Search Results (185)

Heart rate (HR) is strongly affected by the autonomic nervous system (ANS), while its spontaneous fluctuations, called heart rate variability (HRV), report about the dynamics of the complex, vegetative regulation of the heart rhythm. Hence, HRV is widely considered an important marker of the ANS effects on the cardiac system, and as such, a crucial diagnostic tool in cardiology. In order to obtain nontrivial results from HRV analysis, it would be desirable to establish exact, universal interrelations between the typical HRV parameters and HR itself. That, however, has not yet been fully accomplished. Hence, our aim was to perform a comparative statistical analysis of ECG recordings from a public database, with a focus on the HR dependence of typical HRV parameters. We revealed their fundamental connections, which were substantiated by basic mathematical considerations, and were experimentally demonstrated via the analysis of 24 h of ECG recordings of more than 200 healthy individuals. The large database allowed us to perform unique age-cohort analyses. We confirmed the HR dependence of typical time-domain parameters, such as RMSSD and SDNN, frequency-domain parameters such as the VLF, LF, and HF components, and nonlinear indices such as sample entropy and DFA exponents. In addition to shedding light on their relationship, we are the first, to our knowledge, to identify a new, diffuse structure in the VHF regime as an important indicator of SNS activity. In addition, the demonstrated age dependence of the HRV parameters gives important new insight into the long-term changes in the ANS regulation of the cardiac system. As a possible molecular physiological mechanism underlying our new findings, we suggest that they are associated with Piezo2 channel function and its age-related degradation. We expect our results to be utilized in HRV analysis related to both medical research and practice. Full article

This review explores current and emerging neuromodulation techniques targeting the cardiac autonomic nervous system for the treatment and prevention of atrial and ventricular arrhythmias. Arrhythmias remain a significant cause of morbidity and mortality, with the autonomic nervous system playing a crucial role in arrhythmogenesis. Interventions span surgical, pharmacological, and bioelectronic methods. We discuss the range of neuromodulation methods targeting the stellate ganglion, the spinal region, the parasympathetic system, and other promising methods. These include stellate ganglion block, stellate ganglion ablation, cardiac sympathetic denervation, subcutaneous electrical stimulation, thoracic epidural anesthesia, spinal cord stimulation, dorsal root ganglion stimulation, vagus nerve stimulation, baroreflex activation therapy, carotid body ablation, renal denervation, ganglionated plexi ablation, acupuncture, and transcutaneous magnetic stimulation. Both preclinical and clinical studies are presented as evidence for arrhythmia management. Full article

Propranolol, a nonselective beta-adrenergic antagonist, has shown potential for improving anxiety in autistic individuals. Heart rate variability (HRV), a noninvasive cardiac marker of autonomic nervous system functioning, may help identify individuals most likely to benefit from propranolol. Objectives: Determine if baseline resting HRV and other cardiac measures predict the response to propranolol for anxiety and core autism symptomology in autistic children and young adults. Methods: Sixty-two autistic individuals (ages 7–24) participated in a two-phase (i.e., a 12-week randomized controlled trial and a 12-week open-label extension) trial of propranolol. Baseline (i.e., resting state, prior to treatment) HRV and other cardiac measures were obtained from an electrocardiogram. Clinical global impression for anxiety symptoms and overall behavioral treatment impact were assessed after the 12-week trial period. Group-level (i.e., all participants) and responder groups (i.e., strong, minimal, and non-responders to propranolol) were analyzed for treatment effects. Results: HRV variables predicted group-level anxiety response to propranolol, particularly for strong responders. Also, lower baseline values of parasympathetic HRV indices were significantly correlated with greater behavioral improvement after treatment with propranolol. Last, several baseline cardiac variables were associated with improvement in multiple behavioral domains after treatment with propranolol. Conclusions: HRV may be a potential biomarker for predicting reduced anxiety and behavioral symptoms in response to propranolol in autistic children and young adults. Identifying autonomic profiles associated with positive treatment outcomes could guide future personalized interventions in autism. The results presented herein should be regarded as preliminary until the findings are replicated in future clinical trials. Full article

