Low heart rate variability and sudden cardiac death

Heart Rate Variability as a Tool for Seizure Prediction: A Scoping Review

The most critical burden for People with Epilepsy (PwE) is represented by seizures, the unpredictability of which severely impacts quality of life. The design of real-time warning systems that can detect or even predict ictal events would enhance seizure management, leading to high benefits for PwE and their caregivers. In the past, various research works highlighted that seizure onset is anticipated by significant changes in autonomic cardiac control, which can be assessed through heart rate variability (HRV). This manuscript conducted a scoping review of the literature analyzing HRV-based methods for detecting or predicting ictal events. An initial search on the PubMed database returned 402 papers, 72 of which met the inclusion criteria and were included in the review. These results suggest that seizure detection is more accurate in neonatal and pediatric patients due to more significant autonomic modifications during the ictal transitions. In addition, conventional metrics are often incapable of capturing cardiac autonomic variations and should be replaced with more advanced methodologies, considering non-linear HRV features and machine learning tools for processing them. Finally, studies investigating wearable systems for heart monitoring denoted how HRV constitutes an efficient biomarker for seizure detection in patients presenting significant alterations in autonomic cardiac control during ictal events.

Instant and short-term effects of acupuncture for depression and anxiety in unstable angina pectoris patients with percutaneous coronary interventions

Aim

Patients with unstable angina pectoris (UAP) usually present anxiety or depression during percutaneous coronary intervention (PCI). This study sought to investigate the instant and short-term effects of acupuncture for anxiety and depression in UAP patients with PCI.

Methods

A total of 210 UAP patients who underwent PCI were recruited and randomly assigned (1:1:1) to acupuncture, placebo, or control groups. Enzyme-linked immunosorbent assay was used to detect the levels of fasting glucose, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), interleukin-6 (IL-6), high-sensitivity C-reactive protein (Hs-CRP), advanced oxidation protein products (AoPPs), and oxidized low-density lipoprotein (OX-LDL). Serial questionnaires with the Hamilton Anxiety (HAMA) scale and the Pittsburgh Sleep Quality Index were evaluated, and heart rate variability indicators were obtained.

Results

Primary end-point: low frequency/high frequency (HF) was lower in the electroacupuncture group (p = 0.014), while standard deviation of normal-to-normal intervals, average standard deviation of normal-to-normal intervals, percentage of successive intervals that differ more than 50 ms, and HF were increased with acupuncture (p = 0.018, p = 0.043, p = 0.016, and p = 0.002, respectively). Secondary end-point: significant improvements in anxiety levels (HAMA) were observed in the three groups (p < 0.001). The fasting insulin and HOMA-IR levels were similar between the control group and the acupuncture group (p = 0.285 and p = 0.165, respectively). The levels of IL-6 and AoPPs differed among the three groups (p = 0.021 and p < 0.001, respectively). However, no significant differences were found in fasting plasma glucose, fasting c-peptide, Hs-CRP, and OX-LDL levels among the three groups (p = 0.585, p = 0.611, p = 0.902, and p = 0.756, respectively).

Conclusions

In this study, short-term acupuncture may potentially relieve clinical symptoms before PCI treatment.

Clinical Trial Registration

ClinicalTrials.gov, identifier (NCT03789344).

Outcomes of out-of-hospital cardiac arrest in adult congenital heart disease: a Danish nationwide study

AIMS

The risk, characteristics, and outcome of out-of-hospital cardiac arrest (OHCA) in patients with congenital heart disease (CHD) remain scarcely investigated.

METHODS AND RESULTS

An epidemiological registry-based study was conducted. Using time-dependent Cox regression models fitted with a nested case-control design, hazard ratios (HRs) with 95% confidence intervals of OHCA of presumed cardiac cause (2001-19) associated with simple, moderate, and severe CHD were calculated. Moreover, using multiple logistic regression, we investigated the association between pre-hospital OHCA characteristics and 30-day survival and compared 30-day survival in OHCA patients with and without CHD. Overall, 43 967 cases (105 with simple, 144 with moderate, and 53 with severe CHD) and 219 772 controls (median age 72 years, 68.2% male) were identified. Any type of CHD was found to be associated with higher rates of OHCA compared with the background population [simple CHD: HR 1.37 (1.08-1.70); moderate CHD: HR 1.64 (1.36-1.99); and severe CHD: HR 4.36 (3.01-6.30)]. Pre-hospital cardiopulmonary resuscitation and defibrillation were both associated with improved 30-day survival in patients with CHD, regardless of CHD severity. Among patients with OHCA, simple, moderate, and severe CHD had a similar likelihood of 30-day survival compared with no CHD [odds ratio 0.95 (0.53-1.69), 0.70 (0.43-1.14), and 0.68 (0.33-1.57), respectively].

CONCLUSION

A higher risk of OHCA was found throughout the spectrum of CHD. Patients with and without CHD showed the same 30-day survival, which relies on the pre-hospital chain of survival, namely cardiopulmonary resuscitation and defibrillation.

Imbalance of Peripheral Temperature, Sympathovagal, and Cytokine Profile in Long COVID

A persistent state of inflammation has been reported during the COVID-19 pandemic. This study aimed to assess short-term heart rate variability (HRV), peripheral body temperature, and serum cytokine levels in patients with long COVID. We evaluated 202 patients with long COVID symptoms categorized them according to the duration of their COVID symptoms (≤120 days, n = 81; >120 days, n = 121), in addition to 95 healthy individuals selected as controls. All HRV variables differed significantly between the control group and patients with long COVID in the ≤120 days group (p < 0.05), and participants in the long COVID ≤120 days group had higher temperatures than those in the long COVID >120 days group in all regions analysed (p < 0.05). Cytokine analysis showed higher levels of interleukin 17 (IL-17) and interleukin 2 (IL-2), and lower levels of interleukin 4 (IL-4) (p < 0.05). Our results suggest a reduction in parasympathetic activation during long COVID and an increase in body temperature due to possible endothelial damage caused by the maintenance of elevated levels of inflammatory mediators. Furthermore, high serum levels of IL-17 and IL-2 and low levels of IL-4 appear to constitute a long-term profile of COVID-19 cytokines, and these markers are potential targets for long COVID-treatment and prevention strategies.

