Neurocardiology: close interaction between heart and brain

Risk factors and outcomes associated with systolic dysfunction following traumatic brain injury

Systolic dysfunction has been observed following isolated moderate-severe traumatic brain injury (Ims-TBI). However, early risk factors for the development of systolic dysfunction after Ims-TBI and their impact on the prognosis of patients with Ims-TBI have not been thoroughly investigated. A prospective observational study among patients aged 16 to 65 years without cardiac comorbidities who sustained Ims-TBI (Glasgow Coma Scale [GCS] score ≤12) was conducted. Systolic dysfunction was defined as left ventricular ejection fraction <50% or apparent regional wall motion abnormality assessed by transthoracic echocardiography within 24 hours after admission. The primary endpoint was the incidence of systolic dysfunction after Ims-TBI. The secondary endpoint was survival on discharge. Clinical data and outcomes were assessed within 24 hours after admission or during hospitalization. About 23 of 123 patients (18.7%) developed systolic dysfunction after Ims-TBI. Higher admission heart rate (odds ratios [ORs]: 1.05, 95% confidence interval [CI]: 1.02-1.08; P = .002), lower admission GCS score (OR: 0.77, 95% CI: 0.61-0.96; P = .022), and higher admission serum high-sensitivity cardiac troponin T (Hs-cTnT) (OR: 1.14, 95% CI: 1.06-1.22; P < .001) were independently associated with systolic dysfunction among patients with Ims-TBI. A combination of heart rate, GCS score, and serum Hs-cTnT level on admission improved the predictive performance for systolic dysfunction (area under curve = 0.85). Duration of mechanical ventilation, intensive care unit length of stay, and in-hospital mortality of patients with systolic dysfunction was higher than that of patients with normal systolic function (P < .05). Lower GCS (OR: 0.66, 95% CI: 0.45-0.82; P = .001), lower admission oxygen saturation (OR: 0.82, 95% CI: 0.69-0.98; P = .025), and the development of systolic dysfunction (OR: 4.85, 95% CI: 1.36-17.22; P = .015) were independent risk factors for in-hospital mortality in patients with Ims-TBI. Heart rate, GCS, and serum Hs-cTnT level on admission were independent early risk factors for systolic dysfunction in patients with Ims-TBI. The combination of these 3 parameters can better predict the occurrence of systolic dysfunction.

Age as an Effect Modifier of the Effects of Transcutaneous Auricular Vagus Nerve Stimulation (taVNS) on Heart Rate Variability in Healthy Subjects

Background: Evidence suggests that vagus nerve stimulation can modulate heart rate variability (HRV). However, there is a lack of mechanistic studies in healthy subjects assessing the effects of bilateral transcutaneous auricular vagus nerve stimulation (taVNS) on HRV. Our study aims to investigate how taVNS can influence the HRV response, including the influence of demographic variables in this response. Methods: Therefore, we conducted a randomized controlled study with 44 subjects, 22 allocated to active and 22 to sham taVNS. Results: Our results showed a significant difference between groups in the high-frequency (HF) metric. Active taVNS increased the HF metric significantly as compared to sham taVNS. Also, we found that age was a significant effect modifier of the relationship between taVNS and HF-HRV, as a larger increase in HF-HRV was seen in the older subjects. Importantly, there was a decrease in HF-HRV in the sham group. Conclusions: These findings suggest that younger subjects can adapt and maintain a constant level of HF-HRV regardless of the type of stimulation, but in the older subjects, only the active taVNS recipients were able to maintain and increase their HF-HRV. These results are important because they indicate that taVNS can enhance physiological regulation processes in response to external events.

Modification of heart rate variability induced by focal muscle vibration in patients with severe acquired brain injury

BACKGROUND/PURPOSE

Heart rate variability (HRV) is a biomarker of autonomic nervous system (ANS) reaction in persons with severe acquired brain injury (sABI) who undergo a rehabilitation treatment, such as focal muscle vibration (FMV).This study aims to evaluate if and how FMV can modulate HRV and to compare potential differences in FMV modulation in HRV between patients with sABI and healthy controls.

METHODS

Ten patients with sABI and seven healthy controls have been recruited. Each individual underwent the same stimulation protocol (four consecutive trains of vibration of 5 minutes each with a 1-minute pause). HRV was analyzed through the ratio of frequency domain heart-rate variability (LF/HF).

