Linear and nonlinear measures of blood pressure variability: increased chaos of blood pressure time series in patients with panic disorder

Association between mental illness and blood pressure variability: a systematic review

Background

Mental illness represents a major global burden of disease worldwide. It has been hypothesised that individuals with mental illness have greater blood pressure fluctuations that lead to increased cardiovascular risk and target organ damage. This systematic review aims to (i) investigate the association between mental illness and blood pressure variability (BPV) and (ii) describe methods of BPV measurements and analysis which may affect pattern and degree of variability.

Methods

Four electronic databases were searched from inception until 2020. The quality assessment was performed using STROBE criteria. Studies were included if they investigated BPV (including either frequency or time domain analysis) in individuals with mental illness (particularly anxiety/generalised anxiety disorder, depression/major depressive disorder, panic disorder and hostility) and without hypertension. Two authors independently screened titles, abstracts and full texts. A third author resolved any disagreements.

Results

Twelve studies met the inclusion criteria. Three studies measured short-term BPV, two measured long-term BPV and seven measured ultra-short-term BPV. All studies related to short-term BPV using ambulatory and home blood pressure monitoring found a higher BPV in individuals with depression or panic disorder. The two studies measuring long-term BPV were limited to the older population and found mixed results. Mental illness is significantly associated with an increased BPV in younger and middle-aged adults. All studies of ultra-short-term BPV using standard cardiac autonomic assessment; non-invasive continuous finger blood pressure and heart rate signals found significant association between BPV and mental illness. A mixed result related to degree of tilt during tilt assessment and between controlled and spontaneous breathing were observed in patients with psychological state.

Conclusions

Current review found that people with mental illness is significantly associated with an increased BPV regardless of age. Since mental illness can contribute to the deterioration of autonomic function (HRV, BPV), early therapeutic intervention in mental illness may prevent diseases associated with autonomic dysregulation and reduce the likelihood of negative cardiac outcomes. Therefore, these findings may have important implications for patients' future physical health and well-being, highlighting the need for comprehensive cardiovascular risk reduction.

Psychiatric correlates of blood pressure variability in the elderly: The Three City cohort study

BACKGROUND

The modifiable factors associated with blood pressure variability (BPV) are still being established and their clinical relevance is poorly understood. Generalized anxiety disorder (GAD) and depression have been implicated with higher BPV in the short term (e.g. hours, days) however their effects on BPV over longer periods are unknown.

METHODS

In a prospective cohort study, 1454 elderly participants (age 78.5±3.78years, 59% women) underwent structured interview for GAD and major depression. Participants performed home blood pressure monitoring (HBPM) over 3 consecutive days and underwent serial clinic BP measures on 4 separate follow-ups over an 8year period. Systolic and diastolic BPV was calculated using the coefficient of variation (CV) and standard deviation method. Generalized linear models assessed the association between GAD and depression with BPV over an 8year period.

RESULTS

GAD was associated with significantly increased systolic BPV over 8years in age, sex and mean systolic BP (β=0.25, SE=0.09; p=0.007) and fully adjusted models (β=0.23, SE=0.10; p=0.017). BPV from HBPM was strongly associated with 8year systolic BPV in age-sex (β=3.10, SE=0.82; p<0.001) and fully adjusted models (β=3.09, SE=0.84; p<0.001). The association between GAD and longer term BPV was consistent when analyzing morning and evening HBPM measures of BPV. There was no association between diastolic BPV over 8years with GAD or depression.

CONCLUSIONS

GAD but not depression was associated with increased systolic BPV over an 8year period controlling for HBPM. GAD has clinical relevance for control of systolic BPV in elderly participants.

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.

