Nonlinear broad band dynamics are less complex in major depression

Different heart rate variability profile during sleep in mid-later life adults with remitted early-onset versus late-onset depression

BACKGROUND

In mid-later life adults, early-onset and late-onset (i.e., onset ≥50 years) depression appear to be underpinned by different pathophysiology yet have not been examined in relation to autonomic function. Sleep provides an opportunity to examine the autonomic nervous system as the physiology changes across the night. Hence, we aimed to explore if autonomic profile is altered in mid-later life adults with remitted early-onset, late-onset and no history of lifetime depression.

METHODS

Participants aged 50-90 years (n = 188) from a specialised clinic underwent a comprehensive clinical assessment and completed an overnight polysomnography study. General Linear Models were used to examine the heart rate variability differences among the three groups for four distinct sleep stages and the wake after sleep onset. All analyses controlled for potential confounders - age, sex, current depressive symptoms and antidepressant usage.

RESULTS

For the wake after sleep onset, mid-later life adults with remitted early-onset depression had reduced standard deviation of Normal to Normal intervals (SDNN; p = .014, d = -0.64) and Shannon Entropy (p = .004, d = -0.46,) than those with no history of lifetime depression. Further, the late-onset group showed a reduction in high-frequency heart rate variability (HFn.u.) during non-rapid eye movement sleep stage 2 (N2; p = .005, d = -0.53) and non-rapid eye movement sleep stage 3 (N3; p = .009, d = -0.55) when compared to those with no lifetime history.

LIMITATIONS

Causality between heart rate variability and depression cannot be derived in this cross-sectional study. Longitudinal studies are needed to examine the effects remitted depressive episodes on autonomic function.

CONCLUSION

The findings suggest differential autonomic profile for remitted early-onset and late-onset mid-later life adults during sleep stages and wake periods. The differences could potentially serve as peripheral biomarkers in conjunction with more disease-specific markers of depression to improve diagnosis and prognosis.

Cardiac autonomic function is preserved in young adults with major depressive disorder

The prevalence of major depressive disorder (MDD) is highest in young adults and contributes to an increased risk of developing future cardiovascular disease (CVD). However, the underlying mechanisms remain unclear. The studies examining cardiac autonomic function that have included young unmedicated adults with MDD report equivocal findings, and few have considered the potential influence of disease severity or duration. We hypothesized that heart rate variability (HRV) and cardiac baroreflex sensitivity (BRS) would be reduced in young unmedicated adults with MDD (18-30 yr old) compared with healthy nondepressed young adults (HA). We further hypothesized that greater symptom severity would be related to poorer cardiac autonomic function in young adults with MDD. Heart rate and beat-to-beat blood pressure were continuously recorded during 10 min of supine rest to assess HRV and cardiac BRS in 28 HA (17 female, 22 ± 3 yr old) and 37 adults with MDD experiencing current symptoms of mild-to-moderate severity (unmedicated; 28 female, 20 ± 3 yr old). Neither HRV [root mean square of successive differences between normal heartbeats (RMSSD): 63 ± 34 HA vs. 79 ± 36 ms MDD; P = 0.14] nor cardiac BRS (overall gain, 21 ± 10 HA vs. 23 ± 7 ms/mmHg MDD; P = 0.59) were different between groups. In young adults with MDD, there was no association between current depressive symptom severity and either HRV (RMSSD, R2 = 0.004, P = 0.73) or cardiac BRS (overall gain, R2 = 0.02, P = 0.85). Taken together, these data suggest that cardiac autonomic dysfunction may not contribute to elevated cardiovascular risk factor profiles in young unmedicated adults with MDD of mild-to-moderate severity.NEW & NOTEWORTHY This study investigated cardiac autonomic function in young unmedicated adults with major depressive disorder (MDD). The results demonstrated that both heart rate variability and cardiac baroreflex sensitivity were preserved in young unmedicated adults with MDD compared with healthy nondepressed young adults. Furthermore, in young adults with MDD, current depressive symptom severity was not associated with any indices of cardiac autonomic function.

When Heart Beats Differently in Depression: Review of Nonlinear Heart Rate Variability Measures

BACKGROUND

Disturbed heart dynamics in depression seriously increases mortality risk. Heart rate variability (HRV) is a rich source of information for studying this dynamics. This paper is a meta-analytic review with methodological commentary of the application of nonlinear analysis of HRV and its possibility to address cardiovascular diseases in depression.

OBJECTIVE

This paper aimed to appeal for the introduction of cardiological screening to patients with depression, because it is still far from established practice. The other (main) objective of the paper was to show that nonlinear methods in HRV analysis give better results than standard ones.

METHODS

We systematically searched on the web for papers on nonlinear analyses of HRV in depression, in line with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2020 framework recommendations. We scrutinized the chosen publications and performed random-effects meta-analysis, using the esci module in jamovi software where standardized effect sizes (ESs) are corrected to yield the proof of the practical utility of their results.

RESULTS

In all, 26 publications on the connection of nonlinear HRV measures and depression meeting our inclusion criteria were selected, examining a total of 1537 patients diagnosed with depression and 1041 healthy controls (N=2578). The overall ES (unbiased) was 1.03 (95% CI 0.703-1.35; diamond ratio 3.60). We performed 3 more meta-analytic comparisons, demonstrating the overall effectiveness of 3 groups of nonlinear analysis: detrended fluctuation analysis (overall ES 0.364, 95% CI 0.237-0.491), entropy-based measures (overall ES 1.05, 95% CI 0.572-1.52), and all other nonlinear measures (overall ES 0.702, 95% CI 0.422-0.982). The effectiveness of the applied methods of electrocardiogram analysis was compared and discussed in the light of detection and prevention of depression-related cardiovascular risk.

CONCLUSIONS

We compared the ESs of nonlinear and conventional time and spectral methods (found in the literature) and demonstrated that those of the former are larger, which recommends their use for the early screening of cardiovascular abnormalities in patients with depression to prevent possible deleterious events.

Alteration of power law scaling of spontaneous brain activity in schizophrenia

Nonlinear dynamical analysis has been used to quantify the complexity of brain signal at temporal scales. Power law scaling is a well-validated method in physics that has been used to describe the dynamics of a system in the frequency domain, ranging from noisy oscillation to complex fluctuations. In this research, we investigated the power-law characteristics in a large-scale resting-state fMRI data of schizophrenia and healthy participants derived from Taiwan Aging and Mental Illness cohort. We extracted the power spectral density (PSD) of resting signal by Fourier transform. Power law scaling of PSD was estimated by determining the slope of the regression line fitting to the logarithm of PSD. t-Test was used to assess the statistical difference in power law scaling between schizophrenia and healthy participants. The significant differences in power law scaling were found in six brain regions. Schizophrenia patients have significantly more positive power law scaling (i.e., more homogenous frequency components) at four brain regions: left precuneus, left medial dorsal nucleus, right inferior frontal gyrus, and right middle temporal gyrus and less positive power law scaling (i.e., more dominant at lower frequency range) in bilateral putamen compared with healthy participants. Moreover, significant correlations of power law scaling with the severity of psychosis were found. These findings suggest that schizophrenia has abnormal brain signal complexity linked to psychotic symptoms. The power law scaling represents the dynamical properties of resting-state fMRI signal may serve as a novel functional brain imaging marker for evaluating patients with mental illness.

