The autonomic nervous system and heart failure

Autonomic Dysregulation in Pulmonary Hypertension: Role of Physical Exercise

Pulmonary hypertension (PH) is a rare and severe condition characterized by increased pressure in the pulmonary circulation, often resulting in right ventricular failure and death. The autonomic nervous system (ANS) plays a crucial role in the cardiovascular and pulmonary controls. Dysfunction of ANS has been implicated in the pathogenesis of cardiopulmonary diseases. Conversely, dysfunctions in ANS can arise from these diseases, impacting cardiac and pulmonary autonomic functions and contributing to disease progression. The complex interaction between ANS dysfunction and PH plays a crucial role in the disease progression, making it essential to explore interventions that modulate ANS, such as physical exercise, to improve the treatment and prognosis of patients with PH. This review addresses autonomic dysfunctions found in PH and their implications for the cardiopulmonary system. Furthermore, we discuss how physical exercise, a significant modulator of ANS, may contribute to the prognosis of PH. Drawing from evidence of aerobic and resistance exercise training in patients and experimental models of PH, potential cardiovascular benefits of exercise are presented. Finally, we highlight emerging therapeutic targets and perspectives to better cope with the complex condition. A comprehensive understanding of the interaction between ANS and PH, coupled with targeted physical exercise interventions, may pave the way for innovative therapeutic strategies and significantly improve the treatment and prognosis of vulnerable patients.

Remote Monitoring of Sympathovagal Imbalance During Sleep and Its Implications in Cardiovascular Risk Assessment: A Systematic Review

Nocturnal sympathetic overdrive is an early indicator of cardiovascular (CV) disease, emphasizing the importance of reliable remote patient monitoring (RPM) for autonomic function during sleep. To be effective, RPM systems must be accurate, non-intrusive, and cost-effective. This review evaluates non-invasive technologies, metrics, and algorithms for tracking nocturnal autonomic nervous system (ANS) activity, assessing their CV relevance and feasibility for integration into RPM systems. A systematic search identified 18 relevant studies from an initial pool of 169 publications, with data extracted on study design, population characteristics, technology types, and CV implications. Modalities reviewed include electrodes (e.g., electroencephalography (EEG), electrocardiography (ECG), polysomnography (PSG)), optical sensors (e.g., photoplethysmography (PPG), peripheral arterial tone (PAT)), ballistocardiography (BCG), cameras, radars, and accelerometers. Heart rate variability (HRV) and blood pressure (BP) emerged as the most promising metrics for RPM, offering a comprehensive view of ANS function and vascular health during sleep. While electrodes provide precise HRV data, they remain intrusive, whereas optical sensors such as PPG demonstrate potential for multimodal monitoring, including HRV, SpO2, and estimates of arterial stiffness and BP. Non-intrusive methods like BCG and cameras are promising for heart and respiratory rate estimation, but less suitable for continuous HRV monitoring. In conclusion, HRV and BP are the most viable metrics for RPM, with PPG-based systems offering significant promise for non-intrusive, continuous monitoring of multiple modalities. Further research is needed to enhance accuracy, feasibility, and validation against direct measures of autonomic function, such as microneurography.

Impact of neonatal hyperoxia on adult cardiac autonomic function in rats: Role of angiotensin II type 1 receptor activation

Individuals born preterm present altered cardiac autonomic function, a risk factor to heart diseases. Neonatal renin-angiotensin-system activation contributes to adult cardiomyopathy in rats exposed to neonatal hyperoxia, a well-established model of preterm birth-related conditions. Central angiotensin II receptor activation is a key modulator of the autonomic drive to the heart. Whether neonatal hyperoxia leads to alteration of the cardiac autonomic function through activation of the angiotensin II receptor type 1 (AT1) is unknown and was examined in the present study. Sprague-Dawley pups were exposed to hyperoxia or room air from postnatal days 3-10. AT1 antagonist losartan or water was given orally postnatal days 8-10. Blood pressure, autonomic function, left ventricular sympathetic innervation, β-adrenergic-receptors expression, and AT1 expression in the solitary-tract-nucleus were examined in adult rats. Neonatal hyperoxia led to loss of day-night blood pressure variation, decreased heart rate variability, increased sympathovagal balance, increased AT1 expression in the solitary-tract, decreased left ventricle sympathetic innervation, and increased β1-adrenergic-receptor protein expression. Losartan prevented the autonomic changes and AT1 expression in the solitary-tract but did not impact the loss of circadian blood pressure variation nor the changes in sympathetic innervation and in β1-adrenergic-receptor expression. In conclusion, neonatal hyperoxia leads to both central autonomic and cardiac sympathetic changes, partly programmed by neonatal activation of the renin-angiotensin system.

Noninvasive risk assessment and prediction of cardiac outcomes in patients with congestive heart failure or myocardial infarction

BACKGROUND

Heart rate turbulence (HRT) and T-wave alternans (TWA), recognized as promising noninvasive markers for ventricular tachyarrhythmias and cardiac death, have been studied predominantly in Western populations, specifically in patients with myocardial infarction (MI) or heart failure (HF) with reduced ejection fraction (EF).

OBJECTIVE

The purpose of this study was to investigate the clinical implications of HRT and TWA in predicting adverse cardiac events, including cardiac death, ventricular tachyarrhythmia, and heart failure-related hospitalization (HFH).

METHODS

The K-REDEFINE study, a prospective, observational, multicenter analysis of 26 tertiary hospitals in South Korea, investigated the prognostic implications of Holter-based variables including HRT and TWA in 1116 patients with acute MI or HF (age 60.8 ± 2.9 years; 76.3% male). All participants underwent 24-hour Holter recording within 6.8 ± 16.5 days after hospitalization. The primary composite outcome included cardiac death, ventricular tachyarrhythmias, and HFH.

RESULTS

During 4.3 ± 1.2 years of follow-up, impaired HRT demonstrated the most powerful predictive value for the composite (adjusted hazard ratio [aHR] 3.41, 95% confidence interval [CI] 2.27-5.13) or individual events: cardiac death (aHR 4.08, 95% CI 2.17-7.70), ventricular tachyarrhythmia (aHR 3.72, 95% CI 1.29-10.77), and HFH (aHR 4.32, 95% CI 2.25-8.28). The predictive power of abnormal HRT remained consistently significant across subgroups of MI and HF, or across varying degrees of EF. When combined with reduced EF (<50%), the predictive power was further enhanced. However, abnormal TWA was significantly associated only with the composite outcome (aHR 1.51, 95% CI 1.06-2.16).

CONCLUSION

The K-REDEFINE study identified abnormal HRT, mostly assessed within 1 month after hospitalization, as a significant predictor not only for cardiac death and ventricular tachyarrhythmia but also for HFH.

Association between early blood glucose dynamic trajectory and mortality for critically ill patients with heart failure: Insights from real-world data

AIMS

This study endeavors to explore the ramifications of early dynamic blood glucose (BG) trajectories within the initial 48 h of intensive care unit (ICU) admission on mortality among critically ill heart failure (HF) patients.

METHODS

The study employed a retrospective observational design, analyzing dynamic BG data of HF patients from the Medical Information Mart for Intensive Care IV database. The BG trajectory subphenotypes were identified using the hierarchical clustering based on the dynamic time-warping algorithm. The primary outcome of the study was 28-day mortality, with secondary outcomes including 180-day and 1-year mortality.

RESULTS

We screened a total of 21,098 HF patients and finally 15,092 patients were included in the study. Our results identified three distinct BG trajectory subphenotypes: increasing (n = 3503), stabilizing (n = 6250), and decreasing (n = 5339). The increasing subphenotype was associated with the highest mortality risk at 28 days, 180 days, and 1 year. The stabilizing and decreasing subphenotypes showed significantly lower mortality risks across all time points, with hazard ratios ranging from 0.85 to 0.88 (P<0.05 for all). Sensitivity analyses confirmed the robustness of these findings after adjusting for various covariates.

CONCLUSIONS

Increasing BG trajectory within 48 h of admission is significantly associated with higher mortality in patients with HF. It is necessary to devote greater attention to the early BG dynamic changes in HF patients to optimize clinical BG management and enhance patient prognosis.

Circulating brain-derived neurotrophic factor levels and heart failure: A systematic review and meta-analysis

AIMS

Biomarkers are paramount for managing heart failure (HF) patients as prognostic and therapeutic efficacy index tools. Systemic levels of brain-derived neurotrophic factor (BDNF) can add to the HF biomarker scenario, allowing for potentiated efficacy in diagnosis, prognostic stratification, and prediction of patient response to a given therapeutic intervention because BDNF is one of the primary rulers of myocardial function. Yet, whether BDNF is a reliable clinical biomarker awaits clinical validation. Hence, we aimed to answer this relevant question via a systematic review and meta-analysis of existing studies.

METHODS AND RESULTS

International databases, including PubMed, Scopus, Embase, and the Web of Science, were comprehensively searched for studies assessing BDNF levels in patients with HF versus non-HF controls or as a prognostic factor for HF complications. Data were extracted and analysed by random-effect meta-analysis. Standardized mean difference (SMD) and 95% confidence intervals (CIs) were computed to pool the results of studies. We included 11 studies in the final review, among which six underwent meta-analysis. These studies analysed 1420 HF patients, with a mean age of 65.4 ± 11.2 years. Meta-analysis revealed that patients with HF had significantly lower circulating BDNF levels than healthy controls (SMD -2.47, 95% CI -4.39 to -0.54, P-value = 0.01). Moreover, patients with higher New York Heart Association functional classification had lower levels of BDNF. Adverse clinical outcomes such as all-cause mortality and HF rehospitalization were also associated with lower levels of BDNF in individual studies.

CONCLUSIONS

BDNF levels are decreased in patients with HF. Most importantly, we observed an association between lower BDNF levels and poor prognosis in patients with HF. Our study supports BDNF as an easy-to-dose diagnostic and prognostic biomarker to be implemented in clinical practice for HF. Further studies are warranted to address this ability specifically.