Cardiovascular and single-unit responses to L-glutamate injection into the posterior insular cortex in rat

The insular cortex in rat is a longitudinal strip that runs along the rostral half of the rhinal fissure. The previous studies showed connections between the posterior insular cortex (PIC) and some major cardiovascular centers. Based on the stimulation site, electrical or chemical stimulation of the PIC induced an increase or a decrease in blood pressure (BP) and heart rate (HR). There is no report of simultaneous cardiovascular and single-unit recording microinjection of Glut in the PIC. In this study, L-glutamate was microinjected into the PIC of urethane anesthetized rats and arterial pressure, HR and single-unit responses were recorded simultaneously. Also the response of the neurons to baroreceptor activation was explored. Glut produced five types of long oscillatory, pressor, depressor, bradycardic and tachycardic cardiovascular responses, with no association between pressure and HR responses. We also observed five single-unit responses, consisting of short excitatory, long oscillatory, excitatory, inhibitory and mixed responses. There was an association between oscillation in BP and in single-unit response. There were some differences between the two sides especially for single-unit responses. In conclusion, there were five types of cardiovascular and five types of single-unit responses, to Glut microinjection into PIC, from which three types were correlated. The left side of the PIC is involved more in the cardiovascular functions. These data along with the fact that most recorded neurons responded to baroreceptor activation, might imply the presence of feedback systems in the PIC, producing irregularity in BP and HR.

Heart rate variability and pre-competitive anxiety in BMX discipline

Altered neural mechanisms implying autonomic functioning have been described related to anxiety. Pre-competitive stress may be considered as an anxiety-state associated with disorders (i.e. somatic and cognitive alterations, and self-confidence worsening) that severely impair sport performance, conditioning short-lasting strength-related disciplines like BMX. From the psychological perspective, coaches use questionnaires like CSAI-2R to identify these alterations. However, with the emergence of psycho-physiological and non-linear approaches, recent studies suggest that HRV analysis provides a non-invasive tool to assess them. Hence, our purpose was to analyze how BMX competition affects subjective perception of anxiety, and if this emotional alteration is reflected in HR dynamics, analyzed both linear and nonlinearly, exploring the evolution of this relationship in a 2-day competition. Eleven male athletes from the BMX Spanish National Team were assessed from baseline HRV the morning of a training session (rT) and on two successive days of competition (rC1 and rC2), repeating HRV recording with CSAI-2R 20 min prior to training (aT) and competition (pre-competitive: aC1 and aC2). Repeated measures MANOVA showed significant vagal slow-down responses in aC1 and aC2 comparing not only with aT, but also comparing with rT, rC1 and rC2, coinciding with significant greater scores for the somatic and cognitive anxiety (SA and CA) in aC1 and aC2 versus aT. Pearson analysis showed a large and positive correlation between α1 and SA in C1, and close to it between SampEn and CA in aC2; both were confirmed by Bland-Altman chart analysis. Our results confirm that HRV analysis provide a complementary tool to assess competitive pressure.

Sensitivity to mental effort and test-retest reliability of heart rate variability measures in healthy seniors

OBJECTIVES

To determine (1) whether heart rate variability (HRV) was a sensitive and reliable measure in mental effort tasks carried out by healthy seniors and (2) whether non-linear approaches to HRV analysis, in addition to traditional time and frequency domain approaches were useful to study such effects.

METHODS

Forty healthy seniors performed two visual working memory tasks requiring different levels of mental effort, while ECG was recorded. They underwent the same tasks and recordings 2 weeks later. Traditional and 13 non-linear indices of HRV including Poincaré, entropy and detrended fluctuation analysis (DFA) were determined.

RESULTS

Time domain, especially mean R-R interval (RRI), frequency domain and, among non-linear parameters - Poincaré and DFA were the most reliable indices. Mean RRI, time domain and Poincaré were also the most sensitive to different mental effort task loads and had the largest effect size.

CONCLUSIONS

Overall, linear measures were the most sensitive and reliable indices to mental effort. In non-linear measures, Poincaré was the most reliable and sensitive, suggesting possible usefulness as an independent marker in cognitive function tasks in healthy seniors.

