failure, aortic stenosis, and a cardiovascular event 3 within months before enrolment will be excluded. Results: The primary end point is to test whether BAT reduces 24-hour systolic ABMP at 8 months of follow-up compared to pharmacotherapy. Secondary/tertiary endpoints are the effects of BAT on home and office blood pressure, measures of autonomic function, arterial and cardiac structure and function during follow-up, and extended long-term follow-up. Two patients have been included in the study so far. An interim analysis will be done after 50 patients. Conclusions: This initiative will increase the understanding of the mechanisms and role of BAT in the treatment of RH.

Ranolazine Therapy Reduces Non-ST-Segment-Elevation Myocardial Infarction and Unstable Angina in Coronary Disease Patients with Angina.

High sympathetic tone and cardiac autonomic neuropathy (CAN) are associated with major adverse cardiac events (MACE). We have shown ranolazine (RAN) improves autonomic function. RAN was introduced to 51 successive anginal CD patients (RANCD). A control group of 54 successive nonanginal CD patients (NORANCD) continued baseline therapy. Mean study duration was 6.1 years, which included semi-annual autonomic function measures (ANX 3.0, ANSAR Medical Technologies, Inc., Philadelphia, PA) and yearly myocardial perfusion SPECT studies (MPI). MACE were experienced by 29% RANCD patients versus 46% NORANCD patients (p = 0.0105). The patients from both groups with abnormal parasympathetic and sympathetic (P&S) measures and MACE totaled 52 of those patients with MACE versus 17% of those patients without MACE (p = 0.0274). Abnormal MPI was demonstrated in 35% of those with abnormal (P&S) measures and MACE versus 12% without MACE. Sympathovagal balance (SB) was lower, indicating higher, relative parasympathetic tone (known to be cardioprotective) in the RANCD group. Acute coronary syndromes occurred 4.5 times as often in NORANCD patients. High SB occur more frequently than abnormal MPI in CD patients experiencing MACE. In addition to increased myocardial blood flow as its proposed mechanism of angina relief, RAN improves P&S measures, a potentially new mechanism whereby RAN improves outcomes.

Abstract WP301: Noninvasive Beat-to-Beat Assessment of Blood Pressure Variability, Heart Rate Variability and Baroreflex Sensitivity: Which Parameters Best Predict Clinical Outcome After Acute Ischemic Stroke?

Background and Objectives: Blood pressure variability (BPV), heart rate variability (HRV) and baroreflex sensitivity (BRS) as measures of autonomic function might provide prognostic information in ischemic stroke. We aimed to study noninvasive beat-to-beat assessment of BPV, HRV and BRS in the acute phase of ischemic stroke to determine whether any of them predicted clinical outcome. Methods &amp; Patients: Consecutive ischemic stroke patients within 7 days of symptom onset were enrolled. The frequency components of BPV and HRV by means of power spectral analysis [very low frequency (VLF; &lt; 0.04 Hz); low frequency (LF; 0.04-0.15 Hz); high frequency (HF; 0.15-0.40 Hz); power spectral density (PSD; &lt;0.40 Hz) and LF/HF ratio] were calculated from 10-minute recordings of beat-to-beat blood pressure and heart rate monitoring. The baroreflex slope and baroreflex effectiveness index (BEI) were determined using the sequence method for BRS. Clinical outcome was assessed at 3 months after stroke onset as good or poor by modified Rankin Scale (mRS) (good outcome, mRS ≤ 2). Results: 82 patients were recruited (mean age, 64.6 ± 9.9 years; 89.3% males). Univariate analysis showed that there were significant differences in National Institutes of Health Stroke Scale (NIHSS) at recruitment, VLF diastolic BPV, VLF, HF and PSD systolic BPV, and down ramp BEI between the good and poor outcome groups (all P &lt; 0.05). After adjusting for NIHSS, multivariate logistic regression showed that only HF systolic BPV (OR 1.320; 95% CI, 1.050-1.659; P=0.017) and down BEI (OR 0.950; 95% CI, 0.912-0.990; P=0.014) were independently correlated with poor functional outcome. Conclusions: Beat-to beat highly variable systolic blood pressure and impaired BRS as evaluated by decreased down BEI are associated with an unfavorable functional outcome after acute ischemic stroke. Important prognostic information can be readily obtained from a short period of noninvasive hemodynamics monitoring in the acute stroke patient.

Subclinical cardiopulmonary dysfunction in stage 3 chronic kidney disease

ObjectiveReduced exercise capacity is well documented in end-stage chronic kidney disease (CKD), preceded by changes in cardiac morphology in CKD stage 3. However, it is unknown whether subclinical cardiopulmonary dysfunction...

Measures of Autonomic Dysfunction in Diabetic and Idiopathic Gastroparesis.

