Sympathetic nervous system activation in human heart failure: clinical implications of an updated model

K-means panning - Developing a new standard in automated MSNA signal recognition with a weakly supervised learning approach

BACKGROUND

Accessibility of labelled datasets is often a key limitation for the application of Machine Learning in clinical research. A novel semi-automated weak-labelling approach based on unsupervised clustering was developed to classify a large dataset of microneurography signals and subsequently used to train a Neural Network to reproduce the labelling process.

METHODS

Clusters of microneurography signals were created with k-means and then labelled in terms of the validity of the signals contained in each cluster. Only purely positive or negative clusters were labelled, whereas clusters with mixed content were passed on to the next iteration of the algorithm to undergo another cycle of unsupervised clustering and labelling of the clusters. After several iterations of this process, only pure labelled clusters remained which were used to train a Deep Neural Network.

RESULTS

Overall, 334,548 individual signal peaks form the integrated data were extracted and more than 99.99% of the data was labelled in six iterations of this novel application of weak labelling with the help of a domain expert. A Deep Neural Network trained based on this dataset achieved consistent accuracies above 95%.

DISCUSSION

Data extraction and the novel iterative approach of labelling unsupervised clusters enabled creation of a large, labelled dataset combining unsupervised learning and expert ratings of signal-peaks on cluster basis in a time effective manner. Further research is needed to validate the methodology and employ it on other types of physiologic data for which it may enable efficient generation of large labelled datasets.

Chronic Heart Failure: Clinical Implications of Iron Homeostasis Disturbances Revisited

Iron deficiency is prevalent in chronic heart failure (CHF) patients. Nonetheless, the diagnosis is often overlooked and, often, the treatment is commenced just when overt anemia has ensued. Therefore, a better appreciation of this disease is needed, and all seasoned cardiologists should know how to approach CHF patients with iron deficiency correctly, as mandated by clinical practice guidelines. In this comprehensive review, we describe iron homeostasis, the pathophysiologic changes of iron homeostasis, and the clinical implications of iron deficiency on CHF patients. In addition, we delineate the evolution of clinical trials, ranging from the inception to the ongoing clinical trials of iron deficiency treatment in CHF patients. Iron deficiency contributes to the worse clinical outcome of the patients. Numerous studies have reported the clinical benefit of iron supplementation, particularly in intravenous preparation, in heart failure patients regarding symptoms, functional capacity, and quality of life (QoL) improvement. Therefore, the current guidelines recommend routine screening of iron status in all newly diagnosed heart failure patients. Eventually, intravenous iron replacement is recommended for symptomatic heart failure patients with iron deficiency, irrespective of anemia.

Treatment of Cheyne-Stokes Respiration in Heart Failure with Adaptive Servo-Ventilation: An Integrative Model

The SERVE-HF (Treatment of Predominant Central Sleep Apnea by Adaptive Servo Ventilation in Patients with Heart Failure) multicenter trial found a small but significant increase in all-cause and cardiovascular mortality in patients assigned to adaptive servo-ventilation (ASV) versus guideline-based medical treatment. To better understand the physiological underpinnings of this clinical outcome, we employ an integrative computer model to simulate congestive heart failure with Cheyne-Stokes respiration (CHF-CSR) in subjects with a broad spectrum of underlying pathogenetic mechanisms, as well as to determine the in silico changes in cardiopulmonary and autonomic physiology resulting from ASV. Our simulation results demonstrate that while the elimination of CSR through ASV can partially restore cardiorespiratory and autonomic physiology toward normality in the vast majority of CHF phenotypes, the degree of restoration can be highly variable, depending on the combination of CHF mechanisms in play. The group with the lowest left ventricular ejection fraction (LVEF) appears to be most vulnerable to the potentially adverse effects of ASV, but the level of pulmonary capillary wedge pressure (PCWP) plays an important role in determining the nature of these effects.

Increased myocardial oxygen consumption rates are associated with maladaptive right ventricular remodeling and decreased event-free survival in heart failure patients

BACKGROUND

Reduced left ventricular (LV) function is associated with increased myocardial oxygen consumption rate (MVO2) and altered sympathetic activity, the role of which is not well described in right ventricular (RV) dysfunction.

METHODS AND RESULTS

33 patients with left heart failure were assessed for RV function/size using echocardiography. Positron emission tomography (PET) was used to measure 11C-acetate clearance rate (kmono), 11C-hydroxyephedrine (11C-HED) standardized uptake value (SUV), and retention rate. RV MVO2 was estimated from kmono. 11C-HED SUV and retention indicated sympathetic neuronal function. A composite clinical endpoint was defined as unplanned cardiac hospitalization within 5 years. Patients with (n = 10) or without (n = 23) RV dysfunction were comparable in terms of sex (male: 70.0 vs 69.5%), LV ejection fraction (39.6 ± 9.0 vs 38.6 ± 9.4%), and systemic hypertension (70.0 vs 78.3%). RV dysfunction patients were older (70.9 ± 13.5 vs 59.4 ± 11.5 years; P = .03) and had a higher prevalence of pulmonary hypertension (60.0% vs 13.0%; P = .01). RV dysfunction was associated with increased RV MVO2 (.106 ± .042 vs .068 ± .031 mL/min/g; P = .02) and decreased 11C-HED SUV and retention (6.05 ± .53 vs 7.40 ± 1.39 g/mL (P < .001) and .08 ± .02 vs .11 ± .03 mL/min/g (P < .001), respectively). Patients with an RV MVO2 above the median had a shorter event-free survival (hazard ratio = 5.47; P = .01). Patients who died within the 5-year follow-up period showed a trend (not statistically significant) for higher RV MVO2 (.120 ± .026 vs .074 ± .038 mL/min/g; P = .05).

CONCLUSIONS

RV dysfunction is associated with increased oxygen consumption (also characterized by a higher risk for cardiac events) and impaired RV sympathetic function.

Endovascular denervation (EDN): From Hypertension to Non-Hypertension Diseases

Recently, the use of endovascular denervation (EDN) to treat resistant hypertension has gained significant attention. In addition to reducing sympathetic activity, EDN might also have beneficial effects on pulmonary arterial hypertension, insulin resistance, chronic kidney disease, atrial fibrillation, heart failure, obstructive sleep apnea syndrome, loin pain hematuria syndrome, cancer pain and so on. In this article we will summarize the progress of EDN in clinical research.

Heart Rate Variability and Cardiovascular Fitness: What We Know so Far

Fluctuation analysis in intervals between heartbeats provides important indices related to autonomic modulation of heart rate variability (HRV). These indices are considered predictors of morbidity and mortality as they are frequently altered in patients with chronic degenerative diseases, especially in those with cardiovascular and metabolic diseases. Similarly, a reduction in HRV is common with aging. In all cases, cardiovascular fitness is often reduced to below the predicted values. In turn, increases in cardiovascular fitness through regular physical exercise, especially aerobic exercise, represent an important therapeutic tool capable of promoting positive adjustments in cardiac autonomic modulation. These adjustments are characterized by reduced sympathetic modulatory influence and/or increased vagal modulatory influence on the heart, increasing the HRV. Therefore, several methodological tools have been used to assess the degree of impairment of autonomic modulation and the therapeutic effects of physical exercise. In contrast, establishment of strict protocols in experimental design is a main challenge in establishing HRV analysis as a robust parameter for evaluating cardiovascular homeostasis. Thus, this review aimed to contribute to the understanding of autonomic modulation of HRV and its relationship with cardiovascular fitness, highlighting the advances made thus far, the applicability of analysis tools, and the confounding factors observed frequently.

The sympathies of the body: functional organization and neuronal differentiation in the peripheral sympathetic nervous system

During the last 30 years, our understanding of the development and diversification of postganglionic sympathetic neurons has dramatically increased. In parallel, the list of target structures has been critically extended from the cardiovascular system and selected glandular structures to metabolically relevant tissues such as white and brown adipose tissue, lymphoid tissues, bone, and bone marrow. A critical question now emerges for the integration of the diverse sympathetic neuron classes into neural circuits specific for these different target tissues to achieve the homeostatic regulation of the physiological ends affected.

Higher Serum Phosphorus Is Not an Independent Risk Factor of Mortality in Heart Failure with Reduced Ejection Fraction

Higher serum phosphorus has detrimental health effects. Even high-normal rage sP is associated with worse outcomes. The relationship of serum phosphorus with prognostic markers in heart failure remains unclear. We investigated the association of serum phosphorus with heart failure prognostic factors and risk of mortality related to serum phosphorus. In 1029 stable heart failure patients, we investigated the distribution of markers of more advanced heart failure stage across quintiles of serum phosphorus and estimated the relative risk of mortality in comparison to reference. Higher serum phosphorus levels sP were associated with markers of a worse outcome. The best survival was observed in low-normal serum levels. The unadjusted hazard ratio for mortality increased toward higher phosphorus quintiles but not to lower levels of sP. The correction for age, sex, BMI, percent weight loss, inflammation, kidney function, and LVEF did not modify the risk profile substantially. The adjustment for NYHA, natriuretic peptides, serum sodium, and treatment characteristics broke down the risk relationship completely. A higher serum phosphorus is associated with markers of a more risky profile of heart failure. Elevated serum levels of phosphorus sP does not provide independent prognostic information beyond the strongest markers of the severity of the syndrome. The potential involvement of higher serum phosphorus as a mediator in the pathophysiology of heart failure warrants further study.