Change in heart rate variability during two firefighting work cycles

This study aimed to determine whether the change in heart rate variability from pre to post firefighting is modulated by different work cycles. Thirteen male firefighters underwent two firefighting simulations that comprised two identical 25-min work bouts intercalated by a passive recovery period of either 20 min (T20) or 5 min (T5). The square root of the mean squared differences of successive R-R intervals (RMSSD) and aural temperature were measured at rest before (PRE) and after (POST) firefighting simulations. The decrease in RMSSD was different between firefighting simulations (T20: -10 ± 21.2 ms, T5: -19.9 ± 20.9 ms, interaction, p = 0.02). Post-firefighting aural temperature was greater (p = 0.05) in T5 (37.18 ± 0.53 °C) than in T20 (36.88 ± 0.49 °C). In conclusion, a shorter recovery period of 5 min between firefighting work bouts decreases post-firefighting heart rate variability, possibly attributed to a lower parasympathetic reactivation and a higher absolute value of body temperature.

Following the Rhythm of the Heart: HeartMath Institute's Path to HRV Biofeedback

This paper outlines the early history and contributions our laboratory, along with our close advisors and collaborators, has made to the field of heart rate variability and heart rate variability coherence biofeedback. In addition to the many health and wellness benefits of HRV feedback for facilitating skill acquisition of self-regulation techniques for stress reduction and performance enhancement, its applications for increasing social coherence and physiological synchronization among groups is also discussed. Future research directions and applications are also suggested.

Heart rate variability changes by non-invasive ventilation in obesity hypoventilation syndrome

BACKGROUND

Non-invasive positive pressure ventilation (NIPPV) is known to enhance hypoventilation and is particularly adopted as a treatment for patients diagnosed with obesity hypoventilation syndrome (OHS). The augmented risk of cardiovascular morbidity is known as a side effect of OHS.

AIMS

In this paper, this inference is examined that hypoventilation and the increased risk of morbidity can be diagnosed via the assessment of changes in heart rate variability (HRV). More specifically, the study investigates the effect of NIPPV on both HRV and hypoventilation among OHS patients. The linear relationship between different HRV measures and ventilation parameters is also examined.

MATERIALS & METHODS

The reported results are attained via an interventional clinical trial study. HRV measures are evaluated before and after treatment, in a group of patients which are newly diagnosed with OHS and receive bi-level positive airway pressure (BiPAP) treatment for three months.

RESULTS

The results are compared and interpreted via statistical analysis.

DISCUSSION

Throughout the study, the relationship between hypoventilation and HRV is confirmed, as well as the effect of BiPAP on some HRV measures in both time and frequency domains. Particularly significant connections are observed between hypoventilation and low-frequency components of HRV.

CONCLUSION

The enhanced respiration due to the application of BiPAP can improve the performance of autonomous nervous and cardiovascular systems, in terms of HRV. Moreover, it is suggested to consider some HRV parameters to control the cardiovascular side-effects of OHS and confine the resulting mortality rate in long term.

Sounds of Silence in Times of COVID-19: Distress and Loss of Cardiac Coherence in People With Misophonia Caused by Real, Imagined or Evoked Triggering Sounds

The extreme, unprecedented situations in the current COVID-19 pandemic are risk factors for psychosocial stress for the entire population. However, strict confinement had a particular impact on people suffering from misophonia and their families. Misophonia is a condition in which hearing certain sounds triggers intense anger, disgust and even severe autonomic nervous system responses. This prospective cohort study examined the impact of strict confinement (Spain, March 14-June 21, 2020) on a sample of 24 people (16 women and eight men) who had been diagnosed with moderate to extreme misophonia and were regularly attending a medical psychology center in Barcelona. The 3-month period of confinement caused general emotional maladjustment, distress, and a transitory crisis. Long-term biomonitoring of their heart variability rate (HRV) enabled to identify a significant increase in physiological arousal after the confinement period, which had already been recorded in a loss of cardiac coherence under basal rest/relaxation conditions. Certain auditory stimuli triggered adverse responses, lowered HRV scores, and an increased stress level and heart rate. Loss of cardiac coherence in their responses to these auditory stimuli (triggering mouth, nose and other sounds), as well as to non-triggering mouth, nose and other sounds was increased when compared to two assessments performed during the previous year. Despite the limited sample size, sex differences were observed in the incidence. Loss of cardiac coherence worsened with the severity of the misophonia. Most importantly, imagined or evoked triggering sounds, as well as real ones, were enough to cause the aversive responses, as displayed by the increased loss of cardiac coherence with respect to the at-rest basal level. A semi-structured interview revealed the exceptional nature of the situations, increased hyper-sensorial sensitivity, fear of being infected with or dying from COVID-19, the patients' coping strategies, and the difficulties and constraints they faced. Finally, the article gives recommendations for better management of misophonia. Improved knowledge of this disorder would help address the current lack of health and social care, hopefully preventing this shortfall's impact on social and affective relationships, which are particulary important for well-being now and in the coming periods of physical distancing measures.