BackgroundGastroparesis is a condition classically characterized by delayed gastric emptying and is associated with considerable morbidity. While the etiology of gastroparesis remains elusive, autonomic dysfunction may play an important role, especially as many patients with gastroparesis also have diabetes. The aim of this study was to determine whether measures of autonomic function differ between adults with diabetic gastroparesis (DG) and adults with idiopathic gastroparesis (IG).MethodsTests of systemic autonomic function were performed among 20 adults with GD (six men and 14 women, mean age: 42 years) and 21 adults with IG (seven men and 14 women, mean age: 37 years). Measures included vagal cholinergics by R-R interval percentage variation (RRI-PV) and sympathetic adrenergics by vasoconstriction to cold (VC) and postural adjustment ratio (PAR). The two groups were compared using Wilcoxon rank sum tests and linear regression analysis (STATA 10.0).ResultsIn univariate analysis, the following autonomic measures differed significantly between DG and IG: VC (P = 0.004), PAR (P = 0.045), VC + PAR (P = 0.002) and RRI-PV (P < 0.001). In multivariate analysis (P = 0.002, R2 = 0.55), only RRI-PV (adjusted odds ratio (aOR): 1.02, 95% confidence interval (CI): 1.01 - 1.03) differed significantly between DG and IG patients.ConclusionsVagal cholinergics are affected to a greater degree in DG compared to IG, suggesting that impaired vagal tone is not a universal mechanism for gastroparesis.

Sex differences in autonomic function following maximal exercise.

BackgroundHeart rate variability (HRV), blood pressure variability, (BPV) and heart rate recovery (HRR) are measures that provide insight regarding autonomic function. Maximal exercise can affect autonomic function, and it is unknown if there are sex differences in autonomic recovery following exercise. Therefore, the purpose of this study was to determine sex differences in several measures of autonomic function and the response following maximal exercise.MethodsSeventy-one (31 males and 40 females) healthy, nonsmoking, sedentary normotensive subjects between the ages of 18 and 35 underwent measurements of HRV and BPV at rest and following a maximal exercise bout. HRR was measured at minute one and two following maximal exercise.ResultsMales have significantly greater HRR following maximal exercise at both minute one and two; however, the significance between sexes was eliminated when controlling for VO2 peak. Males had significantly higher resting BPV-low-frequency (LF) values compared to females and did not significantly change following exercise, whereas females had significantly increased BPV-LF values following acute maximal exercise. Although males and females exhibited a significant decrease in both HRV-LF and HRV-high frequency (HF) with exercise, females had significantly higher HRV-HF values following exercise. Males had a significantly higher HRV-LF/HF ratio at rest; however, both males and females significantly increased their HRV-LF/HF ratio following exercise.ConclusionsPre-menopausal females exhibit a cardioprotective autonomic profile compared to age-matched males due to lower resting sympathetic activity and faster vagal reactivation following maximal exercise. Acute maximal exercise is a sufficient autonomic stressor to demonstrate sex differences in the critical post-exercise recovery period.

Effects of vibroacoustic stimulation in music therapy for palliative care patients: a feasibility study.

BackgroundThe present study aimed at examining whether methodological strategies from a previously implemented study design could be transferred to the evaluation of the psychological and physiological effects of a music therapy intervention working with vibroacoustic stimulation in palliative care.MethodNine participants suffering from advanced cancer took part in single-sessions of music therapy, lasting for 30 min. The live music therapy intervention utilized singing chair sounds and vocal improvisation. Visual analogue scales (VAS) were used to assess self-ratings of pain, relaxation, and well-being before and after each session. During the intervention, we continuously recorded heart rate variability (HRV) as a measure of autonomic functioning. Data collection was complemented by a semi-structured interview to explore subjective experiences in more detail. Feasibility was defined as the ability to complete 80 % of the sessions in accordance with the study protocol.ResultsIn 5 out of 9 sessions (55 %) it was possible to deliver the intervention and obtain all data as intended. VAS assessment was feasible, although graphical and statistical examination revealed only marginal mean changes between pre and post. HRV recordings were subject to artifacts. While HRV parameters differed between individuals, mean changes over time remained relatively constant. Interview data confirmed that the individual perception was very heterogeneous, ranging from “calming” to “overwhelming”.ConclusionThe criterion of feasibility was not met in this study. Physiological data showed high attrition rates, most likely due to movement artifacts and reduced peripheral blood flow in some participants’ extremities. Examination of individual-level trajectories revealed that vibroacoustic stimulation may have an impact on the autonomic response. However, the direction and mechanisms of effects needs to be further explored in future studies.Trial registrationGerman Clinical Trials Register – DRKS00006137 (July 4th, 2014).

Prognostic Value of Heart Rate Variability in Patients With Cancer.