Emerging Implantable Device Technology for Patients at the Intersection of Electrophysiology and Heart Failure Interdisciplinary Care

Cardiac implantable electronic devices (CIEDs), including implantable cardioverter-defibrillators (ICDs) and cardiac resynchronization therapy (CRT), are part of guideline- indicated treatment for a subset of patients with heart failure with reduced ejection fraction (HFrEF). Current technological advancements in CIEDs have allowed the detection of specific patient physiologic parameters used for forecasting clinical decompensation through algorithmic, multiparameter remote monitoring. Other recent emerging technologies, including cardiac contractility modulation (CCM) and baroreflex activation therapy (BAT), may provide symptomatic or physiologic benefit in patients without an indication for CRT. Our goal in this state-of-the-art review is to describe the commercially available new technologies, purported mechanisms of action, evidence surrounding their clinical role, limitations, and future directions. Finally, we underline the need for standardized workflow and close interdisciplinary management of this population to ensure the delivery of high-quality care.

Targeting Two-Pore-Domain Potassium Channels by Mechanical Stretch Instantaneously Modulates Action Potential Transmission in Mouse Sciatic Nerves

Recent reports indicate dominant roles of TRAAK and TREK-1 channels, i.e., mechanosensitive two-pore-domain potassium channels (K2P) at the nodes of Ranvier for action potential repolarization in mammalian peripheral nerves. Functional changes in mammalian peripheral nerve conduction by mechanical stretch studied by recording compound action potentials lack the necessary resolution to detect subtle neuromodulatory effects on conduction velocity. In this study, we developed a novel in vitro approach that enables single-fiber recordings from individual mouse sciatic nerve axons while delivering computer-controlled stepped stretch to the sciatic nerve trunk. Axial stretch instantaneously increased the conduction delay in both myelinated A-fibers and unmyelinated C-fibers. Increases in conduction delay linearly correlated with increases in axial stretch ratio for both A- and C-fibers. The slope of the increase in conduction delay versus stretch ratio was steeper in C-fibers than in A-fibers. Moderate axial stretch (14-19% of in vitro length) reversibly blocked 37.5% of unmyelinated C-fibers but none of the eight myelinated A-fibers tested. Application of arachidonic acid, an agonist to TRAAK and TREK-1 to sciatic nerve trunk, blocks axonal transmission in both A- and C-fibers with delayed onset and prolonged block. Also, the application of an antagonist ruthenium red showed a tendency of suppressing the stretch-evoked increase in conduction delay. These results could draw focused research on pharmacological and mechanical activation of K2P channels as a novel neuromodulatory strategy to achieve peripheral nerve block.

BDNF shifts excitatory-inhibitory balance in the paraventricular nucleus of the hypothalamus to elevate blood pressure

Presympathetic neurons in the paraventricular nucleus of the hypothalamus (PVN) play a key role in cardiovascular regulation. We have previously shown that brain-derived neurotrophic factor (BDNF), acting in the PVN, increases sympathetic activity and blood pressure and serves as a key regulator of stress-induced hypertensive responses. BDNF is known to alter glutamatergic and GABA-ergic signaling broadly in the central nervous system, but whether BDNF has similar actions in the PVN remains to be investigated. Here, we tested the hypothesis that increased BDNF expression in the PVN elevates blood pressure by enhancing N-methyl-d-aspartate (NMDA) receptor (NMDAR)- and inhibiting GABA_A receptor (GABA_AR)-mediated signaling. Sprague-Dawley rats received bilateral PVN injections of AAV2 viral vectors expressing green fluorescent protein (GFP) or BDNF. Three weeks later, cardiovascular responses to PVN injections of NMDAR and GABA_AR agonists and antagonists were recorded under α-chloralose-urethane anesthesia. In addition, expressions of excitatory and inhibitory signaling components in the PVN were assessed using immunofluorescence. Our results showed that NMDAR inhibition led to a greater decrease in blood pressure in the BDNF vs. GFP group, while GABA_AR inhibition led to greater increases in blood pressure in the GFP group compared to BDNF. Conversely, GABA_AR activation decreased blood pressure significantly more in GFP vs. BDNF rats. In addition, immunoreactivity of NMDAR1 was upregulated, while GABA_AR-α1 and K⁺/Cl^- cotransporter 2 were downregulated by BDNF overexpression in the PVN. In summary, our findings indicate that hypertensive actions of BDNF within the PVN are mediated, at least in part, by augmented NMDAR and reduced GABA_AR signaling.NEW & NOTEWORTHY We have shown that BDNF, acting in the PVN, elevates blood pressure in part by augmenting NMDA receptor-mediated excitatory input and by diminishing GABA_A receptor-mediated inhibitory input to PVN neurons. In addition, we demonstrate that elevated BDNF expression in the PVN upregulates NMDA receptor immunoreactivity and downregulates GABA_A receptor as well as KCC2 transporter immunoreactivity.

Sympathetic activation in heart failure with reduced and mildly reduced ejection fraction: the role of aetiology

Aim

While sympathetic overactivity in heart failure (HF) with reduced ejection fraction (HFrEF; EF < 40%) is well‐documented, it is ill‐defined in patients with mildly reduced EF (HFmrEF; EF 40–49%). Furthermore, the significance of ischaemic versus non‐ischaemic aetiology in sympathetic activation is also unclear and has yet to be studied in HF. Our goal was to compare muscle sympathetic nerve activity (MSNA) in HFmrEF and HFrEF patients and in healthy subjects, as well as to elucidate the influence of the underlying disease.

Methods and results

Twenty‐three HFrEF (age 58 ± 10 years), 33 HFmrEF patients (age 61 ± 10 years), including 11 subjects with non‐ischaemic cardiomyopathy in each HF groups and 10 healthy controls (age 55 ± 10 years), were studied. MSNA—detected by peroneal microneurography, continuous arterial pressure, and ECG—was recorded. MSNA frequency (burst/min) and incidence (burst/100 cycles) were calculated. Association with the patients' characteristics were assessed, and aetiology‐based comparisons were performed. Burst frequency demonstrated a significant stepwise increase in both HFmrEF (41 ± 11 burst/min) and HFrEF (58 ± 17 burst/min, P < 0.001) patients as compared with controls (27 ± 9; P < 0.001 for both HF groups). Similarly, burst incidences were 66 ± 17, 82 ± 15, and 36 ± 10 burst/100 cycles in HFmrEF, HFrEF patients, and in healthy controls, respectively (P < 0.001 for all). Burst frequencies in HF patients showed significant correlation with NT‐proBNP levels, and significant inverse correlations with the subjects' mean RR intervals, stroke volumes, pulse pressures, and EF.

Conclusions

Muscle sympathetic nerve activity parameters indicated significant sympathetic activation in both HFmrEF and HFrEF patients as compared with healthy controls with no difference in relation to ischaemic versus non‐ischaemic aetiology.

Vascular sympathetic neurotransmission and its serotonergic regulation are modified by chronic fluoxetine treatment

Given the interconnection between depressive and cardiovascular disorders, we investigated whether antidepressant treatment (fluoxetine) modifies the serotonergic influence on rat vascular noradrenergic outflow. Twelve-week-old male Wistar rats received fluoxetine treatment (10 mg/kg/day; p.o.) for 14 days; then, they were pithed and prepared for sympathetic stimulation. Vasopressor responses were obtained by electrical stimulation of the sympathetic outflow (0.1, 0.5, 1, and 5 Hz) or i.v. noradrenaline (NA; 0.01, 0.05, 0.1, and 0.5 μg/kg). In fluoxetine-treated group, the electrical-induced vasoconstrictions were lower compared to non-treated rats. Intravenous infusion of 5-HT (10 μg/kg/min) inhibited the sympathetically-induced vasoconstrictions. Only 5-CT, 8-OH-DPAT and L-694,247 (5-HT1/7, 5-HT1A and 5-HT1D agonists, respectively) mimicked 5-HT-induced inhibition, while α-methyl-5-HT (5-HT2 agonist) increased the vasopressor responses. The inhibitory effect of 5-HT was: a) no modified by SB269970 (5-HT7 antagonist); b) abolished by WAY-100,635 (5-HT1A antagonist) plus LY310762 (5-HT1D antagonist); and c) potentiated by ritanserin (5-HT2A receptor antagonist). The vasoconstrictions induced by exogenous NA were not modified by 5-CT but were increased by α-methyl-5-HT. Our results suggest that fluoxetine treatment decreases NA release at vascular level and changes 5-HT modulation on rat vascular noradrenergic neurotransmission, inducing sympatho-inhibition via prejunctional 5-HT1A/1D receptors, and sympatho-potentiation via pre and/or postjunctional 5-HT2A receptors.