Heart and Brain Interaction of Psychiatric Illness: A Review Focused on Heart Rate Variability, Cognitive Function, and Quantitative Electroencephalography

Heart rate variability (HRV) reflects beat-to-beat variability in the heart rate due to the dynamic interplay of the sympathetic and parasympathetic nervous systems. HRV is considered an index of the functional status of the autonomic nervous system. A decrease in HRV is thus observed in individuals with autonomic dysfunction. Abnormal HRV has been reported in a range of mental disorders. In this review, we give an overview of HRV in patients with major depressive disorder (MDD), schizophrenia, and posttraumatic stress disorder (PTSD), one of whose core symptoms is cognitive dysfunction. The association between HRV and cognitive function is highlighted in this review. This review consists of three main sections. In the first section, we examine how HRV in patients with MDD, schizophrenia, and PTSD is characterized, and how it is different when compared to that in healthy controls. In the second section, beyond the heart itself, we discuss the intimate connection between the heart and the brain, focusing on how HRV interacts with quantitative electroencephalography (qEEG) in the context of physiological changes in the sleep cycle. Lastly, we finish the review with the examination of the association between HRV and cognitive function. The overall findings indicate that the reduction in HRV is one of main manifestations in MDD, schizophrenia, and PTSD, and also more generally HRV is closely linked to the change in qEEG and also to individual differences in cognitive performance.

Early identification of impending cardiac arrest in neonates and infants in the cardiovascular ICU: a statistical modelling approach using physiologic monitoring data

OBJECTIVE

To develop a physiological data-driven model for early identification of impending cardiac arrest in neonates and infants with cardiac disease hospitalised in the cardiovascular ICU.

METHODS

We performed a single-institution retrospective cohort study (11 January 2013-16 September 2015) of patients ≤1 year old with cardiac disease who were hospitalised in the cardiovascular ICU at a tertiary care children's hospital. Demographics and diagnostic codes of cardiac arrest were obtained via the electronic health record. Diagnosis of cardiac arrest was validated by expert clinician review. Minute-to-minute physiological monitoring data were recorded via bedside monitors. A generalized linear model was used to compute a minute by minute risk score. Training and test data sets both included data from patients who did and did not develop cardiac arrest. An optimal risk-score threshold was derived based on the model's discriminatory capacity for impending arrest versus non-arrest. Model performance measures included sensitivity, specificity, accuracy, likelihood ratios, and post-test probability of arrest.

RESULTS

The final model consisting of multiple clinical parameters was able to identify impending cardiac arrest at least 2 hours prior to the event with an overall accuracy of 75% (sensitivity = 61%, specificity = 80%) and observed an increase in probability of detection of cardiac arrest from a pre-test probability of 9.6% to a post-test probability of 21.2%.

CONCLUSIONS

Our findings demonstrate that a predictive model using physiologic monitoring data in neonates and infants with cardiac disease hospitalised in the paediatric cardiovascular ICU can identify impending cardiac arrest on average 17 hours prior to arrest.

Co-Existence of hypertension worsens post-exercise cardiac autonomic recovery in type 2 diabetes

BACKGROUND

Cardiac autonomic neuropathy (CAN) is a commonly overlooked complication of Type 2 Diabetes Mellitus (T2DM) characterized by imbalance between sympathetic and parasympathetic supply to the heart. The susceptibility of heart to dysrhythmias and fatal events increases during and after exercise due to a shift in autonomic regulation. Diabetes and hypertension (HTN) frequently occur concurrently and both conditions lead to impaired cardiac autonomic control. However, their impact together on post-exercise autonomic recovery remains to be explored.

OBJECTIVE

The objective of the study was to investigate the effect of co-existence of HTN on cardiac autonomic recovery (assessed by heart rate recovery and heart rate variability) in patients with T2DM.

METHODS

Forty eight type 2 diabetic patients (24 normotensive, 24 hypertensive), 24 non-diabetic patients with essential HTN, and 27 healthy controls, were recruited into the study and assessed for heart rate recovery (HRR) following a graded maximal test. Also, heart rate variability (HRV) was recorded before and following the bout of maximal exercise.

RESULTS

Heart rate recovery at 1 (HRR1min) and 2 (HRR2min) minute(s) showed significant effects for DM (p < 0.001) and HTN (p < 0.001), while DM × HTN interaction was found to be non-significant. Resting HRV showed a significant decline in time-domain variables for the DM group (p < 0.01). Recovery of HRV showed a significant effect of time (p < 0.05) for all indices, the group effect was found significant only for time-domain measures (p < 0.05).

CONCLUSION

Both HRR and HRV recovery were impaired in DM and HTN. Moreover, the co-existence of HTN had a synergistic effect, causing further worsening of autonomic recovery in T2DM.

Diplomats' Mystery Illness and Pulsed Radiofrequency/Microwave Radiation

Importance: A mystery illness striking U.S. and Canadian diplomats to Cuba (and now China) "has confounded the FBI, the State Department and US intelligence agencies" (Lederman, Weissenstein, & Lee, 2017). Sonic explanations for the so-called health attacks have long dominated media reports, propelled by peculiar sounds heard and auditory symptoms experienced. Sonic mediation was justly rejected by experts. We assessed whether pulsed radiofrequency/microwave radiation (RF/MW) exposure can accommodate reported facts in diplomats, including unusual ones. Observations: (1) Noises: Many diplomats heard chirping, ringing or grinding noises at night during episodes reportedly triggering health problems. Some reported that noises were localized with laser-like precision or said the sounds seemed to follow them (within the territory in which they were perceived). Pulsed RF/MW engenders just these apparent "sounds" via the Frey effect. Perceived "sounds" differ by head dimensions and pulse characteristics and can be perceived as located behind in or above the head. Ability to hear the "sounds" depends on high-frequency hearing and low ambient noise. (2) Signs/symptoms: Hearing loss and tinnitus are prominent in affected diplomats and in RF/MW-affected individuals. Each of the protean symptoms that diplomats report also affect persons reporting symptoms from RF/MW: sleep problems, headaches, and cognitive problems dominate in both groups. Sensations of pressure or vibration figure in each. Both encompass vision, balance, and speech problems and nosebleeds. Brain injury and brain swelling are reported in both. (3) Mechanisms: Oxidative stress provides a documented mechanism of RF/MW injury compatible with reported signs and symptoms; sequelae of endothelial dysfunction (yielding blood flow compromise), membrane damage, blood-brain barrier disruption, mitochondrial injury, apoptosis, and autoimmune triggering afford downstream mechanisms, of varying persistence, that merit investigation. (4) Of note, microwaving of the U.S. embassy in Moscow is historically documented. Conclusions and relevance: Reported facts appear consistent with pulsed RF/MW as the source of injury in affected diplomats. Nondiplomats citing symptoms from RF/MW, often with an inciting pulsed-RF/MW exposure, report compatible health conditions. Under the RF/MW hypothesis, lessons learned for diplomats and for RF/MW-affected civilians may each aid the other.