RESULTS

In the control group, after performing FMV, a significant LF/HF difference was observed in the in the second vibration session compared to the POST phase. Patients with SABI treated on the affected side showed a statistically significant LF/HF difference in the PRE compared to the first vibration session.

CONCLUSION

These preliminary results suggest that FMV may modify the cardiac ANS activity in patients with sABI.

From Neurocardiology to Stroke-Heart Syndrome

The Stroke-Heart syndrome is a major chapter in neurocardiology. Both brain-heart and stroke-heart correlations are based on neurophysiological studies that define and describe the relation between the central autonomic system and cardiac function and it will be presented in this narrative review. The Stroke-Heart syndrome groups the entire spectrum of cardiac changes - clinical, ECG, echocardiographic, biological, morphological - that occur in the first 30 days from the onset of stroke, especially in the first days. Their presence significantly marks the evolution and prognosis of stroke. The damage resulted from hypothalamus-pituitary-adrenal axis activation and high catecholamine release (adrenergic storm) targets mainly the myocyte and the microcirculation.The Takotsubo syndrome and Stunned myocardium are distinct forms of neurogenic myocardial ischemia - with changes in ECG, parietal motility, and biological markers - usually reversible although evolution towards cardiac dysfunction is also possible. The concept of Stroke-Heart syndrome and the brain-heart correlation brought new scientific information regarding stress cardiomyopathy or neurogenic myocardial injury.

Heart Rate Variability Indices of Student Pilots Undergo Modifications During Flight Training

INTRODUCTION: Heart rate variability (HRV) indicates the temporal fluctuation of the intervals between adjacent beats. HRV expresses neuro-cardiac activity and is generated by heart-brain interactions and dynamics related to the function of the autonomous nervous system and other components. To investigate this issue, we started a series of experiments by coupling the flight tasks of student pilots and their HRV.METHODS: Before each experimental session, the participating student was fitted with a five-electrode, three-channel Holter electrocardiogram monitor. We defined three time-phases for each training mission: before flight operations on the ground, during flight operations, and after flight operations on the ground. The HRV analysis was performed by quantifying some indices of the time domain and the frequency domain.RESULTS: The analysis of RR-wave intervals revealed two types of trends: 1) students whose RR intervals decreased during flight operations compared to before flight ground operations; and 2) students whose RR intervals increased during flight operations compared to before flight ground operations. These differences found in the RR intervals produced changes in the indices of both the time and frequency domains of the two students' samples.DISCUSSION: Flight training involves regular and advanced tasks and/or emergency situations. When this happens, the total power of the heart decreases because the RR intervals are forced toward low values. Flight activity involves continuous demanding tasks that can be potentially read by an analysis of the HRV; a high HRV ensures better management of tasks that require a greater commitment of cardiovascular function.Li Volsi G, Monte IP, Aruta A, Gulizzi A, Libra A, Mirulla S, Panebianco G, Patti G, Quattrocchi F, Bellantone V, Castorina W, Arcifa S, Papale F. Heart rate variability indices of student pilots undergo modifications during flight training. Aerosp Med Hum Perform. 2023; 94(11):835-842.

Effects of fastigial nucleus electrostimulation on cardiac nerve regeneration, neurotransmitter release, and malignant arrhythmia inducibility in a post-infarction rat model

The reduced density of cardiac autonomic nerves plays an important role in malignant arrhythmia after myocardial infarction (MI). Previous studies have shown that there is an interaction between the brain and the heart, and fastigial nucleus electrostimulation (FNS) promotes central nerve regeneration. Whether and how it can promote cardiac nerve regeneration after MI and the underlying mechanisms remain unknown. This study investigated whether FNS promotes cardiac nerve regeneration and reduces malignant arrhythmia inducibility in a post-infarction rat model. Ninety-eight Wistar rats were randomly assigned to Sham control, MI (left anterior descending coronary artery ligation without FNS), FNS (MI plus FNS), and FNL (fastigial nucleus lesion plus FNS plus MI) groups. The frequency of malignant arrhythmia was significantly lower in the FNS group than in the MI and FNL groups. The density of cardiac autonomic nerves was less in the MI group than in the Sham group, which was promoted by FNS. The nerve growth factor (NGF) mRNA expression was downregulated in the MI group compared to the Sham group, which was significantly enhanced by FNS. The expression levels of norepinephrine (NE) and acetylcholine (ACh) were higher and lower respectively in the MI and FNL groups than in the Sham group. After FNS, NE concentration was reduced and Ach level was elevated compared to the MI group. These data suggested that FNS promoted the regeneration of cardiac autonomic nerves and reduced the incidence of malignant arrhythmias in MI rat model. The mechanisms might involve up-regulation of NGF mRNA expression, decrease of NE release and increase of ACh release.