Neurocardiology: translational advancements and potential

In our original white paper published in the The Journal of Physiology in 2016, we set out our knowledge of the structural and functional organization of cardiac autonomic control, how it remodels during disease, and approaches to exploit such knowledge for autonomic regulation therapy. The aim of this update is to build on this original blueprint, highlighting the significant progress which has been made in the field since and major challenges and opportunities that exist with regard to translation. Imbalances in autonomic responses, while beneficial in the short term, ultimately contribute to the evolution of cardiac pathology. As our understanding emerges of where and how to target in terms of actuators (including the heart and intracardiac nervous system (ICNS), stellate ganglia, dorsal root ganglia (DRG), vagus nerve, brainstem, and even higher centres), there is also a need to develop sensor technology to respond to appropriate biomarkers (electrophysiological, mechanical, and molecular) such that closed-loop autonomic regulation therapies can evolve. The goal is to work with endogenous control systems, rather than in opposition to them, to improve outcomes.

Characterisation and distribution of human coronary artery innervation

BACKGROUND

A detailed understanding of the sympathetic innervation of coronary arteries is relevant to facilitate the development of novel treatment approaches.

AIMS

This study aimed to quantitatively examine periarterial innervation in human epicardial coronary arteries.

METHODS

Coronary arteries with adjacent epicardial adipose tissue were excised along the left main coronary artery (LMCA), left anterior descending artery (LAD), left circumflex artery (LCx), and right coronary artery (RCA) from 28 body donors and examined histologically. Immunofluorescence staining was performed to characterise sympathetic nerve fibres.

RESULTS

A total of 42,573 nerve fibres surrounding 100 coronary arteries (LMCA: n=21, LAD: n=27, LCx: n=26, RCA: n=26) were analysed. The nerve fibre diameter decreased along the vessel course (median [interquartile range]): (proximal 46 μm [31-73], middle 38 μm [26-58], distal 31 μm [22-46]; p<0.001), with the largest nerve fibre diameter along the LMCA (50 μm [31-81]), followed by the LAD (42 μm [27-72]; p<0.001). The total nerve fibre density was highest along the RCA (123 nerves/cm² [82-194]). Circumferentially, nerve density was higher in the myocardial tissue area of the coronary arteries (132 nerves/cm² [76-225]) than in the epicardial tissue area (101 nerves/cm² [61-173]; p<0.001). The median lumen-nerve distance was smallest around the LMCA (2.2 mm [1.2-4.1]), followed by the LAD (2.5 mm [1.1-4.5]; p=0.005).

CONCLUSIONS

Human coronary arteries are highly innervated with sympathetic nerve fibres, with significant variation in the distribution and density. Understanding these patterns informs pathophysiological understanding and, potentially, the development of catheter-based approaches for cardiac autonomic modulation.

Cardiac Neuroanatomy and Fundamentals of Neurocardiology

Cardiac control is mediated via nested-feedback reflex control networks involving the intrinsic cardiac ganglia, intra-thoracic extra-cardiac ganglia, spinal cord, brainstem, and higher centers. This control system is optimized to respond to normal physiologic stressors; however, it can be catastrophically disrupted by pathologic events such as myocardial ischemia. In fact, it is now recognized that cardiac disease progression reflects the dynamic interplay between adverse remodeling of the cardiac substrate coupled with autonomic dysregulation. With advances in understanding of this network dynamic in normal and pathologic states, neuroscience-based neuromodulation therapies can be devised for the management of acute and chronic cardiac pathologies.

Heart rate variability: reference values and role for clinical profile and mortality in individuals with heart failure

AIMS

To establish reference values and clinically relevant determinants for measures of heart rate variability (HRV) and to assess their relevance for clinical outcome prediction in individuals with heart failure.

METHODS

Data from the MyoVasc study (NCT04064450; N = 3289), a prospective cohort on chronic heart failure with a highly standardized, 5 h examination, and Holter ECG recording were investigated. HRV markers were selected using a systematic literature screen and a data-driven approach. Reference values were determined from a healthy subsample. Clinical determinants of HRV were investigated via multivariable linear regression analyses, while their relationship with mortality was investigated by multivariable Cox regression analyses.

RESULTS

Holter ECG recordings were available for analysis in 1001 study participants (mean age 64.5 ± 10.5 years; female sex 35.4%). While the most frequently reported HRV markers in literature were from time and frequency domains, the data-driven approach revealed predominantly non-linear HRV measures. Age, sex, dyslipidemia, family history of myocardial infarction or stroke, peripheral artery disease, and heart failure were strongly related to HRV in multivariable models. In a follow-up period of 6.5 years, acceleration capacity [HRperSD 1.53 (95% CI 1.21/1.93), p = 0.0004], deceleration capacity [HRperSD: 0.70 (95% CI 0.55/0.88), p = 0.002], and time lag [HRperSD 1.22 (95% CI 1.03/1.44), p = 0.018] were the strongest predictors of all-cause mortality in individuals with heart failure independently of cardiovascular risk factors, comorbidities, and medication.

CONCLUSION

HRV markers are associated with the cardiovascular clinical profile and are strong and independent predictors of survival in heart failure. This underscores clinical relevance and interventional potential for individuals with heart failure.

CLINICALTRIALS

GOV IDENTIFIER

NCT04064450.

Neuromodulatory co-expression in cardiac vagal motor neurons of the dorsal motor nucleus of the vagus

Vagal innervation is well known to be crucial to the maintenance of cardiac health, and to protect and recover the heart from injury. Only recently has this role been shown to depend on the activity of the underappreciated dorsal motor nucleus of the vagus (DMV). By combining neural tracing, transcriptomics, and anatomical mapping in male and female Sprague-Dawley rats, we characterize cardiac-specific neuronal phenotypes in the DMV. We find that the DMV cardiac-projecting neurons differentially express pituitary adenylate cyclase-activating polypeptide (PACAP), cocaine- and amphetamine-regulated transcript (CART), and synucleins, as well as evidence that they participate in neuromodulatory co-expression involving catecholamines. The significance of these findings is enhanced by previous knowledge of the role of PACAP at the heart and of the other neuromodulators in peripheral vagal targets.

Combination therapy of acupuncture and herbal medicine for heart failure: A systematic review and meta-analysis

BACKGROUND

Heart failure (HF) is characterized by functional or structural dysfunction of the heart, resulting in impaired blood ejection or ventricular filling. Conventional Western Medicine (CWM) remains the mainstay of treatment for HF; however, the occurrence of adverse events (AEs) necessitates the exploration of alternative treatments. Herbal medicine and acupuncture are adjunctive therapies for HF and have shown potential for improving heart function. This systematic review and meta-analysis aimed to assess the effectiveness and safety of acupuncture and herbal medicine in treating HF.

METHODS

PubMed, Embase, Cochrane Central Register of Controlled Trials, China National Knowledge Infrastructure, Citation Information by National Institute of Informatics, KoreaMed, Research Information Sharing Service, and DBpia were searched for randomized controlled trials (RCTs) evaluating the effects of acupuncture and herbal medicine along with CWM as adjunctive treatments for HF, published from inception to May 31, 2024. Treatment effectiveness was determined by evaluating the left ventricular ejection fraction as the primary metric, along with the measurement of the total effective rate, brain natriuretic peptide level, N-terminal prohormone of brain natriuretic peptide level, left ventricular end-diastolic volume, and left ventricular end-systolic volume; the administration of the Minnesota Living with Heart Failure Questionnaire; and the conduct of a 6-minute walk test. Treatment safety was evaluated based on the incidence of AEs. The methodological quality of all included RCTs was assessed using the Cochrane risk of bias tool. A meta-analysis was performed using Review Manager, version 5.4.1.

RESULTS

Of the 133 publications identified, 8 RCTs met the inclusion criteria. The meta-analysis showed significant improvements in left ventricular ejection fraction, brain natriuretic peptide levels, N-terminal prohormone of brain natriuretic peptide levels, left ventricular end-systolic volume, left ventricular end-diastolic volume, and 6-minute walk test results. Additionally, significant differences were observed in the total effective rate and Minnesota Living with Heart Failure Questionnaire responses. No significant medication-related AEs occurred in the intervention group. Conversely, 7 control patients developed well-known AEs associated with CWM.

CONCLUSION

Acupuncture combined with herbal medicine and CWM is more effective than CWM alone, indicating a safe treatment approach. Consequently, the proactive administration of acupuncture alongside herbal medicine to patients with HF can be undertaken without concerns regarding AEs.

Heart failure causally affects the brain cortical structure: a Mendelian randomization study

Background

The effects of heart failure (HF) on cortical brain structure remain unclear. Therefore, the present study aimed to investigate the causal effects of heart failure on cortical structures in the brain using Mendelian randomization (MR) analysis.

Methods

We conducted a two-sample MR analysis utilizing genetically-predicted HF trait, left ventricular ejection fraction (LVEF), and N-terminal prohormone brain natriuretic peptide (NT-proBNP) levels to examine their effects on the cortical surface area (SA) and thickness (TH) across 34 cortical brain regions. Genome-wide association study summary data were extracted from studies by Rasooly (1,266,315 participants) for HF trait, Schmidt (36,548 participants) for LVEF, the SCALLOP consortium (21,758 participants) for NT-proBNP, and the ENIGMA Consortium (51,665 participants) for cortical SA and TH. A series of MR analyses were employed to exclude heterogeneity and pleiotropy, ensuring the stability of the results. Given the exploratory nature of the study, p-values between 1.22E-04 and 0.05 were considered suggestive of association, and p-values below 1.22E-04 were defined as statistically significant.

Results

In this study, we found no significant association between HF and cortical TH or SA (all p > 1.22E-04). We found that the HF trait and elevated NT-proBNP levels were not associated with cortical SA, but were suggested to decrease cortical TH in the pars orbitalis, lateral orbitofrontal cortex, temporal pole, lingual gyrus, precuneus, and supramarginal gyrus. Reduced LVEF was primarily suggested to decrease cortical SA in the isthmus cingulate gyrus, frontal pole, postcentral gyrus, cuneus, and rostral middle frontal gyrus, as well as TH in the postcentral gyrus. However, it was suggested to causally increase in the SA of the posterior cingulate gyrus and medial orbitofrontal cortex and the TH of the entorhinal cortex and superior temporal gyrus.