We examined heart rate (HR) and heart rate variability (HRV) in young and middle-aged men after a period of detraining that immediately followed the completion of an exercise training program. Eight young (27.8 ± 3.8 years) and ten middle-aged (41.9 ± 3.8 years) men were randomly assigned to complete an 8-week exercise training program that included either aerobic (young: n = 3; middle-aged: n = 2), resistance (young: n = 3; middle-aged: n = 3), or combined (aerobic/resistance) (young: n = 2; middle-aged: n = 5) exercise. Thereafter, participants ceased all planned exercise training activities during an 8-week detraining period. Resting HR and HRV were assessed at baseline, after exercise training, and after detraining. An analysis of mean differences between age groups at each time-point revealed a significantly higher standard deviation of normal RR intervals (SDNN), square root of the mean of squared differences between successive RR intervals (RMSSD), high-frequency (HF) band (0.15–0.40 Hz), and cardiac vagal index (CVI) in young participants when compared to middle-aged participants at baseline (p ≤ 0.019) and after detraining (p ≤ 0.045), but not after the 8-week exercise training intervention (p ≥ 0.057). Additionally, in middle-aged participants, we observed a significant negative association between the percent change in HRV indices (RMSSD, HF, and CVI) and systolic blood pressure in response to detraining (p < 0.05). In conclusion, young participants had higher levels of HRV indices at baseline, reflecting greater cardiac vagal modulation when compared to middle-aged participants. We showed that these age-related differences in HRV are diminished following exercise training but are reestablished following 8 weeks of detraining. Given that age-related attenuations in HRV may reflect changes in cardiovascular health, it is important to further investigate the relationships between HRV, exercise training and detraining, aging, and the risk of poor health outcomes. Full article

The imbalance in the interaction between the autonomic nervous system and the immune system serves as a central mechanism in the onset and progression of cardiovascular diseases. The excessive activation of the sympathetic nervous system and suppression of vagal function contribute to chronic inflammation and cardiac remodeling. Precision medicine, by integrating multidimensional data such as genomics and metabolomics, offers a novel perspective for the personalized design of exercise interventions. This systematic review explores the bidirectional regulatory mechanisms of exercise interventions on the autonomic nervous system–immune axis and examines the potential applications of precision medicine in optimizing exercise prescriptions and clinical translation. Exercise significantly improves cardiovascular function through immunometabolic reprogramming, which includes suppressing sympathetic overactivity, enhancing vagal tone, and modulating the IL-6/IL-10 balance, as well as activating the short-chain fatty acid (SCFA)–Treg axis. Moreover, precision-medicine-driven ACE I/D gene typing provides a basis for selecting tailored exercise prescriptions, thereby significantly enhancing the efficacy of exercise interventions. By leveraging a multi-tiered “neuro–immune–metabolic” regulatory framework, exercise interventions contribute to improved cardiovascular health. The application of precision medicine technology overcomes individual variability constraints, advancing exercise prescription design from generalized recommendations toward personalized and dynamically adaptive strategies. Full article

Cardiac adaptations induced by aerobic exercise have been shown to reduce the risk of cardiovascular disease, and the autonomic nervous system is closely associated with the development of cardiovascular disease. Aerobic exercise intervention has been shown to enhance cardiac function and mitigate myocardial fibrosis and hypertrophy in heart failure mice. Further insights reveal that cardiomyocytes experiencing chronic heart failure undergo modifications in their lipidomic profile, including remodeling of multiple myocardial membrane phospholipids. Notably, there is a decrease in the total content of cardiolipin, as well as in the levels of total lysolipid CL and the CL (22:6). These alterations disrupt mitochondrial quality control processes, leading to abnormal expressions of proteins such as Drp1, MFN2, OPA1, and BNIP3, thereby resulting in a disrupted mitochondrial dynamic network. Whereas aerobic exercise ameliorated mitochondrial damage to a large extent by activating parasympathetic nerves, this beneficial effect was accomplished by modulating myocardial membrane phospholipid remodeling and restoring the mitochondrial dynamic network. In conclusion, aerobic exercise activated the parasympathetic state in mice and attenuated lipid peroxidation and oxidative stress injury, thereby maintaining mitochondrial dynamic homeostasis and improving cardiac function. Full article