Heart rate variability changes in major depressive disorder during sleep: Fractal index correlates with BDI score during REM sleep

We investigated the relationship between autonomic nervous system activity during each sleep stage and the severity of depressive symptoms in patients with major depressive disorder (MDD) and healthy control subjects. Thirty patients with MDD and thirty healthy control subjects matched for sex, age, and body mass index completed standard overnight polysomnography. Depression severity was assessed using the Beck Depression Inventory (BDI). Time- and frequency-domain, and fractal HRV parameters were derived from 5-min electrocardiogram segments during light sleep, deep sleep, rapid eye movement (REM) sleep, and the pre- and post-sleep wake periods. Detrended fluctuation analysis (DFA) alpha-1 values during REM sleep were significantly higher in patients with MDD than in control subjects, and a significant correlation existed between DFA alpha-1 and BDI score in all subjects. DFA alpha-1 was the strongest predictor for the BDI score, along with REM density as a covariate. This study found that compared with controls, patients with MDD show reduced complexity in heart rate during REM sleep, which may represent lower cardiovascular adaptability in these patients, and could lead to cardiac disease. Moreover, DFA alpha-1 values measured during REM sleep may be useful as an indicator for the diagnosis and monitoring of depression.

Cardiac dysautonomia in depression - heart rate variability biofeedback as a potential add-on therapy

Depressive disorders are among the most important health problems and are predicted to constitute the leading cause of disease burden by the year 2030. Aside significant impact on quality of life, psychosocial well-being and socioeconomic status of affected patients, depression is associated with impaired cardiovascular health and increased mortality. The link between affective and cardiovascular disease has largely been attributed to dysregulation of the autonomic nervous system resulting in a chronic shift toward increased sympathetic and decreased parasympathetic activity and, consecutively, cardiac dysautonomia. Among proposed surrogate parameters to capture and quantitatively analyze this shift, heart rate variability (HRV) and baroreflex sensitivity have emerged as reliable tools. Attenuation of these parameters is frequently seen in patients suffering from depression and is closely linked to cardiovascular morbidity and mortality. Therefore, diagnostic and therapeutic strategies were designed to assess and counteract cardiac dysautonomia. While psychopharmacological treatment can effectively improve affective symptoms of depression, its effect on cardiac dysautonomia is limited. HRV biofeedback is a non-invasive technique which is based on a metronomic breathing technique to increase parasympathetic tone. While some small studies observed beneficial effects of HRV biofeedback on dysautonomia in patients with depressive disorders, larger confirmatory trials are lacking. We reviewed the current literature on cardiac dysautonomia in patients suffering from depression with a focus on the underlying pathophysiology as well as diagnostic workup and treatment.

Heart rate variability in patients with major depressive disorder and healthy controls during non-REM sleep and REM sleep

The objectives of this study are to investigate heart rate variability (HRV) in major depressive disorder patients (MDD) and healthy controls during different sleep stages, and to examine the association of HRV during sleep and depression severity. Polysomnography was recorded from 15 depressive patients with a higher beck depression inventory index (BDI > 25, H-BDI-D), 15 depressive patients with a lower BDI index (BDI ≤ 25, L-BDI-D) and 15 healthy controls. HRV was calculated during the first three rapid eye movements (REM) periods and non-REM stages (i.e. sleep stage 2 and 3) with time domain, power spectral and fractal analysis. As a result, H-BDI-D patients showed the highest short-term fractal alpha-1 exponent during first REM period and healthy controls had the lowest values. Our results suggest an association between the depression severity and the autonomic nerve function, especially during the first REM sleep. The pathophysiological analysis for this property should be conducted in future prospective studies.

Nonlinear analysis of heart rate variability for the assessment of Dysphoria

Dysphoric patients show symptoms associated with Major Depression, although within a narrowed symptomatology spectrum. In prevailing practice, clinicians assess Dysphoria through psychological scores and questionnaires exclusively, therefore without taking into account objective biomarkers. In this study, we investigated heartbeat linear and nonlinear dynamics aiming to an objective assessment of Dysphoria. To this end, we derived standard and nonlinear measures from heart rate variability (HRV) series gathered from dysphoric (n=14) and nondysphoric (n=17) undergraduate students during 5 minutes of resting state. We performed both statistical and pattern recognition analyses in order to discern the two groups. Results showed significant group-wise differences in HRV nonlinear metrics exclusively, suggesting a crucial role of nonlinear sympatho-vagal dynamics in Dysphoria. Furthermore, we achieved a classification accuracy of 77.52% for the automatic identification of Dysphoria at a single-subject level.

Differences of sympathetic and parasympathetic modulation in major depression

Inconsistent results have been reported with respect to cardiac autonomic function in major depression. The aim of our study was to investigate autonomic function in various branches of the autonomic nervous system in order to better understand parasympathetic and sympathetic modulation in the disease. We investigated 29 unmedicated patients suffering from major depression (MD) in comparison to matched control subjects (gender, age, BMI). The autonomic assessment at rest included values of heart rate variability (HRV), blood pressure variability (BPV), baroreflex sensitivity (BRS), respiration, skin conductance (SC) as well as the calculation of pupillary diameter and the unrest index (PUI). Results were compared by means of a multivariate analysis of variance. In a classification analysis, we identified suitable parameters for patient - control separation. Finally, to analyze interrelations of pupillometric parameters and autonomic indices, we estimated Pearson correlation coefficients and fitted a linear regression model. Apart from a significantly increased heart rate (75±12 vs. 65±6min^-1, p<0.001) and decreased BRS (14±13 vs. 20±15ms/mmHg, p<0.05), we observed a lack of significant differences in HRV and BPV analysis between patients and controls. However, pupillary diameter (left: 4.3±0.9 vs. 3.8±0.6, p<0.01; right: 4.3±0.9 vs. 3.7±0.6mm, p<0.01) and PUI (left: 14.8±6.0 vs. 10.7±4.5mm/min, p<0.01; right: 14.1±5.5 vs. 10.7±4.8mm/min, p<0.01), as well as the level (left: 7.3±6.2 vs. 4.3±4.4 μS, p<0.05) and fluctuations of skin conductance (left: 4.2±4.1 vs. 2.5±3.6, p<0.05; right: 4.2±4.4 vs. 2.6±3.2, p<0.05) were significantly different. The classification accuracy was 88.5% with high specificity (e=92.9%) and sensitivity (s=83.3%) including heart rate, PUI and skin conductance. HRV indices correlated to PUI in controls but not in patients. Our data add evidence to the current debate on autonomic function in major depression. We suggest that diverse results are mainly caused by methodological shortcomings, in particular by the application of HRV assessment only, which misses changes of sympathetic modulation. The application of broader analyzing tools will clarify the pattern of autonomic function in depression and ultimately its role in cardiac morbidity and mortality.

The sensitivity of 38 heart rate variability measures to the addition of artifact in human and artificial 24-hr cardiac recordings

BACKGROUND

Artifact is common in cardiac RR interval data derived from 24-hr recordings and has a significant impact on heart rate variability (HRV) measures. However, the relative impact of progressively added artifact on a large group of commonly used HRV measures has not been assessed. This study compared the relative sensitivity of 38 commonly used HRV measures to artifact to determine which measures show the most change with increasing increments of artifact. A secondary aim was to ascertain whether short-term and long-term HRV measures, as groups, share similarities in their sensitivity to artifact.