The Emerging Role of Metabolism in Brain-Heart Axis: New Challenge for the Therapy and Prevention of Alzheimer Disease. May Thioredoxin Interacting Protein (TXNIP) Play a Role?

Alzheimer disease (AD) is the most frequent cause of dementia and up to now there is not an effective therapy to cure AD. In addition, AD onset occurs decades before the diagnosis, affecting the possibility to set up appropriate therapeutic strategies. For this reason, it is necessary to investigate the effects of risk factors, such as cardiovascular diseases, in promoting AD. AD shows not only brain dysfunction, but also alterations in peripheral tissues/organs. Indeed, it exists a reciprocal connection between brain and heart, where cardiovascular alterations participate to AD as well as AD seem to promote cardiovascular dysfunction. In addition, metabolic dysfunction promotes both cardiovascular diseases and AD. In this review, we summarize the pathways involved in the regulation of the brain-heart axis and the effect of metabolism on these pathways. We also present the studies showing the role of the gut microbiota on the brain-heart axis. Herein, we propose recent evidences of the function of Thioredoxin Interacting protein (TXNIP) in mediating the role of metabolism on the brain-heart axis. TXNIP is a key regulator of metabolism at both cellular and body level and it exerts also a pathological function in several cardiovascular diseases as well as in AD.

Prognostic Significance of Fragmented QRS in Patients with Acute Ischemic Stroke

OBJECTIVES

There are studies in the literature showing the clinical importance of fragmented QRS (fQRS) in many systemic diseases. In this study, we aimed to investigate the frequency and prognostic value of fQRS on electrocardiogram (ECG) in patients with acute ischemic stroke.

MATERIALS AND METHODS

We prospectively enrolled 241 patients with acute ischemic stroke between January 2018 and January 2020. ST depression and elevation, QRS duration, PR interval, RR interval, QTc interval, QTc dispersion (QTcd), T negativity, Q wave, and fQRS were evaluated on ECG. Brain computed tomography (CT) and diffusion magnetic resonance imaging (MRI) images were obtained in the acute period and the National Institute of Health Stroke Scale (NIHSS) score was calculated for each patient. Patients were followed up for a period of two years.

RESULTS

The 241 patients comprised 121 (50.2%) men and 120 (49.8%) women with a mean age of 67.52 ± 13.00 years. In Cox regression analysis, age, NIHSS, QTcd, and fQRS were found to be independent predictors of mortality (age, hazard ratio [HR]: 1.063, p < 0.001; NIHSS, HR: 1.116, p = 0.006; QTcd, HR: 1.029, p = 0.042; fQRS, HR: 2.048, p = 0.037). Two-year mortality was higher in patients with fQRS than in patients without fQRS (31% vs. 9%, p = 0.001).

CONCLUSIONS

The fQRS is associated with poor prognosis in patients with acute ischemic stroke.

Brain-heart autonomic axis across different clinical status and severity of chronic obstructive pulmonary disease

PURPOSE

Impairment of cardiac autonomic integrity is common in chronic obstructive pulmonary disease (COPD) patients. The influence of the interaction between clinical and severity status on brain-heart autonomic axis (BHAA) is not well known. We aimed to investigate the BHAA function across different clinical status and severity of COPD.

METHODS

Cross-sectional study involving 77 COPD patients allocated into four groups according to clinical status [acute exacerbation (GAE) or stable (GST)] and severity [less (-) or more (+)]: 1) GAE-, n = 13; 2) GAE+, n = 20; 3) GST-, n = 23; and 4) GST+, n = 21. Heart rate variability (HRV) at rest and heart rate recovery (HRR) after 6-min walk test were markers of BHAA. Mean R-R, STDRR, RMSSD, RRtri, HF, LF, SD1, SD2, ApEn and SampEn were the HRV indexes and, HRR was obtained as: HR at 1st min of recovery minus peak HR.