Differential Effect of the Morning Blood Pressure Surge on Prognoses Between Heart Failure With Reduced and Preserved Ejection Fractions

BACKGROUND

Rising blood pressure (BP) in the morning, known as the morning BP surge (MBPS), is known to pose a risk for cardiovascular events in hypertensive individuals. It was not known whether the MBPS was associated with a worse prognosis in patients with heart failure (HF) with a reduced (HFrEF) or preserved (HFpEF) ejection fraction.Methods and Results:We performed a prospective, observational cohort study of hospitalized HF patients who underwent ambulatory BP monitoring (ABPM). The MBPS was calculated by subtracting the mean systolic BP (SBP) during the 1 h that included the lowest sleep BP from the mean SBP during the 2 h after waking. The MBPS group was defined as the top decile of MBPS (>40 mmHg). In all, 456 hospitalized HF patients (mean [±SD] age 68±13 years, 63.9% male) were followed-up for a median of 1.67 years. There were 90 events (16.3 per 100 person-years) of the composite outcome (all-cause mortality and worsening HF) in the HFrEF group, compared with 53 events (19.6 per 100 person-years) in the HFpEF group. Multivariate Cox regression analysis showed that MBPS was a significant predictor of outcome (hazard ratio 2.84, 95% confidence interval 1.58-5.10, P<0.01) in the HFrEF but not HFpEF group.

CONCLUSIONS

MBPS was found to be a novel predictor of worsening HF in patients with HFrEF.

The effect of principal component analysis in the diagnosis of congestive heart failure via heart rate variability analysis

In this study, we investigated the effect of principal component analysis (PCA) in congestive heart failure (CHF) diagnosis using various machine learning algorithms from 5-min HRV data. The extracted 59 heart rate variability (HRV) features consist of statistical time-domain measures, frequency-domain measures (power spectral density estimations from Fourier transform and Lomb-Scargle methods), time-frequency HRV measures (Wavelet transform), and nonlinear HRV measures (Poincare plot, symbolic dynamics, detrended fluctuation analysis, and sample entropy). All these HRV features are the classifiers' inputs. We repeated the study ten times using the first one to the first 10 principal components from PCA instead of all HRV features. Nine different classifiers, namely logistic regression, Naive Bayes, k-nearest neighbors, decision tree, AdaBoost, support vector machines, stochastic gradient descent, random forest, and artificial neuronal network (multilayer perceptron) are examined. The proposed study results in the 100% accuracy, 100% specificity, and 100% sensitivity after utilizing PCA (with the first eight principal components) using the Random Forest classifier where the maximum classifier performances are the 86% accuracy, 79% specificity, and 86% sensitivity before PCA. In conclusion, PCA is beneficial in the diagnosis of patients with CHF. In addition, we experienced the online Python-based visual machine learning tool, Orange, which can implement well-known machine learning algorithms.

Machine learning powered tools for automated analysis of muscle sympathetic nerve activity recordings

Automated analysis and quantification of physiological signals in clinical practice and medical research can reduce manual labor, increase efficiency, and provide more objective, reproducible results. To build a novel platform for the analysis of muscle sympathetic nerve activity (MSNA), we employed state-of-the-art data processing and machine learning applications. Data processing methods for integrated MSNA recordings were developed to evaluate signals regarding the overall quality of the signal, the validity of individual signal peaks regarding the potential to be MSNA bursts and the timing of their occurrence. An overall probability score was derived from this flexible platform to evaluate each individual signal peak automatically. Overall, three deep neural networks were designed and trained to validate individual signal peaks randomly sampled from recordings representing only electrical noise and valid microneurography recordings. A novel data processing method for the whole signal was developed to differentiate between periods of valid MSNA signal recordings and periods in which the signal was not available or lost due to involuntary movement of the recording electrode. A probabilistic model for timing of the signal bursts was implemented as part of the system. Machine Learning algorithms and data processing tools were implemented to replicate the complex decision-making process of manual MSNA analysis. Validation of manual MSNA analysis including intra- and inter-rater validity and a comparison with automated MSNA tools is required. The developed toolbox for automated MSNA analysis can be extended in a flexible way to include algorithms based on other datasets.

Current and emerging drug targets in heart failure treatment

After initial strategies targeting inotropism and congestion, the neurohormonal interpretative model of heart failure (HF) pathophysiology has set the basis for current pharmacological management of HF, as most of guideline recommended drug classes, including beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and mineralocorticoid receptor antagonists, blunt the activation of detrimental neurohormonal axes, namely sympathetic and renin–angiotensin–aldosterone (RAAS) systems. More recently, sacubitril/valsartan, a first-in-class angiotensin receptor neprilysin inhibitor, combining inhibition of RAAS and potentiation of the counter-regulatory natriuretic peptide system, has been consistently demonstrated to reduce mortality and HF-related hospitalization. A number of novel pharmacological approaches have been tested during the latest years, leading to mixed results. Among them, drugs acting directly at a second messenger level, such as the soluble guanylate cyclase stimulator vericiguat, or other addressing myocardial energetics and mitochondrial function, such as elamipretide or omecamtiv-mecarbil, will likely change the therapeutic management of patients with HF. Sodium glucose cotransporter 2 inhibitors, initially designed for the management of type 2 diabetes mellitus, have been recently demonstrated to improve outcome in HF, although mechanisms of their action on cardiovascular system are yet to be elucidated. Most of these emerging approaches have shifted the therapeutic target from neurohormonal systems to the heart, by improving cardiac contractility, metabolism, fibrosis, inflammation, and remodeling. In the present paper, we review from a pathophysiological perspective current and novel therapeutic strategies in chronic HF.

The 2021 Carl Ludwig Lecture. Unsympathetic autonomic regulation in heart failure: patient-inspired insights

Defined as a structural or functional cardiac abnormality accompanied by symptoms, signs, or biomarkers of altered ventricular pressures or volumes, heart failure also is a state of autonomic disequilibrium. A large body of evidence affirms that autonomic disturbances are intrinsic to heart failure; basal or stimulated sympathetic nerve firing or neural norepinephrine (NE) release more often than not exceed homeostatic need, such that an initially adaptive adrenergic or vagal reflex response becomes maladaptive. The magnitude of such maladaptation predicts prognosis. This Ludwig lecture develops two theses: the elucidation and judiciously targeted amelioration of maladaptive autonomic disturbances offers opportunities to complement contemporary guideline-based heart failure therapy, and serendipitous single-participant insights, acquired in the course of experimental protocols with entirely different intent, can generate novel insight, inform mechanisms, and launch entirely new research directions. I précis six elements of our current synthesis of the causes and consequences of maladaptive sympathetic disequilibrium in heart failure, shaped by patient-inspired epiphanies: arterial baroreceptor reflex modulation, excitation stimulated by increased cardiac filling pressure, paradoxical muscle sympathetic activation as a peripheral neurogenic constraint on exercise capacity, renal sympathetic restraint of natriuresis, coexisting sleep apnea, and augmented chemoreceptor reflex sensitivity and then conclude by envisaging translational therapeutic opportunities.

CENTRAL AND PERIPHERAL SYMPATHETIC ACTIVATION IN HEART FAILURE

The sympathetic nervous system overdrive occurring in heart failure has been reported since more than half a century. Refinements in the methodological approaches to assess human sympathetic neural function have allowed during recent years to better define various aspects related to the neuroadrenergic alteration. These include 1) the different participation of the individual regional sympathetic cardiovascular districts at the process, 2) the role of the central nervous system in determining the neuroadrenergic overdrive, 3) the involvement of baroreflex, cardiopulmonary reflex and chemoreflex mechanisms in the phoenomenon, which is also closely linked to inflammation and the immune reaction, 4) the relationships with the severity of the disease, its ischaemic or idiopathic nature and the preserved or reduced left ventricular ejection fraction and 5) the adverse functional and structural impact of the sympathetic activation on cardiovascular organs, such as the brain, the heart and the kidneys. Information have been also gained on the active role exerted by the sympathetic activation on the disease outcome and its potential relevance as target of the therapeutic interventions based on non-pharmacological, pharmacological and invasive approaches, including the renal denervation, the splanchnic sympathetic nerve ablation and the carotid baroreflex stimulation. The still undefined aspects of the neurogenic alterations and the unmet goals of the therapeutic approach having the sympathetic activation as a target of the intervention will be finally mentioned.

Efficacy and safety of propranolol in infants with heart failure due to moderate-to-large ventricular septal defect (VSD-PHF study) - A prospective randomized trial

AIMS

The utility of beta-blocker therapy in infants with heart failure (HF) due to significant left-to-right shunt lesions is not known. The study aimed to assess the efficacy and safety of propranolol in infants with HF due to moderate-to-large ventricular septal defect (VSD).

METHODS

The prospective randomized trial included 80 infants with HF and moderate-to-large VSD, randomly allocated to receive either conventional therapy alone (n = 40) or propranolol plus conventional therapy (n = 40). The primary endpoint was a composite of all-cause mortality, hospitalization for HF and/or chest infection, and referral for surgery. The secondary clinical outcomes were the individual components of the composite endpoint. In addition, the patients were followed up to detect safety outcomes, for example, bronchospasm, bradyarrhythmia, and worsening HF symptoms.

RESULTS

The addition of propranolol therapy to the conventional medications did not result in significant improvement in the primary composite endpoint (32.50% vs. 52.50%; P = 0.07). There was a trend toward improvement, but the study is underpowered for this important question. However, propranolol therapy significantly decreased the risk of hospitalization (12.50% vs. 32.50%; P = 0.03) and worsening of Ross HF class (5.41% vs. 28.21%; P = 0.01) as compared to conventional therapy (estimated number needed to treat = 5). Propranolol did not result in any significant safety concerns in these infants except bronchospasm in an infant.