SIGNIFICANCE

A large number of HRV parameters was both reliable as well as sensitive indices of mental effort, although the simple linear methods were the most sensitive.

Heart rate and blood pressure changes during autonomic nervous system challenge in panic disorder patients

OBJECTIVE

To test the hypothesis that panic disorder (PD) patients have a heightened or deregulated autonomic nervous system at rest and during autonomic challenge compared with healthy controls (HC); and to test a second hypothesis that severity of illness differentiates patients'; sympathovagal balance both at rest and during orthostatic challenge.

METHODS

Spectral analysis of heart rate (HR) and blood pressure was performed on 30 PD and 10 HC participants during an orthostatic challenge (head-up tilt).

RESULTS

PD patients presented higher HR (p < .001), lower heart rate variability (HRV) (p < .015), higher mean diastolic blood pressure (p < .006), higher low-frequency component of HR (p < .001), and a higher ratio of low-frequency to high-frequency component of HR (LF/HF) (p < .022) than HC at baseline. During tilt, PD patients responded with higher HR (p < .039), lower HRV (p < .043), increased mean diastolic blood pressure (p < .028), and a mild increase in LF/HF, whereas controls responded with a five-fold increase in LF/HF (p < .022). Patients with higher illness severity ratings (Clinical Global Impression Scale) showed higher HR (p < .002), lower HRV (p < .026), and a lower total power of systolic blood pressure (p < .02) compared with less ill patients.

CONCLUSION

These findings demonstrate a consistently higher or deregulated autonomic arousal in PD patients at rest and during orthostatic challenge compared with HC. These data also reveal a possible association between the level of anxiety illness severity and sympathovagal balance, which may imply greater cardiac risk.

Temporal analysis of the spontaneous baroreceptor reflex during mild emotional stress in the rat

The effect of emotional stress on the spontaneous baroreceptor reflex (sBRR) in freely moving rats was investigated. Six male Wistar rats equipped with an intra-arterial polyethylene catheter were exposed to a 2-min air-jet stress. For time course analysis of the sBRR response to stress, the records of systolic blood pressure (SBP) and pulse interval (PI) were divided into five regions: baseline (BASELINE), acute exposure to air-jet stress (STRESS), immediate recovery (IMMED. RECOVERY), remaining recovery (RECOVERY), and delayed response (DELAYED RESPONSE). In addition to sBRR sensitivity and effectiveness, we introduce the sequence coverage area and its median for evaluation of the sBRR operating range and set point. During exposure to STRESS and IMMED. RECOVERY, sBRR sensitivity was preserved, its effectiveness was decreased, its operating range was enlarged, and the set point was shifted towards higher SBP and lower PI values. According to the joint symbolic dynamics analysis, the SBP and PI relationship became less predictable hence more prone to respond to stress. In RECOVERY the parameters regained baseline values and DELAYED RESPONSE occurred during which re-setting of sBRR was noted. It follows that emotional stress modulates sBRR differentially during the time course of stress and recovery, affecting both linearity and unpredictability of the BP and PI relationship.

[Heart rate variability analysis in sports]

Differences in the duration of the cycles reflects the balance of the sympathetic and parasympathetic influence on the heart. Variance in the heart rate correlates to the breathing cycle, to baroreflex sensitivity, to day and night alternations and to changes in the vegetative tone evoked by physical exercises. Analysis of the time and/or frequency power domain of the heart rate variance is expected to have diagnostic value in physiological and pathological situations as adaptation to training, overtraining, heart disease etc. Both time- and frequency domains reflect the same physiological phenomenon but from different point of view. Vagus tonus is reflected in the high frequency part of the range of variance, while an increased sympathetic tone enriches the low frequency part of the variations of the duration of the consecutive heart cycles. This technically simple and relatively inexpensive method has inspired a couple of clinical and sports medical studies. Certain tendencies seem to be clear, but for individual diagnosis or for prognosis the data must be treated very carefully.