Depression and cardiac dysautonomia in eating disorders

PURPOSE

Individuals with eating disorder (ED) are at an increased risk of cardiac arrhythmias due to cardiac dysautonomia, which may be exacerbated if depression is also present. The aim of the study was to use heart rate analysis as a marker for cardiac dysautonomia in patients with eating disorders and depression as a comorbidity.

METHODS

Clinical data, including presence of depression, was obtained from all participants. A three-lead ECG was used to determine interbeat intervals, and these were analyzed using time domain, frequency domain, and nonlinear heart rate variability measures.

RESULTS

Thirty ED patients and 44 healthy controls participated in the research. The presence of depression was associated with additional decreased time domain (RMSSD 36.8 ± 26 vs. 22.9 ± 12.3; p < 0.05), frequency domain (HF power 788 ± 1075 vs. 279 ± 261; p < 0.05), and nonlinear domain (DFAα₂ 0.82 ± 0.1 vs. 0.97 ± 0.1; p < 0.01) which results in the ED group compared to patients with no depression.

CONCLUSIONS

The presence of depression in ED patients decreased HRV even further compared to the non-depressed patient group and controls, suggesting that higher vigilance and a holistic treatment approach may be required for these patients to avoid cardiac arrhythmia complications.

Synchronization of Human Autonomic Nervous System Rhythms with Geomagnetic Activity in Human Subjects

A coupling between geomagnetic activity and the human nervous system’s function was identified by virtue of continuous monitoring of heart rate variability (HRV) and the time-varying geomagnetic field over a 31-day period in a group of 10 individuals who went about their normal day-to-day lives. A time series correlation analysis identified a response of the group’s autonomic nervous systems to various dynamic changes in the solar, cosmic ray, and ambient magnetic field. Correlation coefficients and p values were calculated between the HRV variables and environmental measures during three distinct time periods of environmental activity. There were significant correlations between the group’s HRV and solar wind speed, Kp, Ap, solar radio flux, cosmic ray counts, Schumann resonance power, and the total variations in the magnetic field. In addition, the time series data were time synchronized and normalized, after which all circadian rhythms were removed. It was found that the participants’ HRV rhythms synchronized across the 31-day period at a period of approximately 2.5 days, even though all participants were in separate locations. Overall, this suggests that daily autonomic nervous system activity not only responds to changes in solar and geomagnetic activity, but is synchronized with the time-varying magnetic fields associated with geomagnetic field-line resonances and Schumann resonances.

Management of Arrhythmias in Heart Failure

Heart failure patients are predisposed to develop arrhythmias. Supraventricular arrhythmias can exacerbate the heart failure symptoms by decreasing the effective cardiac output and their control require pharmacological, electrical, or catheter-based intervention. In the setting of atrial flutter or atrial fibrillation, anticoagulation becomes paramount to prevent systemic or cerebral embolism. Patients with heart failure are also prone to develop ventricular arrhythmias that can present a challenge to the managing clinician. The management strategy depends on the type of arrhythmia, the underlying structural heart disease, the severity of heart failure, and the range from optimization of heart failure therapy to catheter ablation. Patients with heart failure, irrespective of ejection fraction are at high risk for developing sudden cardiac death, however risk stratification is a clinical challenge and requires a multiparametric evaluation for identification of patients who should undergo implantation of a cardioverter defibrillator. Finally, patients with heart failure can also develop symptomatic bradycardia, caused by sinus node dysfunction or atrio-ventricular block. The treatment of bradycardia in these patients with pacing is usually straightforward but needs some specific issue.

Cardiovascular Manifestations of Acute Intracranial Lesions: Pathophysiology, Manifestations, and Treatment

The objective of this article was to review the effects of acute intracranial lesions on myocardial function. The authors reviewed scientific and clinical literature retrieved from a computerized MEDLINE search from January 1965 through January 2002. Pertinent literature was referenced, including clinical and laboratory investigations, to demonstrate the effects of acute intracranial lesions on the cardiovascular system. The literature was reviewed to summarize the mechanisms of cardiac damage and clinical manifestations and treatment of cardiovascular dysfunction caused by acute intracranial lesions. Myocardial damage and rhythm disturbances were shown to occur with acute intracranial neurological disease. The subgroup of patients used in this study formed a substantial pool of cardiac donors for cardiac transplantation. The pathophysiology of myocardial dysfunction and the optimal management continues to be a source of debate. In this article, the authors will review the anatomy, the available evidence of the pathophysiology, and the management of this complex group of patients. They will also discuss areas that need to be further investigated. Cardiovascular effects of acute intracranial lesions are common and contribute to increased morbidity and mortality.

The role of variability in night-time mean heart rate on the prediction of ventricular arrhythmias and all-cause mortality in implantable cardioverter defibrillator patients

AIMS

This study was to use implantable cardioverter defibrillator (ICD) home monitoring (HM) feature to evaluate the role of mean night-time heart rate (MNHR) in the occurrence of ventricular arrhythmias (VAs) and mortality.