Heart rate variability (HRV) has been established as a measure for the variation in time intervals between successive cardiac actions as a marker of the autonomic nervous system. However, despite many efforts in this field, there are no reference values that are generally accepted. The objective of this systematic review is, therefore, to present an overview of the studies on HRV normal values published to date, with due consideration of any influencing factors. A systematic database query was carried out in PubMed, Scopus, Ovid Medline, and PsychInfo using the search string “((hrv) or (heart rate variability)) and ((reference values) or (reference range) or (normal values))”. Of the 6640 studies yielded by the query, 58 were used for this systematic review. The STARD-HRV procedure was used to assess the quality of the studies. The studies considered date from 1989 to 2022. The number of subjects examined was between 20 and 84,772. The age of the subjects was between 1 day and 99 years. A total of 51 of the studies examined both male and female subjects. In total, 19 studies used long-term measurements, 22 studies used short-term measurements, and 17 studies used intermediate measuring periods. Many different HRV parameters were analyzed, most often traditional time-domain and frequency-domain ones. Nine studies described the subjects as “healthy” without giving more detailed explanations. There are no generally accepted HRV normal values (yet). Some large studies provide values that may be used for orientation purposes. However, further studies are required to collect HRV normal values. It was not possible to merge the results of the studies in terms of a meta-analysis; this would also not be practical since, among other reasons, the consideration of confounders as well as recording and measuring modalities sometimes vary to a large extent and impede the comparability of the studies. Generally, HRV seems to be influenced by various mechanisms and external factors that are still not fully understood. An exploration of these factors will ultimately allow HRV normal values to be obtained in a manner that is generally accepted. Full article

The intricate brain–heart interaction, essential for physiological balance, is largely governed by the autonomic nervous system (ANS). This bidirectional communication, involving both the sympathetic and parasympathetic branches of the ANS, is critical for maintaining cardiac homeostasis. Dysregulation of the ANS is a significant factor in cardiovascular diseases. Beyond the ANS, higher brain functions, particularly through interoceptive prediction, contribute to this dynamic interplay. The Cav1.3 L-type calcium channel, expressed in both the central nervous system (CNS) and the heart, is crucial for this interaction. Cav1.3, a key regulator of cellular excitability, exhibits genetic variations that are linked to both neurological and cardiac disorders, highlighting its pivotal role in the brain–heart axis. This review aims to delve into the under-explored role of Cav1.3 in brain–heart interaction, specifically examining how it modulates ANS activity and, consequently, the cardiac function. This will illuminate its significant role in the broader context of brain–heart interactions. Full article

Background: Alzheimer’s disease (AD) is the most common cause of dementia. In addition to cognitive decline, non-cognitive symptoms, including dysautonomia, have been reported, although these symptoms are rarely acknowledged by patients. Dysautonomia in AD is thought to arise from either cholinergic deficits or hypothalamic involvement. A wide range of tests has been used to investigate the role of the autonomic nervous system; however, the results have been inconsistent. Aim: To systematically review all published research investigating autonomic nervous system (ANS) involvement in patients with AD. A comprehensive literature search was conducted in December 2024 across the following databases: PubMed, Cochrane Library, ScienceDirect, and Scopus. Results: A total of 1422 records were identified, of which 30 studies fulfilled the inclusion criteria and were included in the review. Several autonomic tests were employed, with Heart Rate Variability (HRV) being the most frequently used. Other tests included assessments of orthostatic hypotension (OH), postprandial hypotension (PPH), sympathetic skin response (SSR), the tilt test, 123I-MIBG cardiac scintigraphy, norepinephrine (NE) measurements in serum and cerebrospinal fluid, and baroreflex sensitivity. In most studies, AD patients were compared to either healthy controls or patients with other types of dementia. Discussion: The primary finding of this review is that, although patients with AD rarely report dysautonomic symptoms, they frequently exhibit abnormal results on various autonomic tests. In some cases, these findings were sufficient to differentiate AD patients from healthy controls as well as from patients with Diffuse Lewy Body disease (DLB). The inconsistency in reporting symptoms, along with the variability in test results, suggests that autonomic dysfunction in AD may be under-recognized and warrants further investigation. Conclusions: The heterogeneity of the included studies limits the generalizability of the results. However, given the potential impact of dysautonomia on both quality of life and mortality, it is recommended that AD patients be systematically assessed for autonomic dysfunction. Even in the absence of overt symptoms, appropriate treatment should be considered where indicated to mitigate potential risks. Full article