CONCLUSIONS

Propranolol therapy in infants with significant left-to-right shunt may prevent worsening in HF symptoms and hospitalization and is well tolerated. However, it does not reduce mortality or need for surgery.

Algebraic formulas characterizing an alternative to Guyton's graphical analysis relevant for heart failure

Although Guyton's graphical analysis of cardiac output-venous return has become a ubiquitous tool for explaining how circulatory equilibrium emerges from heart-vascular interactions, this classical model relies on a formula for venous return that contains unphysiological assumptions. Furthermore, Guyton's graphical analysis does not predict pulmonary venous pressure, which is a critical variable for evaluating heart failure patients' risk of pulmonary edema. Therefore, the purpose of the present work was to use a minimal closed-loop mathematical model to develop an alternative to Guyton's analysis. Limitations inherent in Guyton's model were addressed by 1) partitioning the cardiovascular system differently to isolate left ventricular function and lump all blood volumes together, 2) linearizing end-diastolic pressure-volume relationships to obtain algebraic solutions, and 3) treating arterial pressures as constants. This approach yielded three advances. First, variables related to morbidities associated with left ventricular failure were predicted. Second, an algebraic formula predicting left ventricular function was derived in terms of ventricular properties. Third, an algebraic formula predicting flow through the portion of the system isolated from the left ventricle was derived in terms of mechanical properties without neglecting redistribution of blood between systemic and pulmonary circulations. Although complexities were neglected, approximations necessary to obtain algebraic formulas resulted in minimal error, and predicted variables were consistent with reported values.

Anti-arrhythmic and anti-heart failure effects of low-level electrical stimulation on aortic root ventricular ganglionated plexi

BACKGROUND

It remains uncertain whether low-level electrical stimulation (LL-ES) of the ventricular ganglionated plexi (GP) improves heart function. This study investigated the anti-arrhythmic and anti-heart failure effects of LL-ES of the aortic root ventricular GP (ARVGP).

METHODS

Thirty dogs were divided randomly into control, drug, and LL-ES groups after performing rapid right ventricular pacing to establish a heart failure (HF) model. The inducing rate of arrhythmia; levels of bioactive factors influencing HF, including angiotensin II type I receptor (AT-1R), transforming growth factor-beta (TGF-β), matrix metalloproteinase (MMP), and phosphorylated extracellular signal-regulated kinase (p-ERK1/2); left ventricular stroke volume (LVSV), and left ventricular ejection fraction (LVEF)were measured after treatment with placebo, drugs, and LL-ES.

RESULTS

The inducing rate of atrial arrhythmia decreased from 60% in the control group to 50% in the drug group and 10% in the LL-ES group (p = .033 vs. drug group) after 1 week of treatment. The ventricular effective refractory period was prolonged from 139 ± 8 ms in the drug group to 166 ± 13 ms in the LL-ES group (p = .001). Compared to the drug group, the expressions of AT-1R, TGF-β, and MMP proteins were down-regulated in the LL-ES group, whereas that of p-ERK1/2 was significantly increased (all p = .001). Moreover, in the LL-ES group, LVSV increased markedly from 13.16 ± 0.22 to 16.86 ± 0.27 mL, relative to that in the drug group (p = .001), and LVEF increased significantly from 38.48% ± 0.53% to 48.94% ± 0.57% during the same time frame (p = .001).

CONCLUSION

Short-term LL-ES of ARVGP had both anti-arrhythmic and anti-inflammatory effects and contributed to the treatment of tachycardia-induced HF and its associated arrhythmia.

Clinical impact of heart rate change in patients with acute heart failure in the early phase

Aims

Patients with acute heart failure (AHF) often present with an increased heart rate (HR), and the HR changes dramatically after initial treatment for AHF. However, the HR change after admission and the relationship between HR change in the early phase and prognosis have not been fully elucidated.

Methods and results

From a multicentre AHF registry, we retrospectively evaluated 1527 consecutive patients admitted with AHF. HR change (%) was calculated by [HR (at admission) − HR (24 h after admission)] × 100∕HR (at admission). The median HR change was 15.1% (range, 2.0–28.4%). The HR decreased most in the first 24 h and then gradually thereafter [admission: 98 (81–117) b.p.m., 24 h: 80 (70–92) b.p.m., 48 h: 78 (68–90) b.p.m., and 72 h: 77 (67–88) b.p.m.]. In Kaplan–Meier analysis, the cumulative event‐free rates in the composite endpoint of death and rehospitalization due to AHF showed better according to larger HR change (P = 0.012, log rank). Cox proportional hazards analysis showed that HR change was a prognostic factor for composite endpoint adjusted by age and sex [hazard ratio, 0.995; 95% confidence interval (CI), 0.991–0.998; P = 0.006]. HR change was associated with outcome adjusted by age and sex in patients with sinus rhythm (hazard ratio, 0.993; 95% CI, 0.988–0.999; P = 0.015), but not in patients with atrial fibrillation (hazard ratio, 0.996; 95% CI, 0.990–1.002; P = 0.15).

Conclusions

A decrease in HR in the first 24 h after admission indicates better prognosis in patients with AHF, although the prognostic influence may differ between patients with sinus rhythm and those with atrial fibrillation.

MONITORIA: The start of a new era of ambulatory heart failure monitoring? Part I - Theoretical Rationale

Heart failure (HF) is a multifactorial chronic syndrome with progressive increasing incidence causing a huge financial burden worldwide. Remote monitoring should, in theory, improve HF management, but given increasing morbidity and mortality, a question remains: are we monitoring it properly? Device-based home monitoring enables objective and continuous measurement of vital variables and non-invasive devices should be first choice for elderly patients. There is no shortage of literature on the subject, however, most studies were designed to monitor a single variable or class of variables that were not properly assembled and, to the best of our knowledge, there are no large randomized studies about their impact on HF patient management. To overcome this problem, we carefully selected the most critical possible HF decompensating factors to design MONITORIA, a non-invasive device for comprehensive HF home monitoring. MONITORIA stands for MOnitoring Non-Invasively To Overcome mortality Rates of heart Insufficiency on Ambulatory, and in this paper, which is part I of a series of three articles, we discuss the theoretical basis for its design. MONITORIA and its inherent follow-up strategy will optimize HF patient care as it is a promising device, which will essentially adapt innovation not to the disease but rather to the patients.

Long-Term Effects of Ivabradine on Cardiac Vagal Parasympathetic Function in Normal Rats

Background: The complex interactions that exist between the pacemaker current, I _f, and the parasympathetic nervous system could significantly influence the course of patients undergoing chronic therapy with the I _f blocker ivabradine. We thus aimed to assess the effects of chronic ivabradine therapy on autonomic modulation and on the cardiovascular response to in situ and in vitro parasympathetic stimulation. The right atrial expression of HCN genes, encoding proteins for I _f, was also evaluated. Methods: Sympathetic and parasympathetic heart rate variability parameters and right atrial HCN(1-4) RNA levels were analyzed in 6 Control and 10 ivabradine-treated male Wistar rats (IVA; 3 weeks, 10 mg/kg/day). The heart rate (HR) and systolic blood pressure (SBP) responses to in situ electrical stimulation of the vagus nerve (2-20 Hz) were assessed in 6 additional Control and 10 IVA rats. The spontaneous sinus node discharge rate (SNDR) response to in vitro cholinergic receptors stimulation using carbamylcholine (10^-9-10^-6 mol/L) was also assessed in these later rats. Results: Ivabradine significantly increased vagal modulation and shifted the sympatho-vagal balance toward vagal dominance. In Control, in situ vagus nerve stimulation induced progressive decrease in both the SBP (p = 0.0001) and the HR (p< 0.0001). Meanwhile, in IVA, vagal stimulation had no effect on the HR (p = 0.16) and induced a significantly lower drop in SBP (p< 0.05). IVA also displayed a significantly lower SNDR drop in response to carbamylcholine (p< 0.01) and significantly higher right atrial HCN4 expression (p = 0.02). Conclusion: Chronic ivabradine administration enhanced vagal modulation in healthy rats. In addition, ivabradine reduced the HR response to direct muscarinic receptors stimulation, canceled the cardioinhibitory response and blunted the hemodynamic response to in situ vagal stimulation. These data bring new insights into the mechanisms of ivabradine-related atrial proarrhythmia and suggest that long-term I _f blockade may protect against excessive bradycardia induced by acute vagal activation.