Conclusion

We found 15 brain regions potentially affected by HF, which may lead to impairments in cognition, emotion, perception, memory, language, sensory processing, vision, and executive control in HF patients.

Sympathetic dysfunction is associated with worse fatigue and early and subtle symptoms in heart failure: an exploratory sex-stratified analysis

AIMS

Physical symptoms impact patients with heart failure (HF) despite treatment advancements; however, our understanding of the pathogenic mechanisms underlying HF symptoms remains limited, including sex differences therein. The objective of this study was to quantify associations between sympathetic markers [norepinephrine (NE) and 3,4-dihydroxyphenylglycol (DHPG)] and physical symptoms in patients with HF and to explore sex differences in these associations.

METHODS AND RESULTS

We performed a secondary analysis of combined data from two studies: outpatients with HF (n = 111), and patients prior to left ventricular assist device implantation (n = 38). Physical symptoms were measured with the Heart Failure Somatic Perception Scale (HFSPS) dyspnoea and early/subtle symptom subscales and the Functional Assessment in Chronic Illness Therapy Fatigue Scale (FACIT-F) to capture dyspnoea, early symptoms of decompensation, and fatigue. Norepinephrine and DHPG were measured with high-performance liquid chromatography with electrochemical detection. Multivariate linear regression was used to quantify associations between symptoms and sympathetic markers. The sample (n = 149) was 60.8 ± 15.7 years, 41% women, and 71% non-ischaemic aetiology. Increased plasma NE and NE:DHPG ratio were associated with worse FACIT-F scores (P = 0.043 and P = 0.013, respectively). Increased plasma NE:DHPG ratio was associated with worse HFSPS early/subtle symptoms (P = 0.025). In sex-stratified analyses, increased NE:DHPG ratio was associated with worse FACIT-F scores (P = 0.011) and HFSPS early/subtle scores (P = 0.022) among women but not men.

CONCLUSION

In patients with HF, sympathetic dysfunction is associated with worse fatigue and early/subtle physical symptoms with associations stronger in women than men.

Cardiac Uptake of the Adrenergic Imaging Agent meta-Iodobenzylguanidine (mIBG) Is Mediated by Organic Cation Transporter 3 (Oct3)

Heart failure (HF) is a chronic disease affecting 1%-2% of the global population.123I-labeled meta-iodobenzylguanidine (mIBG) is US Food and Drug Administration-approved for cardiac imaging and prognosis risk assessment in patients with HF. As a norepinephrine analog, mIBG is believed to be transported into adrenergic nerve terminals by the neuronal norepinephrine transporter (NET) and hence image sympathetic innervation of the myocardium. We previously showed that mIBG is an excellent substrate of organic cation transporter 3 (OCT3), an extraneuronal transporter expressed in cardiomyocytes. Here, we evaluated the in vivo impact of Oct3 on mIBG disposition and tissue distribution using Oct3 knockout mice. Oct3 +/+ and Oct3 -/- mice were administered with mIBG intravenously, and mIBG plasma pharmacokinetics and tissue exposures were determined. In Oct3 +/+ mice, mIBG exhibited extensive accumulation in multiple tissues (heart, salivary gland, liver, and adrenal gland). No difference was observed in overall plasma exposure between Oct3 +/+ and Oct3 -/- mice. Strikingly, cardiac mIBG was depleted in Oct3 -/- mice, resulting in 83% reduction in overall cardiac exposure (AUC0-24 h: 12.7 vs. 2.1 μg × h/g). mIBG tissue exposure (AUC0-24 h) was also reduced by 66%, 36%, and 31% in skeletal muscle, salivary gland, and lung, respectively, in Oct3 -/- mice. Our data demonstrated that Oct3 is the primary transporter responsible for cardiac mIBG uptake in vivo and suggested that cardiac mIBG imaging mainly measures OCT3 activity in cardiomyocytes but not NET-mediated uptake in adrenergic nerve endings. Our findings challenge the current paradigm in interpreting cardiac mIBG imaging results and suggest OCT3 as a potential genetic risk marker for HF prognosis. SIGNIFICANCE STATEMENT: 123I-labeled meta-iodobenzylguanidine is used for cardiac imaging and risk assessment in heart failure patients. Contrary to the current belief that meta-iodobenzylguanidine (mIBG) tracks cardiac sympathetic innervation due to its uptake by the neuronal norepinephrine transporter, the authors demonstrated that cardiac mIBG uptake is mediated by the extraneuronal transporter Oct3. Their findings warrant a re-evaluation of the scientific rationale behind cardiac mIBG scan and further suggest organic cation transporter 3 as a risk factor for disease progression in heart failure patients.

Stem cell-derived cardiomyocytes expressing a dominant negative pacemaker HCN4 channel do not reduce the risk of graft-related arrhythmias

Background

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) show tremendous promise for cardiac regeneration following myocardial infarction (MI), but their transplantation gives rise to transient ventricular tachycardia (VT) in large-animal MI models, representing a major hurdle to translation. Our group previously reported that these arrhythmias arise from a focal mechanism whereby graft tissue functions as an ectopic pacemaker; therefore, we hypothesized that hPSC-CMs engineered with a dominant negative form of the pacemaker ion channel HCN4 (dnHCN4) would exhibit reduced automaticity and arrhythmogenic risk following transplantation.

Methods

We used CRISPR/Cas9-mediated gene-editing to create transgenic dnHCN4 hPSC-CMs, and their electrophysiological behavior was evaluated in vitro by patch-clamp recordings and optical mapping. Next, we transplanted WT and homozygous dnHCN4 hPSC-CMs in a pig MI model and compared post-transplantation outcomes including the incidence of spontaneous arrhythmias and graft structure by immunohistochemistry.

Results

In vitro dnHCN4 hPSC-CMs exhibited significantly reduced automaticity and pacemaker funny current (I f ) density relative to wildtype (WT) cardiomyocytes. Following transplantation with either dnHCN4 or WT hPSC-CMs, all recipient hearts showed transmural infarct scar that was partially remuscularized by scattered islands of human myocardium. However, in contrast to our hypothesis, both dnHCN4 and WT hPSC-CM recipients exhibited frequent episodes of ventricular tachycardia (VT).

Conclusions

While genetic silencing of the pacemaker ion channel HCN4 suppresses the automaticity of hPSC-CMs in vitro, this intervention is insufficient to reduce VT risk post-transplantation in the pig MI model, implying more complex mechanism(s) are operational in vivo.

Reduced congestion and improved response to a fluid/sodium challenge in chronic heart failure patients after initiation of sacubitril/valsartan: The NATRIUM-HF study

AIMS

The effects of initiating sacubitril/valsartan in patients with stable heart failure with reduced ejection fraction (HFrEF) on response to fluid and sodium expansion are unknown.

METHODS AND RESULTS

We have explored changes in natriuresis, diuresis, and congestion in response to the administration of intravenous fluid/sodium load in patients with HFrEF before as compared to after the initiation of sacubitril/valsartan. At baseline (before sacubitril/valsartan initiation) and 2 and 3 months after the initiation, patients underwent an evaluation that consisted of three phases of 3 h: the rest phase (0-3 h), the load phase (3-6 h) in which 1 L of intravenous Ringer solution was administered, and the diuretic phase (6-9 h) at the beginning of which furosemide was administered. Overall, 216 patients completed the study. In comparison to baseline values, at 2 and 3 months after sacubitril/valsartan initiation, patients' diuresis and natriuresis in response to Ringer administration significantly increased (mean difference: 38.8 [17.38] ml, p = 0.0040, and 9.6 [2.02] mmol, p < 0.0001, respectively). Symptoms and signs of congestion after the fluid/sodium challenge were significantly decreased at months 2 and 3 compared to baseline. Compared to baseline, there was also an increment of natriuresis after furosemide administration on sacubitril/valsartan (9.8 [5.13] mmol, p = 0.0167). There was a significant decrease in body weight in subsequent visits when compared to baseline values (-0.50 [-12.7, 7.4] kg at 2 months, and -0.75 [-15.9, 7.5] kg at 3 months; both p < 0.0001).

CONCLUSIONS

The initiation of sacubitril/valsartan in HFrEF patients was associated with improvements in natriuresis, diuresis, and weight loss and better clinical adaptation to potentially decongestive stressors.

Electroacupuncture Improves Cardiac Function via Inhibiting Sympathetic Remodeling Mediated by Promoting Macrophage M2 Polarization in Myocardial Infarction Mice

Electroacupuncture (EA) at the Neiguan acupoint (PC6) has shown significant cardioprotective effects. Sympathetic nerves play an important role in maintaining cardiac function after myocardial infarction (MI). Previous studies have found that EA treatment may improve cardiac function by modulating sympathetic remodeling after MI. However, the mechanism in how EA affects sympathetic remodeling and improves cardiac function remains unclear. The aim of this study is to investigate the cardioprotective mechanism of EA after myocardial ischemic injury by improving sympathetic remodeling and promoting macrophage M2 polarization. We established a mouse model of MI by occluding coronary arteries in male C57/BL6 mice. EA treatment was performed at the PC6 with current intensity (1 mA) and frequency (2/15 Hz). Cardiac function was evaluated using echocardiography. Heart rate variability in mice was assessed via standard electrocardiography. Myocardial fibrosis was evaluated by Sirius red staining. Levels of inflammatory factors were assessed using RT-qPCR. Sympathetic nerve remodeling was assessed through ELISA, western blotting, immunohistochemistry, and immunofluorescence staining. Macrophage polarization was evaluated using flow cytometry. Our results indicated that cardiac systolic function improved significantly after EA treatment, with an increase in fractional shortening and ejection fraction. Myocardial fibrosis was significantly mitigated in the EA group. The sympathetic nerve marker tyrosine hydroxylase and the nerve sprouting marker growth-associated Protein 43 were significantly reduced in the EA group, indicating that sympathetic remodeling was significantly reduced. EA treatment also promoted macrophage M2 polarization, reduced levels of inflammatory factors TNF-α, IL-1β, and IL-6, and decreased macrophage-associated nerve growth factor in myocardial tissue. To sum up, our results suggest that EA at PC6 attenuates sympathetic remodeling after MI to promote macrophage M2 polarization and improve cardiac function.