METHODS

Up to 10% of artifact was added to 20 artificial RR (ARR) files and 20 human cardiac recordings, which had been assessed for artifact by a cardiac technician. The added artifact simulated deletion of RR intervals and insertion of individual short RR intervals. Thirty-eight HRV measures were calculated for each file. Regression analysis was used to rank the HRV measures according to their sensitivity to artifact as determined by the magnitude of slope.

RESULTS

RMSSD, SDANN, SDNN, RR triangular index and TINN, normalized power and relative power linear measures, and most nonlinear methods examined are most robust to artifact.

CONCLUSION

Short-term time domain HRV measures are more sensitive to added artifact than long-term measures. Absolute power frequency domain measures across all frequency bands are more sensitive than normalized and relative frequency domain measures. Most nonlinear HRV measures assessed were relatively robust to added artifact, with Poincare plot SD1 being most sensitive.

Complexity and nonlinear biomarkers in emotional disorders: A meta-analytic study

This meta-analysis aimed at gathering and summarising the findings on nonlinear biomarkers in the field of emotional disorders under the hypothesis that diseased systems show lowered complexity and hence less flexibility to adjust daily contexts. Scientific manuscripts from 1970 to 2014 were reviewed, 58 articles were analysed, and independent meta-analyses on anxiety disorders, bipolar disorders, and depressive disorders were conducted. Results revealed that anxious patients exhibited lower complexity than controls (p<0.05) despite panic patients showed more irregular respiratory activity. Inconclusive results were found for bipolar patients but pointed to higher randomness when suffering manic episodes. Finally, depressed patients showed a loss of complexity in the cardiac system and a loss of orderliness (despite a higher complexity) in brain and stress-related hormonal systems. As a conclusion, our findings highlight that either a loss of complexity or a loss of ordered complexity characterise the physiological systems of patients with emotional disorders. Several considerations for complexity, its related measurements, and suggestions for further research are discussed.

Autonomic nervous system dysfunction in psychiatric disorders and the impact of psychotropic medications: a systematic review and meta-analysis

BACKGROUND

Autonomic nervous system (ANS) dysfunction is a putative underlying mechanism for increased cardiovascular disease risk in individuals with psychiatric disorders. Previous studies suggest that this risk may be related to psychotropic medication use. In the present study we systematically reviewed and analyzed published studies of heart rate variability (HRV), measuring ANS output, to determine the effect of psychiatric illness and medication use.

METHODS

We searched for studies comparing HRV in physically healthy adults with a diagnosed psychiatric disorder to controls and comparing HRV pre- and post-treatment with a psychotropic medication.

RESULTS

In total, 140 case-control (mood, anxiety, psychosis, dependent disorders, k = 151) and 30 treatment (antidepressants, antipsychotics; k = 43) studies were included. We found that HRV was reduced in all patient groups compared to controls (Hedges g = -0.583) with a large effect for psychotic disorders (Hedges g = -0.948). Effect sizes remained highly significant for medication-free patients compared to controls across all disorders. Smaller and significant reductions in HRV were observed for specific antidepressants and antipsychotics.

LIMITATIONS

Study quality significantly moderated effect sizes in case-control analyses, underscoring the importance of assessing methodological quality when interpreting HRV findings.

CONCLUSION

Combined findings confirm substantial reductions in HRV across psychiatric disorders, and these effects remained significant even in medication-free individuals. Reductions in HRV may therefore represent a significant mechanism contributing to elevated cardiovascular risk in individuals with psychiatric disorders. The negative impact of specific medications on HRV suggest increased risk for cardiovascular disease in these groups, highlighting a need for treatment providers to consider modifiable cardiovascular risk factors to attenuate this risk.

Immediate effect of basic body awareness therapy on heart rate variability

OBJECTIVE

To determine the immediate effect of a Basic Body Awareness Therapy (BAT) session on measures of heart rate variability (HRV) in healthy young people.

METHODS

13 healthy young subjects of both genders, who showed no illnesses related to the autonomic nervous system (ANS) underwent an ANS evaluation before and after conducting a session of BAT. The assessment of ANS activity was conducted through the HR with the aid of Nerve-Express(®) software. The BAT session lasted for 50 min and was performed by one investigator (blinded to the assessment procedures).

RESULTS

After BAT session significant improvement was found in the sympathetic and parasympathetic modulation (p < 0.05), and the general estimate of heart rate variability (p < 0.04).

CONCLUSION

BAT was found to be an effective, easy to apply and inexpensive therapeutic technique, able to change ANS in order to improve HR which may suggest better health conditions for participating individuals.

Comparative Study of Heart Rate Variability in Patients with Schizophrenia, Bipolar Disorder, Post-traumatic Stress Disorder, or Major Depressive Disorder

Objective

Heart rate variability (HRV) changes as a function of psychiatric illness. This study aimed to evaluate HRV among patients with various psychiatric disorders.

Methods

The present study recruited patients with schizophrenia (n=35), bipolar disorder (n=41), post-traumatic stress disorder (PTSD; n=34), or major depressive disorder (n=34) as well as healthy controls (n=27). The time-domain analysis (the standard deviation of all RR intervals [SDNN] and the square root of the mean squared differences of successive normal sinus intervals [RMSSD]), the frequency-domain analysis (very low frequency, low frequency [LF], high frequency [HF], and total power [TP]), and a non-linear complexity measure the approximate entropy were computed.

Results

SDNN and HF were significantly reduced in patients with schizophrenia compared with healthy controls. SDNN, RMSSD, TP, LF, and HF were significantly reduced in bipolar patients compared with healthy controls. HF was significantly reduced in PTSD patients compared with healthy controls.

Conclusion

Our findings indicate that HRV is not sufficiently powerful to discriminate among various psychiatric illnesses. However, our results suggest that HRV, particularly HF, could be used as a tool for discriminating between psychiatric patients and healthy controls.

Heart rate time irreversibility is impaired in adolescent major depression

We aimed to study heart rate time irreversibility--a nonlinear qualitative characteristics of heart rate variability indicating complexity of cardiac autonomic control at rest and in response to physiological stress (orthostasis) in never-treated major depressive disorder (MDD) adolescent female patients.

METHODS

We studied 20 MDD girls and 20 healthy age-matched girls at the age of 15 to 18 years. The ECG was recorded in supine position and in response to position change from lying to standing (orthostasis). Time irreversibility analysis was performed using Porta's (P%), Guzik's (G%) and Ehlers' (E) index. The depressive disorder severity was evaluated using Montgomery-Asberg Depression Rating Scale (MADRS) and Children's Depression Inventory (CDI).

RESULTS

Resting heart rate time irreversibility indices (logG%, logP%, Ehlers' index) were significantly reduced in MDD female patients without significant differences in response to orthostasis in MDD girls compared to controls. No significant correlations between time irreversibility and MDD severity were observed.

CONCLUSION

This study revealed the impaired heart rate asymmetry pattern indicating an altered complexity of cardiac autonomic regulation in adolescent female patients suffering from MDD.

Cardio-respiratory coupling in untreated patients with major depression

BACKGROUND

Depressive disorders are known to be associated with higher risks of cardiovascular diseases. Several studies have reported an imbalance within the autonomic nervous system (ANS) as one putative cause. Previous investigations showed decreased cardio-respiratory coupling in depressive patients that were treated with nortriptyline. We aimed to compare parameters of heart rate variability and cardio-respiratory coupling between unmedicated patients suffering from major depressive disorder (MDD) and healthy controls in order to further understand autonomic dysfunction in the disease.