From Brain to Blood Vessel: Insights From Muscle Sympathetic Nerve Recordings: Arthur C. Corcoran Memorial Lecture 2020

Multiunit recordings of postganglionic sympathetic outflow to muscle yield otherwise imperceptible insights into sympathetic neural modulation of human vascular resistance and blood pressure. This Corcoran Lecture will illustrate the utility of microneurography to investigate neurogenic cardiovascular regulation; review data concerning muscle sympathetic nerve activity of women and men with normal and high blood pressure; explore 2 concepts, central upregulation of muscle sympathetic outflow and cortical autonomic neuroplasticity; present sleep apnea as an imperfect model of neurogenic hypertension; and expose the paradox of sympathetic excitation without hypertension. In awake healthy normotensive individuals, resting muscle sympathetic nerve activity increases with age, sleep fragmentation, and obstructive apnea. Its magnitude is not signaled by heart rate. Age-related changes are nonlinear and differ by sex. In men, sympathetic nerve activity increases with age but without relation to their blood pressure, whereas in women, both rise concordantly after age 40. Mean values for muscle sympathetic nerve activity burst incidence are consistently higher in cohorts with hypertension than in matched normotensives, yet women's sympathetic nerve traffic can increase 3-fold between ages 30 and 70 without causing hypertension. Thus, increased sympathetic nerve activity may be necessary but is insufficient for primary hypertension. Moreover, its inhibition does not consistently decrease blood pressure. Despite a half-century of microneurographic research, large gaps remain in our understanding of the content of the sympathetic broadcast from brain to blood vessel and its specific individual consequences for circulatory regulation and cardiovascular, renal, and metabolic risk.

Sympathetic neural responses in heart failure during exercise and after exercise training

The sympathetic nervous system coordinates the cardiovascular response to exercise. This regulation is impaired in both experimental and human heart failure with reduced ejection fraction (HFrEF), resulting in a state of sympathoexcitation which limits exercise capacity and contributes to adverse outcome. Exercise training can moderate sympathetic excess at rest. Recording sympathetic nerve firing during exercise is more challenging. Hence, data acquired during exercise are scant and results vary according to exercise modality. In this review we will: (1) describe sympathetic activity during various exercise modes in both experimental and human HFrEF and consider factors which influence these responses; and (2) summarise the effect of exercise training on sympathetic outflow both at rest and during exercise in both animal models and human HFrEF. We will particularly highlight studies in humans which report direct measurements of efferent sympathetic nerve traffic using intraneural recordings. Future research is required to clarify the neural afferent mechanisms which contribute to efferent sympathetic activation during exercise in HFrEF, how this may be altered by exercise training, and the impact of such attenuation on cardiac and renal function.

Resting heart rate predicts all-cause mortality in sub-Saharan African patients with heart failure: a prospective analysis from the Douala Heart failure registry (Do-HF)

Background

Higher resting heart rate (HR) is associated with mortality amongst Caucasians with heart failure (HF), but its significance has yet to be established in sub-Saharan Africans in whom HF differs in terms of characteristics and etiologies. We assessed the association of HR with all-cause mortality in patients with HF in sub-Saharan Africa.

Methods

The Douala HF registry (Do-HF) is an ongoing prospective data collection on patients with HF receiving care at four cardiac referral services in Douala, Cameroon. Patients included in this report were followed-up for 12 months from their index admission, for all-cause mortality. We used Cox-regression analysis to study the association of HR with all-cause mortality during follow-up.

Results

Of 347 patients included, 343 (98.8%) completed follow-up. The mean age was 64±14 years, 176 (50.7%) were female, and median admission HR was 85 bpm. During a median follow-up of 12 months, 78 (22.7%) patients died. Mortality increased steadily with HR increase and ranged from 12.2% in the lower quartile of HR (≤69 bpm) to 34.1% in the upper quartile of HR (>100 bpm). Hazard ratio of 12-month death per 10 bpm higher HR was 1.16 (1.04-1.29), with consistent effects across most subgroups, but a higher effect in participants with hypertension vs. those without (interaction P=0.044).

Conclusions

HR was independently associated with increased risk of all-cause mortality in this study, particularly among participants with hypertension. The implication of this finding for risk prediction or reduction should be actively investigated.

MONITORIA: The start of a new era of ambulatory heart failure monitoring? Part I - Theoretical Rationale

Heart failure (HF) is a multifactorial chronic syndrome with progressive increasing incidence causing a huge financial burden worldwide. Remote monitoring should, in theory, improve HF management, but given increasing morbidity and mortality, a question remains: are we monitoring it properly? Device-based home monitoring enables objective and continuous measurement of vital variables and non-invasive devices should be first choice for elderly patients. There is no shortage of literature on the subject, however, most studies were designed to monitor a single variable or class of variables that were not properly assembled and, to the best of our knowledge, there are no large randomized studies about their impact on HF patient management. To overcome this problem, we carefully selected the most critical possible HF decompensating factors to design MONITORIA, a non-invasive device for comprehensive HF home monitoring. MONITORIA stands for MOnitoring Non-Invasively To Overcome mortality Rates of heart Insufficiency on Ambulatory, and in this paper, which is part I of a series of three articles, we discuss the theoretical basis for its design. MONITORIA and its inherent follow-up strategy will optimize HF patient care as it is a promising device, which will essentially adapt innovation not to the disease but rather to the patients.

Impairments in Blood Pressure Regulation and Cardiac Baroreceptor Sensitivity Among Patients With Heart Failure Supported With Continuous-Flow Left Ventricular Assist Devices

BACKGROUND

Continuous-flow (CF) left ventricular assist devices (LVADs) improve outcomes for patients with advanced heart failure (HF). However, the lack of a physiological pulse predisposes to side-effects including uncontrolled blood pressure (BP), and there are little data regarding the impact of CF-LVADs on BP regulation.

METHODS

Twelve patients (10 males, 60±11 years) with advanced heart failure completed hemodynamic assessment 2.7±4.1 months before, and 4.3±1.3 months following CF-LVAD implantation. Heart rate and systolic BP via arterial catheterization were monitored during Valsalva maneuver, spontaneous breathing, and a 0.05 Hz repetitive squat-stand maneuver to characterize cardiac baroreceptor sensitivity. Plasma norepinephrine levels were assessed during head-up tilt at supine, 30^o and 60^o. Heart rate and BP were monitored during cardiopulmonary exercise testing.

RESULTS

Cardiac baroreceptor sensitivity, determined by Valsalva as well as Fourier transformation and transfer function gain of Heart rate and systolic BP during spontaneous breathing and squat-stand maneuver, was impaired before and following LVAD implantation. Norepinephrine levels were markedly elevated pre-LVAD and improved-but remained elevated post-LVAD (supine norepinephrine pre-LVAD versus post-LVAD: 654±437 versus 323±164 pg/mL). BP increased during cardiopulmonary exercise testing post-LVAD, but the magnitude of change was modest and comparable to the changes observed during the pre-LVAD cardiopulmonary exercise testing.

CONCLUSIONS

Among patients with advanced heart failure with reduced ejection fraction, CF-LVAD implantation is associated with modest improvements in autonomic tone, but persistent reductions in cardiac baroreceptor sensitivity. Exercise-induced increases in BP are blunted. These findings shed new light on mechanisms for adverse events such as stroke, and persistent reductions in functional capacity, among patients supported by CF-LVADs. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03078972.

Measuring Peripheral Chemoreflex Hypersensitivity in Heart Failure

Heart failure with reduced ejection fraction (HFrEF) induces chronic sympathetic activation. This disturbance is a consequence of both compensatory reflex disinhibition in response to lower cardiac output and patient-specific activation of one or more excitatory stimuli. The result is the net adrenergic output that exceeds homeostatic need, which compromises cardiac, renal, and vascular function and foreshortens lifespan. One such sympatho-excitatory mechanism, evident in ~40-45% of those with HFrEF, is the augmentation of carotid (peripheral) chemoreflex ventilatory and sympathetic responsiveness to reductions in arterial oxygen tension and acidosis. Recognition of the contribution of increased chemoreflex gain to the pathophysiology of HFrEF and to patients' prognosis has focused attention on targeting the carotid body to attenuate sympathetic drive, alleviate heart failure symptoms, and prolong life. The current challenge is to identify those patients most likely to benefit from such interventions. Two assumptions underlying contemporary test protocols are that the ventilatory response to acute hypoxic exposure quantifies accurately peripheral chemoreflex sensitivity and that the unmeasured sympathetic response mirrors the determined ventilatory response. This Perspective questions both assumptions, illustrates the limitations of conventional transient hypoxic tests for assessing peripheral chemoreflex sensitivity and demonstrates how a modified rebreathing test capable of comprehensively quantifying both the ventilatory and sympathoneural efferent responses to peripheral chemoreflex perturbation, including their sensitivities and recruitment thresholds, can better identify individuals most likely to benefit from carotid body intervention.

Cardiovascular Autonomic Disturbances in Heart Failure With Preserved Ejection Fraction

In heart failure with reduced ejection fraction (HFrEF), diminished tonic and reflex vagal heart rate modulation and exaggerated sympathetic outflow and neural norepinephrine release are evident from disease inception. Each of these disturbances of autonomic regulation has been independently associated with shortened survival, and β-adrenoceptor antagonism and therapeutic autonomic modulation by other means have been demonstrated, in clinical trials, to lessen symptoms and prolong survival. In contrast, data concerning the autonomic status of patients with heart failure with preserved ejection fraction (HFpEF) are comparatively sparse. Little is known concerning the prognostic consequences of autonomic dysregulation in such individuals, and therapies applied with success in HFrEF have in most trials failed to improve symptoms or survival of those with HFpEF. A recent HFpEF Expert Scientific Panel report emphasised that without a deeper understanding of the pathophysiology of HFpEF, establishing effective treatment will be challenging. One aspect of such pathology may be cardiovascular autonomic disequilibrium, often worsened by acute exercise or routine daily activity. This review aims to summarise existing knowledge concerning parasympathetic and sympathetic function of patients with HFpEF, consider potential mechanisms and specific consequences of autonomic disturbances that have been identified, and propose hypotheses for future investigation.