Complexity of cardiovascular regulation in small animals

Oscillations of heart rate and blood pressure are related to the activity of the underlying control mechanism. They have been investigated mostly with linear methods in the time and frequency domains. Also, in recent years, many different nonlinear analysis methods have been applied for the evaluation of cardiovascular variability. This review presents the most commonly used nonlinear methods. Physiological understanding is obtained from various results from small animals.

Exaggerated beat-to-beat R amplitude variability in patients with panic disorder after intravenous isoproterenol

BACKGROUND

Anxiety symptoms are associated with a marked increase in sudden cardiac death, suggesting an abnormality in cardiac autonomic function. Our previous studies show a relationship between R amplitude variability and sympathetic function.

METHODS

We examined the effects of beta-adrenergic stimulation on R and T amplitude variability in panic disorder patients by infusing the beta-adrenergic agonist isoproterenol in 6 panic disorder patients and 11 normal subjects. The ECG signal was analyzed before the infusion and 5 min after the infusion was started. The outcome measures were the R and T detrended variance normalized for mean amplitudes (R(vm) and T(vm)) and the R(vi) and T(vi), measures which are normalized for the inter-beat interval variability in addition.

RESULTS

Patients with panic disorder had significantly more variability in R and T amplitude than normal controls and the R amplitude variability was increased further by beta-adrenergic stimulation with isoproterenol, which was more pronounced in the patients.

CONCLUSIONS

The isoproterenol-associated increase in R amplitude variability occurred in controls in the absence of significant anxiety. However, the increase in R amplitude variability was greater in patients with panic disorder, suggesting a greater sensitivity to beta-adrenergic effects of isoproterenol or to isoproterenol-induced anxiety.

An autonomic flexibility–neurovisceral integration model of anxiety and cardiac vagal tone

Research on heart rate variability (HRV), cardiac vagal tone, and their relationship to anxiety is reviewed in the context of the autonomic flexibility and neurovisceral integration models of adaptive functioning. These perspectives address the qualities of response flexibility and inhibition across multiple levels, incorporating central and autonomic nervous system mechanisms of environmental engagement, as well as principles derived from non-linear dynamics. These models predict reduced HRV and vagal tone in anxiety, and the literature has generally supported this prediction, with exceptions as are noted. State, trait, and clinical expressions of anxiety are considered, along with the clinical, methodological, and theoretical implications of this research. A portrayal of anxiety as a restricted response range across biological and behavioral realms of functioning is drawn from the literature on anxiety and HRV.

Fractal dimension in health and heart failure

BACKGROUND

Non-linear analysis of heart rate variability (HRV) can give additional information about autonomic control of the heart rate. This study applied the fractal dimension (FD) in a congestive heart failure (CHF) population.

METHODS

FD and HRV were evaluated in a healthy population (n=21) and an end-stage heart failure population (n=21) using 1-h segments during the day and night from Holter recordings.

RESULTS

CHF patients presented a loss of circadian variation in both FD and conventional time- and frequency-domain HRV indices. FD was higher in the CHF population both during the day and night. In the CHF population the correlation between FD and high-frequency power of HRV was lost.

CONCLUSION

Day-night variations of heart rate fluctuations are lost in heart failure. Changes in FD reflecting physiological and pathophysiological changes were observed.

Panic symptoms at the interface of body and mind

Panic disorder is a common illness with significant impact on function and, at times, disabling consequences. Advances over recent years have yielded potential pathophysiologic mechanisms, including neurotransmitter systems and neural substrates. This article provides an overview of various models and hypotheses regarding the etiology of panic disorder. Because its symptoms overlap with the symptoms of various medical disorders, this discussion reviews the comorbidity of panic disorder with medical conditions, especially cardiac and respiratory disorders.