METHODS

We investigated eighteen unmedicated patients with major depressive disorder and eighteen matched healthy controls. Electrocardiogram and respiratory signals were obtained during a twenty minute resting period. Time- and frequency based parameters of HRV, respiratory sinus arrhythmia (RSA), approximate entropy of heart rate (ApEn(RR)) and respiratory rate (ApEn(Resp)) were calculated. Additionally, cross-ApEn between RR-intervals and respiration time series was determined, reflecting coupling of both signals.

RESULTS

Patients showed an increased heart rate and LF/HF-ratio. Respiratory sinus arrhythmia (RSA) and ApEn(RR) were reduced in patients in comparison to controls. Breathing rate, ApEn(Resp) and cross-ApEn did not differ between the two groups.

DISCUSSION

Increased heart rate, increased LF/HF-ratio, reduced RSA and reduced ApEn(RR) indicate a decrease of cardiac vagal modulation in depressive patients. No difference of cardio-respiratory coupling was observed. Respiratory parameters and cross-ApEn did not differ between both groups, and thus we conclude that diminished vagal modulation is mainly limited to cardiac modulation.

Autonomic modulation in healthy first-degree relatives of patients with major depressive disorder

BACKGROUND

Cardiac mortality is known to be increased in patients with major depression. Several studies have reported an imbalance within the autonomic nervous system (ANS) of patients with major depressive disorder (MDD) as one putative cause. Since a heritability of autonomic modulation was demonstrated in healthy subjects, we aimed to investigate autonomic modulation in first-degree relatives of patients with MDD to find potential autonomic imbalances.

METHODS

We included 30 patients with MDD, 30 of their first-degree relatives (siblings or offspring) and 30 matched healthy controls in our study. We obtained a high resolution electrocardiogram and beat to beat blood pressure measurements for 30 min at rest. Linear and nonlinear parameters of heart rate variability (HRV) and baroreflex sensitivity (BRS) were calculated.

RESULTS

Parameters of HRV and BRS did not differ significantly between relatives and controls. We found significant differences between patients and controls for some HRV and BRS parameters confirming results of previous studies.

DISCUSSION

Findings of our study suggest that an imbalance of autonomic function is related to patients with depression and not to first-degree relatives. Thus, a genetic background for autonomic dysfunction is rather unlikely.

Decreased neuroautonomic complexity in men during an acute major depressive episode: analysis of heart rate dynamics

Major depression affects multiple physiologic systems. Therefore, analysis of signals that reflect integrated function may be useful in probing dynamical changes in this syndrome. Increasing evidence supports the conceptual framework that complex variability is a marker of healthy, adaptive control mechanisms and that dynamical complexity decreases with aging and disease. We tested the hypothesis that heart rate (HR) dynamics in non-medicated, young to middle-aged males during an acute major depressive episode would exhibit lower complexity compared with healthy counterparts. We analyzed HR time series, a neuroautonomically regulated signal, during sleep, using the multiscale entropy method. Our results show that the complexity of the HR dynamics is significantly lower for depressed than for non-depressed subjects for the entire night (P<0.02) and combined sleep stages 1 and 2 (P<0.02). These findings raise the possibility of using the complexity of physiologic signals as the basis of novel dynamical biomarkers of depression.

Reduced physiologic complexity is associated with poor sleep in patients with major depression and primary insomnia

BACKGROUND

Depression is known to be associated with altered cardiovascular variability and increased cardiovascular comorbidity, yet it is unknown whether altered cardiac autonomic function in depression is associated with insomnia, a common symptom comorbid with depression. This study aimed to investigate the long-term diurnal profile of autonomic function as measured by heart rate variability (HRV) in both major depression and primary insomnia patients.

METHOD

A total of 52 non-medicated patients with major depression, 47 non-medicated patients with primary insomnia, and 88 matched controls without insomnia were recruited. Each subject was assessed by means of sleep and mood questionnaires and underwent twenty-four-hour ambulatory electrocardiogram monitoring. Standard HRV analysis and a well-validated complexity measure, multiscale entropy, were applied to comprehensively assess the diurnal profiles of autonomic function and physiologic complexity in our study sample.

RESULTS

Compared with the controls, the patients with major depression and those with primary insomnia exhibited significant reductions in parasympathetic-related HRV indices, and this association was mainly driven by the presence of poor sleep. Both groups of patients also exhibited significant reductions in physiologic complexity during the sleep period as compared with the healthy controls. Alterations in HRV indices were correlated with perceived sleep questionnaire scores but not with depression scales.

CONCLUSIONS

Our findings suggest a pivotal role of sleep disturbance in regulating cardiovascular variability in major depression and primary insomnia patients. These findings could highlight the importance of treating insomnia as an independent disease rather than a symptom.

Gender-dependent impact of major depression on autonomic cardiovascular modulation

Depression has been shown to increase the risk for cardiovascular disease (CVD) more strongly in women than in men. Although the underlying mechanisms are unknown, a putative role of increased sympathetic modulation has been suggested for the association of CVD and depression. The aim of this study was to investigate possible gender-associated differences of autonomic function in healthy volunteers and patients suffering from major depressive disorder (MDD). Linear as well as non-linear measures of heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity (BRS) were obtained in each 18 male and 18 female unmedicated patients and respective control subjects. Gender differences were detectable in healthy subjects showing predominant sympathetic modulation in males. This was most obvious in BPV analysis. These gender differences were abolished in patients suffering from MDD, mainly due to altered autonomic modulation in female patients. Our results indicate that BPV is more sensitive to reveal depression-associated changes of autonomic function as compared to HRV. Moreover, female patients contribute most to the overall difference between patients and controls. The shift in the balance of autonomic function in women might account for the increased prevalence of CVD in these patients.

Increased QT variability in patients with anorexia nervosa--an indicator for increased cardiac mortality?

OBJECTIVE

Increased mortality in anorexia nervosa is associated with autonomic dysfunction and prolongation of the QT interval. In this study, we examined the relative importance of repolarization abnormalities and vagal modulation of heart rate. In particular, we hypothesized that patients with anorexia nervosa show increased QT interval variability, particularly since this measure has been shown to correlate with serious cardiac arrhythmias.

METHOD

We assessed linear and nonlinear heart rate variability (HRV) parameters as well as measures of QT variability in 20 female patients with anorexia nervosa and 20 controls. In patients, parameters were correlated with serum electrolytes.

RESULTS

QT variability was significantly increased in the patient group and correlated negatively with serum potassium concentrations. HRV measures showed a shift of autonomic balance towards vagal predominance.

DISCUSSION

The increase in QT variability might at least in part account for the higher risk of cardiac arrhythmias in patients with anorexia nervosa. Once validated in a prospective study design, parameters of QT variability might serve as surrogate markers for arrhythmia risk stratification in anorexia nervosa. Supplementation with potassium might normalize QT variability abnormalities.

Influence of age on linear and nonlinear measures of autonomic cardiovascular modulation

BACKGROUND

Age has been identified as an independent risk factor for cardiovascular diseases. In addition, autonomic imbalance toward sympathetic preponderance has been shown to facilitate the occurrence of heart disease. Here, we aimed to assess autonomic modulation of cardiovascular parameters during normal ageing applying well-established linear and novel nonlinear parameters.

METHODS

Linear and nonlinear measures of heart rate variability and complexity as well as measures of QT interval variability and baroreflex sensitivity were obtained from a total of 131 healthy, medication-free participants from a continuous age range between 20 and 90 years, who were allocated to three different age groups.