Role of comorbidities in heart failure prognosis Part 2: Chronic kidney disease, elevated serum uric acid

Despite improvements in pharmacotherapy, morbidity and mortality rates in community-based populations with chronic heart failure still remain high. The increase in medical complexity among patients with heart failure may be reflected by an increase in concomitant non-cardiovascular comorbidities, which are recognized as independent prognostic factors in this population. Heart failure and chronic kidney disease share many risk factors, and often coexist. The presence of kidney failure is associated with incremented risk of cardiovascular and non-cardiovascular mortality in heart failure patients. Chronic kidney disease is also linked with underutilization of evidence-based heart failure therapy that may reduce morbidity and mortality. More targeted therapies would be important to improve the prognosis of patients with these diseases. In recent years, serum uric acid as a determinant of cardiovascular risk has gained interest. Epidemiological, experimental and clinical data show that patients with hyperuricaemia are at increased risk of cardiac, renal and vascular damage and cardiovascular events. Moreover, elevated serum uric acid predicts worse outcome in both acute and chronic heart failure. While studies have raised the possibility of preventing heart failure through the use of uric acid lowering agents, the literature is still inconclusive on whether the reduction in uric acid will result in a measurable clinical benefit. Available evidences suggest that chronic kidney disease and elevated uric acid could worsen heart failure patients' prognosis. The aim of this review is to analyse a possible utilization of these comorbidities in risk stratification and as a therapeutic target to get a prognostic improvement in heart failure patients.

Hemodynamic adaptation of heart failure to percutaneous venoarterial extracorporeal circulatory supports

Extracorporeal life support (ECLS) is a treatment modality that provides prolonged blood circulation, gas exchange and can partially support or fully substitute functions of heart and lungs in patients with severe but potentially reversible cardiopulmonary failure refractory to conventional therapy. Due to high-volume bypass, the extracorporeal flow is interacting with native cardiac output. The pathophysiology of circulation and ECLS support reveals significant effects on arterial pressure waveforms, cardiac hemodynamics, and myocardial perfusion. Moreover, it is still subject of research, whether increasing stroke work caused by the extracorporeal flow is accompanied by adequate myocardial oxygen supply. The left ventricular (LV) pressure-volume mechanics are reflecting perfusion and loading conditions and these changes are dependent on the degree of the extracorporeal blood flow. By increasing the afterload, artificial circulation puts higher demands on heart work with increasing myocardial oxygen consumption. Further, this can lead to LV distention, pulmonary edema, and progression of heart failure. Multiple methods of LV decompression (atrial septostomy, active venting, intra-aortic balloon pump, pulsatility of flow) have been suggested to relieve LV overload but the main risk factors still remain unclear. In this context, it has been recommended to keep the rate of circulatory support as low as possible. Also, utilization of detailed hemodynamic monitoring has been suggested in order to avoid possible harm from excessive extracorporeal flow.

J-curve relationship between corrected QT interval and mortality in acute heart failure patients

BACKGROUND/AIMS

This study investigated the prognostic power of corrected QT (QTc) interval in patients with acute heart failure (AHF) according to sex.

METHODS

We analyzed multicenter Korean Acute Heart Failure registry with patients with AHF admitted from 2011 to 2014. Among them, we analyzed 4,990 patients who were followed up to 5 years. Regarding QTc interval based on 12 lead electrocardiogram, patients were classified into quartiles according to sex.

RESULTS

During follow-up with median 43.7 months, 2,243 (44.9%) patients died. The relationship between corrected QT interval and all-cause mortality followed a J-curve relationship. In Kaplan-Meier analysis, both sex had lowest mortality in the second QTc quartile. There were significant prognostic differences between the second and the fourth quartiles in male (log-rank p = 0.002), but not in female (log-rank p = 0.338). After adjusting covariates, the third (hazard ratio [HR], 1.185; 95% confidence interval [CI], 1.001 to 1.404; p = 0.049) and the fourth (HR, 1.404; 95% CI, 1.091 to 1.535; p = 0.003) quartiles demonstrated increased risk of mortality compared to the second quartile in male. In female, however, there was no significant difference across quartiles. QTc interval was associated with 5-year all-cause mortality in J-shape with nadir of 440 to 450 ms in male and 470 to 480 ms in female.

CONCLUSION

QTc interval was an independent predictor of overall death in male, but its significance decreased in female. The relationship between QTc interval and all-cause mortality was J-shaped in both sex.

Sympathetic Markers are Different Between Clinical Responders and Nonresponders After Left Ventricular Assist Device Implantation

BACKGROUND

Clinical response to left ventricular assist devices (LVADs), as measured by health-related quality of life, varies among patients after implantation; however, it is unknown which pathophysiological mechanisms underlie differences in clinical response by health-related quality of life.

OBJECTIVE

The purpose of this study was to compare changes in sympathetic markers (β-adrenergic receptor kinase-1 [βARK1], norepinephrine [NE], and 3,4-dihydroxyphenylglycol [DHPG]) between health-related quality of life clinical responders and nonresponders from pre- to post-LVAD implantation.

METHODS

We performed a secondary analysis on a subset of data from a cohort study of patients from pre- to 1, 3, and 6 months after LVAD implantation. Clinical response was defined as an increase of 5 points or higher on the Kansas City Cardiomyopathy Questionnaire Clinical Summary score from pre- to 6 months post-LVAD implantation. We measured plasma βARK1 level with an enzyme-linked immunosorbent assay and plasma NE and DHPG levels with high-performance liquid chromatography with electrochemical detection. Latent growth curve modeling was used to compare the trajectories of markers between groups.

RESULTS

The mean (SD) age of the sample (n = 39) was 52.9 (13.2) years, and most were male (74.4%) and received LVADs as bridge to transplantation (69.2%). Preimplantation plasma βARK1 levels were significantly higher in clinical responders (n = 19) than in nonresponders (n = 20) (P = .001), but change was similar after LVAD (P = .235). Preimplantation plasma DHPG levels were significantly lower in clinical responders than in nonresponders (P = .002), but the change was similar after LVAD (P = .881). There were no significant differences in plasma NE levels.

CONCLUSIONS

Preimplantation βARK1 and DHPG levels are differentiating factors between health-related quality of life clinical responders and nonresponders to LVAD, potentially signaling differing levels of sympathetic stimulation underlying clinical response.

The role of the tripartite synapse in the heart: how glial cells may contribute to the physiology and pathophysiology of the intracardiac nervous system

One of the major roles of the intracardiac nervous system (ICNS) is to act as the final site of signal integration for efferent information destined for the myocardium to enable local control of heart rate and rhythm. Multiple subtypes of neurons exist in the ICNS where they are organized into clusters termed ganglionated plexi (GP). The majority of cells in the ICNS are actually glial cells; however, despite this, ICNS glial cells have received little attention to date. In the central nervous system, where glial cell function has been widely studied, glia are no longer viewed simply as supportive cells but rather have been shown to play an active role in modulating neuronal excitability and synaptic plasticity. Pioneering studies have demonstrated that in addition to glia within the brain stem, glial cells within multiple autonomic ganglia in the peripheral nervous system, including the ICNS, can also act to modulate cardiovascular function. Clinically, patients with atrial fibrillation (AF) undergoing catheter ablation show high plasma levels of S100B, a protein produced by cardiac glial cells, correlated with decreased AF recurrence. Interestingly, S100B also alters GP neuron excitability and neurite outgrowth in the ICNS. These studies highlight the importance of understanding how glial cells can affect the heart by modulating GP neuron activity or synaptic inputs. Here, we review studies investigating glia both in the central and peripheral nervous systems to discuss the potential role of glia in controlling cardiac function in health and disease, paying particular attention to the glial cells of the ICNS.

Treatment of Cheyne-Stokes respiration with adaptive servoventilation-analysis of patients with regard to therapy restriction

Purpose

The SERVE-HF study revealed no benefit of adaptive servoventilation (ASV) versus guideline-based medical treatment in patients with symptomatic heart failure, an ejection fraction (EF) ≤45% and a predominance of central events (apnoea-hypopnea Index [AHI] > 15/h). Because both all-cause and cardiovascular mortality were higher in the ASV group, an EF ≤ 45% in combination with AHI 15/h, central apnoea-hyponoea index [CAHI/AHI] > 50% and central apnoea index [CAI] > 10/h were subsequently listed as contraindications for ASV. The intention of our study was to analyse the clinical relevance of this limitation.

Methods

Data were analysed retrospectively for patients treated with ASV who received follow-up echocardiography to identify contraindications for ASV.

Results

Echocardiography was conducted in 23 patients. The echocardiogram was normal in 10 cases, a left ventricular hypertrophy with normal EF was found in 8 patients, there was an EF 45-50% in 2 cases and a valvular aortic stenosis (grade II) with normal EF was found in 1 case. EF <45% was present in just 2 cases, and only 1 of these patients also had more than 50% central events in the diagnostic night.