In this study, we investigate the relationship between breathing patterns and cardiac autonomic nervous activity during spontaneous breathing. Electrocardiograms and respiratory signals were simultaneously monitored in six subjects for 5 min while in a seated position. The inhalation/exhalation ratio (i/e) was calculated, and its variance was compared with the heart rate variability index. The results showed that inhalation time tended to be longer than exhalation time, with the inhalation-to-exhalation ratio ranging from 1.074 to 1.423. Additionally, one subject exhibited an unusually slow respiratory cycle. The inhalation/exhalation ratio was partly associated with changes in the low-frequency to high-frequency ratio (LF/HF) of heart rate variability, indicating individual differences. These findings suggest that while breathing patterns play a role in autonomic nervous system regulation and may have applications in stress and respiratory health management, there are limitations to these associations. Full article

The assessment of cardiac autonomic regulation (CAR) with non-invasive techniques, such as heart rate variability (HRV), might be of practical interest in elite sports, considering its importance in determining training. We studied 117 soccer players (74 male and 43 female) from three First Division European soccer teams. We used a ranked Autonomic Nervous System Index (ANSI, resulting from the combination of multivariate statistical methodologies applied to HRV-derived indices) to assess CAR. We hypothesized that ANSI might differentiate playing positions, considering goalkeepers, defenders, midfielders, and forwards. We also assessed the perception of somatic symptoms and stress. We observed in male athletes that ANSI was significantly greater in males as compared to females (p < 0.001), being higher in midfielders and defenders (p = 0.035), who usually sustain the greatest external load. Interestingly, this result was not observed in female athletes, who, instead, reported a significantly higher perception of somatic symptoms (p = 0.018) and stress (p = 0.049), the latter being particularly high in midfielders and forwards (p = 0.045). This approach might represent a convenient model to study the effects of long-term physical exercise on CAR in soccer, even to unveil possible differences due to sex, different playing positions characterized by distinct exercise routines, or stress perception. Full article

Background: The beat-by-beat fluctuation of heart rate (HR) in its temporal sequence (HR dynamics) provides information on HR regulation by the autonomic nervous system (ANS) and its dysregulation in pathological states. Commonly, linear analyses of HR and its variability (HRV) are used to draw conclusions about pathological states despite clear statistical and translational limitations. Objective: The main aim of this study was to compare linear and nonlinear HR measures, including detrended fluctuation analysis (DFA), based on ECG recordings by radiotelemetry in C57BL/6N mice to identify pathological HR dynamics. Methods: We investigated different behavioral and a wide range of pharmacological interventions which alter ANS regulation through various peripheral and/or central mechanisms including receptors implicated in psychiatric disorders. This spectrum of interventions served as a reference system for comparison of linear and nonlinear HR measures to identify pathological states. Results: Physiological HR dynamics constitute a self-similar, scale-invariant, fractal process with persistent intrinsic long-range correlations resulting in physiological DFA scaling coefficients of α~1. Strongly altered DFA scaling coefficients (α ≠ 1) indicate pathological states of HR dynamics as elicited by (1) parasympathetic blockade, (2) parasympathetic overactivation and (3) sympathetic overactivation but not inhibition. The DFA scaling coefficients are identical in mice and humans under physiological conditions with identical pathological states by defined pharmacological interventions. Conclusions: Here, we show the importance of tonic vagal function for physiological HR dynamics in mice, as reported in humans. Unlike linear measures, DFA provides an important translational measure that reliably identifies pathological HR dynamics based on altered ANS control by pharmacological interventions. Central ANS dysregulation represents a likely mechanism of increased cardiac mortality in psychiatric disorders. Full article