METHODS AND RESULTS

This study retrospectively analysed clinical and ICD device data in 318 ICD patients. Data of the first 30-day MNHR (recorded 02:00-06:00 am) by HM were collected. The average and standard deviation of 30-day MNHR (AVHR and SDHR, respectively) were then determined in each patient. The primary endpoint was appropriate ICD treatment of VAs. The secondary endpoint was all-cause mortality. During a mean follow-up period of 32 ± 10 months, 179 of the 318 patients (56.3%) experienced VAs, 123 patients (38.7%) were treated by ICD shocks, and 37 patients (11.6%) died. The overall SDHR in this study cohort was 4.5 ± 3.0 bpm. Based on the receiver operating characteristic curve, the cut-off value of SDHR = 3.685 bpm was identified to predict VAs. In the Kaplan-Meier survival, SDHR ≥ 3.685 bpm was associated with increased VAs [hazard ratio (HR) = 1.885; 95% confidence interval (CI) = 1.362-2.609; P < 0.001], shock events (HR = 1.637; 95% CI = 1.11-2.414; P = 0.013), all-cause mortality (HR = 2.42; 95% CI = 1.266-4.627; P = 0.008), and the combined endpoints (HR = 1.872; 95% CI = 1.365-2.567; P < 0.001). In univariate and multivariate Cox models (adjusting for clinical factors), SDHR ≥ 3.685 bpm was still an independent predictor for all endpoints.

CONCLUSION

In ICD population, SDHR ≥ 3.685 bpm was an independent predictor for VAs and all-cause mortality.

Effect of a weight reduction program on baseline and stress-induced heart rate variability in children with obesity

OBJECTIVE

Autonomic dysregulation is a well-established feature in adults with obesity but not in children. Since this dysregulation could contribute to weight dynamics, this study aimed to compare autonomic regulation in children with obesity and normal-weight peers and to track autonomic status during weight reduction.

METHODS

Sixty children with obesity and 27 age- and sex-matched normal-weight healthy participants were included. Heart rate variability (HRV) was assessed at baseline and during a mental stress test and a subsequent recovery period. Children with obesity were investigated both upon admission and discharge.

RESULTS

Upon admission, no significant differences in HRV parameters were found for normal-weight participants and those with obesity. Inpatient treatment led to significant changes in HRV with increase in general variability (standard deviation of the normal-to-normal interval (SDNN), P < 0.001) as well as of parasympathetic regulation (root mean square successive difference (RMSSD) and high frequency power (logHF), P < 0.01). Children with obesity had sympathetic activation similar to normal-weight controls during mental stress with subsequent return to baseline values, and weight loss did not affect this profile.

CONCLUSIONS

A weight reduction program induced a change in autonomic activity in children with obesity toward parasympathetic dominance but had no influence on autonomic nervous system reactivity during stress conditions.

Complementary and Integrative Approaches for Pediatric Headache

In this article, the use of complementary and integrative medicine for the management of pediatric headache is reviewed. Despite limited numbers of studies for pediatric headaches, children and families seek these services. Integrative medicine focuses on treating the whole person, integrating conventional medicine with mind-body-spirit methods. Nutriceuticals include dietary supplements in the form of vitamins (vitamin D), minerals (magnesium), coenzyme Q, butterbur, and melatonin. Acupuncture, stimulation, physical therapy and Transcutaneous Electrical Nerve Stimulations (TENS) or Transcranial Magnetic Stimulation (TMS) may also be useful in selected patients. The efficacy of all these therapeutic alternatives in pediatric headache is presented here. Primary care providers, neurologists, and headache specialists alike need to be informed of such interventions and integrate these approaches, when appropriate, in the management of children with headaches.

Postexercise heart rate variability following treadmill and cycle exercise: a comparison study

The purpose of this study was to compare postexercise heart rate variability (HRV) immediately following acute bouts of treadmill (T) and cycle (C) exercise at 65% of mode-specific maximal oxygen consumption reserve (65% VO₂ R). Fourteen apparently healthy men participated in this study. On two separate and randomized days, each participant performed 30 min of exercise at 65% VO₂ R on T and C. Supine HRV was evaluated as normalized and log-transformed (ln) high-frequency (HF) and low-frequency (LF) spectral power, as well as the LF:HF ratio in 5-min segments immediately before (PRE) and at 10-15 min (POST1) and 25-30 min (POST2) following each exercise bout. There were no significant differences in the HRV values at PRE between the modalities. Following each exercise bout, lnHF was significantly lower at POST2 following C compared to T. In addition, lnLF and LF:HF were significantly higher at POST1 and POST2 following C compared to T. All HRV metrics returned towards baseline 30 min following T but remained significantly different than PRE values after C. These results suggest that following exercise at 65% of mode-specific VO₂ R, C is associated with a greater delay of postexercise HRV recovery than T in apparently healthy men.

Heart Rate Variability: New Perspectives on Physiological Mechanisms, Assessment of Self-regulatory Capacity, and Health risk

Heart rate variability, the change in the time intervals between adjacent heartbeats, is an emergent property of interdependent regulatory systems that operates on different time scales to adapt to environmental and psychological challenges. This article briefly reviews neural regulation of the heart and offers some new perspectives on mechanisms underlying the very low frequency rhythm of heart rate variability. Interpretation of heart rate variability rhythms in the context of health risk and physiological and psychological self-regulatory capacity assessment is discussed. The cardiovascular regulatory centers in the spinal cord and medulla integrate inputs from higher brain centers with afferent cardiovascular system inputs to adjust heart rate and blood pressure via sympathetic and parasympathetic efferent pathways. We also discuss the intrinsic cardiac nervous system and the heart-brain connection pathways, through which afferent information can influence activity in the subcortical, frontocortical, and motor cortex areas. In addition, the use of real-time HRV feedback to increase self-regulatory capacity is reviewed. We conclude that the heart's rhythms are characterized by both complexity and stability over longer time scales that reflect both physiological and psychological functional status of these internal self-regulatory systems.