Power spectrum analysis and cardiovascular morbidity in anxiety disorders

Spectral analysis of heart rate variability (HRV) and related measures has been shown to be a reliable noninvasive technique enabling quantitative assessment of cardiovascular autonomic regulatory responses to autonomic regulatory mechanisms; it provides a dynamic probe of sympathetic and parasympathetic tone, reflecting the interactions between the two. Over 20 studies reported abnormalities of HRV in anxiety, and patients with heart disease and anxiety are at increased risk for morbidity and mortality. Psychiatric drugs partly correct abnormalities of HRV and, recently, autonomic drugs (beta-blockers) have been studied in anxiety disorders. The authors call for further studies, especially in patients with co-existing anxiety disorders and heart disease, incorporating assessment of HRV.

EFFECTS OF AUTONOMIC BLOCKADE ON NON-LINEAR CARDIOVASCULAR VARIABILITY INDICES IN RATS

1. The present study assesses the effects of autonomic blockade (alpha- and beta-adrenoceptor and cholinergic) on cardiovascular function studied by heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity in rats using non-linear dynamics. Little is known about the influence of pharmacological autonomic nervous system interventions on non-linear cardiovascular regulatory indices. 2. In 13 conscious rats, heart rate and aortic blood pressure were measured continuously before, during and after autonomic blockade with atropine, phentolamine and propranolol. Non-linear scaling properties were studied using 1/f slope, fractal dimension and long- and short-term correlation. Non-linear complexity was described with correlation dimension, Lyapunov exponent and approximate entropy. Non-linear indices were compared with linear time and frequency domain indices. 3. Beta-adrenoceptor blockade did not alter the non-linear characteristics of HRV and BPV, although low-frequency power of HRV was depressed. Alpha-adrenoceptor blockade decreased the scaling behaviour of HRV, whereas cholinergic blockade decreased the complexity of the non-linear system of HRV. For BPV, the scaling behaviour was increased during alpha-adrenoceptor blockade and the complexity was increased during cholinergic blockade. The linear indices of HRV and BPV were decreased. 4. The present results indicate that the beta-adrenoceptor system has little involvement in the generation of non-linear HRV and BPV in rats. 5. Alpha-adrenoceptor blockade mostly influenced the scaling properties of the time series, whereas cholinergic blockade induced changes in the complexity measures. 6. The absence of the baroreflex mechanism can trigger a compensatory feed-forward system increasing the complexity of BPV.

Aging and nonlinear heart rate control in a healthy population

In recent years more studies are using nonlinear dynamics to describe cardiovascular control. Because of the large dispersion of physiological data, it is important to have large studies with both male and female participants to establish a range of physiological healthy values. This study investigated the effect of gender and age on nonlinear indexes. Nonlinear scaling properties were studied by using 1/f slope (where f is frequency), fractal dimension, and detrended fluctuation analysis short- and long-term correlations (DFAalpha(1) and DFAalpha(2), respectively). Nonlinear complexity was described with correlation dimension (CD), Lyapunov exponent (LE), and approximate entropy (ApEn). The population consisted of 135 women and 141 men (age, 18-71 yr). Twenty-four hour ECG recordings were obtained by using Holter monitoring. The recordings were split into daytime (8 AM-9 PM) and nighttime (11 PM-6 AM). A day-night variation was present in all nonlinear heart rate variability (HRV) indexes, except for the CD in the female population. During the night the percentage of CD values of surrogate data files differing from the CD value of the original data increased. All nonlinear indexes were significantly correlated with age. Deeper analysis per age category of 10 yr showed a stabilization in the age decline of the fractal dimension and ApEn at the age of > or =40 yr. The vagal pathways seemed to be more involved in the generation of nonlinear fluctuations. Higher nonlinear behavior was evident during the night. No clear difference between men and women was found in the nonlinear indexes. Nonlinear indexes decline with age. This can be related to the concept of decreasing autonomic modulation with advancing age.