Hypertension increases sympathetic neuron activity by enhancing intraganglionic cholinergic collateral connections

Autonomic dysregulation, including sympathetic hyperactivity, is a common feature of hypertension (HT) and other cardiovascular diseases. The CNS plays a role in driving chronic sympathetic activation in disease, but several lines of evidence suggest that neuroplasticity in the periphery may also contribute. The potential contribution of postganglionic sympathetic neurons to sustained sympathetic hyperactivity is not well understood. We recently discovered that noradrenergic sympathetic neurons in the stellate ganglion (SG) have excitatory cholinergic collateral connections to other neurons within the ganglion. We hypothesize that remodelling of these neurons and increased cholinergic collateral transmission contributes to sustained sympathetic hyperactivity in cardiovascular diseases, including HT. To test that hypothesis, we examined the activity of sympathetic neurons in isolated SG under control conditions and after 1 week of HT induced by peripheral angiotensin II infusion, using whole-cell patch clamp recordings. Despite the absence of central inputs, we observed elevated spontaneous activity and synaptic transmission in sympathetic SG neurons from hypertensive mice that required generation of action potentials. Genetically disrupting cholinergic transmission in noradrenergic neurons decreased basal neuronal activity and prevented angiotensin II-mediated enhancement of activity. Similar changes in activity, driven by increased collateral transmission, were identified in cardiac projecting neurons and neurons projecting to brown adipose tissue. These changes were not driven by altered A-type K+ currents. This suggests that HT stimulates increased activity throughout the intraganglionic network of collateral connections, contributing to the sustained sympathetic hyperactivity characteristic in cardiovascular disease. KEY POINTS: Sympathetic neurons in ganglia isolated from angiotensin II-treated hypertensive mice are more active than neurons from control mice despite the absence of central activation. The enhanced activity is the result of a ganglionic network of cholinergic collaterals, rather than altered intrinsic excitability. Increased neuronal activity was observed in both cardiac neurons and brown adipose tissue-projecting neurons, which are not involved in cardiovascular homeostasis.

Myocardial infarction causes sex-dependent dysfunction in vagal sensory glutamatergic neurotransmission that is mitigated by 17β-estradiol

Parasympathetic dysfunction after chronic myocardial infarction (MI) is known to predispose ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]). VT/VF after MI is more common in males than females. The mechanisms underlying the decreased vagal tone and the associated sex difference in the occurrence of VT/VF after MI remain elusive. In this study, using optogenetic approaches, we found that responses of glutamatergic vagal afferent neurons were impaired following chronic MI in male mice, leading to reduced reflex efferent parasympathetic function. Molecular analyses of vagal ganglia demonstrated reduced glutamate levels, accompanied by decreased mitochondrial function and impaired redox status in infarcted males versus sham animals. Interestingly, infarcted females demonstrated reduced vagal sensory impairment, associated with greater vagal ganglia glutamate levels and decreased vagal mitochondrial dysfunction and oxidative stress compared with infarcted males. Treatment with 17β-estradiol mitigated this pathological remodeling and improved vagal neurotransmission in infarcted male mice. These data suggest that a decrease in efferent vagal tone following MI results from reduced glutamatergic afferent vagal signaling that may be due to impaired redox homeostasis in the vagal ganglia, which subsequently leads to pathological remodeling in a sex-dependent manner. Importantly, estrogen prevents pathological remodeling and improves parasympathetic function following MI.

Vagus nerve stimulation alleviates cardiac dysfunction and inflammatory markers during heart failure in rats

Vagus nerve stimulation (VNS) is under clinical investigation as a therapy for heart failure with reduced ejection fraction (HFrEF). This study aimed to investigate its therapeutic effects on three main components of heart failure: cardiac function, cardiac remodeling and central neuroinflammation using a pressure overload (PO) rat model. Male Sprague-Dawley rats were divided into four groups: PO, PO + VNS, PO + VNS sham, and controls. All rats, except controls, underwent a PO surgery to constrict the thoracic aorta (~50 %) to induce HFrEF. Open loop VNS therapy was continuously administered to PO + VNS rats at 20 Hz, 1.0 mA for 60 days. Evaluation of cardiac function and structure via echocardiograms showed decreases in stroke volume and relative ejection fraction and increases in the internal diameter of the left ventricle during systole and diastole in PO rats (p < 0.05). However, these PO-induced adverse changes were alleviated with VNS therapy. Additionally, PO rats exhibited significant increases in myocyte cross sectional areas indicating hypertrophy, along with significant increases in myocardial fibrosis and apoptosis, all of which were reversed by VNS therapy (p < 0.05). Furthermore, VNS mitigated microglial activation in two central autonomic nuclei: the paraventricular nucleus of the hypothalamus and locus coeruleus. These findings demonstrate that when VNS therapy is initiated at an early stage of HFrEF progression (<10 % reduction in relative ejection fraction), the supplementation of vagal activity is effective in restoring multi organ homeostasis in a PO model.

The burden of cardiovascular disease and risk for subsequent major adverse cardiovascular events in survivors of childhood cancer: a prospective, longitudinal analysis from the St Jude Lifetime Cohort Study

BACKGROUND

The effect of the increasing lifetime burden of non-major cardiovascular conditions on risk for a subsequent major adverse cardiovascular event among survivors of childhood cancer has not been assessed. We aimed to characterise the prevalence of major adverse cardiovascular events and their association with the cumulative burden of non-major adverse cardiovascular events in childhood cancer survivors.

METHODS

This is a longitudinal cohort study with participant data obtained from an ongoing cohort study at St Jude Children's Research Hospital: the St Jude Lifetime Cohort Study (SJLIFE). Prospective clinical follow-up was of 5-year survivors of childhood cancer who were diagnosed when aged younger than 25 years from 1962 to 2012. Age-frequency, sex-frequency, and race-frequency matched community-control participants completed a similar one-time clinical assessment. 22 cardiovascular events were graded using a St Jude Children's Research Hospital-modified version of the National Cancer Institute Common Terminology Criteria for Adverse Events (version 4.03). Cumulative incidence and burden of the primary outcome of major adverse cardiovascular events (cardiomyopathy, myocardial infarction, stroke, and other cardiovascular-related mortality) were estimated. Rate ratios (RR) of the association of major adverse cardiovascular events with 22 non-major adverse cardiovascular events were estimated using multivariable piecewise-exponential regression adjusting for attained age, age at diagnosis, sex, race and ethnicity, treatment era, diagnosis of diabetes, and exposure to cardiotoxic cancer therapies. The St Jude Lifetime Cohort study is registered with ClinicalTrials.gov, NCT00760656, and is ongoing.

FINDINGS

9602 5-year survivors of childhood cancer, and 737 community controls were included in the longitudinal follow-up (from Sept 13, 2007, to Dec 17, 2021). The median follow-up was 20·3 years (IQR 12·0-31·4) from the date of primary cancer diagnosis (4311 [44.9%] were females). By the age of 50 years (analysis stopped at age 50 years due to the low number of participants older than that age), the cumulative incidence of major adverse cardiovascular events among survivors was 17·7% (95% CI 15·9-19·5) compared with 0·9% (0·0-2·1) in the community controls. The cumulative burden of major adverse cardiovascular events in survivors was 0·26 (95% CI 0·23-0·29) events per survivor compared with 0·009 (0·000-0·021) events per community control participant. Increasing cumulative burden of grade 1-4 non-major adverse cardiovascular events was associated with an increased future risk of major adverse cardiovascular events (one condition: RR 4·3, 95% CI 3·1-6·0; p<0·0001; two conditions: 6·6, 4·6-9·5; p<0·0001; and three conditions: 7·7, 5·1-11·4; p<0·0001). Increased risk for major adverse cardiovascular events was observed with specific subclinical conditions (eg, grade 1 arrhythmias [RR 1·5, 95% CI 1·2-2·0; p=0·0017]), grade 2 left ventricular systolic dysfunction (2·2, 1·6-3·1; p<0·0001), grade 2 valvular disorders (2·2, 1·2-4·0; p=0·013), but not grade 1 hypercholesterolaemia, grade 1-2 hypertriglyceridaemia, or grade 1-2 vascular stenosis.

INTERPRETATION

Among an ageing cohort of survivors of childhood cancer, the accumulation of non-major adverse cardiovascular events, including subclinical conditions, increased the risk of major adverse cardiovascular events and should be the focus of interventions for early detection and prevention of major adverse cardiovascular events.

FUNDING

The US National Cancer Institute and the American Lebanese Syrian Associated Charities.

Heart rate variability-based prediction of early cardiotoxicity in breast-cancer patients treated with anthracyclines and trastuzumab

BACKGROUND

Cardiotoxicity is a recognized complication in breast cancer (BC) patients undergoing chemotherapy with anthracyclines with or without trastuzumab. However, the prognostic value of heart rate variability (HRV) indexes for early cardiotoxicity development remains unknown.

METHODS

Fifty BC patients underwent TTE assessment before and three months after chemotherapy. HRV indexes were obtained from continuous electrocardiograms in supine position with spontaneous breathing, active standing, and supine position with controlled breathing. The magnitude of change (Δ) between supine-standing and supine-controlled breathing was calculated. Variables were compared using t-test or ANOVA. Cardiotoxicity predictive value was assessed by ROC curve analysis. A p value of < 0.05 was considered significant.

RESULTS

TTE revealed reduced left atrial conduit strain in the cardiotoxicity group. Mean heart rate increased during all maneuvers at follow-up, with no differences in HRV indexes between patients with or without cardiotoxicity. However, a lower Δ in supine-controlled breathing of several HRV indexes predicted early cardiotoxicity identified by echocardiography (e.g. SDNN ≤ -8.44 ms: Sensitivity = 75%, Specificity = 69%).

CONCLUSIONS

BC patients treated with chemotherapy maintain cardiac autonomic responses to physiological stimuli after 3 months of chemotherapy. However, a lower Δ during active standing and controlled breathing before chemotherapy may predict early cardiotoxicity.