Previous studies have shown that autonomic dysfunction is associated with shorter survival in patients with advanced cancer. We examined the association between heart rate variability, a measure of autonomic function, and survival in a large cohort of patients with cancer. We retrospectively examined the records of 651 patients with cancer who had undergone ambulatory electrocardiogram monitoring for 20 to 24 hours. Time domain heart rate variability (SD of normal-to-normal beat interval [SDNN]) was calculated using power spectral analysis. Survival data were compared between patients with SDNN ≥ 70 milliseconds (Group 1, n = 520) and SDNN < 70 milliseconds (Group 2, n = 131). Two groups were similar in most variables, except that patients in group 2 had a significantly higher percentage of male patients (P = 0.03), hematological malignancies (P = 0.04), and use of non-selective serotonin reuptake inhibitor antidepressants (P = 0.04). Patients in group 2 had a significantly shorter survival rate (25% of patients in group 2 died by 18.7 weeks vs. 78.9 weeks in group 1 patients; P < 0.0001). Multivariate analysis showed that SDNN < 70 milliseconds remained significant for survival (hazard ratio 1.9 [95% confidence interval: 1.4-2.5]) independent of age, cancer stage, and performance status. The presence of cancer in combination with decreased heart rate variability (SDNN < 70 milliseconds) is associated with shorter survival time.

Contextualizing Parasympathetic Hyperactivity in Functionally Overreached Athletes With Perceptions of Training Tolerance

Heart-rate variability (HRV) as a measure of autonomic function may increase in response to training interventions leading to increases or decreases in performance, making HRV interpretation difficult in isolation. This study aimed to contextualize changes in HRV with subjective measures of training tolerance. Supine and standing measures of vagally mediated HRV (root-mean-square difference of successive normal RR intervals [RMSSD]) and measures of training tolerance (Daily Analysis of Life Demands for Athletes questionnaire, perception of energy levels, fatigue, and muscle soreness) were recorded daily during 1 wk of light training (LT), 2 wk of heavy training (HT), and 10 d of tapering (T) in 15 male runners/ triathletes. HRV and training tolerance were analyzed as rolling 7-d averages at LT, HT, and T. Performance was assessed after LT, HT, and T with a 5-km treadmill time trial (5TTT). Time to complete the 5TTT likely increased after HT (effect size [ES] ± 90% confidence interval = 0.16 ± 0.06) and then almost certainly decreased after T (ES = -0.34 ± 0.08). Training tolerance worsened after HT (ES ≥ 1.30 ± 0.41) and improved after T (ES ≥ 1.27 ± 0.49). Standing RMSSD very likely increased after HT (ES = 0.62 ± 0.26) and likely remained higher than LT at the completion of T (ES = 0.38 ± 0.21). Changes in supine RMSSD were possible or likely trivial. Vagally mediated HRV during standing increased in response to functional overreaching (indicating potential parasympathetic hyperactivity) and also to improvements in performance. Thus, additional measures such as training tolerance are required to interpret changes in vagally mediated HRV.

Gastric emptying is rapid in adolescents with type 1 diabetes and relates to gastrointestinal symptoms

Gastric emptying is a critical determinant in postprandial glycaemic control. This study aimed to assess whether gastric emptying in adolescents with type 1 diabetes (T1D) relates to gastrointestinal symptoms and to heart rate variability (HRV) as a measure of autonomic function. We studied 30 adolescents (age 15 ± 2.5 years, BMI 22 ± 3.1 kg/m2) with T1D. Subjects consumed a 13C labelled pancake meal. Gastric emptying was measured by 13C breath test. Blood glucose was monitored frequently over 4 hours and gastrointestinal symptoms at 30-60 minute intervals, by a visual analogue questionnaire. Chronic gastrointestinal symptoms over the previous 3 months were assessed by a validated Diabetes Bowel Symptoms Questionnaire [1]. HRV was assessed by LabChart Pro [2].15 age and sex matched controls were also studied. Gastric half emptying time was accelerated in adolescents with T1D compared to controls; 77.6 (61.4-99.3) minutes [median (IQR)] versus 109.1 (70.8-124.2), P = 0.02), independent of hyperglycaemia during the study, HbA1c, duration of diabetes, and BMI. There was no difference in the prevalence of chronic symptoms or symptoms of a severity that affected lifestyle between the two groups. The presence of nausea, vomiting, bloating and/or fullness during the study in T1D was associated with faster gastric emptying compared to asymptomatic T1D (r =0.55; p = 0.04), and this was independent of peak glucose and glucose at 4 hours. Rate of gastric emptying in T1D did not correlate with HRV. Adolescents with T1D have rapid gastric emptying associated with acute gastrointestinal symptoms. Symptomatology could be used as a clinical tool to determine the need for further investigation.