Heritability of cardiac vagal control in 24-h heart rate variability recordings: influence of ceiling effects at low heart rates

This study estimated the heritability of 24-h heart rate variability (HRV) measures, while considering ceiling effects on HRV at low heart rates during the night. HRV was indexed by the standard deviation of all valid interbeat intervals (SDNN), the root mean square of differences between valid, successive interbeat intervals (RMSSD), and peak-valley respiratory sinus arrhythmia (pvRSA). Sleep and waking levels of cardiac vagal control were assessed in 1,003 twins and 285 of their non-twin siblings. Comparable heritability estimates were found for SDNN (46%-53%), RMSSD (49%-54%), and pvRSA (48%-57%) during the day and night. A nighttime ceiling effect was revealed in 10.7% of participants by a quadratic relationship between mean pvRSA and the interbeat interval. Excluding these participants did not change the heritability estimates. The genetic factors influencing ambulatory pvRSA, RMSSD, and SDNN largely overlap. These results suggest that gene-finding studies may pool the different cardiac vagal indices and that exclusion of participants with low heart rates is not required.

Progressive dysautonomia in two patients with xeroderma pigmentosum group A

BACKGROUND

Xeroderma pigmentosum group A (XPA) is a rare autosomal-recessive disorder caused by a defect in nucleotide excision repair. Progressive dysautonomia in patients with XPA is rarely described.

PATIENTS

Two juvenile male patients with XPA suffered from dysphagia, sleep interruption, and dysuria from the age of 10 to 19 years, successively. These autonomic symptoms might have been caused by progressive descending degeneration of cranial nerves IX and X and the sacral parasympathetic nerve, including Onuf's nucleus. One patient died from sudden cardiopulmonary arrest during postural change and tracheal suction.

RESULTS

Heart rate variability analyses of these patients revealed parasympathetic dysautonomia, based on decreased high-frequency values.

CONCLUSIONS

The insidiously progressive dysautonomia in these two patients with XPA suggested progressive descending degeneration extending from the medulla oblongata to the sacral spinal cord, which is an ominous sign of end-stage disease and a risk factor of sudden death attributable to XPA.

Relationship between post-exercise heart rate variability and skinfold thickness

This investigation aimed to determine if groupings based upon sum of skinfold thickness (SF) would reflect the differences in heart rate variability (HRV) measured for up to 30-minutes following maximal exercise, and to determine the extent in variation in post-exercise HRV that could be accounted for between the following independent variables: SF, body mass index (BMI) and maximal oxygen consumption (VO2max). SF and BMI measurements were performed on fifty-four men who completed maximal exercise testing to determine VO2max. HRV was evaluated for five-minutes before (Pre), at 0-5 minutes post- (Post1) and 25-30 minutes post-exercise (Post2), and analyzed by frequency domain [high frequency (HF) power, and HF to low frequency power ratio (LF:HF)). Two groups were formed based on being above or below the sample mean value of SF. HF and LF:HF were significantly higher and lower, respectively, at Pre and Post 2 in Group 1 compared to Group 2 (p < 0.05), which remained after controlling for VO2max and BMI. Furthermore, there was a significant trend toward baseline in post-exercise HRV in Group 1 (p < 0.05) but not in Group 2 (p > 0.05). In addition, SF was the only variable to significantly relate to the post-exercise HRV parameters (p < 0.05). The findings of this investigation suggest greater SF is related to a delayed return of HRV toward baseline from maximal exercise. The association between SF and HRV is independent of VO2max and BMI.

Effects of acupuncture on heart rate variability in beagles; preliminary results

Evidence-based animal experimental research concerning the effects of acupuncture on autonomic function was performed by two research teams from China and Austria. This study describes measurements in beagles. Heart rate variability (HRV) recordings were performed under stable conditions in Beijing, China, and the data analysis and interpretation were completed in Graz, Austria. The electrocardiograms were recorded during bilateral body acupuncture (PC6, Neiguan). Power of the low frequency (LF), high frequency (HF), and the ratio (LF/HF) changed significantly during acupuncture stimulation in beagles after injection of atropine and β -blocker. However, there was no significant change in HF power after needling the Neiguan acupoint when a cervical vagotomy has been performed. Our findings show that acupuncture can mediate the HRV even after pharmaceutical blocking of autonomic function. Acupuncture effects on HRV should rely not only on autonomic nervous system but on complete central nervous system.

Heart rate variability in the irritable bowel syndrome: a review of the literature

BACKGROUND

Patients with irritable bowel syndrome (IBS) often present with disturbances of bowel habits (diarrhea, constipation) and abdominal pain/discomfort that are modulated by the autonomic nerve system (ANS). In this narrative review, we analyzed studies that measured ANS functioning in IBS by means of heart rate variability (HRV).

METHODS

The PUBMED was searched with the keywords 'irritable bowel syndrome' AND ('heart rate variability' OR 'autonomic function'). We included only papers that used 'traditional' HRV indices and diagnosed IBS based on Manning or Rome criteria. Studies were sub-grouped according to methodological features of HRV analysis (24-h monitoring, short-term laboratory records, records during sleep).

KEY RESULTS

Most studies reported no difference in HRV when the IBS population was compared to healthy controls. Dividing the IBS sample into subgroups--according to their predominant bowel symptoms, the severity of clinical course, the presence of depressive symptoms, or a history of abuse in the past--revealed changes in autonomic functioning.

CONCLUSIONS & INFERENCES

Patients with IBS appear to experience symptoms that may be the result of changes in ANS functioning. HRV measures in clinical routine may allow assessing these changes, but further studies performed in a standardized fashion should improve the validity of HRV measures for clinical research first.

Autonomic changes in preoperative uncomplicated diabetic patients with postural changes

Diabetic autonomic neuropathy is a critical complication frequently encountered in anaesthetic and surgical practice. Power spectral analysis is a noninvasive tool for monitoring frequency analysis of heart rate variability (HRV) and autonomic control of the heart. This study examined HRV changes in preoperative diabetic patients without overt signs of autonomic dysfunction and in matched controls (n=18 per group). HRV values at -15 degrees, 0 degrees, 15 degrees, 45 degrees and sitting positions were compared between groups and for each position. HRV in diabetic patients was lower than in controls at all positions (absolute units). Low-frequency power (normalized units) and the low-frequency/high-frequency ratio increased significantly at 45 degrees and in sitting positions in controls but not in diabetic patients. Pre-existing autonomic derangements in diabetic patients without overt clinical symptoms can be aggravated by high-degree tilting or sitting positions. Consequently, great care should be taken during the intra- and perioperative management of these patients.