Differential Modulation of Catecholamine and Adipokine Secretion by the Short Chain Fatty Acid Receptor FFAR3 and α2-Adrenergic Receptors in PC12 Cells

Sympathetic nervous system (SNS) hyperactivity is mediated by elevated catecholamine (CA) secretion from the adrenal medulla, as well as enhanced norepinephrine (NE) release from peripheral sympathetic nerve terminals. Adrenal CA production from chromaffin cells is tightly regulated by sympatho-inhibitory α2-adrenergic (auto)receptors (ARs), which inhibit both epinephrine (Epi) and NE secretion via coupling to Gi/o proteins. α2-AR function is, in turn, regulated by G protein-coupled receptor (GPCR)-kinases (GRKs), especially GRK2, which phosphorylate and desensitize them, i.e., uncouple them from G proteins. On the other hand, the short-chain free fatty acid (SCFA) receptor (FFAR)-3, also known as GPR41, promotes NE release from sympathetic neurons via the Gi/o-derived free Gβγ-activated phospholipase C (PLC)-β/Ca2+ signaling pathway. However, whether it exerts a similar effect in adrenal chromaffin cells is not known at present. In the present study, we examined the interplay of the sympatho-inhibitory α2A-AR and the sympatho-stimulatory FFAR3 in the regulation of CA secretion from rat adrenal chromaffin (pheochromocytoma) PC12 cells. We show that FFAR3 promotes CA secretion, similarly to what GRK2-dependent α2A-AR desensitization does. In addition, FFAR3 activation enhances the effect of the physiologic stimulus (acetylcholine) on CA secretion. Importantly, GRK2 blockade to restore α2A-AR function or the ketone body beta-hydroxybutyrate (BHB or 3-hydroxybutyrate), via FFAR3 antagonism, partially suppress CA production, when applied individually. When combined, however, CA secretion from PC12 cells is profoundly suppressed. Finally, propionate-activated FFAR3 induces leptin and adiponectin secretion from PC12 cells, two important adipokines known to be involved in tissue inflammation, and this effect of FFAR3 is fully blocked by the ketone BHB. In conclusion, SCFAs can promote CA and adipokine secretion from adrenal chromaffin cells via FFAR3 activation, but the metabolite/ketone body BHB can effectively inhibit this action.

Adrenoceptor Desensitization: Current Understanding of Mechanisms

G-protein coupled receptors (GPCRs) transduce a wide range of extracellular signals. They are key players in the majority of biologic functions including vision, olfaction, chemotaxis, and immunity. However, as essential as most of them are to body function and homeostasis, overactivation of GPCRs has been implicated in many pathologic diseases such as cancer, asthma, and heart failure (HF). Therefore, an important feature of G protein signaling systems is the ability to control GPCR responsiveness, and one key process to control overstimulation involves initiating receptor desensitization. A number of steps are appreciated in the desensitization process, including cell surface receptor phosphorylation, internalization, and downregulation. Rapid or short-term desensitization occurs within minutes and involves receptor phosphorylation via the action of intracellular protein kinases, the binding of β-arrestins, and the consequent uncoupling of GPCRs from their cognate heterotrimeric G proteins. On the other hand, long-term desensitization occurs over hours to days and involves receptor downregulation or a decrease in cell surface receptor protein level. Of the proteins involved in this biologic phenomenon, β-arrestins play a particularly significant role in both short- and long-term desensitization mechanisms. In addition, β-arrestins are involved in the phenomenon of biased agonism, where the biased ligand preferentially activates one of several downstream signaling pathways, leading to altered cellular responses. In this context, this review discusses the different patterns of desensitization of the α 1-, α 2- and the β adrenoceptors and highlights the role of β-arrestins in regulating physiologic responsiveness through desensitization and biased agonism. SIGNIFICANCE STATEMENT: A sophisticated network of proteins orchestrates the molecular regulation of GPCR activity. Adrenoceptors are GPCRs that play vast roles in many physiological processes. Without tightly controlled desensitization of these receptors, homeostatic imbalance may ensue, thus precipitating various diseases. Here, we critically appraise the mechanisms implicated in adrenoceptor desensitization. A better understanding of these mechanisms helps identify new druggable targets within the GPCR desensitization machinery and opens exciting therapeutic fronts in the treatment of several pathologies.

Efficacy of spinal cord stimulation as an adjunctive therapy in heart failure: A systematic review

Neuromodulation therapy, like spinal cord stimulation (SCS), benefits individuals with chronic diseases, improving outcomes of patients with heart failure (HF). This systematic review aims to investigate the efficacy of SCS when used as an adjunctive therapy in HF. A systematic analysis of all studies that included SCS therapy in human participants with HF was conducted. After excluding studies not meeting specific criteria, 4 studies involving a total of 125 participants were selected. All participants had heart failure with the New York Heart Association (NYHA) classification ranging from 2.2 ± 0.4 to 3. The primary endpoints for assessment included the impact of SCS in HF-related symptoms, Left ventricular function, VO2 max, and NT-proBNP. All the studies could demonstrate safety and feasibility of SCS therapy, although the outcomes varied. Two studies reported improvement in NYHA classification, MLHFQ and QoL parameters after SCS. Concerning LVEF and VO2 max, only one study indicated positive changes. None of the studies found a significant change of NT-proBNP following SCS therapy. Given methodological variation, discrepancies in the results could be attributed to the diversity of the induction technique. Further studies are needed to develop a solid approach for employing SCS in human patients with HF.

SGLT2 inhibition, plasma proteins, and heart failure: a proteome-wide Mendelian Randomization and colocalization study

Objective

To investigate the causal contributions of Sodium-glucose cotransporter 2 (SGLT2) inhibition on Heart Failure (HF) and identify the circulating proteins that mediate SGLT2 inhibition's effects on HF.

Methods

Applying a two-sample, two-step Mendelian Randomization (MR) analysis, we aimed to estimate: (1) the causal impact of SGLT2 inhibition on HF; (2) the causal correlation of SGLT2 inhibition on 4,907 circulating proteins; (3) the causal association of SGLT2 inhibition-driven plasma proteins on HF. Genetic variants linked to SGLT2 inhibition derived from the previous studies. The 4,907 circulating proteins were derived from the deCODE study. Genetic links to HF were obtained through the Heart Failure Molecular Epidemiology for Therapeutic Targets (HERMES) consortium.

Results

SGLT2 inhibition demonstrated a lower risk of HF (odds ratio [OR] = 0.44, 95% CI [0.26, 0.76], P = 0.003). Among 4,907 circulating proteins, we identified leucine rich repeat transmembrane protein 2 (LRRTM2), which was related to both SGLT2 inhibition and HF. Mediation analysis revealed that the impact of SGLT2 inhibition on HF operates indirectly through LRRTM2 [β = -0.20, 95% CI (-0.39, -0.06), P = 0.02] with a mediation proportion of 24.6%. Colocalization analysis provided support for the connections between LRRTM2 and HF.

Conclusion

The study indicated a causative link between SGLT2 inhibition and HF, with plasma LRRTM2 potentially serving as a mediator.

Intrathecal Anesthesia Prevents Ventricular Arrhythmias in Rats with Myocardial Ischemia/Reperfusion

INTRODUCTION

Ventricular arrhythmia is commonly provoked by acute cardiac ischemia through sympathetic exaggeration and is often resistant to anti-arrhythmic therapies. Thoracic epidural anesthesia has been reported to terminate fatal ventricular arrhythmia; however, its underlying mechanism is unknown.

METHODS

Rats were randomly divided into four groups: sham, sham plus bupivacaine, ischemia/reperfusion (IR), and IR plus bupivacaine groups. Bupivacaine (1 mg/mL, 0.05 mL/100 g body weight) was injected intrathecally into the L5-L6 intervertebral space prior to establishing a myocardial IR rat model. Thereafter, cardiac arrhythmia, cardiac function, myocardial injury, and electrical activities of the heart and spinal cord were evaluated.

RESULTS

Intrathecal bupivacaine inhibited spinal neural activity, improved heart rate variability, reduced ventricular arrhythmia score, and ameliorated cardiac dysfunction in IR rats. Furthermore, intrathecal bupivacaine attenuated cardiac injury and myocardial apoptosis and regulated cardiomyocyte autophagy and connexin-43 distribution during myocardial IR.

CONCLUSION

Our results indicate that intrathecal bupivacaine blunts spinal neural activity to prevent cardiac arrhythmia and dysfunction induced by IR and that this anti-arrhythmic activity may be associated with regulation of autonomic balance, myocardial apoptosis and autophagy, and cardiac gap junction function.

Comparative specialization of intrinsic cardiac neurons in humans, mice, and pigs

Intrinsic cardiac neurons (ICNs) play a crucial role in the proper functioning of the heart; yet a paucity of data pertaining to human ICNs exists. We took a multidisciplinary approach to complete a detailed cellular comparison of the structure and function of ICNs from mice, pigs, and humans. Immunohistochemistry of whole and sectioned ganglia, transmission electron microscopy, intracellular microelectrode recording and dye filling for quantitative morphometry were used to define the neurophysiology, histochemistry, and ultrastructure of these cells across species. The densely packed, smaller ICNs of mouse lacked dendrites, formed axosomatic connections, and had high synaptic efficacy constituting an obligatory synapse. At Pig ICNs, a convergence of subthreshold cholinergic inputs onto extensive dendritic arbors supported greater summation and integration of synaptic input. Human ICNs were tonically firing, with synaptic stimulation evoking large suprathreshold excitatory postsynaptic potentials like mouse, and subthreshold potentials like pig. Ultrastructural examination of synaptic terminals revealed conserved architecture, yet small clear vesicles (SCVs) were larger in pigs and humans. The presence and localization of ganglionic neuropeptides was distinct, with abundant VIP observed in human but not pig or mouse ganglia, and little SP or CGRP in pig ganglia. Action potential waveforms were similar, but human ICNs had larger after-hyperpolarizations. Intrinsic excitability differed; 93% of human cells were tonic, all pig neurons were phasic, and both phasic and tonic phenotypes were observed in mouse. In combination, this publicly accessible, multimodal atlas of ICNs from mice, pigs, and humans identifies similarities and differences in the evolution of ICNs.