RESULTS

A main effect of clinical status (p < 0.001) was found to vagal modulation in GAE-vs. GST- (RMSSD: 25.0 ± 14.8 vs. 12.6 ± 5.5 ms; SD1: 18.0 ± 10.6 vs. 8.9 ± 3.9 ms) and to GAE + vs. GST+ (RMSSD: 26.4 ± 15.2 vs. 15.4 ± 6.3 ms; SD1: 18.3 ± 11.2 vs. 10.9 ± 4.5 ms). An effect of clinical status (p = 0.032) and severity (p = 0.030) were found to HF (vagal) in GAE + compared to GAE- and GST+ (264.7 ± 239.0 vs. 134.7 ± 169.7 and 135.8 ± 139.7 ms²). Lower HRR was found in GAE-compared to GST- (8.0 ± 2.4 vs. 19.6 ± 2.4 bpm), p = 0.002.

CONCLUSION

In COPD patients, clinical status (AECOPD or stable) was more dominant than the severity on BHAA function. A more pronounced parasympathetic modulation was found in AECOPD patients with a lower HRR to exercise.

Acupuncture as Adjuvant Therapy for Treating Stable Angina Pectoris with Moderate Coronary Artery Lesions and the Mechanism of Heart-Brain Interactions: A Randomized Controlled Trial Protocol

Background. Stable angina pectoris with moderate coronary artery lesions is a syndrome caused by coronary artery stenosis, which endangers the quality of life. Previous acupuncture studies have shown effectiveness as a complementary therapy for ischaemic heart disease. However, more clinical evidence is needed for verification, and the mechanism should be investigated, especially involving the functional interactions between the heart and brain. Therefore, we designed a clinical trial to provide more evidence for acupuncture efficacy and its mechanism in ischaemic heart disease. Methods/Design. A total of 80 participants will be randomized to the electroacupuncture group and sham-electroacupuncture group at a ratio of 1 : 1. This trial will be conducted over 8 weeks, including a 2-week screening, 2-week treatment, and 4-week follow-up. All participants will continue to receive similar basic disease treatment procedures before the trial (including lifestyle changes and treatment for standard supportive medications, hypertension, and hyperlipidaemia, such as aspirin, metoprolol succinate, atorvastatin, and sodium fosinopril). Additionally, 12 sessions of acupuncture will be administered during the treatment period. The main outcome is Seattle Angina Questionnaire scores. The other observation indices are the heart rate variability and self-rating anxiety scale and self-rating depression scale scores. To explore mechanisms based on the hypothesis of a correlation between heart and brain function, fMRI scans will be used to detect functional brain changes in 15 patients from each group at baseline and at the end of treatment. Finally, the efficacy of acupuncture will be evaluated, and the HRV and imaging data will be correlated with clinical data to investigate the possible relationships between the brain and heart activity. Discussion. This trial will provide evidence for acupuncture as adjuvant therapy for the treatment of stable angina pectoris with moderate coronary artery lesions. The results will shed light on potential mechanisms of heart-brain interactions underlying acupuncture as an adjuvant therapy for treating ischaemic heart disease. Trials registration: Clinical Trial, https://clinicaltrials.gov/ct2/show/ChiCTR1900024937. Registered 4 August 2019, http://www.chictr.org.cn/.

The impact of sex and gender on heart-brain axis dysfunction: current concepts and novel perspectives

The heart-brain axis (HBA) recapitulates all the circuits that regulate bidirectional flow of communication between heart and brain. Several mechanisms may underlie the interdependent relationship involving heterogeneous tissues at rest and during specific target organ injury such as myocardial infarction, heart failure, arrhythmia, stroke, mood disorders, or dementia. In-depth translational studies of the HBA dysfunction under single-organ injury should include both male and female animals to develop sex- and gender-oriented prevention, diagnosis, and treatment strategies. Indeed, sex and gender are determining factors as females and males exhibit significant differences in terms of susceptibility to risk factors, age of onset, severity of symptoms, and outcome. Despite most studies having focused on the male population, we have conducted a careful appraisal of the literature investigating HBA in females. In particular, we have (i) analyzed sex-related heart and brain illnesses, (ii) recapitulated the most significant studies simultaneously conducted on cardio- and cerebro-vascular systems in female populations, and (iii) hypothesized future perspectives for the development of a gender-based approach to HBA dysfunction. Although sex- and gender-oriented research is at its infancy, the impact of sex on HBA dysfunction is opening unexpected new avenues for managing the health of female subjects exposed to risk of lifestyle multi-organ disease.