Background/Objective: Heart rate variability (HRV) is a key biomarker of autonomic function, linked to morbidity and mortality across various diseases. Transcutaneous auricular vagus nerve stimulation (taVNS) shows therapeutic promise, but its effects on HRV and the influence of specific stimulation parameters remain unclear. This study investigated whether the acute effects of taVNS on HRV depend on combinations of stimulation frequency and pulse width. Methods: Seventy-eight healthy adults participated in seven randomized sessions, each testing one of six active taVNS protocols or an inactive sham condition applied to the cymba conchae of the left ear. The active protocols varied by frequency (10 Hz or 25 Hz) and pulse width (100 µs, 250 µs, or 500 µs). The sessions included 15 min of baseline, 15 min of taVNS or sham condition, and 10 min of recovery. HRV was calculated using the standard deviation of NN intervals (SDNN) and the root mean square of successive differences (RMSSD) from continuous ECG recordings. Results: The 10 Hz/250 µs, 10 Hz/500 µs, and 25 Hz/100 µs protocols significantly increased SDNN time series compared to the sham condition. Exploratory analysis revealed SDNN increases during the second 5 min of stimulation with the 10 Hz/500 µs protocol and during the first 5 min of recovery with the 10 Hz/250 µs and 25 Hz/100 µs protocols. No significant changes in the RMSSD were found for any protocol. Conclusions: TaVNS is safe in healthy adults, and specific frequency and pulse width combinations can acutely enhance overall HRV, as reflected in SDNN, but do not affect vagally mediated HRV, as reflected by the RMSSD. Future studies should optimize taVNS parameters to maximize physiological and clinical outcomes. Full article

Background: Heart rate turbulence (HRT) is a non-invasive technique that can be used to evaluate autonomic nervous system (ANS) function and cardiac arrhythmia. The objective of this study is to investigate whether COVID-19 can lead to long-term blunted HRT following recovery. Methods: This retrospective cohort study included 253 individuals with a confirmed history of COVID-19, referred to as the recovered COVID-19 group, along with 315 healthy participants who had no history of the virus. The recovered COVID-19 group was categorized into three subgroups based on their chest CT severity scores. The HRT analyses were obtained from a 24-h electrocardiography-Holter recording. Results: This study revealed that the HRT onset value was elevated in the recovered COVID-19 group, while the HRT slope value showed a significant decrease when compared to the control group. Correlation analyses indicated a positive relationship between the chest CT severity score and HRT onset, whereas a negative correlation was observed between the chest CT severity score and HRT slope. Regression analyses identified recovery from severe COVID-19, chest CT severity score, hypertension (HT), and smoking as independent predictors of both abnormal HRT onset and the existence of an abnormal HRT slope. Conclusions: Individuals who have recovered from severe COVID-19 are expected to encounter a permanent blunting of HRT, which is regarded as a significant indicator of an increased risk of ventricular arrhythmias and impaired autonomic nervous system (ANS) function. Recovered severe COVID-19 individuals should be carefully evaluated for HRT with 24-h ECG-Holter. Full article

Background: Considering that the nervous system regulates cardiac autonomic modulation (CAM) and that low CAM is associated with poorer performance, it is essential to evaluate the effects of training to increase parasympathetic modulation in Muay Thai (MT) fighters. Therefore, the aim of this study was to evaluate the effects of an 8-week intervention based on strength training and nutritional counseling on performance, CAM, and nutritional status in amateur MT fighters. Methods: This is a longitudinal and interventional study in which 22 MT fighters underwent a strength training program and nutritional protocol. Before and after the intervention, they underwent the ten-second frequency speed of kick test (FSKT-10s), multiple frequency speed of kick test (FSKT-mult), bioimpedance analysis (BIA), and assessment of heart rate variability. Results: After the intervention, there was an increase in the number of kicks in both FSKT-10s and FSKT-mult (p = 0.0008 and p = 0.032, respectively). In BIA, there was a significant increase in both fat-free mass and basal metabolic rate (p = 0.031 and p = 0.020, respectively). After the intervention, significant increases were observed during the physical test in the following variables that denote improvement in parasympathetic modulation: square root of the mean squared differences of successive RR intervals (p = 0.005); percentage of adjacent RR intervals with a difference in duration greater than 50 ms (p = 0.002); high frequency range (p < 0.0001); and standard deviation measuring the dispersion of points in the plot perpendicular to the line of identity (p = 0.004). Conclusions: In amateur MT fighters, an intervention with strength training and nutritional guidance is able to improve CAM through greater parasympathetic activation. Furthermore, there is an improvement in performance and body composition after the intervention. Full article