RESULTS

Heart rate variability and complexity significantly decreased with age, while regularity of heart rate time series increased. In addition, QT interval variability linearly increased with age, while baroreflex sensitivity showed a pronounced decrease. Overall, concerning effects of ageing, linear and nonlinear parameters showed equal differentiation between groups.

CONCLUSION

These data indicate a shift of autonomic balance toward sympathetic predominance in higher age groups, limiting the reactiveness of the cardiovascular system to adjust to different demands and increasing the risk for developing tachyarrhythmias.

Does parasympathetic modulation prior to ECT treatment influence therapeutic outcome?

Electroconvulsive therapy (ECT) is an established treatment option for major depressive disorder when other treatments have failed. However, the underlying mechanisms responsible for these therapeutical effects are insufficiently understood to date. Furthermore, treatment outcome is difficult to predict. Recent research suggested an important role of autonomic modulation for successful treatment. We aimed to examine putative associations between autonomic modulation and response to ECT treatment and hypothesized a role for vagal modulation prior to therapy. Twenty-four patients with MDD who received ECT were assessed by means of heart rate and blood pressure variability analysis as well as baroreflex sensitivity measurements before, during and after a course of ECT. Autonomic parameters from the complete study population revealed that ECT did not significantly alter basic autonomic modulation after six sessions. Analyses showed a significant association of the reduction of HAMD scores during therapy when compared with baseline autonomic function as reflected in SDNN(RR) (p<0.004), Forbword(RR) (p<0.025) and compression entropy Hc(RR) (p<0.0003). A significant correlation was observed when overall HAMD reduction and changes of LFnu(RR) (p<0.026) or HFnu(RR) (p<0.026) during the course of therapy were analyzed. Our findings suggest that high levels of parasympathetic modulation at baseline might be associated with a beneficial effect upon ECT treatment. Adding to this, levels of parasympathetic activity seemed to increase in patients who respond to ECT treatment. Given these findings can be confirmed in future studies, autonomic modulation might be used as a predictor for therapeutic efficacy of ECT.

Gastric dysmotility in healthy first-degree relatives of patients with schizophrenia

Gastric dysmotility has been reported in patients suffering from major depression or schizophrenia. An increased sympathetic activity modulating the gastric pacemaker located in the antrum of the stomach has been suggested as the underlying pathology. Similar to patients suffering from schizophrenia, their first-degree relatives showed alterations in cardiac autonomic modulation. Here we aimed to investigate gastric myoelectrical activity in healthy relatives of patients suffering from paranoid schizophrenia. Electrogastrography (EGG) was performed before and after test meal ingestion in 20 patients with paranoid schizophrenia, 20 of their first-degree relatives and 20 healthy matched controls. Autonomic and abdominal symptoms were assessed by the autonomic symptom score as previously reported. Autonomic parameters were correlated with the positive and negative syndrome scale (PANSS). Only minimal differences were observed before test meal ingestion between relatives and controls. In contrast, after test meal ingestion we observed a significantly increased tachygastria within the signal of the gastric pacemaker in relatives compared to controls, whereas normogastria was reduced. Significant difference between relatives and controls were also found for postprandial ICDF (instability coefficient of dominant frequency) and slow wave, which represents the dominant frequency of gastric pacemaker activity, indicating gastric dysmotility in relatives. Between relatives and patients just a difference for ICDP (instability coefficient of dominant power) was observed. After stimulation of the enteric nervous system we have observed an increased sympathetic modulation in first-degree relatives of patients suffering from schizophrenia. This result adds evidence to an ongoing debate on the genetic influence of autonomic dysfunction in the disease.

Autonomic dysfunction in unaffected first-degree relatives of patients suffering from schizophrenia

Recent studies revealed cardiac autonomic dysfunction in patients with acute schizophrenia, which appears to be mainly related to reduced vagal and increased sympathetic modulation. To understand the significance of cardiac autonomic function in patients with schizophrenia, we extended these studies to relatives of patients. In this study, we assessed cardiac autonomic modulation in healthy first-degree relatives of patients with schizophrenia (n = 36) to investigate a putative genetic influence. Data were compared with control subjects matched for age, gender, and physical activity as well as to patients suffering from schizophrenia. First-degree relatives showed an attenuated, yet identical pattern in autonomic dysfunction as patients with decreased vagal modulation of heart rate, decreased baroreflex sensitivity, but no difference in blood pressure variability could be detected. The patients' relatives also showed a similar pattern in regards to QT variability. In addition, the subgroup comparison of offspring vs. siblings showed a significant difference in heart rate variability suggesting a higher degree of heritability in offspring. In conclusion, the pattern of autonomic dysfunction seen in patients and relatives might indicate underlying disease-inherent genetic vulnerability, especially because autonomic parameters are heritable. In addition, these findings may be of value to identify the high-risk group of patients' relatives in regards to serious cardiovascular events so that early preventive measures can be taken.

Is successful electroconvulsive therapy related to stimulation of the vagal system?

BACKGROUND

Electroconvulsive therapy (ECT) has been shown to exhibit strong beneficial effects in the treatment of major depressive disorder (MDD). While the exact underlying mechanisms are under debate, a role for the sympathetic response upon ECT has been suggested. When assessing patients with MDD for autonomic function, however, a loss of vagal function is prominent.

OBJECTIVE

Here, we aimed to assess the immediate effects of ECT on vagal activity and to test the hypothesis that surrogates of the latter correlate with therapeutic outcome.

METHODS

Twenty patients with MDD who underwent ECT treatment were assessed regarding their vagal function using electrophysiological measures and determination of pancreatic polypeptide (PP), which is known to be released upon vagal stimulation. Parameters were correlated to the improvement of disease severity upon ECT treatment.

RESULTS

Patients showed a significant increase of PP shortly after ECT which correlated with clinical improvement. Furthermore, the described association with the sympathetic phase after ECT could be verified.

CONCLUSION

ECT increases vagal activity which might be associated with the beneficial effect seen following this treatment. PP elevation after administration of ECT might be a useful parameter to estimate the degree of such vagal stimulation after treatment.

Ventilatory inefficiency in major depressive disorder: a potential adjunct for cardiac risk stratification in depressive disorders?

BACKGROUND

Cardiopulmonary exercise testing (CPET) provides insights into ventilatory, cardiac and metabolic dysfunction in heart and lung diseases and might play a role in cardiac risk stratification in major depressive disorder (MDD).

OBJECTIVE

The VE/VCO(2)-slope indicates ventilatory efficiency and has been applied to stratify the cardiac risk in heart failure (HF). Therefore, the current study was conducted to evaluate and classify ventilatory efficiency and its relationship to physical fitness and disease severity in MDD.

METHODS

Exhaustive incremental exercise testing was completed by 15 female MDD patients and pair matched controls. The ventilatory threshold (VT) and the VE/VCO(2)-slope were assessed. Statistical analyses were conducted by means of MANOVAs and follow-up univariate ANOVAs.

RESULTS

In patients with MDD, significant different relative work rates and oxygen uptakes at the VT in comparison to healthy controls were observed. Furthermore, we found an increased VE/VCO(2)-slope in depressed patients. We additionally report an inverse relationship between the VE/VCO(2)-slope and peak power output as well as peak oxygen uptake solely in patients. We did not observe any association of assessed parameters with disease severity.