Heart Rate Variability, Deceleration Capacity of Heart Rate, and Death: A Veteran Twins Study

BACKGROUND

Autonomic function can be measured noninvasively using heart rate variability (HRV), which indexes overall sympathovagal balance. Deceleration capacity (DC) of heart rate is a more specific metric of vagal modulation. Higher values of these measures have been associated with reduced mortality risk primarily in patients with cardiovascular disease, but their significance in community samples is less clear.

METHODS AND RESULTS

This prospective twin study followed 501 members from the VET (Vietnam Era Twin) registry. At baseline, frequency domain HRV and DC were measured from 24-hour Holter ECGs. During an average 12-year follow-up, all-cause death was assessed via the National Death Index. Multivariable Cox frailty models with random effect for twin pair were used to examine the hazard ratios of death per 1-SD increase in log-transformed autonomic metrics. Both in the overall sample and comparing twins within pairs, higher values of low-frequency HRV and DC were significantly associated with lower hazards of all-cause death. In within-pair analysis, after adjusting for baseline factors, there was a 22% and 27% lower hazard of death per 1-SD increment in low-frequency HRV and DC, respectively. Higher low-frequency HRV and DC, measured during both daytime and nighttime, were associated with decreased hazard of death, but daytime measures showed numerically stronger associations. Results did not substantially vary by zygosity.

CONCLUSIONS

Autonomic inflexibility, and especially vagal withdrawal, are important mechanistic pathways of general mortality risk, independent of familial and genetic factors.

Potential consequences of cardioneuroablation for vasovagal syncope: A call for appropriately designed, sham-controlled clinical trials

Cardioneuroablation (CNA) is being increasingly used to treat patients with vasovagal syncope (VVS). Bradycardia, in the cardioinhibitory subtype of VVS, results from transient parasympathetic overactivity leading to sinus bradycardia and/or atrioventricular block. By mitigating parasympathetic overactivity, CNA has been shown to improve VVS symptoms in clinical studies with relatively small sample sizes and short follow-up periods (<5 years) at selected centers. However, CNA may potentially tip the autonomic balance to a state of sympathovagal imbalance with attenuation of cardiac parasympathetic activity. A higher heart rate is associated with adverse cardiovascular events and increased mortality in healthy populations without cardiovascular diseases. Chronic sympathovagal imbalance may also affect the pathophysiology of spectra of cardiovascular disorders including atrial and ventricular arrhythmias. This review addresses potential long-term pathophysiological consequences of CNA for VVS.

The vagus nerve in cardiovascular physiology and pathophysiology: From evolutionary insights to clinical medicine

The parasympathetic nervous system via the vagus nerve exerts profound influence over the heart. Together with the sympathetic nervous system, the parasympathetic nervous system is responsible for fine-tuned regulation of all aspects of cardiovascular function, including heart rate, rhythm, contractility, and blood pressure. In this review, we highlight vagal efferent and afferent innervation of the heart, with a focus on insights from comparative biology and advances in understanding the molecular and genetic diversity of vagal neurons, as well as interoception, parasympathetic dysfunction in heart disease, and the therapeutic potential of targeting the parasympathetic nervous system in cardiovascular disease.

Circulating noradrenaline leads to release of neuropeptide Y from cardiac sympathetic nerve terminals via activation of β-adrenergic receptors

Cardiac disease is marked by sympathoexcitation and elevated levels of noradrenaline (NA) and cotransmitter neuropeptide Y (NPY). Increased NPY levels are associated with a greater risk of ventricular arrhythmias and mortality. Nonetheless, the factors that cause NPY release remain poorly understood. We hypothesized that circulating catecholamines might lead to NPY release from myocardial sympathetic nerve terminals via a β-receptor-mediated mechanism that enhances sympathoexcitation. Ventricular interstitial NA and NPY levels were measured in six Yorkshire pigs after i.v. administration of NA (1 mg) and before and after propranolol infusion (1 mg/kg). Real-time interstitial NPY levels were measured using ventricular capacitive immunoprobes (CIs) affixed with NPY antibodies and quantified as the change in CI input current (INPY ) upon binding of NPY. Interstitial NA was measured with adjacent fast-scan cyclic voltammetry probes (INA ). A left ventricular pressure catheter and continuous ECGs were used for haemodynamic recordings, and an epicardial 56-electrode sock was used for measurements of activation recovery interval, a surrogate of action potential duration. Upon administration of NA, heart rate and left ventricular pressure increased, and activation recovery interval shortened. Notably, NA significantly increased interstitial myocardial NPY levels. After propranolol, changes in heart rate and activation recovery interval were largely mitigated. The INA increased to a similar extent post-propranolol vs. pre-propranolol, but changes in INPY were significantly reduced post-propranolol. Coronary sinus plasma analyses confirmed fast-scan cyclic voltammetry and CI findings. Hence, this study demonstrates that circulating NA induces NPY release from ventricular sympathetic nerve terminals, the mechanism for which is mediated via β-adrenergic receptors and can be blocked by the non-selective β-blocker, propranolol. KEY POINTS: Cardiovascular disease is characterized by sympathovagal imbalance, with increased plasma noradrenaline (NA) and neuropeptide Y (NPY) concentrations. Increased NPY levels are associated with increased ventricular arrhythmias and mortality in heart failure. Limited data are available on the specific factors that cause NPY release. In this study, fast-scan cyclic voltammetry and capacitive immunoprobes were used to allow for real-time in vivo measurements of interstitial myocardial neurotransmitters and neuropeptides, respectively. Using an in vivo porcine model with cardiac fast-scan cyclic voltammetry and capacitive immunoprobes, it was shown that systemic NA can increase ventricular interstitial NPY levels, suggesting that NA induces NPY release from postganglionic sympathetic nerves. The release of NPY was blocked by administration of the non-selective β-blocker propranolol, suggesting that release of NPY is dependent on activation of β-adrenergic receptors by NA.

Circulating mitochondria promoted endothelial cGAS-derived neuroinflammation in subfornical organ to aggravate sympathetic overdrive in heart failure mice

BACKGROUND

Sympathoexcitation contributes to myocardial remodeling in heart failure (HF). Increased circulating pro-inflammatory mediators directly act on the Subfornical organ (SFO), the cardiovascular autonomic center, to increase sympathetic outflow. Circulating mitochondria (C-Mito) are the novel discovered mediators for inter-organ communication. Cyclic GMP-AMP synthase (cGAS) is the pro-inflammatory sensor of damaged mitochondria.

OBJECTIVES

This study aimed to assess the sympathoexcitation effect of C-Mito in HF mice via promoting endothelial cGAS-derived neuroinflammation in the SFO.

METHODS

C-Mito were isolated from HF mice established by isoprenaline (0.0125 mg/kg) infusion via osmotic mini-pumps for 2 weeks. Structural and functional analyses of C-Mito were conducted. Pre-stained C-Mito were intravenously injected every day for 2 weeks. Specific cGAS knockdown (cGAS KD) in the SFO endothelial cells (ECs) was achieved via the administration of AAV9-TIE-shRNA (cGAS) into the SFO. The activation of cGAS in the SFO ECs was assessed. The expression of the mitochondrial redox regulator Dihydroorotate dehydrogenase (DHODH) and its interaction with cGAS were also explored. Neuroinflammation and neuronal activation in the SFO were evaluated. Sympathetic activity, myocardial remodeling, and cardiac systolic dysfunction were measured.

RESULTS

C-Mito were successfully isolated, which showed typical structural characteristics of mitochondria with double-membrane and inner crista. Further analysis showed impaired respiratory complexes activities of C-Mito from HF mice (C-MitoHF) accompanied by oxidative damage. C-Mito entered ECs, instead of glial cells and neurons in the SFO of HF mice. C-MitoHF increased the level of ROS and cytosolic free double-strand DNA (dsDNA), and activated cGAS in cultured brain endothelial cells. Furthermore, C-MitoHF highly expressed DHODH, which interacted with cGAS to facilitate endothelial cGAS activation. C-MitoHF aggravated endothelial inflammation, microglial/astroglial activation, and neuronal sensitization in the SFO of HF mice, which could be ameliorated by cGAS KD in the ECs of the SFO. Further analysis showed C-MitoHF failed to exacerbate sympathoexcitation and myocardial sympathetic hyperinnervation in cGAS KD HF mice. C-MitoHF promoted myocardial fibrosis and hypertrophy, and cardiac systolic dysfunction in HF mice, which could be ameliorated by cGAS KD.

CONCLUSION

Collectively, we demonstrated that damaged C-MitoHF highly expressed DHODH, which promoted endothelial cGAS activation in the SFO, hence aggravating the sympathoexcitation and myocardial injury in HF mice, suggesting that C-Mito might be the novel therapeutic target for sympathoexcitation in HF.

Vagal dysautonomia in patients with Chagas disease and mortality: 14-year results of a population cohort of the elderly

INTRODUCTION

Great part of Chagas disease (ChD) mortality occurs due to ventricular arrhythmias, and autonomic function (AF) may predict unfavorable outcomes. We aimed to evaluate the predictive value of AF indexes in ChD patients.

METHODS

The Bambuí Study of Aging is a prospective cohort of residents ≥60 years at study onset (1997), in the southeastern Brazilian city of Bambuí (15,000 inhabitants). Consented participants underwent annual follow-up visits, and death certificates were tracked. AF was assessed by the maximum expiration on minimum inspiration (E:I) ratio during ECG acquisition and by heart rate variability indices: SDRR (standard deviation of adjacent RR intervals) and RMSSD (square root of the mean of the sum of squares of the differences between adjacent RR intervals)), calculated using a computer algorithm. Cox proportional hazards regression was performed to access the prognostic value of AF indexes, expressed as terciles, for all-cause mortality, after adjustment for demographic, clinical and ECG variables.

RESULTS

From 1742 qualifying residents, 1000 had valid AF tests, being 321 with ChD. Among these, median age was 68 (64-74) years, and 32.5% were men. In Cox survival analyses, only SDRR was associated with all-cause mortality in non-adjusted models: SDRR (hazard ratio (HR): 1.26 (95% CI 1.08-1.47), p < 0.001), E:I ratio (HR: 1.13 (95% CI 0,98-1.31), p = 0.10) and RMSSD (HR: 0.99 (0.86-1.16), p = 0.95). After adjustment for sex and age, none of the indexes remained as independent predictors.