Bacomics: a comprehensive cross area originating in the studies of various brain-apparatus conversations

The brain is the most important organ of the human body, and the conversations between the brain and an apparatus can not only reveal a normally functioning or a dysfunctional brain but also can modulate the brain. Here, the apparatus may be a nonbiological instrument, such as a computer, and the consequent brain-computer interface is now a very popular research area with various applications. The apparatus may also be a biological organ or system, such as the gut and muscle, and their efficient conversations with the brain are vital for a healthy life. Are there any common bases that bind these different scenarios? Here, we propose a new comprehensive cross area: Bacomics, which comes from brain-apparatus conversations (BAC) + omics. We take Bacomics to cover at least three situations: (1) The brain is normal, but the conversation channel is disabled, as in amyotrophic lateral sclerosis. The task is to reconstruct or open up new channels to reactivate the brain function. (2) The brain is in disorder, such as in Parkinson's disease, and the work is to utilize existing or open up new channels to intervene, repair and modulate the brain by medications or stimulation. (3) Both the brain and channels are in order, and the goal is to enhance coordinated development between the brain and apparatus. In this paper, we elaborate the connotation of BAC into three aspects according to the information flow: the issue of output to the outside (BAC-1), the issue of input to the brain (BAC-2) and the issue of unity of brain and apparatus (BAC-3). More importantly, there are no less than five principles that may be taken as the cornerstones of Bacomics, such as feedforward and feedback control, brain plasticity, harmony, the unity of opposites and systems principles. Clearly, Bacomics integrates these seemingly disparate domains, but more importantly, opens a much wider door for the research and development of the brain, and the principles further provide the general framework in which to realize or optimize these various conversations.

Prognostic Value of NT-proBNP After Ischemic Stroke: A Systematic Review and Meta-analysis of Prospective Cohort Studies

BACKGROUND

Many studies have evaluated the relationship between N-terminal pro-brain natriuretic peptide (NT-proBNP) and its prognostic value in ischemic stroke. However, a widespread consensus has not been reached. Therefore, we completed a meta-analysis to evaluate the prognostic significance of NT-proBNP for mortality and functional outcome in patients with ischemic stroke.

METHODS

We performed a systematic search and review using the PubMed and EMBASE databases to identify literature that reported a correlation between NT-proBNP and mortality and functional outcome in ischemic stroke patients.

RESULTS

Eleven studies inclusive of 10,498 patients met the inclusion criteria. Elevated plasma NT-proBNP levels were associated with increased risk of mortality in ischemic stroke patients (all-cause mortality: odds ratio [OR] = 2.43, 95% confidence interval [CI] 1.62-3.64, P < .001, I²=74.3%; cardiovascular mortality: OR = 2.01, 95% CI 1.55-2.61, P < .001, I² = 42.6%). In addition, unfavorable functional outcomes were observed in patients with higher levels of NT-proBNP (OR = 1.68, 95% CI 1.13-2.50, P = .01, I² = 90.8%) after ischemic stroke.

CONCLUSIONS

This meta-analysis demonstrates that NT-proBNP could be a predictor of mortality and functional outcome in ischemic stroke patients.

A pilot study evaluating a simple cardiac dysfunction score to predict complications and survival among critically-ill patients with traumatic brain injury

PURPOSE

To describe the frequency of cardiovascular complications and cardiac dysfunction in critically-ill patients with moderate-severe traumatic brain injury (msTBI) and cardiac factors associated with in-hospital survival.

METHODS

Retrospective analysis of a prospective cohort study at a single Level-1 trauma center with a dedicated neuro-trauma intensive care unit (ICU). Adult patients admitted to the ICU with msTBI were consecutively enrolled in the prospective OPTIMISM study between November 2009 and January 2017. Cardiac dysfunction was measured using a combination of EKG parameters, echocardiography abnormalities, and peak serum troponin-I levels during the index hospitalization. These items were combined into a cardiac dysfunction index (CDI), ranging from 0 to 3 points and modeled in a Cox regression analysis.

RESULTS

A total of 326 patients with msTBI were included. For every one-point increase in the CDI, the multivariable adjusted risk of dying during the patient's acute hospitalization more than doubled (adjusted HR 2.41; 95% CI 1.29-4.53).

CONCLUSION

Cardiac dysfunction was common in patients with msTBI and independently associated with more severe brain injury and a reduction in hospital survival in this population. Further research is needed to validate the CDI and create more precise scoring tools.

Baroreflex sensitivity and heart rate variability are predictors of mortality in patients with aneurysmal subarachnoid haemorrhage

OBJECT

We aimed to investigate the link between the autonomic nervous system (ANS) impairment, assessed using baroreflex sensitivity (BRS) and heart rate variability (HRV) indices, and mortality after aneurysmal subarachnoid haemorrhage (aSAH).