CONCLUSION

CPET measures indicate ventilatory inefficiency in patients with MDD. The elevated VE/VCO(2)-slope indicates that patients with MDD need to ventilate significantly more to a given amount of developing CO(2). Further investigations are needed to verify the application of the ventilatory classification system to stratify cardiovascular risk in depressive disorder.

Impact of depression and antidepressant treatment on heart rate variability: a review and meta-analysis

BACKGROUND

Depression is associated with an increase in the likelihood of cardiac events; however, studies investigating the relationship between depression and heart rate variability (HRV) have generally focused on patients with cardiovascular disease (CVD). The objective of the current report is to examine with meta-analysis the impact of depression and antidepressant treatment on HRV in depressed patients without CVD.

METHODS

Studies comparing 1) HRV in patients with major depressive disorder and healthy control subjects and 2) the HRV of patients with major depressive disorder before and after treatment were considered for meta-analysis.

RESULTS

Meta-analyses were based on 18 articles that met inclusion criteria, comprising a total of 673 depressed participants and 407 healthy comparison participants. Participants with depression had lower HRV (time frequency: Hedges' g = -.301, p < .001; high frequency: Hedges' g = -.293, p < .001; nonlinear: Hedges' g = -1.955, p = .05; Valsalva ratio: Hedges' g = -.712, p < .001) than healthy control subjects, and depression severity was negatively correlated with HRV (r = -.354, p < .001). Tricyclic medication decreased HRV, although serotonin reuptake inhibitors, mirtazapine, and nefazodone had no significant impact on HRV despite patient response to treatment.

CONCLUSIONS

Depression without CVD is associated with reduced HRV, which decreases with increasing depression severity, most apparent with nonlinear measures of HRV. Critically, a variety of antidepressant treatments do not resolve these decreases despite resolution of symptoms, highlighting that antidepressant medications might not have HRV-mediated cardioprotective effects and the need to identify individuals at risk among patients in remission.

Gastric dysmotility in major depression

BACKGROUND

Somatic symptoms of the gastrointestinal tract occur frequently in major depressive disorder (MDD) and might be associated with the known autonomic imbalance in the disease. Hence, we have investigated gastric electrical activity in patients suffering from major depression before and after treatment by means of electrogastrography (EGG) to investigate a putative association with either the disease state and its symptoms or its relation to the treatment.

METHODS

EGG readings before and after ingestion of a test meal of 27 patients suffering from major depression were recorded before and after treatment with antidepressants and compared with age-matched controls. Abdominal symptoms were rated by a specific Autonomic Nervous Symptom-score.

RESULTS

We found a significantly increased amount of tachygastria before and after medication, indicating increased sympathetic modulation. A significant difference was observed for the instability coefficients before and after medication, indicating gastric dysmotility in our patients prior to treatment. The elevated approximate entropy measure points to increased complexity and dysregulation. Furthermore, we have observed a correlation between subjective sensation of sweating and dry mouth with the sympathetic parameter tachygastria.

DISCUSSION

Our results suggest that major depression is associated with gastric dysrhythmia possibly caused by increased sympathetic modulation. Linear and non-linear EGG measures emphasize a possible role of the autonomic nervous system in the development of gastric symptoms. The treatment with antidepressants seems to increase the activity of the sympathetic nervous system, without aggravating gastric symptoms. The association of increased sympathetic modulation with somatic symptoms was indicated by correlation analysis with these symptoms.

Heart rate variability in bipolar mania and schizophrenia

BACKGROUND

Autonomic nervous system (ANS) dysfunction and reduced heart rate variability (HRV) have been reported in a wide variety of psychiatric disorders, but have not been well characterized in bipolar mania. We recorded cardiac activity and assessed HRV in acutely hospitalized manic bipolar (BD) and schizophrenia (SCZ) patients compared to age- and gender-matched healthy comparison (HC) subjects.

METHOD

HRV was assessed using time domain, frequency domain, and nonlinear analyses in 23 manic BD, 14 SCZ, and 23 HC subjects during a 5min rest period. Psychiatric symptoms were assessed by administration of the Brief Psychiatric Rating Scale (BPRS) and the Young Mania Rating Scale (YMRS).

RESULTS

Manic BD patients demonstrated a significant reduction in HRV, parasympathetic activity, and cardiac entropy compared to HC subjects, while SCZ patients demonstrated a similar, but non-significant, trend towards lower HRV and entropy. Reduction in parasympathetic tone was significantly correlated with higher YMRS scores and the unusual thought content subscale on the BPRS. Decreased entropy was associated with increased aggression and diminished personal hygiene on the YMRS scale.

CONCLUSION

Cardiac function in manic BD individuals is characterized by decreased HRV, reduced vagal tone, and a decline in heart rate complexity as assessed by linear and nonlinear methods of analysis. Autonomic dysregulation is associated with more severe psychiatric symptoms, suggesting HRV dysfunction in this disorder may be dependent on the phase of the illness.

Dissociation of performance parameters at the IAT requires specific exercise recommendations for depressed patients

Aerobic exercise training is considered an adequate complementary treatment strategy for major depressive disorder (MDD). However, there is a need for comparative methodological investigations to determine the appropriate exercise intensity for these patients. The study compared submaximal exercise intensity determination with those derived from maximal parameters such as percentages of heart rate reserve (HRR), maximal heart rate (HR(max)) and peak oxygen uptake (VO(2peak)) of patients and controls. An exhaustive incremental bicycle exercise test was completed by 15 female MDD patients and matched controls. The individual anaerobic lactate threshold (IAT) as a gold standard to determine individual aerobic exercise intensity was assessed according to Stegmann and coworkers. Exercise intensities at 70 and 85% of HR(max), 70 and 85% of HRR and 50 to 80% of VO(2peak) were compared to the IAT. Patients suffering from MDD switched earlier to anaerobic metabolism than matched healthy controls. But interestingly, the level of self-rated perceived exertion, concentration of lactate, respiratory exchange ratio and heart rate at the IAT level revealed no significant difference between both groups. Due to a growing number of clinical aerobic exercise treatments in depressive disorders exercise intensities >70% of (a) HR(max), (b) HRR, (c) VO(2peak) should be amended by the IAT and Borg scale measurements to avoid over challenging as well as increased anaerobic metabolism.

The altered complexity of cardiovascular regulation in depressed patients

Major depressive disorders (MDD) are associated with an increased risk for cardiovascular morbidity and mortality. Even if it is known that MDD are accompanied by an autonomic dysbalance with increased sympathetic and/or reduced parasympathetic activity, to date only limited information is available about the degree and complexity of cardiovascular regulation. The aim of this study was to investigate the influence of MDD on the autonomous nervous system and cardiovascular complexity by means of linear and nonlinear indices from heart rate and blood pressure variability (HRV, BPV). From 57 non-medicated patients and 57 matched healthy controls with respect to age and gender HRV and BPV in time and frequency domain, symbolic dynamics, compression entropy, multiscale entropy, detrended fluctuation analysis, Poincaré plot analysis and baroreflex sensitivity were analysed from 30 min short-term recordings. Complexity indices from nonlinear dynamics demonstrated considerable changes in autonomous regulation due to MDD. For the first time we could show that non-medicated depressed patients who were matched with respect to age and gender reveal a significantly changed short-term as well as long-term complexity of cardiovascular regulation. These results suggest substantial changes in autonomic control probably due to a change of interactions between different physiological control loops in MDD.