CONCLUSION

Among elderly patients with ChD, AF indexes available in this cohort were not independent predictors of 14-year mortality.

Commonalities and differences in carotid body dysfunction in hypertension and heart failure

Carotid body pathophysiology is associated with many cardiovascular-respiratory-metabolic diseases. This pathophysiology reflects both hyper-sensitivity and hyper-tonicity. From both animal models and human patients, evidence indicates that amelioration of this pathophysiological signalling improves disease states such as a lowering of blood pressure in hypertension, a reduction of breathing disturbances with improved cardiac function in heart failure (HF) and a re-balancing of autonomic activity with lowered sympathetic discharge. Given this, we have reviewed the mechanisms of carotid body hyper-sensitivity and hyper-tonicity across disease models asking whether there is uniqueness related to specific disease states. Our analysis indicates some commonalities and some potential differences, although not all mechanisms have been fully explored across all disease models. One potential commonality is that of hypoperfusion of the carotid body across hypertension and HF, where the excessive sympathetic drive may reduce blood flow in both models and, in addition, lowered cardiac output in HF may potentiate the hypoperfusion state of the carotid body. Other mechanisms are explored that focus on neurotransmitter and signalling pathways intrinsic to the carotid body (e.g. ATP, carbon monoxide) as well as extrinsic molecules carried in the blood (e.g. leptin); there are also transcription factors found in the carotid body endothelium that modulate its activity (Krüppel-like factor 2). The evidence to date fully supports that a better understanding of the mechanisms of carotid body pathophysiology is a fruitful strategy for informing potential new treatment strategies for many cardiovascular, respiratory and metabolic diseases, and this is highly relevant clinically.

Cholinesterase inhibitors associated with lower rate of mortality in dementia patients with heart failure: a nationwide propensity weighting study

PURPOSE

This study investigates the potential impact of cholinesterase inhibitors (ChEIs) on patients with heart failure (HF) and dementia. ChEIs are known to boost acetylcholine levels and benefit cognition in patients with dementia; however, their effect on patients with HF is uncertain. This study aimed to assess whether cardiovascular events and mortality among patients with HF and dementia are altered by ChEI therapy.

METHODS

Data from the National Health Insurance Research Database in Taiwan were retrospectively analyzed. Dementia patients diagnosed with HF were followed for 5 years until all-cause mortality, cardiovascular mortality, hospitalization for worsening HF, or the end of the study. Multivariable Cox models and inverse probability of treatment weighting (IPTW) were employed.

RESULTS

Out of 20,848 patients with dementia, 5138 had HF. Among them, 726 were ChEI users and 4412 were non-users. Based on IPTW, the ChEI users had significantly lower estimated risks of all-cause mortality [hazard ratio (HR) 0.43; 95% confidence interval (CI) 0.38-0.49, p < 0.001] and cardiovascular mortality (HR 0.41; 95% CI 0.33-0.53, p < 0.001) compared with the non-users, but there was no significant difference in hospitalization for worsening HF (HR 0.73; 95% CI 0.51-1.05, p = 0.091) after 5 years. The survival benefits of ChEIs were consistent across subgroups.

CONCLUSIONS

The results of this retrospective cohort study suggest that ChEIs may be beneficial in reducing all-cause and cardiovascular mortality in patients with dementia with HF. Further research is needed to validate these findings and explore the potential benefits of ChEIs in all patients with HF, including those without dementia.

The neurometabolic axis: A novel therapeutic target in heart failure

Abnormal cardiac metabolism or cardiac metabolic remodeling is reported before the onset of heart failure with reduced ejection fraction (HFrEF) and is known to trigger and maintain the mechanical dysfunction and electrical, and structural abnormalities of the ventricle. A dysregulated cardiac autonomic tone characterized by sympathetic overdrive with blunted parasympathetic activation is another pathophysiological hallmark of HF. Emerging evidence suggests a link between autonomic nervous system activity and cardiac metabolism. Chronic β-adrenergic activation promotes maladaptive metabolic remodeling whereas cholinergic activation attenuates the metabolic aberrations through favorable modulation of key metabolic regulatory molecules. Restoration of sympathovagal balance by neuromodulation strategies is emerging as a novel nonpharmacological treatment strategy in HF. The current review attempts to evaluate the 'neuro-metabolic axis' in HFrEF and whether neuromodulation can mitigate the adverse metabolic remodeling in HFrEF.

Telemetric long-term assessment of autonomic function in experimental heart failure

Despite medical advances in the treatment of heart failure (HF), mortality remains high. It has been shown that alterations of the autonomic-nervous-system (ANS) are associated with HF progression and increased mortality. Preclinical models are required to evaluate the effectiveness of novel treatments modulating the autonomic imbalance. However, there are neither standard models nor diagnostic methods established to measure sympathetic and parasympathetic outflow continuously. Digital technologies might be a reliable tool for continuous assessment of autonomic function within experimental HF models. Telemetry devices and pacemakers were implanted in beagle dogs (n = 6). HF was induced by ventricular pacing. Cardiac hemodynamics, plasma catecholamines and parameter describing the ANS ((heart rate variability (HRV), deceleration capacity (DC), and baroreflex sensitivity (BRS)) were continuously measured at baseline, during HF conditions and during recovery phase. The pacing regime led to the expected depression in cardiac hemodynamics. Telemetric assessment of the ANS function showed a significant decrease in Total power, DC, and Heart rate recovery, whereas BRS was not significantly affected. In contrast, plasma catecholamines, revealing sympathetic activity, showed only a significant increase in the recovery phase. A precise diagnostic of the ANS in the context of HF is becoming increasingly important in experimental models. Up to now, these models have shown many limitations. Here we present the continuous assessment of the autonomic function in the progression of HF. We could demonstrate the advantage of highly resolved ANS measurement by HR and BP derived parameters due to early detection of an autonomic imbalance in the progression of HF.

Protein kinase A: A potential marker of sympathovagal imbalance in heart failure

Mitigation of cardiac autonomic dysregulation by neuromodulation technologies is emerging as a new therapeutic modality of heart failure (HF). This recent progress has necessitated the identification of a biomarker for the quantification of sympathovagal balance, the potential target of 'neuromodulation' strategies. The currently available autonomic nervous system assessment parameters do not truly reflect the sympathovagal balance of the ventricle. Protein kinase A (PKA) is an intracellular enzyme that plays a major role in the pathophysiology of functional and structural ventricular remodeling in HF. Interestingly, sympathetic and parasympathetic activations exert reciprocal influence on the activity of PKA. The current review attempts to evaluate the potential concept and feasibility of using in vitro assessment of PKA activity as a marker of sympathovagal balance in HF.

The Sympathetic Nervous System in Hypertensive Heart Failure with Preserved LVEF

The neurohormonal model of heart failure (HF) pathogenesis states that a reduction in cardiac output caused by cardiac injury results in sympathetic nervous system (SNS) activation, that is adaptive in the short-term and maladaptive in the long-term. This model has proved extremely valid and has been applied in HF with a reduced left ventricular (LV) ejection fraction (LVEF). In contrast, it has been undermined in HF with preserved LVEF (HFpEF), which is due to hypertension (HTN) in the vast majority of the cases. Erroneously, HTN, which is the leading cause of cardiovascular disease and premature death worldwide and is present in more than 90% of HF patients, is tightly linked with SNS overactivity. In this paper we provide a contemporary overview of the contribution of SNS overactivity to the development and progression of hypertensive HF (HHF) as well as the clinical implications resulting from therapeutic interventions modifying SNS activity. Throughout the manuscript the terms HHF with preserved LVEF and HfpEF will be used interchangeably, considering that the findings in most HFpEF studies are driven by HTN.

Outcomes of hypothalamic oxytocin neuron-driven cardioprotection after acute myocardial infarction

Altered autonomic balance is a hallmark of numerous cardiovascular diseases, including myocardial infarction (MI). Although device-based vagal stimulation is cardioprotective during chronic disease, a non-invasive approach to selectively stimulate the cardiac parasympathetic system immediately after an infarction does not exist and is desperately needed. Cardiac vagal neurons (CVNs) in the brainstem receive powerful excitation from a population of neurons in the paraventricular nucleus (PVN) of the hypothalamus that co-release oxytocin (OXT) and glutamate to excite CVNs. We tested if chemogenetic activation of PVN-OXT neurons following MI would be cardioprotective. The PVN of neonatal rats was transfected with vectors to selectively express DREADDs within OXT neurons. At 6 weeks of age, an MI was induced and DREADDs were activated with clozapine-N-oxide. Seven days following MI, patch-clamp electrophysiology confirmed the augmented excitatory neurotransmission from PVN-OXT neurons to downstream nuclei critical for parasympathetic activity with treatment (43.7 ± 10 vs 86.9 ± 9 pA; MI vs. treatment), resulting in stark improvements in survival (85% vs. 95%; MI vs. treatment), inflammation, fibrosis assessed by trichrome blue staining, mitochondrial function assessed by Seahorse assays, and reduced incidence of arrhythmias (50% vs. 10% cumulative incidence of ventricular fibrillation; MI vs. treatment). Myocardial transcriptomic analysis provided molecular insight into potential cardioprotective mechanisms, which revealed the preservation of beneficial signaling pathways, including muscarinic receptor activation, in treated animals. These comprehensive results demonstrate that the PVN-OXT network could be a promising therapeutic target to quickly activate beneficial parasympathetic-mediated cellular pathways within the heart during the early stages of infarction.

Cardiac Vagal Nerve Activity Increases During Exercise to Enhance Coronary Blood Flow

BACKGROUND

The phrase complete vagal withdrawal is often used when discussing autonomic control of the heart during exercise. However, more recent studies have challenged this assumption. We hypothesized that cardiac vagal activity increases during exercise and maintains cardiac function via transmitters other than acetylcholine.