Heart rate variability as a measure of cardiac autonomic function in anorexia nervosa: a review of the literature

OBJECTIVE

Patients with anorexia nervosa (AN) exhibit a wide range of autonomic system disturbances; these patients have also high mortality risk due to cardio-vascular complications. Origin and pathogenesis of such changes are not absolutely clear.

METHODS

Relevant publications were drawn from PUBMED using the keywords 'anorexia nervosa' AND 'autonomic'. Fifty two abstracts were identified and screened for papers that measured the state of autonomic regulation by means of analysis of heart rate variability either during 24-hour electrocardiography (ECG) monitoring or during a short-term laboratory test. Studies selected were analysed for the number of patients included, the presence and quality of control groups, gender, age and body mass index (BMI) of patients, type of AN as well as methods used to determine heart rate variability (HRV).

RESULTS

Twenty papers on HRV in patients with anorexia were identified and analysed, revealing three distinct positions regarding changes of autonomic nervous system (ANS) functions in patients with AN. The majority of papers identified parasympathetic/sympathetic imbalance with parasympathetic dominance and decreased sympathetic modulation; others could not replicate these findings, but instead described sympathetic dominance; finally a group of papers could not identify any autonomic differences in comparison to control samples. We conclude that in its current state of analysis HRV may not be suitable for routine assessment of ANS function in AN patients but rather remains a research tool.

Lower interbreath interval complexity is associated with extubation failure in mechanically ventilated patients during spontaneous breathing trials

OBJECTIVE

To determine whether lower complexity of interbreath interval as measured with nonlinear analysis techniques will identify patients who fail to separate from mechanical ventilation after 30-minute spontaneous breathing trials (SBTs).

METHODS

Respiratory waveforms from SBT of patients in surgical or burn intensive care units were recorded for later analysis. The decision to extubate was made by attending physician. Extubated patients were observed for 48 hours; during this time, reintubation or noninvasive positive pressure ventilation was considered as a failure. Analysis of waveform data by software was performed post hoc. Sample entropy (SampEn) and other nonlinear measures were 48 hours of extubation.

RESULTS

Thirty-two patients (24 burn, 8 trauma/surgical admissions; mean age, 40.2 +/- 16.9 years; 26 men and 6 women) who were intubated >24 hours were extubated after SBT. Twenty-four patients were successfully separated from mechanical ventilation and eight failed. Age, gender, and mechanism of injury did not influence outcome. SampEn calculated for the two groups presented in this study was different with the cohort that failed extubation having a lower mean value (1.35 +/- 0.39 vs. 1.87 +/- 0.27; p < 0.001). Other nonlinear metrics were moved in concert with SampEn. The stationarity in the respiratory signal was not different between groups.

CONCLUSION

In intubated patients, the interbreath interval in those who were successfully separated from mechanical ventilation was more irregular than those who failed, as measured by nonlinear techniques. When available at bedside, these metrics may be useful markers of pulmonary health and assist in clinical decision making.

Relation of high heart rate variability to healthy longevity

The population's aging underscores the need to understand the process and define the physiologic markers predictive of healthy longevity. The findings that aging is associated with a progressive decrease in heart rate variability (HRV), an index of autonomic function, suggests that longevity might depend on preservation of autonomic function. However, little is known about late life changes. We assessed the relation between autonomic function and longevity by a cross-sectional study of HRV of 344 healthy subjects, 10 to 99 years old. The HRV was determined from 24-hour Holter records, using 4 time domain measures of HRV (the root mean square of the successive normal sinus RR interval difference [rMSSD], percentage of successive normal sinus RR intervals >50 ms [pNN50], standard deviation of all normal sinus RR intervals during a 24-hour period [SDNN], and standard deviation of the averaged normal sinus RR intervals for all 5-minute segments [SDANN]). Autonomic modulation of the 4 measures differs, permitting distinctions between changes in HRV-parasympathetic function, using rMSSD and pNN50, and HRV-sympathetic function using SDNN and SDANN. Decade values were compared using analysis of variance and t-multiple comparison testing. The HRV of all measures decreases rapidly from the second to fifth decades. It then slows. The HRV-sympathetic function continues to decrease throughout life. In contrast, the decrease in HRV-parasympathetic function reaches its nadir in the eighth decade, followed by reversal and a progressive increase to higher levels (p <0.05), more characteristic of a younger population. In conclusion, healthy longevity depends on preservation of autonomic function, in particular, HRV-parasympathetic function, despite the early age-related decrease. The eighth decade reversal of the decrease in HRV-parasympathetic function and its subsequent increase are key determinants of longevity. Persistently high HRV in the elderly represents a marker predictive of longevity.

Irreversibility of cardiac autonomic dysfunction in female adolescents diagnosed with anorexia nervosa after short- and long-term weight gain

Anorexia nervosa (AN) patients may present with cardiac autonomic system dysfunction. Power spectral analysis of heart rate variability (HRV) is a reliable noninvasive examination for the quantitative assessment of the central sympathovagal interaction that modulates cardiovascular autonomic function. In the present study, HRV parameters were assessed in female adolescent AN inpatients in the malnourished phase at admission, at discharge when achieving weight restoration, and 24-36 months after discharge, when considered remitted. Nineteen normal-weight female controls were similarly assessed. Spectral analysis of HRV was done with the fast Fourier transform algorithm. At admission and discharge, patients underwent routine laboratory examinations and responded to questionnaires assessing eating-related preoccupations, behaviors, and personality attributes, depression and anxiety. Compared with the controls, AN patients had significantly lower heart-rate and HRV, lower total power and low frequency components, elevated high frequency components, and decreased low to high frequency power ratio as assessed with the power spectral analysis at all three evaluation points. These disturbances were not correlated with the baseline laboratory and psychometric measures. Our preliminary findings suggest that female adolescent AN inpatients may have a cardiovascular autonomic dysfunction in the form of vagal abnormality present not only in malnourished patients, but also persisting following short-term and long-term weight restoration.