The influence of negative mood on heart rate complexity measures and baroreflex sensitivity in healthy subjects

BACKGROUND

Decreased cardiac vagal function is linked with increased cardiac mortality and depression is associated with decreased heart rate variability. We have previously shown that the Mood Induction Procedure (MIP) in healthy subjects alters pain perception and thalamic activity during pain perception.

AIM

To study the effect of negative emotion on heart rate variability and complexity measures as well as on baroreceptor sensitivity, as these parameters reflect cardiac autonomic function.

PATIENTS AND METHODS

We studied 20 healthy female controls before and after neutral MIP and 20 healthy female subjects before and after negative MIP. We investigated measures of valence of mood, heart rate variability and complexity and the baroreceptor sensitivity index.

RESULTS

While there was a significant difference in the valence of mood between the neutral and the negative effect condition, there were no significant differences in any of the heart rate or baroreceptor sensitivity measures between the two groups.

CONCLUSIONS

Our findings did not show any significant influence of acute negative MIP on heart rate variability and complexity measures and baroreceptor sensitivity, even though depressive disorder and stress are associated with decreased heart rate variability. These findings are discussed in the context of clinical depression and anxiety and the increased risk for cardiac mortality. In contrast to the presented results here, we have previously shown that MIP in healthy subjects alters pain perception and thalamic activity.

The relation of ventromedial prefrontal cortex activity and heart rate fluctuations at rest

Recent studies applying functional magnetic resonance imaging have focused on the description of cerebral substrates of changes in cardiac function during diverse autonomic maneuvers or stressful cognitive tasks. These studies might be limited by the indistinguishable neuronal activity due to cognitive processes, which are known to influence autonomic function, and the 'baseline' activity in the central autonomic network. We therefore investigated 26 healthy volunteers in the magnetic resonance scanner to simultaneously obtain functional brain images and RR intervals (intervals between ventricular depolarizations) of the high-resolution electrocardiogram. The mean RR interval length within each functional scan was computed, which was finally convolved with the canonical hemodynamic response function to obtain a regressor for the functional time series. The resulting individual contrast image indicated a positive covariation of the blood oxygen level-dependent signal and RR interval length in the ventromedial prefrontal cortex (vmPFC). Furthermore, a reduced mean cross-approximate entropy value was shown for the interaction between the vmPFC and individual RR intervals. This suggests reduced asynchrony between the heart rate and vmPFC activity in contrast to other brain areas. Our findings confirm data obtained in animals describing the vmPFC as an important forebrain structure of the central autonomic network and an influence of the vmPFC in the cortical generation of efferent vagal activity. This finding needs to be investigated in diseases with known suppression of efferent vagal modulation.

Linear and non-linear measures indicate gastric dysmotility in patients suffering from acute schizophrenia

Cardiac autonomic dysfunction has been reported in patients suffering from schizophrenia. The aim of the present study was to evaluate gastric electrical activity in unmedicated patients suffering from acute schizophrenia in relation to their symptoms. Electrogastrography was performed before and after test meal ingestion in 26 patients suffering from schizophrenia and 26 matched controls. The non-linear measure approximate entropy (ApEn) was calculated for the first time from the obtained signal in addition to standardized measures. Results were correlated with the scales for the assessment of positive symptoms and negative symptoms. In addition, autonomic and abdominal symptoms were assessed by the autonomic symptom score. We found a significantly increased amount of tachygastria and arrhythmia within the signal of the activity of the gastric pacemaker before and after test meal digestion in patients compared to controls, indicating increased sympathetic modulation within the enteric nervous system. A significant difference was observed for slow wave, which represents the dominant frequency of gastric pacemaker activity, indicating gastric dysmotility in our patients. The elevated ApEn measure points to increased complexity and dysregulation. In addition, we have observed a correlation between delusions and tachygastria. Sympathetic function seems to be altered in the enteric nervous system of patients suffering from schizophrenia. Future studies need to explore the influence of the disease on different branches of the autonomic nervous system and clinical consequences of enteric dysfunction. Our findings point to a possible systemic autonomic imbalance that needs to be studied in respect to the neurobiology of schizophrenia.

Autonomy of autonomic dysfunction in major depression

OBJECTIVE

To investigate cardiac autonomic dysfunction in patients with major depressive disorder (MDD). Research in this area has faced several limitations because of the heterogeneity of the disease, the influence of medication, and methodological shortcomings.

METHODS

Participants were 75 patients suffering from an acute recurrent episode of MDD and 75 matched controls. All participants were assessed at baseline for linear and nonlinear parameters of heart rate variability, QT variability and baroreflex sensitivity. Participants with MDD were reassessed after 7 to 9 days of treatment with either a selective serotonin reuptake inhibitor (SSRI) or a serotonin and noradrenaline selective reuptake inhibitor (SNRI) antidepressant.

RESULTS

In the initial examination, patients showed an overall shift of autonomic balance toward sympathetic predominance as compared with matched controls, with a decrease in parasympathetic parameters and baroreflex sensitivity, and an increase in sympathetically influenced QT variability. Overall, antidepressant treatment exacerbated this imbalance, with differential effects observed for SSRI and SNRI treatment. In contrast to autonomic dysfunction in other disorders, such as schizophrenia, autonomic dysfunction in MDD appeared to be independent of disease severity.

CONCLUSIONS

Patients suffering from MDD show profound autonomic dysfunction, which is exacerbated by SNRI and to a lesser degree by SSRI treatment. This information could prove important when selecting antidepressant medication for patients at risk for cardiac arrhythmias.

Differential pattern of heart rate variability in patients with schizophrenia

The cardiac autonomic dysfunction has been reported in patients with schizophrenia. Heart rate variability (HRV) provides non-invasive indices of cardiac autonomic modulation. This study examined whether patients with schizophrenia may show a distinctive pattern of HRV compared to healthy controls. Nine measures of time, frequency and complexity domains were extracted from 5-min resting evaluation of HRV in 30 unmedicated patients with schizophrenia and 30 age- and gender-matched controls. In addition to inferential statistics, a hierarchical clustering (HC) was used to examine difference in the interrelationships among HRV measures between the two groups. Multivariate analysis of variance revealed a significant group effect. Significantly lower sample entropy (SampEn) and a trend towards a higher ratio of low- to high frequency (LF/HF) were observed in the schizophrenia group. In the results of HC using Ward's method, SampEn co-clustered with LF/HF ratio in patients with schizophrenia compared to the separation of LF/HF ratio in healthy controls. In concert with decreased parasympathetic activity, low complexity of heart rate dynamics may reduce adaptability of cardiovascular system to changes in internal or external environment, thus increasing the risk of cardiovascular events. Diverse HRV measures combined in a multivariate fashion appear to be useful in understanding the pattern of neurocardiac modulation in patients with schizophrenia.