Conclusion

The population typically treated with ASV is entirely different from the study population in SERVE-HF, as nearly half of the patients treated with ASV showed a normal echocardiogram. Thus, the modified indication for ASV has little impact on the majority of treated patients. The current pathomechanistic hypothesis of central apnoea must be reviewed.

Cardiac Autonomic Modulation Is Different in Terms of Clinical Variant of Multiple Sclerosis

This study evaluates whether the cardiac autonomic response to head-up tilt test (HUTT) differs between patients with relapsing-remitting multiple sclerosis (RRMS) and those with progressive MS (PMS) as compared to healthy controls (HC). Baroreflex sensitivity, cardiac parameters, heart rate (HRV) and blood pressure variability (BPV) were compared between 28 RRMS, 21PMS and 25 HC during HUTT. At rest, PMS patients had higher values of the sympathovagal ratio, a low-frequency band HRV (LFnu-RRI) and lower values of parasympathetic parameters (HFnu-RRI, HF-RRI) compared to RRMS and HC. Resting values of cardiac parameters were significantly lower in RRMS compared to PMS patients. No intergroup differences were observed for post-tilt cardiac and autonomic parameters, except for delta HF-RRI with lower values in the PMS group. The MS variant corrected for age, sex and Expanded Disability Status Scale (EDSS) score was an independent predictor of changes in the sympathovagal ratio as measured by HRV. Furthermore, a higher overall EDDS score was related to a higher sympathovagal ratio, lower parasympathetic parameters at rest, and decrease post-tilt changes of the sympathovagal ratio of sBP BPV. Autonomic imbalance is markedly altered in the MS patient group compared to control changes were most pronounced in the progressive variant of MS disease. The MS variant appeared to have a potential influence on cardiac autonomic imbalance at rest.

Delay in seeking treatment before emergent heart failure readmission and its association with clinical phenotype

Background

Many patients with emergent heart failure (HF) readmission have a delay between symptom onset and hospitalization. The present study aimed to characterize the interval between symptom onset and hospitalization in patients being readmitted for HF and to compare the clinical phenotypes of patients with delay before emergent readmission with those who presented to the hospital earlier.

Methods

Data for a total of 2073 consecutive patients was collected from the Tokyo CCU Network database; the patients were divided into delayed (those who sought medical help > 2 days after symptom onset; n = 271) and early groups (remaining patients; n = 1802), and their clinical characteristics and mode of presentation were compared.

Results

Age, sex, and laboratory findings including brain natriuretic peptide and serum creatinine levels were not significantly different between the two groups. Patients in the delayed group had greater chronic fluid retention and symptoms not associated with respiratory failure, whereas those in the early group were more likely to have acute respiratory distress, faster heart and respiration rates, and higher systolic blood pressure.

Conclusions

More than one in ten patients with HF readmission delay seeking treatment > 2 days after symptom onset. Patients who delayed seeking treatment showed the phenotype of chronic fluid retention, whereas those who presented to the hospital earlier had the phenotype of acute respiratory failure.

Review of the health benefits of habitual consumption of miso soup: focus on the effects on sympathetic nerve activity, blood pressure, and heart rate

High salt intake increases blood pressure, and dietary salt intake has been clearly demonstrated to be associated with hypertension incidence. Japanese people consume higher amounts of salt than Westerners. It has been reported that miso soup was one of the major sources of daily salt intake in Japanese people. Adding salt is indispensable to make miso, and therefore, in some cases, refraining from miso soup is recommended to reduce dietary salt intake. However, recent studies using salt-sensitive hypertensive models have revealed that miso lessens the effects of salt on blood pressure. In other word, the intake of miso dose not increase the blood pressure compared to the equivalent intake of salt. In addition, many clinical observational studies have demonstrated the absence of a relationship between the frequency of miso soup intake and blood pressure levels or hypertension incidence. The mechanism of this phenomenon seen in the subjects with miso soup intake has not been fully elucidated yet. However, in basic studies, it was found that the ingredients of miso attenuate sympathetic nerve activity, resulting in lowered blood pressure and heart rate. Therefore, this review focused on the differences between the effects of miso intake and those of the equivalent salt intake on sympathetic nerve activity, blood pressure, and heart rate.

Subclinical decrease in cardiac autonomic and diastolic function in patients with metabolic disorders: HSCAA study

Heart failure due to decreased diastolic function, HFpEF, is a growing health concern with rising prevalence. We examined subclinical cardiac autonomic and diastolic functions in 605 patients with metabolic diseases classified as pre-heart failure. Presence of glucose intolerance or diabetes, or visceral adiposity was significantly associated with reduced cardiac autonomic and diastolic functions. Higher autonomic functions were significantly associated with a parameter of better cardiac diastolic function (E/A) (SDNN: r = 0.306, p < 0.01; HF: r = 0.341, p < 0.01), with the association independent of diabetes, body mass index, visceral adiposity and insulin resistance index. Thus, reduced autonomic function may be a potential predictor for decreased cardiac diastolic functions in metabolic disorders.

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Metabolic disorders, including diabetes and obesity, are known risk factors for HFpEF.

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Reduced autonomic function may be involved in pathogenesis of HFpEF.

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Cardiac diastolic function in metabolic disorders in pre-HF phase is not well examined.

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In pre-HF subjects, reduced autonomic function is associated with lower cardiac diastolic functions.

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Our findings provide new insights into HFpEF etiology in metabolic disorders.

Cardiac autonomic control during non-REM and REM sleep stages in paediatric patients with Prader-Willi syndrome

Cardiac death is the second most prevalent cause in Prader-Willi syndrome (PWS). Paediatric patients with PWS often present cardiac autonomic dysfunction during wakefulness, obesity and sleep-disordered breathing. However, the extent of cardiac autonomic modulation during sleep in PWS has not been documented. The objective of this study was to assess alterations in cardiac autonomic modulation of paediatric patients with PWS during different sleep stages. Thirty-nine participants in three groups: 14 PWS, 13 sex and age-matched lean controls (LG) and 12 obese-matched controls (OB). All participants underwent overnight polysomnography, including continuous electrocardiogram recordings. Heart rate variability (HRV) was analysed during representative periods of each sleep stage through time and frequency domains calculated across 5-min periods. Between-within ANOVAs were employed (p < .05). The results show that total HRV was lower in PWS than OB and LG during slow-wave sleep (SWS) (standard deviation of all NN intervals [SDNN] ms, p = .006). Parasympathetic modulation assessed by time-domain analysis was lower during SWS in PWS compared to both OB and LG (square root of the mean of the sum of the squares of differences between adjacent NN intervals [RMSSD] ms, p = .004; SDSD, standard deviation of differences between adjacent NN intervals [SDSD] ms, p = .02; number of adjacent NN intervals differing by >50 ms [NN50] ms, p = .03; proportion of adjacent NN intervals differing by >50 ms [pNN50] ms, p = .01). Sympathovagal balance assessed by frequency-domain analysis was lower during both N2 and SWS than during the rapid eye movement (REM) sleep stage, but not different among groups. In conclusion, this group of paediatric patients with PWS had impaired cardiac autonomic balance due to reduced parasympathetic modulation during SWS. This result could imply an underlying increased cardiovascular risk in PWS even during early age and independent of obesity.

Sympathetic activation: a potential link between comorbidities and COVID-19

In coronavirus disease 2019 (COVID-19), higher morbidity and mortality are associated with age, male gender, and comorbidities, such as chronic lung diseases, cardiovascular pathologies, hypertension, kidney diseases, diabetes mellitus, and obesity. All of the above conditions are characterized by increased sympathetic discharge, which may exert significant detrimental effects on COVID-19 patients, through actions on the lungs, heart, blood vessels, kidneys, metabolism, and/or immune system. Furthermore, COVID-19 may also increase sympathetic discharge, through changes in blood gases (chronic intermittent hypoxia, hyperpnea), angiotensin-converting enzyme (ACE)1/ACE2 imbalance, immune/inflammatory factors, or emotional distress. Nevertheless, the potential role of the sympathetic nervous system has not yet been considered in the pathophysiology of COVID-19. In our opinion, sympathetic overactivation could represent a so-far undervalued mechanism for a vicious circle between COVID-19 and comorbidities.

Effects of occlusal disharmony on cardiac fibrosis, myocyte apoptosis and myocyte oxidative DNA damage in mice

Occlusal disharmony leads to morphological changes in the hippocampus and osteopenia of the lumbar vertebra and long bones in mice, and causes stress. Various types of stress are associated with increased incidence of cardiovascular disease, but the relationship between occlusal disharmony and cardiovascular disease remain poorly understood. Therefore, in this work, we examined the effects of occlusal disharmony on cardiac homeostasis in bite-opening (BO) mice, in which a 0.7 mm space was introduced by cementing a suitable applicance onto the mandibular incisior. We first examined the effects of BO on the level of serum corticosterone, a key biomarker for stress, and on heart rate variability at 14 days after BO treatment, compared with baseline. BO treatment increased serum corticosterone levels by approximately 3.6-fold and the low frequency/high frequency ratio, an index of sympathetic nervous activity, was significantly increased by approximately 4-fold by the BO treatment. We then examined the effects of BO treatment on cardiac homeostasis in mice treated or not treated with the non-selective β-blocker propranolol for 2 weeks. Cardiac function was significantly decreased in the BO group compared to the control group, but propranolol ameliorated the dysfunction. Cardiac fibrosis, myocyte apoptosis and myocyte oxidative DNA damage were significantly increased in the BO group, but propranolol blocked these changes. The BO-induced cardiac dysfunction was associated with increased phospholamban phosphorylation at threonine-17 and serine-16, as well as inhibition of Akt/mTOR signaling and autophagic flux. These data suggest that occlusal disharmony might affect cardiac homeostasis via alteration of the autonomic nervous system.