Dysautonomia and heart rate variability following severe traumatic brain injury

PRIMARY OBJECTIVE

To investigate disconnection theories postulated as the cause of dysautonomia following severe traumatic brain injury (TBI) through analysis of heart rate variability (HRV).

METHODS AND PROCEDURES

Data were collected on age-matched subjects with and without dysautonomia (eight subjects in each group) and 16 non-injured controls. Data included injury details, continuous electrocardiograph recordings and rehabilitation outcome.

MAIN OUTCOMES AND RESULTS

The TBI group revealed significant differences in HRV parameters both compared to controls and between dysautonomic and non-dysautonomic subjects. Additionally, HRV parameters for dysautonomic subjects showed evidence of an uncoupling of the normal relationship between heart rate and sympathetic/parasympathetic balance. HRV changes persisted for the dysautonomia group for a mean of 14 months post-injury.

CONCLUSIONS

Dysautonomic subjects revealed prolonged uncoupling of heart rate and HRV parameters compared to non-dysautonomic subjects and controls. These findings represent direct pathophysiological evidence supporting the disconnection theory postulated to produce dysautonomia following TBI.

New hope for correctional officers: an innovative program for reducing stress and health risks

This study investigated the impact of a new stress management program on physiological and psychological stress and health risk factors among 75 correctional officers. The experimental group received training in emotion self-regulation techniques intended to reduce stress and health risk factors. Practice of the techniques was enhanced by heart rate variability feedback, which helped participants learn and sustain use of the self-management tools. Measures of physiological stress included cortisol, DHEA, cholesterol, triglycerides, fasting glucose levels, 10-min resting electrocardiogram, heart rate variability, and blood pressure. Three psychological questionnaires assessed emotional stress and work-related variables. There were significant improvements in the experimental group in cholesterol, glucose, heart rate, blood pressure and positive outlook and significant reductions in overall psychological distress. There were significant increases in productivity, motivation, goal clarity, and perceived support. The mean difference between pre- and post-intervention projected health care costs was calculated to be $1,179 per employee per year.

Type D personality as a prognostic factor in heart disease: assessment and mediating mechanisms

Type D personality, a synergy between negative affectivity and social inhibition, has established itself as a serious risk factor for morbidity and mortality in patients suffering from cardiovascular disease. In this review, we summarize studies on the validity of the assessment methods of Type D, emphasizing its role as an independent vulnerability factor in the progression of cardiovascular disease. We further present evidence on the physiological characteristics that accompany the 2 psychological traits negative affectivity and social inhibition and may mediate the relation between personality and prognosis in heart disease. Further research needs to determine the mechanisms by which Type D affects the course and outcome of cardiovascular disease as well as how Type D patients may benefit from psychosocial intervention.

Comparison of time and frequency domain measures of RSA in ambulatory recordings

The extent to which various measures of ambulatory respiratory sinus arrhythmia (RSA) capture the same information across conditions in different subjects remains unclear. In this study the root mean square of successive differences (RMSSD), peak valley RSA (pvRSA), and high frequency power (HF power) were assessed during ambulatory recording in 84 subjects, of which 64 were retested after about 3 years. We used covariance structure modeling to test the equality of the correlations among three RSA measures over two test days and three conditions (daytime sitting or walking and nighttime sleep) and in groups with low, medium, and high mean heart rate (HR), or low, medium, and high mean respiration rate (RR). Results showed that ambulatory RMSSD, pvRSA, and HF power are highly correlated and that their correlation is stable across time, ambulatory conditions, and a wide range of resting HR and RR values. RMSSD appears to be the most cost-efficient measure of RSA.

Physiological reaction to work in cold microclimate

OBJECTIVES

In Poland, occupational exposure to cold microclimate is quite common (5.1 workers/1000 occupationally active people). Reports on health effects of this exposure are rather scarce. The aim of the study was to evaluate the physiological reaction in workers occupationally exposed to cold microclimate.

MATERIALS AND METHODS

Examinations were performed in a group of 102 workers (41 women and 61 men) employed at cold storage units. The mean age in the group was 39.1 +/- 9.9 years and the duration of employment under conditions of cold environment was over 12 years. The study population was divided into four groups, according to microclimate conditions (group I, ambient temperature -26 degrees C; group II, 10-14 degrees C; group III, 18-20 degrees C, control group; and group IV, 0-10 degress C). The workers underwent the following procedures: general medical examinations, cold pressor test, ambulatory blood pressure monitoring, and heart rate variability (HRV) analysis (time- and frequency-domain parameters).

RESULTS

The results were adjusted for confounding factors (age, smoking and drinking habits). The analysis of HRV parameters did not reveal any significant differences between the study groups. However, systolic and diastolic blood pressure (BP) in the daytime and at night was significantly higher in group IV compared to group II. Mean heart rate (HR) in the daytime and at night and the BP and HR day/night ratio did not differ between the groups. The analysis of BP by gender revealed that in women, systolic BP during the day and at night was significantly higher in group IV than in group II. In the group of workers with hypertension (18 men and 5 women), men reacted to the cold pressor test either by increased or decreased BP while all the women reacted by the increased BP.

CONCLUSIONS

Our findings indicated that in workers exposed to cold microclimate, the physiological reaction was dependent on gender and ambient temperature. Women seemed to be more sensitive to cold stress than men. However, this finding must be further investigated.

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.