Short-term heart rate variability and cardiac norepinephrine spillover in patients with depression and panic disorder

Changes in measures of heart rate variability (HRV) have been associated with an increased risk for sudden cardiac death. The mechanisms underlying this association are not known. The objective of this study was to assess the relationship between the amount of norepinephrine (NE) released from the cardiac sympathetic terminals and short-term HRV. The study comprised 8 healthy subjects, 12 patients with major depression, and 7 patients with panic disorder. Cardiac NE spillover was determined using direct coronary sinus blood sampling coupled with an NE isotope dilution methodology. Short-term HRV was quantified using detrended fluctuation analysis, symbolic dynamics, sample entropy, and standard time and frequency domain measures. Neither HRV nor cardiac NE spillover was significantly different between the analyzed groups. None of the standard HRV metrics was significantly correlated with cardiac NE spillover, but there was a moderate correlation between two complexity measures of HRV (symbolic dynamics) and cardiac NE spillover (patterns with 2 like variations, r = −0.37 and P = 0.05; and patterns with no variations: r = 0.34 and P = 0.06). In conclusion, there is no correlation between standard HRV measures and cardiac NE spillover in humans. Short-term complexity of heart rate is only moderately affected by sympathetic neural outflow. Therefore, the predictive value of most HRV measures for sudden cardiac death may predominantly result from their capacity to capture vagally mediated heart rate modulations.

Indices of fetal development derived from heart rate patterns

BACKGROUND

The fetal precursors of mental and cardiovascular disease caused by adverse prenatal environmental influences and manifesting in later age are an important issue of developmental medicine. However the number of measurable functional parameters of a fetus is limited. Evaluation of key parameters involving fetal autonomic control could permit an earlier detection of developmental problems and improved therapeutic strategies. Thus far, however, even the maturation of normal autonomic control has not been sufficiently assessed.

AIM

The objective of the present work is to describe normal fetal maturation based on indices of autonomic heart rate modulation.

STUDY DESIGN

Heart beat interval series were magnetocardiographically recorded with 1 kHz sampling rate over 30 min in 78 normal fetuses, gestational age (GA) 23-40 weeks. Indices considered were: number of accelerations (AC) and decelerations (DC), RMSSD, SDNN, and short-term/long-term autonomic information flows (AIF_NN, AIF_fVLF). These were measured from the entire 30 min data sets and from activity-specific subsets (10 min).

RESULTS

In the 30 min recordings: the number of AC increased, number of DC decreased, rMSSD and SDNN increased and AIF_fVLF increased with GA, but AIF_NN remained constant. In the 10 min subsets: SDNN increased in the active state but remained constant in the quiet state and AIF_NN decreased with GA in the quiet state.

CONCLUSION

Heart rate patterns from 30 min biomagnetic recordings may provide new indices with which to assess the normal and abnormal maturation of fetal autonomic control and to identify risk of possible disorders in later life.

Physical fitness and heart rate recovery are decreased in major depressive disorder

OBJECTIVE

To investigate whether physical fitness is decreased in patients with major depressive disorder (MDD) in comparison to matched healthy controls because low physical fitness has been shown to be associated with metabolic syndrome or autonomic dysfunction. Cardiovascular morbidity and mortality are known to be increased in patients with MDD. Furthermore, the effect of a single exhaustive exercise task on heart rate recovery (HRR) and mood was examined.

METHODS

Peak oxygen consumption (VO(2)peak), maximum workload (P peak), and individual anaerobic threshold (IAT) were assessed in 22 patients suffering from MDD and 22 controls in a stepwise exhaustion protocol, using spirometry and lactate diagnostics. HRR was detected within the first minute after recovery. The Self-Assessment Manikin (SAM) was used to assess mood before and after exercise.

RESULTS

VO(2)peak, P peak, and IAT were decreased significantly in patients, indicating reduced physical fitness in MDD as compared with control subjects. A single exercise exhaustion significantly improved mood in patients, but not in controls. Mood improvement in patients correlated with maximum lactate levels. Significantly reduced HRR values in patients further point to an elevated cardiovascular risk profile and autonomic dysfunction.

CONCLUSIONS

Our results indicate reduced physical fitness in patients with MDD. Thus, special training programs should be developed to improve their cardiovascular risk profile. In addition, the intriguing finding of a correlation between lactate levels and mood changes should be followed up in future studies to unravel putative mechanisms.

Multiscale, multiorgan and multivariate complexity analyses of cardiovascular regulation

Cardiovascular system complexity is confirmed by both its generally variegated structure of physiological modelling and the richness of information detectable from processing of the signals involved in it, with strong linear and nonlinear interactions with other biological systems. In particular, this behaviour may be accordingly described by means of what we call MMM paradigm (i.e. multiscale, multiorgan and multivariate). Such an approach to the cardiovascular system emphasizes where the genesis of its complexity is potentially allocated and how it is possible to detect information from it. No doubt that processing signals from multi-leads of the same system (multivariate), from the interaction of different physiological systems (multiorgan) and integrating all this information across multiple scales (from genes, to proteins, molecules, cells, up to the whole organ) could really provide us with a more complete look at the overall phenomenon of cardiovascular system complexity, with respect to the one which is obtainable from its single constituent parts. In this paper, some examples of approaches are discussed for investigating the cardiovascular system in different time and spatial scales, in studying a different organ involvement (such as sleep, depression and multiple organ dysfunction) and in using a multivariate approach via various linear and nonlinear methods for cardiovascular risk stratification and pathology assessment.

Increased vagal modulation in atopic dermatitis

BACKGROUND

Atopic dermatitis has been shown to be associated with neurogenic and psychosocial factors. In related atopic diseases such as rhinitis or asthma, a shift in autonomic balance towards a parasympathetic modulation has been described. On the other hand, the psychiatric symptoms known for atopic dermatitis are often associated with decreased vagal modulation. Furthermore, an increased parasympathetic activity has been shown to exhibit anti-inflammatory effects, thus rather alleviating dermatitis symptoms.

OBJECTIVE

In order to address these intriguing discrepancies, we aimed to assess the autonomic state in patients suffering from atopic dermatitis.

METHODS

Heart rate variability assessment was performed in 30 patients and data were compared to those obtained from matched controls. Furthermore, questionnaires for disease activity and psychosocial stressors were employed.

RESULTS

Patients showed higher values for parasympathetic modulation than controls. This was mainly reflected by an increase in the root mean square of successive differences (RMSSD). This parameter further correlated with dermatological symptoms and the time since the last severe exacerbation of the disease. In addition, subgroups of patients with dyshidrosis or photophobia showed significant differences in autonomic modulation under deep respiration. Moreover, cardiac autonomic modulation was hardly altered upon postural change, indicating that autonomic reactivity is only mildly influenced in these patients.

CONCLUSION

Patients with atopic dermatitis showed an autonomic dysbalance which is comparable to other diseases related to atopy or allergy. Our findings point to the question whether these alterations are disease-inherent or counter-regulatory, which should be addressed in future studies.

Gastric dysmotility in patients with major depression

BACKGROUND

Depressed patients frequently complain about vegetative symptoms. The aim of the present study was to evaluate gastric electrical activity in patients suffering from major depression in relation to their symptoms.

METHODS

Electrogastrography (EGG) was performed before and after a test meal ingestion in 21 patients suffering from major depression and control subjects. A structured interview was used to assess the severity of clinical as well as abdominal symptoms.

RESULTS

Patients presented with significantly elevated proportions of tachygastria. Significant differences were found for the parameter arrhythmia, the coefficient of dominant frequency and slow wave after the test meal ingestion. A positive correlation was found between tachygastria and ANS score as well as tachygastria and the item "sweating".

LIMITATIONS

Further studies are warranted to include more patients and to investigate interaction with specific antidepressive drugs.

DISCUSSION

This is the first study demonstrating an increased amount of tachygastria in patients suffering from major depression which might be caused by increased sympathetic modulation. The correlation of tachygastria with the amount of gastric symptoms underlines the clinical significance of this finding.