Effects of central apneas on sympathovagal balance and hemodynamics at night: impact of underlying systolic heart failure

BACKGROUND

Increased sympathetic drive is the key determinant of systolic heart failure progression, being associated with worse functional status, arrhythmias, and increased mortality. Central sleep apnea is highly prevalent in systolic heart failure, and its effects on sympathovagal balance (SVB) and hemodynamics might depend on relative phase duration and background pathophysiology.

OBJECTIVE

This study compared the effects of central apneas in patients with and without systolic heart failure on SVB and hemodynamics during sleep.

METHODS

During polysomnography, measures of SVB (heart rate and diastolic blood pressure variability) were non-invasively recorded and analyzed along with baroreceptor reflex sensitivity and hemodynamic parameters (stroke volume index, cardiac index, total peripheral resistance index). Data analysis focused on stable non-rapid eye movement N2 sleep, comparing normal breathing with central sleep apnea in subjects with and without systolic heart failure.

RESULTS

Ten patients were enrolled per group. In heart failure patients, central apneas had neutral effects on SVB (all p > 0.05 for the high, low, and very low frequency components of heart rate and diastolic blood pressure variability). Patients without heart failure showed an increase in very low and low frequency components of diastolic blood pressure variability in response to central apneas (63 ± 18 vs. 39 ± 9%; p = 0.001, 43 ± 12 vs. 31 ± 15%; p = 0.002). In all patients, central apneas had neutral hemodynamic effects when analyzed over a period of 10 min, but had significant acute hemodynamic effects.

CONCLUSION

Effects of central apneas on SVB during sleep depend on underlying systolic heart failure, with neutral effects in heart failure and increased sympathetic drive in idiopathic central apneas.

Inverse relationship of subjective daytime sleepiness to mortality in heart failure patients with sleep apnoea

Aims

Patients with sleep apnoea (SA) and heart failure (HF) are less sleepy than SA patients without HF. HF and SA both increase sympathetic nervous system activity (SNA). SNA can augment alertness. We previously showed that in HF patients, the degree of daytime sleepiness was not related to the severity of SA but was inversely related to SNA. Elevated SNA is associated with increased mortality in HF. Therefore, we hypothesized that in HF patients with SA, the degree of daytime sleepiness will be inversely related to mortality.

Methods and results

In a prospective cohort study, 218 consecutive patients with systolic HF had overnight polysomnography. Among them, 80 subjects with SA (apnoea–hypopnoea index ≥15) were followed for a mean of 28 months to determine all‐cause mortality rate. Subjective daytime sleepiness was assessed by the Epworth Sleepiness Scale (ESS). During follow‐up, 20 patients died. The 5 year death rate in patients with ESS less than 6 (i.e. less sleepy) was significantly higher than in patients with an ESS at or above the median of 6 (i.e. sleepier) [21.3 deaths/100 patient‐years vs. 6.2 deaths/100 patient‐years, unadjusted hazard ratio (HR) 2.94, 95% confidence interval (CI) 1.20 to 7.20, P = 0.018]. After adjusting for confounding factors that included sex, history of hypertension, and mean arterial oxyhaemoglobin saturation, compared with the sleepier patients, less sleepy patients had greater risk of mortality (HR 2.56, 95% CI 1.01 to 6.47, P = 0.047). As a continuous variable, ESS scores were inversely related to mortality risk (HR 0.86, 95% CI 0.75 to 0.98, P = 0.022).

Conclusions

In patients with HF and SA, the degree of subjective daytime sleepiness is inversely related to the mortality risk, suggesting that among HF patients with SA, those with the least daytime sleepiness are at greater risk of death. They may therefore have greater potential for mortality benefit from therapy of SA than those with greater daytime sleepiness.

Does empagliflozin modulate the autonomic nervous system among individuals with type 2 diabetes and coronary artery disease? The EMPA-HEART CardioLink-6 Holter analysis

Context

We examined if empagliflozin was associated with modulation of cardiac autonomic tone among subjects with type 2 diabetes and stable coronary artery disease (CAD) relative to placebo.

Methods

Using ambulatory 24-h Holter electrocardiographic data prospectively collected from a randomized trial, we compared changes in heart rate variability (HRV) parameters between empagliflozin- and placebo-assigned subjects over a follow-up period of 6 months. Measured HRV domains included: standard deviation (SD) of NN intervals (SDNN), SD of average NN intervals per 5-min (SDANN), root mean square of successive RR interval differences (RMSSD), % successive NN intervals differing >50 ms (ms) (pNN50), low frequency (LF), high frequency (HF) and the LF/HF ratio (LF:HF). Differences in HRV parameters between the 2 groups were compared with analysis of covariance (ANCOVA). Statistical measures of significance were reported as adjusted differences between the 2 groups and their corresponding 95% confidence intervals.

Results

Sixty-six subjects completed 24-h Holter monitoring at baseline and 6-months. Over 6 months, the change in HRV was similar between subjects treated with empagliflozin vs. placebo for the following parameters: RMSSD -1.2 ms (-6.0 to 3.6 ms); pNN50 0.5% (-2.6 to 3.6%); VLF -907.8 ms² (-2388.8 to 573.1 ms²); LF -341 ms² (-878.7 to 196.7 ms²); HF -33.8 ms² (-111.1 to 43.5 ms²); LF:HF -0.1 (-0.4 to 0.2). Subjects who received placebo experienced an increase in SDNN 18.6 ms (2.8–34.3 ms) and SDANN 20.2 ms (3.2–37.3 ms) relative to those treated with empagliflozin.

Conclusion

Compared to placebo, empagliflozin did not result in changes in autonomic tone among individuals with type 2 diabetes and stable coronary artery disease.

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Sodium-glucose cotransporter-2 (SGLT2) inhibitors’ mechanism of cardiovascular benefit is unknown.

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Impaired autonomic tone is associated with adverse cardiac events.

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Cardiac autonomic tone was assessed with Holter studies from a randomized trial.

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Similar autonomic tone noted between subjects treated with empagliflozin and placebo.

Noninvasive Positive Pressure Ventilation for Acute Decompensated Heart Failure

Noninvasive positive pressure ventilation (NIPPV), which can be applied without endotracheal airway or tracheostomy, has been used as the first-line device for patients with acute decompensated heart failure (ADHF) and cardiogenic pulmonary edema. Positive airway pressure (PAP) devices include continuous PAP, bilevel PAP, and adaptive servoventilation. NIPPV can provide favorable physiologic benefits, including improving oxygenation, respiratory mechanics, and pulmonary and systemic hemodynamics. It can also reduce the intubation rate and improve clinical symptoms, resulting in good quality of life and mortality.

Chronic Sympathetic Hyperactivity Triggers Electrophysiological Remodeling and Disrupts Excitation-Contraction Coupling in Heart

The sympathetic nervous system is essential for maintenance of cardiac function via activation of post-junctional adrenergic receptors. Prolonged adrenergic receptor activation, however, has deleterious long-term effects leading to hypertrophy and the development of heart failure. Here we investigate the effect of chronic adrenergic receptors activation on excitation-contraction coupling (ECC) in ventricular cardiomyocytes from a previously characterized mouse model of chronic sympathetic hyperactivity, which are genetically deficient in the adrenoceptor α2A and α2C genes (ARDKO). When compared to wild-type (WT) cardiomyocytes, ARDKO displayed reduced fractional shortening (~33%) and slower relaxation (~20%). Furthermore, ARDKO cells exhibited several electrophysiological changes such as action potential (AP) prolongation (~50%), reduced L-type calcium channel (LCC) current (~33%), reduced outward potassium (K+) currents (~30%), and increased sodium/calcium exchanger (NCX) activity (~52%). Consistent with reduced contractility and calcium (Ca2+) currents, the cytosolic Ca2+ ([Ca2+]i) transient from ARDKO animals was smaller and decayed slower. Importantly, no changes were observed in membrane resting potential, AP amplitude, or the inward K+ current. Finally, we modified our existing cardiac ECC computational model to account for changes in the ARDKO heart. Simulations suggest that cellular changes in the ARDKO heart resulted in variable and dyssynchronous Ca2+-induced Ca2+ release therefore altering [Ca2+]i transient dynamics and reducing force generation. In conclusion, chronic sympathetic hyperactivity impairs ECC by changing the density of several ionic currents (and thus AP repolarization) causing altered Ca2+ dynamics and contractile activity. This demonstrates the important role of ECC remodeling in the cardiac dysfunction secondary to chronic sympathetic activity.