METHODS

A total of 57 patients (56 ± 18 years) diagnosed with aSAH were retrospectively enrolled in the study, where 25% of patients died in the hospital. BRS was calculated using a modified cross-correlation method. Time- and frequency-domain HRV indices were calculated from a time-series of systolic peak intervals of arterial blood pressure signals. Additionally, cerebral autoregulation (CA) was assessed using the mean velocity index (Mxa), where Mxa > 0 indicates impaired CA.

RESULTS

Both BRS and HRV indices were lower in non-survivors than in survivors. The patients with disturbed BRS and HRV had more extensive haemorrhage in the H-H scale (p = .040) and were more likely to die (p = .013) when compared to patients with the intact ANS. The logistic regression model for mortality included: the APACHE II score (p = .002; OR 0.794) and the normalised high frequency power of the HRV (p < <.001; OR 0.636). A positive relationship was found between the Mxa and BRS (R = 0.48, p = .003), which suggests that increasing BRS is moderately strongly associated with worsening CA.

CONCLUSION

Our results indicated that lower values of HRV indices and BRS correlate with mortality and that there is a link between cerebral dysautoregulation and the analysed estimates of the ANS in aSAH patients.

Acute Cardiac Complications in Critical Brain Disease

Acute cardiac complications in critical brain disease should be understood as a clinical condition representing an intense brain-heart crosstalk and might mimic ischemic heart disease. Two main entities (neurogenic stunned myocardium [NSM] and stress cardiomyopathy) have been better characterized in the neurocritically ill patients and they portend worse clinical outcomes in these cases. The pathophysiology of NSM remains elusive. However, significant progress has been made on the early identification of neurocardiac compromise following acute critical brain disease. Effective prevention and treatment interventions are yet to be determined.

Acute Cardiac Complications in Critical Brain Disease

Acute cardiac complications in critical brain disease should be understood as a clinical condition representing an intense brain-heart crosstalk and might mimic ischemic heart disease. Two main entities (neurogenic stunned myocardium [NSM] and stress cardiomyopathy) have been better characterized in the neurocritically ill patients and they portend worse clinical outcomes in these cases. The pathophysiology of NSM remains elusive. However, significant progress has been made on the early identification of neurocardiac compromise following acute critical brain disease. Effective prevention and treatment interventions are yet to be determined.

The Heart as a Psychoneuroendocrine and Immunoregulatory Organ

The heart can be viewed not just as muscle pump but also as an important checkpoint for a complex network of nervous, endocrine, and immune signals. The heart is able to process neurological signals independently from the brain and to crosstalk with the endocrine and immune systems. The heart communicates with the psyche through the neuro-endocrine-immune system in a highly integrated way, in order to maintain the homeostasis of the whole body with peculiarities specific to males and females.

Using Wavelet Entropy to Demonstrate how Mindfulness Practice Increases Coordination between Irregular Cerebral and Cardiac Activities

In both the East and West, traditional teachings say that the mind and heart are somehow closely correlated, especially during spiritual practice. One difficulty in proving this objectively is that the natures of brain and heart activities are quite different. In this paper, we propose a methodology that uses wavelet entropy to measure the chaotic levels of both electroencephalogram (EEG) and electrocardiogram (ECG) data and show how this may be used to explore the potential coordination between the mind and heart under different experimental conditions. Furthermore, Statistical Parametric Mapping (SPM) was used to identify the brain regions in which the EEG wavelet entropy was the most affected by the experimental conditions. As an illustration, the EEG and ECG were recorded under two different conditions (normal rest and mindful breathing) at the beginning of an 8-week standard Mindfulness-based Stress Reduction (MBSR) training course (pretest) and after the course (posttest). Using the proposed method, the results consistently showed that the wavelet entropy of the brain EEG decreased during the MBSR mindful breathing state as compared to that during the closed-eye resting state. Similarly, a lower wavelet entropy of heartrate was found during MBSR mindful breathing. However, no difference in wavelet entropy during MBSR mindful breathing was found between the pretest and posttest. No correlation was observed between the entropy of brain waves and the entropy of heartrate during normal rest in all participants, whereas a significant correlation was observed during MBSR mindful breathing. Additionally, the most well-correlated brain regions were located in the central areas of the brain. This study provides a methodology for the establishment of evidence that mindfulness practice (i.e., mindful breathing) may increase the coordination between mind and heart activities.