METHODS

Chronic direct recordings of cardiac vagal nerve activity, cardiac output, coronary artery blood flow, and heart rate were recorded in conscious adult sheep during whole-body treadmill exercise. Cardiac innervation of the left cardiac vagal branch was confirmed with lipophilic tracer dyes (DiO). Sheep were exercised with pharmacological blockers of acetylcholine (atropine, 250 mg), VIP (vasoactive intestinal peptide; [4Cl-D-Phe6,Leu17]VIP 25 µg), or saline control, randomized on different days. In a subset of sheep, the left cardiac vagal branch was denervated.

RESULTS

Neural innervation from the cardiac vagal branch is seen at major cardiac ganglionic plexi, and within the fat pads associated with the coronary arteries. Directly recorded cardiac vagal nerve activity increased during exercise. Left cardiac vagal branch denervation attenuated the maximum changes in coronary artery blood flow (maximum exercise, control: 63.5±5.9 mL/min, n=8; cardiac vagal denervated: 32.7±5.6 mL/min, n=6, P=2.5×10-7), cardiac output, and heart rate during exercise. Atropine did not affect any cardiac parameters during exercise, but VIP antagonism significantly reduced coronary artery blood flow during exercise to a similar level to vagal denervation.

CONCLUSIONS

Our study demonstrates that cardiac vagal nerve activity actually increases and is crucial for maintaining cardiac function during exercise. Furthermore, our findings show the dynamic modulation of coronary artery blood flow during exercise is mediated by VIP.

Ganglionated Plexus Ablation Procedures to Treat Vasovagal Syncope

Vasovagal syncope (VVS) refers to a heterogeneous group of conditions whereby the cardiovascular reflexes normally controlling the circulation are interrupted irregularly in response to a trigger, resulting in vasodilation, bradycardia, or both. VVS affects one-third of the population at least once in their lifetime or by the age of 60, reduces the quality of life, and may cause disability affecting certain routines. It poses a considerable economic burden on society, and, despite its prevalence, there is currently no proven pharmacological treatment for preventing VVS. The novel procedure of ganglionated plexus (GP) ablation has emerged rapidly in the past two decades, and has been proven successful in treating syncope. Several parameters influence the success rate of GP ablation, including specific ablation sites, localization and surgical techniques, method of access, and the integration of other interventions. This review aims to provide an overview of the existing literature on the physiological aspects and clinical effectiveness of GP ablation in the treatment of VVS. Specifically, we explore the association between GPs and VVS and examine the impact of GP ablation procedures as reported in human clinical trials. Our objective is to shed light on the therapeutic significance of GP ablation in eliminating VVS and restoring normal sinus rhythm, particularly among young adults affected by this condition.

Extracellular Vesicle MicroRNAs in Heart Failure: Pathophysiological Mediators and Therapeutic Targets

Extracellular vesicles (EVs) are emerging mediators of intracellular and inter-organ communications in cardiovascular diseases (CVDs), especially in the pathogenesis of heart failure through the transference of EV-containing bioactive substances. microRNAs (miRNAs) are contained in EV cargo and are involved in the progression of heart failure. Over the past several years, a growing body of evidence has suggested that the biogenesis of miRNAs and EVs is tightly regulated, and the sorting of miRNAs into EVs is highly selective and tightly controlled. Extracellular miRNAs, particularly circulating EV-miRNAs, have shown promising potential as prognostic and diagnostic biomarkers for heart failure and as therapeutic targets. In this review, we summarize the latest progress concerning the role of EV-miRNAs in HF and their application in a therapeutic strategy development for heart failure.

Chronic vagus nerve stimulation in patients with heart failure: challenge or failed translation?

Autonomic imbalance between the sympathetic and parasympathetic nervous systems contributes to the progression of chronic heart failure (HF). Preclinical studies have demonstrated that various neuromodulation strategies may exert beneficial cardioprotective effects in preclinical models of HF. Based on these encouraging experimental data, vagus nerve stimulation (VNS) has been assessed in patients with HF with a reduced ejection fraction. Nevertheless, the main trials conducted thus far have yielded conflicting findings, questioning the clinical efficacy of VNS in this context. This review will therefore focus on the role of the autonomic nervous system in HF pathophysiology and VNS therapy, highlighting the potential reasons behind the discrepancy between preclinical and clinical studies.

Pathological Heart Rate Regulation in Apparently Healthy Individuals

Cardiovascular diseases are the leading cause of morbidity and mortality in adults worldwide. There is one common pathophysiological aspect present in all cardiovascular diseases-dysfunctional heart rhythm regulation. Taking this aspect into consideration for cardiovascular risk predictions opens important research perspectives, allowing for the development of preventive treatment techniques. The aim of this study was to find out whether certain pathologically appearing signs in the heart rate variability (HRV) of an apparently healthy person, even with high HRV, can be defined as biomarkers for a disturbed cardiac regulation and whether this can be treated preventively by a drug-free method. This multi-phase study included 218 healthy subjects of either sex, who consecutively visited the physician at Gesundheit clinic because of arterial hypertension, depression, headache, psycho-emotional stress, extreme weakness, disturbed night sleep, heart palpitations, or chest pain. In study phase A, baseline measurement to identify individuals with cardiovascular risks was done. Therefore, standard HRV, as well as the new cardiorhythmogram (CRG) method, were applied to all subjects. The new CRG analysis used here is based on the recently introduced LF drops and HF counter-regulation. Regarding the mechanisms of why these appear in a steady-state cardiorhythmmogram, they represent non-linear event-based dynamical HRV biomarkers. The next phase of the study, phase B, tested whether the pathologically appearing signs identified via CRG in phase A could be clinically influenced by drug-free treatment. In order to validate the new CRG method, it was supported by non-linear HRV analysis in both phase A and in phase B. Out of 218 subjects, the pathologically appearing signs could be detected in 130 cases (60%), p < 0.01, by the new CRG method, and by the standard HRV analysis in 40 cases (18%), p < 0.05. Thus, the CRG method was able to detect 42% more cases with pathologically appearing cardiac regulation. In addition, the comparative CRG analysis before and after treatment showed that the pathologically appearing signs could be clinically influenced without the use of medication. After treatment, the risk group decreased eight-fold-from 130 people to 16 (p < 0.01). Therefore, progression of the detected pathological signs to structural cardiac pathology or arrhythmia could be prevented in most of the cases. However, in the remaining risk group of 16 apparently healthy subjects, 8 people died due to all-cause mortality. In contrast, no other subject in this study has died so far. The non-linear parameter which is able to quantify the changes in CRGs before versus after treatment is FWRENYI4 (symbolic dynamic feature); it decreased from 2.85 to 2.53 (p < 0.001). In summary, signs of pathological cardiac regulation can be identified by the CRG analysis of apparently healthy subjects in the early stages of development of cardiac pathology. Thus, our method offers a sensitive biomarker for cardiovascular risks. The latter can be influenced by non-drug treatments (acupuncture) to stop the progression into structural cardiac pathologies or arrhythmias in most but not all of the patients. Therefore, this could be a real and easy-to-use supplemental method, contributing to primary prevention in cardiology.

Microglia-Mediated Neuroimmune Response Regulates Cardiac Remodeling After Myocardial Infarction

Background Sympathetic hyperactivity contributes to pathological remodeling after myocardial infarction (MI). However, the mechanisms underlying the increase in sympathetic activity remain unknown. Microglia are the predominant immune cells in the central nervous system and can regulate sympathetic neuron activity through neuroimmune response in the hypothalamic paraventricular nucleus. The present study aimed to investigate whether microglia-mediated neuroimmune response can regulate sympathetic activity and cardiac remodeling after MI. Methods and Results PLX3397 (pexidartinib) was used to deplete central microglia via intragastric injection or intracerebroventricular injection. After that, MI was induced by ligation of the left anterior descending coronary artery. Our study showed that MI resulted in the activation of microglia in the paraventricular nucleus. Microglia depletion, which was induced by PLX3397 treatment via intragastric injection or intracerebroventricular injection, improved cardiac function, reduced infarction size, and attenuated cardiomyocyte apoptosis, fibrosis, pathological electrical remodeling, and myocardial inflammation after MI. Mechanistically, these protective effects were associated with an attenuated neuroimmune response in the paraventricular nucleus, which contributed to the decrease of sympathetic activity and attenuation of sympathetic remodeling in the heart. However, intragastric injection with PLX3397 obviously depleted macrophages and induced neutrophil and T-lymphocyte disorders in the heart, blood, and spleen. Conclusions Microglia depletion in the central nervous system attenuates pathological cardiac remodeling after MI by inhibiting neuroimmune response and sympathetic activity. Intragastric administration of PLX3397 leads to serious deleterious effects in peripheral immune cells, especially macrophages, which should be a cause for concern in animal experiments and clinical practice.

Renal Oxygen Demand and Nephron Function: Is Glucose a Friend or Foe?

The kidneys and heart work together to balance the body's circulation, and although their physiology is based on strict inter dependence, their performance fulfills different aims. While the heart can rapidly increase its own oxygen consumption to comply with the wide changes in metabolic demand linked to body function, the kidneys physiology are primarily designed to maintain a stable metabolic rate and have a limited capacity to cope with any steep increase in renal metabolism. In the kidneys, glomerular population filters a large amount of blood and the tubular system has been programmed to reabsorb 99% of filtrate by reabsorbing sodium together with other filtered substances, including all glucose molecules. Glucose reabsorption involves the sodium-glucose cotransporters SGLT2 and SGLT1 on the apical membrane in the proximal tubular section; it also enhances bicarbonate formation so as to preserve the acid-base balance. The complex work of reabsorption in the kidney is the main factor in renal oxygen consumption; analysis of the renal glucose transport in disease states provides a better understanding of the renal physiology changes that occur when clinical conditions alter the neurohormonal response leading to an increase in glomerular filtration pressure. In this circumstance, glomerular hyperfiltration occurs, imposing a higher metabolic demand on kidney physiology and causing progressive renal impairment. Albumin urination is the warning signal of renal engagement over exertion and most frequently heralds heart failure development, regardless of disease etiology. The review analyzes the mechanisms linked to renal oxygen consumption, focusing on sodium-glucose management.