Neurocardiology

Neurocardiology refers to the interplay between the nervous system and the cardiovascular system. Stress-related cardiomyopathy exemplifies the brain-heart connection and occurs in several conditions with acute brain injury that share oversympathetic activation. The brain's influences on the heart can include elevated cardiac markers, arrhythmias, repolarization abnormalities on electrocardiogram, myocardial necrosis, and autonomic dysfunction. The neurogenic stunned myocardium in aneurysmal subarachnoid hemorrhage represents one end of the spectrum, and is associated with an explosive rise in intracranial pressure that results in excess catecholamine state and possibly CBN. A brain-heart link is more known to cardiologists than neurologists. This chapter provides some insight into the pathophysiology of these pathologic neurocardiac states and their most appropriate management relevant to neurologists.

Heart rate variability in bipolar disorder: A systematic review and meta-analysis

BACKGROUND

Heart rate variability (HRV) has been suggested reduced in bipolar disorder (BD) compared with healthy individuals (HC). This meta-analysis investigated: HRV differences in BD compared with HC, major depressive disorder or schizophrenia; HRV differences between affective states; HRV changes from mania/depression to euthymia; and HRV changes following interventions.

METHODS

A systematic review and meta-analysis reported according to the PRISMA guidelines was conducted. MEDLINE, Embase, PsycINFO, The Cochrane Library and Scopus were searched. A total of 15 articles comprising 2534 individuals were included.

RESULTS

HRV was reduced in BD compared to HC (g=-1.77, 95% CI: -2.46; -1.09, P<0.001, 10 comparisons, n=1581). More recent publication year, larger study and higher study quality were associated with a smaller difference in HRV. Large between-study heterogeneity, low study quality, and lack of consideration of confounding factors in individual studies were observed.

CONCLUSIONS

This first meta-analysis of HRV in BD suggests that HRV is reduced in BD compared to HC. Heterogeneity and methodological issues limit the evidence. Future studies employing strict methodology are warranted.

Studying the pathophysiologic connection between cardiovascular and nervous systems using stem cells

The cardiovascular and nervous systems are deeply connected during development, health, and disease. Both systems affect and regulate the development of each other during embryogenesis and the early postnatal period. Specialized neural crest cells contribute to cardiac structures, and a number of growth factors released from the cardiac tissue (e.g., glial cell line-derived neurotrophic factor, neurturin, nerve growth factor, Neurotrophin-3) ensure proper maturation of the incoming parasympathetic and sympathetic neurons. Physiologically, the cardiovascular and nervous systems operate in harmony to adapt to various physical and emotional conditions to maintain homeostasis through sympathetic and parasympathetic nervous systems. Moreover, neurocardiac regulation involves a neuroaxis consisting of cortex, amygdala, and other subcortical structures, which have the ability to modify lower-level neurons in the hierarchy. Given the interconnectivity of cardiac and neural systems, when one undergoes pathological changes, the other is affected to a certain extent. In addition, there are specific neurocardiac diseases that affect both systems simultaneously, such as Huntington disease, Lewy body diseases, Friedreich ataxia, congenital heart diseases, Danon disease, and Timothy syndrome. Over the last decade, in vitro modeling of neurocardiac diseases using induced pluripotent stem cells (iPSCs) has provided an invaluable opportunity to elevate our knowledge about the brain-heart connection, since previously primary cardiomyocytes and neurons had been extremely difficult to maintain long-term in vitro. Ultimately, the ability of iPSC technology to model abnormal functional phenotypes of human neurocardiac disorders, combined with the ease of therapeutic screening using this approach, will transform patient care through personalized medicine in the future. © 2016 Wiley Periodicals, Inc.

Peripheral to central: Organ interactions in stroke pathophysiology

Stroke is associated with a high risk of disability and mortality, and with the exception of recombinant tissue-type plasminogen activator for acute stroke, most treatments have proven ineffective. Clinical translation of promising experimental therapeutics is limited by inadequate stroke models and a lack of understanding of the mechanisms underlying acute stroke and how they affect outcome. Bidirectional communication between the ischemic brain and peripheral immune system modulates stroke progression and tissue repair, while epidemiological studies have provided evidence of an association between organ dysfunction and stroke risk. This crosstalk can determine the fate of stroke patients and must be taken into consideration when investigating the pathophysiological mechanisms and therapeutic options for stroke. This review summarizes the current evidence for interactions between the brain and other organs in stroke pathophysiology in basic and clinic studies, and discusses the role of these interactions in the progression and outcome of stroke and how they can direct the development of more effective treatment strategies.

Heart failure and Alzheimer's disease

It has recently been proposed that heart failure is a risk factor for Alzheimer's disease. Decreased cerebral blood flow and neurohormonal activation due to heart failure may contribute to the dysfunction of the neurovascular unit and cause an energy crisis in neurons. This leads to the impaired clearance of amyloid beta and hyperphosphorylation of tau protein, resulting in the formation of amyloid beta plaques and neurofibrillary tangles. In this article, we will summarize the current understanding of the relationship between heart failure and Alzheimer's disease based on epidemiological studies, brain imaging research, pathological findings and the use of animal models. The importance of atherosclerosis, myocardial infarction, atrial fibrillation, blood pressure and valve disease as well as the effect of relevant medications will be discussed.

Central actions of serotonin and fluoxetine on the QT interval of the electrocardiogram in trout

QT interval of the electrocardiogram (ECG) is a measure of the duration of the ventricular depolarization and repolarization. In humans, prolongation of the QT interval is a known clinical risk factor for the development of ventricular arrhythmias including ‘Torsades de Pointes’ and possible sudden cardiac death. After oral administration, fluoxetine (FLX), as well as other selective serotonin (5-hydroxytryptamine, 5-HT) reuptake inhibitors can affect cardiac autonomic control, including the QT interval. However, the action of centrally administered FLX on the QT interval has never been explored. Consequently, using the unanesthetized trout as an animal model, we sought to compare the effects of intracerebroventricular (i.c.v.) injection of FLX (5, 15 or 25 µg) on the QT interval of the ECG with the effects observed following i.c.v. injection of 5-HT (0.05, 0.5 or 5 nmol). The QT interval was corrected for the R–R interval. The highest doses of centrally administered FLX and 5-HT induced a prolongation of the corrected QT (QTc) interval reaching a maximum value of 5–10 min after injection (+8% and +6% respectively, P < 0.05). The intra-arterial (i.a.) injections of 5-HT and FLX were without significant effect on the QTc. The i.a. injection of blockers of the autonomic nervous system indicated that the sympathetic nervous system modulated the QTc interval. In conclusion, our data demonstrate that for the first time in any animal species, cardiac electrophysiology is sensitive to central 5-HT and that FLX within the brain may disrupt the autonomic control of ventricular repolarization.

Brain-heart axis--Review Article

There has been a large confirmation over the last decades that stroke may produce cardiac changes (echocardiographic, electrocardiographic, enzymatic). In ischemic stroke, systolic dysfunction is associated with a high risk of mortality during hospitalization. A recent study demonstrated that cardiac diastolic dysfunction could also accompany acute stroke besides the systolic dysfunction already pointed out by previous studies, being a predictive marker of acute cerebrovascular events. Increased sympathetic activity is contributory, inducing a reversible cardiac myocyte damage and cardiac enzyme surges. Some of the most frequent electrocardiographic abnormalities in stroke are ST segment abnormalities and various tachyarrhythmias (especially atrial fibrillation) and bradyarrhythmias. One can infer the importance of careful and continuous electrocardiographic monitoring of the stroke patient in order to identify these quite frequent electrocardiographic alterations, as it is well known that death due to cardiac arrhythmias is common among acute stroke patients. In order to increase the diagnostic yield, a high level of NTproBNP (N-terminal of the prohormone brain natriuretic peptide) may be used as a discriminant for the patients with a higher probability of cardiac arrhythmias and mortality at presentation, during hospitalization and on the long term. In such patients, cardiac monitoring techniques are more likely to reveal abnormalities. A high BNP level may have potentially important management implications as it may signal a worse prognosis and may prompt the undertaking of certain therapeutic measures. This review summarizes the possible pathological mechanisms of heart-brain connections and their clinical and therapeutical implications.

ABBREVIATIONS

AF = atrial fibrillation, ECG = electrocardiography, HRV = heart rate variability, cTn = cardiac troponin, SAH = subarachnoid hemorrhage, CK-MB = creatine kinase-MB, BNP = brain natriuretic peptide, NT-proBNP = N-terminal of the prohormone brain natriuretic peptide, ANP = atrial natriuretic peptide, mRS = modified Rankin Scale, NIHSS = the National Institutes of Health Stroke Scale.